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First short XC Flight and Slow Cruise Speed
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victorbravo(at)sbcglobal.
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PostPosted: Mon Aug 27, 2018 1:56 pm    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

The other day I made the first flight out of the traffic pattern. I wrote two long and detailed posts on the homebuilt airplanes internet forum, and I am copying them here ont he Kolb List for anyone who is still interested in the subject of my test flight program on the HKS Firestar. These posts will be far too long and detailed for some of the folks on the Kolb List. But for those interested, here are the results from the first flight away from the airport, and the second post is trying to identify the causes of the poor aircraft performance. I am not including the responses from other participants on that forum, but the entire 11 page discussion thread from start to finish can be seen here by anyone with that much time on their hands: http://www.homebuiltairplanes.com/forums/showthread.php?t=30314

I'm the person posting under the screen name Victor Bravo, some of the guys refer to me as VB (Victor Bravo or VB was my old racing competition numbers in sailplanes 35 years ago)

At this stage I am not nearly as concerned with the nose up and nose down trim, or the stabilizer angle. All that is manageable and can be fixed easily enough.This flight showed that I am just not getting the performance out of this aircraft that the average 503 powered Firestar should get.Fixing that problem is now a much bigger deal to me than the trim because it affects the overall usability and desirability of owning and flying it.

Again, this may be far too much detail nd discussion for some people, please accept my apology for that if appropriate.

Post #1 - Saturday evening

Well, today was a two-flight day. Early this morning I did a brief local pattern flight in "Special VFR" visibility conditions to see if the large windshield I had installed (re-installed the one that had come with this aircraft) would make any difference in the aircraft's paint-blistering cruise speed or nose-down trim. I flew three or four times around the pattern, and did not see any significant difference. A little comfort, yes, but significant improvement in speed or nose-down force... no. And a cabin entry/egress process that is very embarrassing. The large windshield makes the front of the aircraft look like a badminton birdie, with about the same amount of drag.

But I had not gotten to anything resembling a cruise altitude, nor had I let the airplane settle into any sort of cruise configuration.

Today was also the first flight with working two-way communication, using a borrowed helmet/headset/handheld radio setup. So later in the day after the control tower opened up, I took advantage of being able to have two-way radio, and set out on the first "major cross country" flight. My goal was to get from Whiteman Airport to Agua Dulce Airport, a distance of 23 miles (including the 90 degree dog-leg detour through the Newhall Pass). I figured this was a modest goal, but it was first trip out of the local airport pattern.

The fuel system I had put in it was not working very well. I have two 5 gallon tanks, but there is no inter-connect between the tanks. They both have pickup lines coming into the tank from the top, because i did not want to put fittings into the bottom of the tanks where I couldn't see or deal with a fuel leak. Both tank pickup lines run to a gascolator, which is on the suction side of the electric and pulse fuele pumps. So I had assumed that the pump would "suck" fuel from both tanks more or less equally. I was wrong, the fuel in the font tank is used much faster than the rear tank.

So I filled the front tank up to the 5 gallon level, and as Lonesome George Thorogood and John Lee Hooker say... "and down the road I went".

The cruise speed is still 45 - 47 MPH IAS at 5300-5400 RPM, which is about 91% of the 5800 max. continuous RPM. So this was "high cruise" and not anywhere near "economy cruise". Worse yet, 5400 is still 85% of the "5 minute takeoff rating" of 6200 RPM. Which means that I'm not even able to take advantage of the HKS' low cruise fuel consumption, on top of all the other issues.

We also had our SoCal light southwest breeze today, about 10 knots. By the time I got to the Sand Canyon Country Club golf course, I had traveled 15 miles, and realized that there was not going to be any significant increase in cruise speed. I also realized that I would have possibly a 10 knot headwind on the way back home. So I turned around at that point, and started heading back. By the time I got through Newhall Pass again (the initial reporting point for traffic going into Whitmen and Van Nuys), I also realized that my trans-sonic speeds were going to become an annoyance for the ATC people and everyone else coming through there on a regular basis. My friend in his Vari-EZ called in at Newhall Pass behind me and I volunteered to displace to the right of the final approach path to allow him to pass.

By the time I landed at Whiteman it had been perhaps a 40-45 minute flight to go 30 miles It looked like I had used over 2 or 2 and 1/3 gallons of fuel from the front tank. To say I was disappointed taxi-ing back in would be quite an understatement.

The engine ran well and the aircraft was reasonably stable and easy to fly. No major complaints there. I was also able to verify that I had reasonable pitch stability, in that it took a little forward pressure to go faster than 45 IAS, and to slow down/flare/land at 30 MPH it took back pressure. No major Grim Reaper lurking around the pitch axis even with my jacked-up stabilizer. Compared to the weight and balance results, and knowing there were a couple more gallons of gas on this flight, I am fairly certain that I was at gross weight, plus or minus five or ten pounds. Full throttle in level flight put me slightly above max continuous RPM but a hundred or two less than max permitted takeoff RPM. So I do not believe I am grossly "under-pitched" on the prop. The aircraft also does NOT "climb like a homesick anglel". It takes off in a couple hundred feet or so, and it climbs well enough to not be "a slug", but this is no Super Cub by any means. If I had this much power but my takeoff weight was 525 pounds (instead of 725) perhaps it would behave like a Super Cub.

I am reasonably convinced that there are 5 or 8 miles an hour to be gained with streamline wing and landing gear struts. But those streamline struts will not get me up to 65 or 70 miles an hour which is about what Kolb aircraft using tis engine really ought to do. 70 miles an hour would allow me to blend in with "normal airplane" traffic and not becomee a PITA to the traffic controllers. 70 miles an hour would also allow me to use this aircraft for the mission I wanted it for. 45 or 50 miles an hour will not.

So now I am at the point of grasping at straws to find out what is slowing this one down so much. It is not the lack of a windshield. Other Kolb Firestars have bush tires and still go 65 MPH. I have a strange oil cooler that works too well, and there's a chance that the air flowingo ut of the cooler is causing some huge drag-producing disturbance on the wing root area. There is a chance that my exposed engine and oil tank in the wing center section are causing huge drag somewhere. There is a chance that my unique exhaust and muffler are destroying the airflow into the propeller disc so much that I have lost a third mf the engine's potential thrust.

But there is also a chance that I have just plain screwed up something so much in my custom engine installation that I am never going to be able to use this Kolb for the mission that I had intended. The Kolb is the only airplane that folds up small enough to fit in my hangar, so if the Kolb will not work then I am basically defeated in pursuing the kind of STOL flying that I wanted.

Post #2 - Sunday evening

Sorry to sound like a broken record, but thank you again to all the people taking time and brain cells to fool with this puzzle.

To answer some random questions in no particular order:

The airplane is at gross weight because I have several components that are heavier than a normal Kolb Firestar. My HKS engine is about 30 pounds heavier than the 503. I put HD oversize gear legs on which probably are 15-20 pounds more than stock. My tires are a LOT heavier than the silly little tires that they come with. I have a 4 foot stainless 2 into 1 exhaust, and then a custom 4 foot long muffler that weighs more than the stock litle "tin can". So when you stop and think about it fairly, it makes sense that this one is nearly 100 pounds over the brochure weight. I have a valid and reasonable mission-driven justification for each and every one of the changes I made, but the digital scale says what it sees without asking why I did anything.

It is theoretically possible that the VG's are screwing around with something somewhere. However, it is known and demonstrated on many other Kolb aircraft that the VG's do not have adverse effects, and they are shown to reduce stall speed. I installed them at the chordwise location, spacing, and angle that was recommended by the VG manufacturer. Numerous similar and non-similar aircraft use VG's at the same location. More importantly, in general the VG's are reasonably known to improve or maintain attached turbulent flow over the wing surface. I am not aware of any "normal" VG installation that created a 33-40% increase in aircraft drag. Anything is possible of course, but I would be surprised if this were the problem. If all else fails I will remove them, but there are other things I'd look at first.

The fuel probelm is that I do not have interconnected fuel tanks. They both feed the same gascolator, but there is no cross-feed or interconnect at the bottom of the tanks. I also cannot install a one-piece tank at that location, they can only be inserted into the airframe one at a time. So considering that I also have a CG that is indeed further aft than most of these aircraft (whether it's within the approved range or not), if I do any work on the fuel system I can get two birds with one stone by moving the fuel forward 18 inches and going to a one-piece tank... solving both the CG and fuel feed issues at the same time.

Some information/observations that I had not discussed here previously. One or more of these may be causing the extraordinary drag and/or loss of thrust that is slowing me down:

1) I thought I had designed a really clever and low drag oil cooler mounting system. I may not have been as clever as I had hoped. The top surface of the cooler is flush with the top surface of the starboard wing root, just behind the maximum thickness of the wing section. I have an aluminum plenum box under it, which takes high pressure ram air from the bottom of the wing, then up through the cooler, and then exits the air into the low pressure field above the wing. It works too good, the first flights I had low oil temp. Even after closing off half of the scoop area, I still only got to 180 degrees F on the last flight. If this slug of pressurized air is shooting up through the cooler at a good clip, shooting into the relative wind at a 60 or 70 degree engle, it could possibly be making a "virtual spoiler" jet of air flowing upward from the wing surface and making a boatload of drag. No other Kolb that I know of has had the oil cooler mounted in this manner. Most of them just put it somewhere with it "facing" into the relative wind.

2) After the last flight I saw oil droplets and oil moisture on parts of the upper wing surface that should not have gotten wet. My oil tank is partially exposed above the upper wing surface, but it is about 55-60% of chors on the port side of the center section. The oil droplets (which presumably came from the overboard vent tube on top of the oil tank) were between 6 and 18 inches OUTBOARD and FORWARD from this oil vent tube. There is no source of oil anywhere forward (chordwise) of this oil wetting on that side of the center section. There is also no source of oil even with or outboard (spanwise) of the oil wetting area on the wing upper surface. So regardless of the actual source of the oil droplets, any oil that is deposited at the areas I am seeing had to be carried there by airflowthat was not moving lengthwise from from leading edge to trailing edge. The air had to be doing something really counterintuitive, going against the general flow direction and outboard at the same time.

3) In an attempt to force the main wing stall to begin at the root end and progress outboard, I left one rib bay near the inboard section of the wings without VG's. The location of the oil stains/droplets is in this "VG-less" rib bay on the port wing. So there is a possibility that there is some bound or stationary vortex. coming off of the VG-less part of the wing, and this vortex or circulation pattern is carrying oil droplets from the overboard vent forward and outboard, which would likely create a boat-load of drag somehow. interestingly, the center section fairing that covers the gap between the wings (20 inches wide) does have VG's on it because I wanted to have attached flow to make sure plenty of high energy airflow got into the Cub-style "eyebrow" cylinder cooling shrouds. So there is the possibility that the boundary between VG covered wing and naked wing is creating some spanwise vortex in addition to whatever other crappy flow thee is in that location. Spanwise vortex rotation (vertical axis of vortex rotation) would at least explain how oil is being thrown outboard from the original source.

4) Most Kolbs do not have any "cowling" or fairing in front of the engine on the top surface of the wing. Mine does not have a shaped cowling either. But the HKS is an opposed engine layout, and mine has some draggy items in the middle, where the 2 stroke engines are usually an inline layout. Between the engine cylinders, facing forward, I have a large 4x6 inch bracket that mounts the engine control cables and "splitters", some -10 size oil lines and several fittings, a few inches of oil tank above the wing, a bunch of wiring, two intake manifolds, etc. So it is possible that the engine and all of this junk is behaving like a 24 inch wide "spolier" taking up the entire center section of the upper rear wing surface, creating whatever parasite drag it creates and ALSO spoiling the in-flow to the propeller.

5) I have more drag-producing and flow-blocking components behind the steel "pylon" or "cage" than other Kolbs. There are a bunch of 1/2 through 3/4 inch steel tubes there on every Kolb, but then on top of that I have two 1.25 inch exhaust pipes right next to each other running vertically down the back side of the pylon. These exhaust pipes are 4 inches in front of the propeller arc, and would serve to disturb the in-flow to the prop more than even the standard "dirty" Kolb airframe.


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lcottrell



Joined: 29 May 2006
Posts: 1392
Location: Jordan Valley, Or

PostPosted: Mon Aug 27, 2018 2:37 pm    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

It would appear as though you may have painted yourself into a corner. When I got my first one it would only fly at about 50 mph. The fabric had not had the full coats that is recommended by poly fiber and the texture of the fabric was rough. Not knowing any better I painted it with auto paint, which necessitated that I recover it some 10 years later, but it gave me about 10 miles more speed. I made a xcountry trip to NMex and used the cloth wrap around fabric that comes from the Kolb full enclosure, and it cut my speed by about 5 MPH. The plane does better with the "shuttle cock" configuration. Streamlined struts and legs gave me about 5-6 MPH increase.

I have a couple of suggestions for you- secure a hose to the relief tube on the oil container and route it out the bottom of the fabric in the fuel compartment. It won't solve your air problem, but it will put the oil where it isn't a problem.  As for the fuel tanks, I ran the "pickup tubes" to a selector switch at the left side of the seat, set the EIS to alarm at one gallon of fuel left, put a double throw switch so that I could monitor both tanks individually. Then from the fuel selector valve I ran a tube to the facet fuel pump that I secured to the cross tubes behind the jump seat. 
Worth what you paid for it,
Larry


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Richard Pike



Joined: 09 Jan 2006
Posts: 1520
Location: Blountville, Tennessee

PostPosted: Mon Aug 27, 2018 6:17 pm    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

I am thinking that a big part of the problem is that you done enough variations from the norm that trying to analyze for a specific problem is going to be tough, but here's an idea: Go ahead and take an absolute boatload of pictures of your airplane, resize them, and post them in a size that will take up a normal full screen so that we can all see the details. Your descriptions are good, but a picture really is worth a thousand words. Maybe one of us will spot something.

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racerjerry



Joined: 15 Dec 2009
Posts: 182
Location: Deer Park, NY

PostPosted: Tue Aug 28, 2018 3:40 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Bill, I too did not want to drill holes in the bottom of the fuel tanks of my 447 powered Firestar II and opted to connect the tanks as you did but was disappointed when they refused to feed equally. They feed somewhat close, but certainly not equal. If you separate the tanks in an effort to correct a CG problem, it will make fuel feed matters worse.

Just remember that when the first tank sucks air, the fuel supply to your engine is GONE.

I was a brand new Kolb pilot practicing "Where would I land now if the engine should quit."
Need I say more?

Jerry King


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PostPosted: Tue Aug 28, 2018 6:59 am    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

It’s always good to have those deadstick landing spots in sight. It’s also good to practice engine off deadsticks now and then.
People tend to worry a lot about things that never happen. I used the rubber grommets (actually they are some kind synthetic stuff.)from the early days of my ultralight career in Eipper MX’s, Spectrum Beavers and my Kolb MKII. If you do your maintenance and change them every two or three years they will never give you a problem. I change my fuel lines every year as a part of my pre-season maintenance.
In my younger days and my MKII, I really liked going upside down so I used a crossover line between the two plastic 5 gallon tanks supplied by Kolb (using the grommets) and metal elbows for the crossover lines. We used what we called clunks which dangled down from top of one of fuel tanks for fuel feed lines to the fuel pump and filter. They moved with the fuel even when you were upside down. They worked great on the Kolb, Avenger and Beavers. Never had an engine go silent. I never did extended inverted flight. But, Kolbs will do a nice split S, lazy 8’s and occasional loops. I never tried negative “G” maneuvers. I wasn’t completely stupid. I’m out of aerobics these days. I survived my youth. 😉 In 35+ years of ultralighting I’ve had two for real engine outs and they were both my fault.
George H.
Firestar, FS100, 2702 Hirth
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

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Quote:
On Aug 28, 2018, at 7:40 AM, racerjerry <gnking2(at)verizon.net> wrote:



Bill, I too did not want to drill holes in the bottom of the fuel tanks of my 447 powered Firestar II and opted to connect the tanks as you did but was disappointed when they refused to feed equally. They feed somewhat close, but certainly not equal. If you separate the tanks in an effort to correct a CG problem, it will make fuel feed matters worse.

Just remember that when the first tank sucks air, the fuel supply to your engine is GONE.

I was a brand new Kolb pilot practicing "Where would I land now if the engine should quit."
Need I say more?

Jerry King

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Jerry King




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neilsenrm(at)gmail.com
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PostPosted: Tue Aug 28, 2018 7:26 am    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

I know Bill has verified the W&B is correct and the wing angle is correct but based on the horizontal stabilizer angle the wing just has to be set with too high of angle of attack. Bill check two things. Check the angle of the underside of the wing and the angle of the horizontal stabilizer from level. I'm betting they are real close to being the same. The wing will have a bit more. 
Then raise the tail and set it on something where the horizontal stabilizer is level. The stand back and look at the airplane. I think you will see the tail is very high and the nose is very low. The ground will represent the direction of airflow the plane will see in flight. Wind hitting the additional surface of the fuselage due to this flight attitude maybe enough additional drag to cause your speed reduction.
See the attached. I have exaggerated the drawing to better show what I think Bill's plane maybe like. Again the drawing shows much more exaggerated angle of the wing and horizontal stabilizer than Bill's plane.
I think the leading edge of the wing needs to be lowered. Get two of the Kolb (Steven Green) adjustable universal joint fittings and install them on both wings raising the trailing edge as far as they go or maybe just a bit at a time and go fly. Be prepared for the need of up elevator. Does your cruise speed increase any? The adjustable universal joint fittings allow you to change the angle of attack of the wing for testing purposes and make it easy to go back to where it was. I think you will need to reduce the angle of attack quite a bit on the wing to get the plane flying level. Remember to lower the horizontal stabilizer.
As always worth what you paid for it.
Rick Neilsen
Redrive VW Powered MKIIIC
On Mon, Aug 27, 2018 at 6:38 PM Larry Cottrell <lcottrell1020(at)gmail.com (lcottrell1020(at)gmail.com)> wrote:

Quote:
It would appear as though you may have painted yourself into a corner. When I got my first one it would only fly at about 50 mph. The fabric had not had the full coats that is recommended by poly fiber and the texture of the fabric was rough. Not knowing any better I painted it with auto paint, which necessitated that I recover it some 10 years later, but it gave me about 10 miles more speed. I made a xcountry trip to NMex and used the cloth wrap around fabric that comes from the Kolb full enclosure, and it cut my speed by about 5 MPH. The plane does better with the "shuttle cock" configuration. Streamlined struts and legs gave me about 5-6 MPH increase.

I have a couple of suggestions for you- secure a hose to the relief tube on the oil container and route it out the bottom of the fabric in the fuel compartment. It won't solve your air problem, but it will put the oil where it isn't a problem.  As for the fuel tanks, I ran the "pickup tubes" to a selector switch at the left side of the seat, set the EIS to alarm at one gallon of fuel left, put a double throw switch so that I could monitor both tanks individually. Then from the fuel selector valve I ran a tube to the facet fuel pump that I secured to the cross tubes behind the jump seat. 
Worth what you paid for it,
Larry



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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Tue Aug 28, 2018 9:36 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Bill..
Some folks (and you) may not appreciate this post. But it's with much respect. From a distance, you are making ME very nervous with what you have done, and what you are doing. Why? A few comments below:

AFTER you have added all kinds of weight, different prop height, stab angle changes, oil coolers, exhaust tubes, and other assorted landing gear truck parts and wheels.. you wonder why it doesn't fly well?

You claim to be a experienced sailplane and GA pilot, but some of the stuff you are doing does not indicate "informed" decisions. To wit:
Who makes a big scoop on the bottom (pressure) side, piped to the low pressure side.. and still expects there to be "lift"? No worries about the tips flying, while you have destroyed the lift in the center of the span. NO BODY should EVER pipe two fuel tanks together, as racerJerry already mentioned, before I started typing. And that is absolute common knowledge among those who.. live.. and some who force land with luck. You couldn't quote ANY of the numbers on your weight and balance, yet you were out flying it, and jacking the stabilizer around. You've taken off for a cross country, with a known bad fuel supply scenario, and a very unknown aircraft?? And from this forum, I don't see where you have listened much to a lot of good input. Instead you want to say it's not acceptable to your flying needs and habits?

Other than this heads up.. I'm gonna pass on any further intelligent commentary on your subjects. I think you need to find some real local EAA guys to help you TRULY make some changes.. and THEN, make some needed changes to your airplane as well!!!

Ya know.. "unacceptable flight characteristics" might be the best thing you have said. Try sailing. Boats fit into narrow hangers very easily.

Jerry


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PostPosted: Tue Aug 28, 2018 10:13 pm    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

Well Jerry I appreciate your comments and the fact that you have shared an opinion. It's hard for me to not feel like I'm being chatised a little, but I will try to respond to your post using facts more than rhetoric.

Yes I added weight to the basic Kolb design. I did it for the same reason that every production aircraft manufacturer both civil and military does... in order to install specific equipment for a specialized purpose. I added steel landing gear legs like John H and many many other Kolb owners did. Because for off-airport flying the Kolb aluminum gear legs have been found to be too light duty (by some of the highly respected people on tis list). The heavy gear legs I used were Kolb brand gear legs only from a different model (Slingshot). Steel gear legs are a very common upgrade for Kolbs as far as I have read on this list. I think Kolb suggests them as an upgrade if I am not mistaken?

My propeller height is within A COUPLE OF INCHES of the stock Firestar. I have researched and read about all the Kolb owners on this list who have figured out how to deal with the high thrust line. The higher the thrust line the more the airplane tries to pitch nose down with power. The lower the thrust line the less it does this. My thrust line is less than 34 inches above the tailboom, which (Kolbers please correct me if I am wrong) is close or identical to everyone else's thrust line.

Yes I made a custom exhaust system. But I did not start out wanting to do this, I had a perfectly good HKS factory exhaust system. The problem is that the stock exhaust pipes prevented the wings from folding normally. I could have raised the engine up higher but this would have made the pitch-over worse, and I wanted to keep the thrust line where everyone else's was. So THAT is the only reason I started making a custom exhaust, not because I was trying to do something radically different.

There's no "truck parts" on this aircraft. I have the original Azusa Tri-Star wheels that came with the aircraft when I bought it, and one of the members of this list kindly sent me a set of bush tires for it. The bush tires I have are the same as Larry C's I believe, and I know others have used these same tires and even larger. By the way they have about the same frontal area as the Carlisle Turf Glide tires that Kolb recommends for off-airport flying.

The stabilizer angle changes were taken from Old Poops' website almost exactly. I also have gotten off-list e-mails from other Kolbers who did the same thing. As a matter of fact I started with 1/8" LESS change than Richard had done, in order to be conservative and less risky.

Yes I am a low to moderately experienced GA and sailplane pilot. No military service and no airline flying. About 1600 total time. Although it clearly has little or NO bearing on Kolb flyiing, I have competed at the Reno Air Races (5th place Silver) and in the US National Soaring Championships (9th place, 17th place). That and five bucks gets you a cup of coffee at Starbucks Smile None of the Reno racing experience has been any help at all with this Kolb, and only a little of the sailplane experience has been relevant.

The scoop on thebottom of the wing and venting it on the top was a precautionary measure because thre HKS engines are known to run hot and the manual has strict limits on oil temp. Over the last 2 months here in Southern California it has been 100-115 degrees during the day. So my "informed' decision was to make sure I had a little too much oil cooling and I could always close some of it off... rather than risk damaging the engine. It seemed like the safer, more responsible thing to do. Also, the oil cooler is located aft of the thicker part of the wing where it should not be as much of an effect on lift.Most of the lift on a Kolb airfoil is made near the front, so I had to make an educated guess and hope that this oil cooler did not put a big hole in my elliptical lift distribution. But now that the drag has become my largest issue, and the engine runs cool, I can close off a large part of that bottom-to-top airflow.

The radiator-in-the-wing design was based on information from a NACA research project in the 1930's, where they tested several ducts, inlets, and outlets. SOME of the outlets on the top surface of the wing in that research study actually were shown to increase lift. If Jerry or anyone on the Kolb list wants to see the NACA report I will gladly post a link.

"Piping two fuel tanks together" is exactly what I did NOT do. I have separate tanks that only have a gascolator in common. Other than that, they have separate pickup tubes and separate vent tubes. By having them connect to the gascolator I had hoped to have them function like one larger tank but they did not do that. HOWEVER, even though one fuel tank was feeding more fuel to the engine than the other, the only effect that could have on the aircraft is making it equal to a stock plans built Kolb ultralight with one 5 gallon tank. How is a Kolb with 5 gallons of usable fuel unsafe? Are all the Firefly ultralights and older Firestar 1 aircraft (with one fuel tank) unsafe to fly outside of the traffic pattern? I took off on a 25 mile flight, planning to land at the halfway point, with AT LEAST 5 USABLE GALLONS of fuel on board. Does this seem unsafe or ill-advised to you Jerry?

I had the weight and balance numbers done by a professional well before I was out flying the aircraft. A quick search of my Kolb List postings will verify this. The weight and balance results from a qualified engineer using good digital scales, indicated the aircraft was near the aft CG limit but did not exceed it. When we did the weight and balance a SECOND time because of this list, I chose to publish those second numbers, which were almost the same as they had been the first time (I lost a few pounds personally). The fact that I did not quote the numerical results form the first weight and balance does not mean those numbers did not exist. I did not quote my pilot's license number before the first flight either. It is 2287853.

I listened to EVERYONE's input and considered it all carefully. The archives will show clearly that I was thanking everyone ten or twelve times for participating in the discussion. Some experienced Kolb owners said that they had also jacked up the tail on their airplane and it was not harmful. Other experienced Kolb owners said that they had never heard of any one jacking up the tail, and it was not safe. Now that the aircraft at least flies hands-off at some speed, whose input was the better option?

A lot of people said "just add weight to the front". I CANNOT ADD WEIGHT to the front of the aircraft without exceeding the maximum takeoff weight of 725 pounds. A lot of people swore that the aircraft had to be horribly tail heavy and way out of the allowable CG range in order to need any significant amount of nose-down stick force. That input turned out to be wrong, unless Kolb's factory CG range is unsafe to fly.

After speaking with John H and others on this list, and LISTENING to the input of the Kolbers, I have come to the conclusion that it is indeed safe to droop the ailerons slightly in an attempt to eliminate some of the forward stick pressure. Rather than just blindly changing the Kolb wing design, I wanted to be conservative and safe, and determine whether drooping the ailerons could cause early tip stall or not. Several people verified tha it was OK to do this (change the Kolb wing design to trim out the aircraft in flight), and so when these other issues are sorted out I know I can safely start drooping the ailerons in order to lower the stabilizer a little.

I cannot see how my being cautious about deviating from the Kolb plans makes me OK in some areas (droop the ailerons below the wing) and wrong/disrespectful in other areas (adjust the stabilizer angle). Jerry perhaps you can make a list of where it is OK to redesign the aerodynamics of the Kolb, and where it is not OK.

By the way I AM one of those "real local EAA" people. Last December was the 40th anniversary of my first solo and 22 years as an EAA chapter member.

I'll let the comment about taking up sailing go, because I promised I would keep my temper under control on this list. Jerry, I would, however, very much like to hear about your specific level of experience with building or flying experimental aircraft, flight testing experimental aircraft, and technical engineering / modifications to aircraft systems.
Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Tue, 8/28/18, Jerry-TS-MkII <12flybellaire(at)gmail.com> wrote:

Subject: Re: First short XC Flight and Slow Cruise Speed
To: kolb-list(at)matronics.com
Date: Tuesday, August 28, 2018, 10:36 AM


"Jerry-TS-MkII" <12flybellaire(at)gmail.com>

Bill..
Some folks (and you) may not appreciate
this post.  But it's with much respect.  From a
distance, you are making ME very nervous with what you have
done, and what you are doing.  Why?  A few
comments below:

AFTER you have added all kinds of
weight, different prop height, stab angle changes, oil
coolers, exhaust tubes, and other assorted landing gear
truck parts and wheels.. you wonder why it doesn't fly
well?

You claim to be a experienced sailplane
and GA pilot, but some of the stuff you are doing does not
indicate "informed" decisions.  To wit:
Who makes a big scoop on the bottom
(pressure) side, piped to the low pressure side.. and still
expects there to be "lift"? No worries about the tips
flying, while you have destroyed the lift in the center of
the span.  NO BODY should EVER pipe two fuel tanks
together, as racerJerry already mentioned, before I started
typing.  And that is absolute common knowledge among
those who.. live.. and some who force land with luck. 
You couldn't quote ANY of the numbers on your weight and
balance, yet you were out flying it, and jacking the
stabilizer around.  You've taken off for a cross
country, with a known bad fuel supply scenario, and a very
unknown aircraft??  And from this forum, I don't see
where you have listened much to a lot of good input. 
Instead you want to say it's not acceptable to your flying
needs and habits?

Other than this heads up.. I'm gonna
pass on any further intelligent commentary on your
subjects.  I think you need to find some real local EAA
guys to help you TRULY make some changes.. and THEN, make
some needed changes to your airplane as well!!!

Ya know.. "unacceptable flight
characteristics" might be the best thing you have
said.  Try sailing.  Boats fit into narrow hangers
very easily.

Jerry




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victorbravo(at)sbcglobal.
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PostPosted: Tue Aug 28, 2018 10:53 pm    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

My aircraft does indeed look like Rick's sketch.

But I HAVE NOT changed the wing-to-fuselage angle (incidence) at all. If the wing looks like it is sitting on the fuselage at a ridiculous angle then it was welded that way in Kentucky. The main spar pin hole (which sets the incidence angle) on my aircraft is within 1/32" of exactly where Kolb says it should be.

Rick's sketch shows the tail pretty much parallel to the bottom of the wing. No Kolb Firestar is this way. The stock plans built Firestar has the stabilizer at a significant angle to the wing, meaning WHATEVER angle the fuselage and wing is flying through the air - the tail is "digging" downward quite a bit.

Rick's sketch looks like there is no difference between the wing and tail angles... this would be unsafe on almost all aircraft, and require the pilot to be pulling back on the stick with all his strength to keep from diving into the ground.

On my aircraft I reduced the stabilizer/tail angle (because I was tired of pushing forward on the stick) but DID NOT ELIMINATE this angle.I have a solid 4 degrees of tail down-angle. Whatever angle that the wing and fuselage are flying through the air, my stabilizer is "digging" downward 4 degrees lower than that.
Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Tue, 8/28/18, Rick Neilsen <neilsenrm(at)gmail.com> wrote:

Subject: Re: First short XC Flight and Slow Cruise Speed
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Tuesday, August 28, 2018, 8:26 AM

I know Bill has verified the
W&B is correct and the wing angle is correct but based
on the horizontal stabilizer angle the wing just has to be
set with too high of angle of attack. Bill check two things.
Check the angle of the underside of the wing and the angle
of the horizontal stabilizer from level. I'm betting
they are real close to being the same. The wing will have a
bit more. 
Then raise the tail and set it on
something where the horizontal stabilizer is level. The
stand back and look at the airplane. I think you will see
the tail is very high and the nose is very low. The ground
will represent the direction of airflow the plane will see
in flight. Wind hitting the additional surface of the
fuselage due to this flight attitude maybe enough additional
drag to cause your speed reduction.
See the attached. I have
exaggerated the drawing to better show what I think
Bill's plane maybe like. Again the drawing shows much
more exaggerated angle of the wing and horizontal stabilizer
than Bill's plane.
I think the leading edge of the
wing needs to be lowered. Get two of the Kolb (Steven Green)
adjustable universal joint fittings and install them on both
wings raising the trailing edge as far as they go or maybe
just a bit at a time and go fly. Be prepared for the need of
up elevator. Does your cruise speed increase any? The
adjustable universal joint fittings allow you to change the
angle of attack of the wing for testing purposes and make it
easy to go back to where it was. I think you will need to
reduce the angle of attack quite a bit on the wing to get
the plane flying level. Remember to lower the horizontal
stabilizer.
As always worth what you paid for
it.
Rick NeilsenRedrive VW Powered
MKIIIC
On Mon, Aug
27, 2018 at 6:38 PM Larry Cottrell <lcottrell1020(at)gmail.com>
wrote:
It would appear as though you may have
painted yourself into a corner. When I got my first one it
would only fly at about 50 mph. The fabric had not had the
full coats that is recommended by poly fiber and the texture
of the fabric was rough. Not knowing any better I painted it
with auto paint, which necessitated that I recover it some
10 years later, but it gave me about 10 miles more speed. I
made a xcountry trip to NMex and used the cloth wrap around
fabric that comes from the Kolb full enclosure, and it cut
my speed by about 5 MPH. The plane does better with the
"shuttle cock" configuration. Streamlined struts
and legs gave me about 5-6 MPH increase.
I have a couple of suggestions for
you- secure a hose to the relief tube on the oil container
and route it out the bottom of the fabric in the fuel
compartment. It won't solve your air problem, but it
will put the oil where it isn't a problem.  As for the
fuel tanks, I ran the "pickup tubes" to a selector
switch at the left side of the seat, set the EIS to alarm at
one gallon of fuel left, put a double throw switch so that I
could monitor both tanks individually. Then from the fuel
selector valve I ran a tube to the facet fuel pump that I
secured to the cross tubes behind the jump
seat. 
Worth what you
paid for
it,Larry


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Rex Rodebush



Joined: 10 Jan 2006
Posts: 186
Location: Branson West area, Missouri

PostPosted: Wed Aug 29, 2018 6:34 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Bill,

I said it before and I'll say it again. I don't care if your "measurement" is what it should be. You should get a digital level and measure the actual wing angle as well as the tube, stabilizer and engine mount angles. Compare these to what Kolb recommends or what the angles on a good flying Firestar are.

There may have been changes to the frame or maybe it got "tweaked" enough that the "measurement" is off.


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stuart(at)harnerfarm.net
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PostPosted: Wed Aug 29, 2018 8:14 am    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

Bill,

Let me try and add something here. I have only read the plans for a Firefly,
but as I understand it the rigging procedure should be the same for a
Firestar.

At the main spar connection on the fuselage you drill a hole through the
center of the bracket. This gives equal metal all around the hole for
maximum strength.

At the main spar connection on the root rib of the wing is a rather large
tab. The builder then mounts the wing at the rear spar connection and props
up and otherwise aligns the wing according to the plans. Once everything is
checked for proper alignment, then you drill the hole in the tab on the
wing. This locks in the alignment.

At least on my Firefly (see pictures here:
http://harnerfarm.net/serenity/building2.html ) this tab is way over sized
so that you have lots of latitude in the angle of incidence.

Going from memory here, but I don't remember anything about measuring a
distance for the location of the hole in the wing tab. There was a note
about making sure to stay at least a minimum distance from the edge of the
tab to the edge of the drilled hole. I think generally you want to stay at
least a hole diameter away from the edge of a piece. More is better.

So what Rex is saying is correct. The rigging of the wing has nothing to do
with the placement of the hole, rather the hole is placed according to the
alignment of the wing.

If the initial rigging of the wing gets messed up by a large amount, it is
easy enough to re-align the wing and drill another hole in the proper
location. If the alignment is off by a small amount, say a half a hole, the
accepted procedure is to weld the hole shut and normalize the metal in the
tab. Then do the wing rigging over so that you get the hole where it needs
to be. This correction procedure is quite easy before covering, not so much
after. But still doable without a complete recover job.

A little disclaimer here. I did not do this myself. I bought a quick build
kit and Bryan did all the rigging for me at the factory. However the
assembly manual and plans laid it all out in an easy to understand way.

I can dig out my plans and send you more detailed information if you desire.
I believe it called for leveling the fuselage using the engine mount tube as
the level point. Then you set the wing incidence based on the bottom of the
root rib. All done with angles, no length measurements involved.

If the plans you have don't have these angles listed, a call to the factory
should get you the proper numbers. An incidence angle that is way out of
whack would necessitate a correspondingly out of whack tail plane angle,
which is what you seem to have.

Have you compared the bottom of the wing to the engine mount tube? If so
what is the angular difference between the two?

Stuart

--


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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Wed Aug 29, 2018 8:01 pm    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Bill..
Did I get your attention? None of that was said to be mean-spirited.. but I don't believe in political correctness either.

And this isn't a p___ing match.. or to compare skill levels, but I'll answer those questions below. Again, you (and possibly others) may look at all of this differently. And you have "explained" whatever you have done to your plane, multiple times, and why. And I have no issues with making sound modifications if needed.. or even building one from scratch. "Truck parts" was a joke about extra heavy landing gear components. Anyway, "modifications" are how many Experimentals came to be, including the Kolbs.. in a easy to build kit form, that works quite well, unmolested.

Your Kolb however??? Let's see.. your well explained modifications have:
Increased the weight significantly
Increased the drag significantly
Reduced the normally available lift
Muddied the flight characteristics.. A LOT!
You have opted for a thrust vector which is contrary to normal flight trim (ie you have reduced the nose down under power aspect, which also applies to stall recovery as well)
And your CG is contrary to any improvement in flight trim by it's rearward location.
And if I understood correctly, you carry 10 gallons of fuel, of which only 5 is usable?? (Could be some weight savings there!) All of these things come from mods "which are there for good reason". Sadly, ALL of the above have penalties to the flying characteristics.. as you have duly noted.

Uh.. Bill.. if you CONTINUE your "improvements".. taking a perfectly good airplane and turning it into mush.. it may just stop flying at an inappropriate moment.. like when you are in it. You post very well, but only disclose "oh, and I did this too".. well down the conversation line. If you know aircraft, then you should be working on corrections to your mods, that actually work. MY only concern, is that in all that you have done.. there are no positive indications (compared to a normal Kolb), with that taken directly from YOUR OWN non-flattering flying reports. That would make ME nervous! So.. carry on. But I'm stepping back from any further commentary. It seems to me that YOUR mods could be "the whole problem". Indeed, I might understand a reluctance by you to make MORE changes.. since the first ones have.. uh.. worked out so well!?!?! (NOT!) Do what you want.. I'm just not interested in participating.. other than to nudge you into the reality, that things are not right with your plane at this time. But you knew that already. Nothing personal.

Me? As a kid was helping to build boats with my dad, and model airplanes by 8. And then he got a destroyed Aeronca Chief for free. Way beyond economical repair.. trashed by a tornado slamming it upside down into a hangar. When finished, it looked better than new.. a total rework. By 13 I knew how to gas weld, and while not associated with the planes, to arc weld too, now I use TIG. Been building models from scratch my whole life.. I know what makes airplanes fly. I've done serious design studies, and applied that to super fine models, a ELSA and multiple U/Ls too. They all worked better after the mods, or flew better, or both. And I test flew all of them myself. My planes, and those of my friends after mods or repair work. I even taught myself to fly. Been at EAA meetings since I was about 10.. attended 3 or 4 fly-ins at ROCKFORD.. then most of them at Oshkosh. I have Sport Aviation magazines from the beginning (when they had real design articles and deep info), and have read all of them.. some several times, and many other design related books. I'm working closely with the designer of my Bellaire making mods that include: A jump seat for the grand-kids, a deeper airfoil, adding flaps, aluminum spars instead of wood, composite ribs instead of built up wooden ones, a hidden bungee system on the LG instead of the exposed J3 types as on the original. It will have a adjustable stabilizer, and motor driven elevator trim tab. The wing tanks will be my own design.. and both will be fully usable too! It's a real plane, and built from PLANS... I will fabricate EVERY part. No pop rivet guns to assemble this plane. Am I worried? No. We rebuilt the Chief, then a 1956 170, and then another BER (beyond economical repair) 150.. also flipped over in a wind storm. I've worked on dad's original design Exp, my own ELSA, and about a dozen U/Ls I've owned, and EXPs and U/Ls for friends. I'm a self taught electronic engineer, ran a consulting business for 20 years, and would evaluate the needs, design the circuit, do the prototype, use CAD to produce the PCB artwork, and I did the programming, all self taught. My designs were bullet-proof. I've also done electro pneumatic and mechanical designs and mods on industrial production equipment.. with great success. I have my own machine shop, shears, brake, lathes, mill, and all kinds of aircraft tools. You do have more hours of GA flying than I do. But none of that helps to make a bad plane fly well. My aircraft related experience includes working with wood, aluminum, steel tube, and composites. I worked avionics in the military and civilian jobs about 2.5 years. News letter editor for 4 different EAA chapters, and taught 3 people to fly ULs. My Kolb was purchased because it had been flying.. and just needed some work. But my real project is the Bellaire. See: http://www.ultralightnews.com/plansbuyerguide/bellaire-aircraftplans.html It won Grand Champion Light Plane in 2001 at the big show! Looks like a Rearwin Speedster!! A true classic beauty.. and that flies just as well.

Wishing you all the best on your plane.
Jerry


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PostPosted: Wed Aug 29, 2018 11:14 pm    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

Fair enough. From one old model airplane builder to another, you have my attention. My modifications to the aircraft have not succeeded as I hoped they would, despite whatever logic and thought I had put into them. Guilty as charged.

To take the Kolb Firestar 2, and make it into a super-STOL off-airport machine, and yet to make it as reliable as humanly possible (because I'm flying it over solid city and houses for 5 miles on the way out of, and back in to my home airport), what changes would you suggest I should and should not have made, and what remedies or repairs to my failed ideas and changes should I make now?

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Wed, 8/29/18, Jerry-TS-MkII <12flybellaire(at)gmail.com> wrote:

Bill..
Did I get your attention? 


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Richard Pike



Joined: 09 Jan 2006
Posts: 1520
Location: Blountville, Tennessee

PostPosted: Thu Aug 30, 2018 4:37 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Go look at Larry Cottrell's and make it just like his?

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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal (Repairing the fiberglass nose bowl. Ugh.)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.
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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Thu Aug 30, 2018 7:14 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Bill,
I've got a lot to do today.. but consider the following. And as others have said, anything you change is YOUR responsibility. I found photos of your stabilizer position, and a side view of your plane. You should post more, showing your center section, oil cooler, from above and below. So here are my quick thoughts. Each item below might be for experimentation, or permanent. Others have mentioned most of this too. Might take all (or none) to make it fly right. And some are serious mods in and of themselves. Will try to go from easy to complex. But you should select which ones and what order.

Nice muffler. Take it off! That reduces your weight slightly, and moves CG forward. Both good. You might end up with even shorter straight pipes (but ask HKS experts first). [Less weight, less drag, moves CG forward slightly more].

Droop both ailerons. Easy. Think 2° (or 3) of flaps. Shouldn't affect flight adversely, but ask others (again if you must.. they have all said this already). Will produce slightly more lift, and pitch forward slightly. This and other things might get your stab angle reduced.

Do I understand you have two 5 gallons tanks, front and back? Remove the rear one, and plumb the front one properly. Less weight, forward CG. This one is just easy, reduces weight, improves CG.. if only for testing purposes.

That stab angle might be needed (as others have done).. but HUGE drag where the two gaps meet the fuse tube. Make bent aluminum fillers.. or fiberglass to clean up that junction and fill the gaps. The effect may be significant, from a stabilizer effectiveness POV.. so do slow incremental run ups to your take off speed. Some have said a filler here did not change much. But did they have a "normal" junction between fuse tube and stab?? You have a open door, and NEED the stab to work. (It has a hole in the middle as is, and your wing does too.. if I read your posts correctly). Not good.

Your wing center section was questioned earlier.. my thoughts then, loose fabric. Then you mentioned weird oil splatters/air flow patterns, and basically venting of your airfoil. I would (early in this process) tape brightly colored yarn in rows across the center section at various chord points.. (since your local wind tunnel was probably sold to the car wash people). Beg, borrow or steal a Go-Pro, or go to ebay and buy a micro cam, and a DVR. With a 9 volt battery, that can assemble into the size of a pill bottle (and your Oxycontin is likely empty anyway). Mount it where it won't go thru the prop, but record what the yarns are doing at various speeds and flight angles. Something there is very wrong. Do this BEFORE and after the next idea.

The oil cooler needs to just stick out into the air stream on the bottom side, and EXIT on the bottom side. Seal the center section gap!!! If your do need more airflow thru the cooler, make a exit surround that is flared outward.. it will suck the air thru.

And if you can reconstruct the top wing center section, with something less draggy, and that looks more like a complete airfoil, that would have to help.

More drastic? Raise your engine back to where the thrust line is by the book. If you need the nose over for trim, (and/or stall recovery), higher is better. You NEED forward trim.. CG helps that, a real airfoil helps, higher thrust line, and even gap seals on stab. Any or all of those should help.. but be sure to do a W&B, and keep records of each incremental change to note which helps the most.

A 503 does have better power to weight ratio. Yeah I know.. sailboats are looking better at that point. Without being there, or flying it.. it's difficult to say or suggest more. But I believe all of the above would be improvements.

The plane (as I recall) was bought used. Did you weigh it before the mods? Paint alone, can add a lot of weight. A well done recover job, and lighter finish could benefit. Again, a BIG step.. but I think weight is a serious problem. And you may end up reworking the angle of the wing relative to the fuse. But.. being heavy, will require a higher angle of attack, to produce more lift (and sadly, drag). If you still have the lighter gear legs you might consider using them. It does however move CG rearward, but maybe the weight savings is worth it.. and with several other things moving CG forward.

I hope some of this makes sense, and even better if it works.
Jerry


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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Thu Aug 30, 2018 7:55 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

Bill..
Quick additions:
You said you had a large air scoop in front of the oil cooler. Yes? Most often cooling issues (like on pusher engines) include cylinder shrouds that flare outward near the prop. So that doubles the suction thru those shrouds. Forward facing scoops often develop a high pressure area in front of them, and REDUCE airflow. (Not the case when you vent the exit to the top of the wing). But a flared (smaller sized) exit shroud might allow removal of a large forward scoop. Easy enough to watch oil temps.. but if you can clean up airflow to the prop and reduce drag in general that's always good. Main thing is to seal the center section of the wing.

And re my earlier post.. and Bellaire comments.. the Grand Champ was the original/prototype built by Berstling and Arnold Gilmore (?). I worked for Rick briefly. What an amazing airplane builder. And indeed the prize was well earned.. just a super slick, well detailed aircraft. At one point he offered some steel tube components.. but most people don't do that kind of "labor of love" airplane building anymore. Sadly.

And my suggestions, and those of others?? I know you had good intentions (and desires) for your plane.. but you might have been asking a lot of a plane that flew well (basically as designed). Then again, if you start writing checks to Just Aircraft... the price of a Kolb could be one months payment. 8-]

Hope it works out,
Jerry


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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Thu Aug 30, 2018 8:46 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

... and as previously mentioned by many.. reduce the drag with some strut fairings if you don't have them already. Several posts with various ideas, or options.

And along those lines... streamlined strut 4130 isn't cheap.. but if you have one or two long exhaust tubes going vertical between the engine and your boom tube, think about buying a larger strut section from Wicks or your fav airplane hardware store.. with the same internal area. Your exhaust tubes are likely larger, and almost as long as your wing struts.. and right in front of the prop! This is drag.. which almost no body else will have, due to your unusual exhaust. Make up new streamlined exhaust tubes!

Wicks used to sell "cut-offs", for welding practice. You might ask them what they have in streamlined shorts.. because your system might have some turns in it anyway. Carefully cut/fit and have it welded.. and pay attention to any possible cracking.. but it could be one more light-weight drag reduction.

Green Sky recently wrote to me about using short stacks on the HKS..

Jerry


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victorbravo(at)sbcglobal.
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PostPosted: Thu Aug 30, 2018 9:03 am    Post subject: First short XC Flight and Slow Cruise Speed Reply with quote

Tell me more about what Green Sky said regarding short stacks.

I had originally spoken to Jerry Olenik (RIP) at Green Sky and he gave me a rough number of 24 inches from the exhaust flange to where the two pipes join. So that is what I used on my system. And the only convenient place to run two 24 inch long tubes was down the back of the cage.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Thu, 8/30/18, Jerry-TS-MkII <12flybellaire(at)gmail.com> wrote:

Subject: Re: First short XC Flight and Slow Cruise Speed
To: kolb-list(at)matronics.com
Date: Thursday, August 30, 2018, 9:46 AM


"Jerry-TS-MkII" <12flybellaire(at)gmail.com>

... and as previously mentioned by
many.. reduce the drag with some strut fairings if you don't
have them already.  Several posts with various ideas,
or options.

And along those lines... streamlined
strut 4130 isn't cheap.. but if you have one or two long
exhaust tubes going vertical between the engine and your
boom tube, think about buying a larger strut section from
Wicks or your fav airplane hardware store.. with the same
internal area.  Your exhaust tubes are likely larger,
and almost as long as your wing struts.. and right in front
of the prop!  This is drag.. which almost no body else
will have, due to your unusual exhaust.  Make up new
streamlined exhaust tubes!

Wicks used to sell "cut-offs", for
welding practice.  You might ask them what they have in
streamlined shorts.. because your system might have some
turns in it anyway.  Carefully cut/fit and have it
welded.. and pay attention to any possible cracking.. but it
could be one more light-weight drag reduction.

Green Sky recently wrote to me about
using short stacks on the HKS..

Jerry




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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Thu Aug 30, 2018 9:15 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

re: short stacks..
Yes, sad about Jerry.. he apparently knew the engines well. I found a early version of the 700.. so I was asking questions. It's probably going to the scrap yard, but would make a cool lawn mower engine! (kidding)

From Jim's email reply:
"One more option that our dad was experimenting with is a straight pipe for each cylinder with what he called Volkswagon stinger exhaust tips on the ends. Probably got them from jbugs. com for $25 a piece. It was considerably louder than a regular muffler but not to the point where it was unbearable. Just some options to spend less money, If you have the skills, tools, and time to do the work."

So apparently like any good half VW or Mosler, short stacks are just noisy. But LIGHT.. simple.. and moves your CG forward. What does your exhaust system weigh??


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Jerry-TS-MkII



Joined: 23 Aug 2017
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Location: Indiana

PostPosted: Thu Aug 30, 2018 9:51 am    Post subject: Re: First short XC Flight and Slow Cruise Speed Reply with quote

With a twin cylinder using a single muffler, the lengths affect how the pressure pulses travel down the tube and any reflections. With 2 straight stacks, I doubt that the lengths are critical, except to be the same.. and some length to develop a scavenging effect or draw. (If you can't convince them with logic, baffle them with BS??) Just speculation. Going to GS, they have tech updates posted which include email and contact info for HKS Japan. Might be worth asking them.

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