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Sky Scout Plans
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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Mon Aug 28, 2017 8:12 am    Post subject: Sky Scout Plans Reply with quote

I did not get many responses to this on the Pietenpol Facebook page so I thought I should try here. In looking at the Sky Scout plans from the 1933 Flying and Glider Manual I noticed that the dimensions for the individual members of the fuselage, when added, come to 147 3/4". This figure does not agree with the given overall dimension of 153 3/4" or 12' 9 3/4". This is true in all views of the fuselage with the exception of the two dimensions given at the bottom of the "Bottom View of the Fuselage" which do add up to 153 3/4." I searched the Matronics Pietenpol archive to see if there had been past discussion on this discrepancy but could not find any. I suspect the 153 3/4" overall length dimension is in error but would welcome any insight you all may have. I can't imagine I am the first person to notice this. Or is there no error and I'm just not seeing something I should?

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glen



Joined: 17 Sep 2013
Posts: 143
Location: Oregon Coast

PostPosted: Mon Aug 28, 2017 8:40 am    Post subject: Sky Scout Plans Reply with quote

Keep in mind that there are three different fuselage lengths based on engine choices there are subtle differences among all three. Weight and balance will b the critical issue to deal with which is greatly simplified by havin a wing able to move fore and aft
Your critical measurements will be at the verticals under cabane struts and seat back keep in mind that Mr pietenpol used to lay out fuselage sides on nails in barn floor
Quote:
On Aug 28, 2017, at 9:12 AM, DonkDoug <douglas.wright(at)okstate.edu> wrote:



I did not get many responses to this on the Pietenpol Facebook page so I thought I should try here. In looking at the Sky Scout plans from the 1933 Flying and Glider Manual I noticed that the dimensions for the individual members of the fuselage, when added, come to 147 3/4". This figure does not agree with the given overall dimension of 153 3/4" or 12' 9 3/4". This is true in all views of the fuselage with the exception of the two dimensions given at the bottom of the "Bottom View of the Fuselage" which do add up to 153 3/4." I searched the Matronics Pietenpol archive to see if there had been past discussion on this discrepancy but could not find any. I suspect the 153 3/4" overall length dimension is in error but would welcome any insight you all may have. I can't imagine I am the first person to notice this. Or is there no error and I'm just not seeing something I should?




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http://forums.matronics.com/viewtopic.php?p=472273#472273




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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Mon Aug 28, 2017 11:48 am    Post subject: Re: Sky Scout Plans Reply with quote

Glen,

You are correct in that there are several different fuselage designs for the Air Camper (counting the wood and steel Gregas there are actually six) but my question was about the Sky Scout plans. As with the Air Camper, you are also correct that two of the critical dimensions are the spacing for the cabane strut attachment points and the seatback location. Could the center of gravity be adjusted by moving the wing to account for a tail post 6" too short or long? Probably, but I would rather know for sure how long it should be to begin with.

Doug


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Ray Krause



Joined: 09 Oct 2013
Posts: 436

PostPosted: Mon Aug 28, 2017 7:01 pm    Post subject: Sky Scout Plans Reply with quote

Doug,

I might be able to help you a bit. I'm just finishing up a SkyScout with an A-65. Just now struggling with the W/B.

I tried to build it according to the Modern Mechanics Blueprint published in 1932. It calls for the fuselage length of 147.75", mine measure 148" firewall to tailpost. I made the fuselage about 2" deeper at the cockpit to accommodate my 6'4" frame. I used a center wing section as in the AirCamper supplemental plans and built the motor mount according to the supplemental plans. It's almost ready for the final A/W cert inspection and subsequent test flight.

The empty weight W/B is at the forward limits of the recommended CG of 15-20" aft of the leading edge (LE). But with a 200 lb pilot and full fuel it is at about 20". With only 3 gals in the header tank, the CG goes to 21". But with a 160 lb pilot, everything stays within the 20" range.

The wing is leaning back 6" to attain this CG, the maximum that I can get.

I should have made the engine mount 2" longer. I would highly recommend you go at least an additional 2-3". I'm going to go to test flying the way it is because I really don't want to make another motor mount and cowl! I will do this if it does not fly well enough. William Winn says to keep the CG well in front of the rear limit in his series of articles in the Broadnead Newsletter. I agree with him. But.....

I will try to include some of my W/B info with this, but if it does not go, I will send it separately.

Have fun building, it is one of the great life experiences....only to be outdone by flying your own plane which I have done with my Waiex!

Ray Krause

SkyScout W/B

Datum is the Leading Edge (LE).
All measurements are in inches (")
from the LE, or pounds (lbs) when plane
was level.
LE = 0.0"
Oil = -10.50"
Fuel = 5.00"
Landing Gear = 5.00"
Tailwheel = 148.00"
Cowl = -.5"
Firewall = -.5"
Pilot = 43.25"
Front prop flange = -32.5"
Fuselage: 148.50" firewall to tailpost
Motor mount: 32.00" firewall to front
prop flange.
Landing gear to tailwheel weigh points
=143.00"
Tail wheel (TW) weight 46 lbs
Right wheel (RW) weight 296 lbs
Left wheel (LW) weight 306 lbs

-------------

CG = D +(R X L / W)

Where:
CG is Center of Gravity in " behind LE.
D is the distance from the Datum to the
LG weighing point (5.0").
R is the weight of the tailwheel at weighing
point (46 lbs).
L is the distance from LG weighing point
to the tailwheel weighing point
(143.00").
W is the total aircraft weight measured
at the three wheel weigh points
when aircraft is level (648 lbs).
+++++++++++++++
EWCG of aircraft W/O cowl

CG= 5.0" + (46 X 143.00/648)
CG = 5.0 + (6578/648)
CG = 5.0 + 10.15
CG = 15.15" aft of LE
25.25% MAC
+++++++++++++

EWCG of aircraft WITH Cowl

WT. ARM. MOMENT
EWCG. 648. 15.15. 9817.2
Cowl. 6. -.50. - 3.0
Totals. 654. 9814.2
EWCG with cowl = 9814.2/654
EWCG with cowl = 15.00" aft of LE
= 25.0% MAC
++++++++++++

CG with 200 lb. pilot plus full fuel (10gal)
WT. ARM. MOMENT
A/C EWCG. 654. 15.00. 9810.0
Pilot. 200. 43.25. 8650.0
Fuel. 60.0 5.0. 300.0
Totals. 914. 18o760.0

CG = 18760.0/914 = 20.53" aft LE
= 34.2% MAC
++++++++++++++++++++
CG with 200 lb pilot plus min fuel (3gal)

A/C EWCG. 654. 15.00. 9810.0
Pilot. 200. 43.25. 8650.0
Fuel. 18. 5.0. 90.0
Totals. 872. 18550.0

CG = 18550/872 = 21.27" aft LE
= 35.5% MAC

++++++++++++++++++
CG with 160 lb pilot and full fuel (10gal)
WT. ARM. MOMENT
A/C EWCG. 654. 15.00. 9810.0
Pilot. 160. 43.25. 6920.0
Fuel. 60.0. 5.0. 300.0
Totals. 874. 17030.0

CG = 17030/874 = 19.49" aft LE
= 32.40% MAC

++++++++++++++++++++++
CG with 160 lb pilot plus min fuel (3gal)

WT. ARM. MOMENT
A/C EWCG. 654. 15.00. 9810.0
Pilot. 160. 43.25. 6920.0
Fuel. 18. 5.0. 90.0
Totals. 832 16820.0

CG = 16820/832 = 20.2" aft LE
= 33.7% MAC

Sent from my iPad

Quote:
On Aug 28, 2017, at 9:12 AM, DonkDoug <douglas.wright(at)okstate.edu> wrote:



I did not get many responses to this on the Pietenpol Facebook page so I thought I should try here. In looking at the Sky Scout plans from the 1933 Flying and Glider Manual I noticed that the dimensions for the individual members of the fuselage, when added, come to 147 3/4". This figure does not agree with the given overall dimension of 153 3/4" or 12' 9 3/4". This is true in all views of the fuselage with the exception of the two dimensions given at the bottom of the "Bottom View of the Fuselage" which do add up to 153 3/4." I searched the Matronics Pietenpol archive to see if there had been past discussion on this discrepancy but could not find any. I suspect the 153 3/4" overall length dimension is in error but would welcome any insight you all may have. I can't imagine I am the first person to notice this. Or is there no error and I'm just not seeing something I should?




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=472273#472273




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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Mon Aug 28, 2017 9:04 pm    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

Thank you for this information. I was not aware of the Modern Mechanics plans for the Sky Scout. Nice to know their plans agree with the 147.75" addition of the individual members dimensions. I had pretty much decided that is what the overall fuselage length should be. I also backed into that number by doing some addition and subtraction off other overall dimensions given in other views of the airplane. The 153.75" must have been a bust on the part of the draftsman back in the day. His drawings are great, very artistic in fact, but there is that error and a guy on the Pietenpol Facebook page said the wing drawings have dimensional errors also.

Your project sounds a lot like what I was considering. I remember seeing pics you had posted several months ago - it looked great. I'm interested to see how your weight and balance works out. The last time I looked at this design using an A-65 I had calculated that to use the supplement plans Continental motor mount I was going to have to extend the firewall forward a few inches. This seems to agree with what you are discovering. Do you have a metal prop? That would help a bit.

Doug


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Ray Krause



Joined: 09 Oct 2013
Posts: 436

PostPosted: Tue Aug 29, 2017 9:17 am    Post subject: Sky Scout Plans Reply with quote

Doug,

No, I'm using a wood prop that came with the engine which was on a Fly Baby. I'm not even sure of the pitch. I intend to test it with the "fish scale meter" the Piet guys refer to! Have not done that, yet. A metal prop would help, but not much.

If you are just starting your build, I would suggest adding 2-3" to the front of the fuselage. Two advantages: it's easy to do over making the motor mount and it gives more room for a header tank. You could also slant the wing back further, if necessary.

The next problem will be the landing gear. The plans-built SkyScout gear is not so great. Getting the right springs is a BITCH! I finally had an air/oil shock made that SEEMS to be working OK, now. It also saved 12 lbs.

Lots to learn, it will make your brain muscles stronger!

Ray

Sent from my iPad

Quote:
On Aug 28, 2017, at 10:04 PM, DonkDoug <douglas.wright(at)okstate.edu> wrote:

also.


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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Tue Aug 29, 2017 10:53 am    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

I found my W/B notes last night after I responded to your post. I calculated, as you did, that the fuselage should be extended 2" to accommodate an A-65 using the Piet Continental motor mount. You are right, a metal prop does not help much. As William demonstrated with his Piet W/B study and subsequent articles, moving the wing can make a huge difference in CG location.

I also re-read some Piet articles last night. One of them stated that the Sky Scout plans in the Flying and Glider Manual were drawn from "shop notes." I imagine that is where some of the errors came from.

Doug


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Ray Krause



Joined: 09 Oct 2013
Posts: 436

PostPosted: Tue Aug 29, 2017 6:11 pm    Post subject: Sky Scout Plans Reply with quote

Doug,

Sure sounds like you will have an easier time building than I did. I should have flown mine last winter, but things got in the way and slowed me down. Now I'm looking at this fall, pretty soon by my standards!

Ray

Sent from my iPad

Quote:
On Aug 29, 2017, at 11:53 AM, DonkDoug <douglas.wright(at)okstate.edu> wrote:



Ray,

I found my W/B notes last night after I responded to your post. I calculated, as you did, that the fuselage should be extended 2" to accommodate an A-65 using the Piet Continental motor mount. You are right, a metal prop does not help much. As William demonstrated with his Piet W/B study and subsequent articles, moving the wing can make a huge difference in CG location.

I also re-read some Piet articles last night. One of them stated that the Sky Scout plans in the Flying and Glider Manual were drawn from "shop notes." I imagine that is where some of the errors came from.

Doug




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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Fri Sep 01, 2017 10:26 am    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

You are right about the "brain muscle" thing. But that is what I like the most about fooling around with this stuff. I'm interested to see how your shock/strut works. That is a great idea.

Doug


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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Fri Sep 01, 2017 10:26 am    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

You are right about the "brain muscle" thing. But that is what I like the most about fooling around with this stuff. I'm interested to see how your shock/strut works. That is a great idea.

Doug


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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Fri Sep 01, 2017 10:27 am    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

You are right about the "brain muscle" thing. But that is what I like the most about fooling around with this stuff. I'm interested to see how your shock/strut works. That is a great idea.

Doug


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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Fri Sep 01, 2017 10:28 am    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

You are right about the "brain muscle" thing. But that is what I like the most about fooling around with this stuff. I'm interested to see how your shock/strut works. That is a great idea.

Doug


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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Tue Sep 05, 2017 8:16 am    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

I was looking at your weight and balance info and I have a question. Did you estimate the pilot moment arm location or did you determine the actual location by weighing the airplane while sitting in it? The reason I ask is because when I looked at the weight and balance sheet Bernard Pietenpol published for his 1966 Air Camper I calculated the pilot moment arm location being about 16" forward of the point where the pilot seat back and bottom intersect. In that the seats for the Sky Scout and Air Camper have about the same geometry if you were to use the same distance it would put your pilot moment arm at approximately 36" from your datum instead of 43.25" That, of course, would make a favorable difference in your calculated CG location.

Doug


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Ray Krause



Joined: 09 Oct 2013
Posts: 436

PostPosted: Tue Sep 05, 2017 7:31 pm    Post subject: Sky Scout Plans Reply with quote

Doug,

For that number, I used a more recent publication of W/B calculations in one of the recent Brodhead newsletters. It seems to have come from the old CAA. It shows three graphs based on seat back angle and pilot weight that gives inches ahead of the seatback/seat bench angle for the CG of the pilot. My seat back is 15 degrees, I'm 200 lbs, it offered 7.5" ahead of the angle for the pilot CG. That's what I used.

Still, the best fix would be the fuselage front 2" longer, or a longer motor mount. That would really solve the problem. Remember that when you build. I would go with the longer mount so the motor would be further ahead of the gear but still the same in relation to the LE. I would also shorten the front leg of the gear so the wheel weigh point would be closer to the LE. Bernard, in his last plans for the Covair engined AirCamper, said the gear should be .5" behind the LE.

If you use 20-21" wheels as I am, the fuselage "slope" is really steep, but I can't remember the angle (AOA) right now but there is a lot of prop clearance. I will get the angle tomorrow. Smaller, lighter wheels would help my CG.

RAY

Sent from my iPad

Quote:
On Sep 5, 2017, at 9:16 AM, DonkDoug <douglas.wright(at)okstate.edu> wrote:



Ray,

I was looking at your weight and balance info and I have a question. Did you estimate the pilot moment arm location or did you determine the actual location by weighing the airplane while sitting in it? The reason I ask is because when I looked at the weight and balance sheet Bernard Pietenpol published for his 1966 Air Camper you can calculate that he used a location approximately 16" forward of the point where the pilot seat back and bottom intersect. In that the seats for the Sky Scout and Air Camper have about the same geometry if you were to use the same distance it would put your pilot moment arm at approximately 36" from your datum, the leading edge of the wing. That, of course, would make a significant, favorable difference in your CG location.

Doug




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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Tue Sep 05, 2017 8:41 pm    Post subject: Re: Sky Scout Plans Reply with quote

Ray,

I think that CAA material you referenced got the pilot CG about right. When you mentioned the Brodhead newsletters I dug out William's article on Piet W/B for Continental powered ships. He had calculated pilot CG location for each of the airplanes he weighed. The location is very close to what you had calculated. The mean of the values was about 7" forward of the seat bottom/seat back intersection. Now I need to figure out how I fouled up the calculation from Mr. Pietenpol's 1966 W/B sheet. I think my assumption as the where there is 8 gallons of fuel stored was incorrect.

Doug


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pietflyer



Joined: 19 Jun 2017
Posts: 6

PostPosted: Wed Sep 06, 2017 4:42 am    Post subject: Sky Scout Plans Reply with quote

Doug,

The old rule of thumb for calculating Pilot CG was to use the location of
the pilot's belt buckle as the CG. That will work out about right with WW's
7" forward of the seat back/bottom intersection, except for the morbidly
obese pilots who will always have to wheel land the airplane because their
gut would interfere with full aft stick for a 3-point landing.

Jack Phillips
Smith Mountain Lake, Virginia
Pietenpol Air Camper NX899JP "Icarus Plummet", flying
RV-10 under construction

--


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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Wed Sep 06, 2017 2:53 pm    Post subject: Re: Sky Scout Plans Reply with quote

Jack,

Yes, I had heard/read the belt buckle/belly button rule before. The data William Wynne collected on Piets pretty much confirms it as being correct.

Thanks,

Doug


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taildrags



Joined: 29 Dec 2009
Posts: 1532
Location: Medford, OR

PostPosted: Thu Sep 07, 2017 7:23 am    Post subject: Re: Sky Scout Plans Reply with quote

Well now I'm curious. When I did the W&B on my airplane (calibrated digital race car scales, first W&B done by me after repairs were completed and second W&B done after I changed the A65 to A75, done by an experienced Tech Counselor who has done dozens of weighings), we weighed the airplane empty and then again with me sitting in the cockpit, so the 49.64" aft of wing leading edge is pretty accurate on mine. My wing is inclined backward 4" and mine is an Air Camper, not a Sky Scout. I'm going to go back to the measurements that I took to see where that places the pilot's CG relative to the bottom corner of the pilot's seat.

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_________________
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
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DonkDoug



Joined: 10 Sep 2010
Posts: 29

PostPosted: Thu Sep 07, 2017 8:05 am    Post subject: Re: Sky Scout Plans Reply with quote

Oscar,

By my estimate your pilot CG at 49.64" from the leading edge leaned back 4" would be about 11" forward of the seat back and bottom interesection if your plane is built according to the long fuselage plans. Or about 7.5" if the seat back is at a 15 degree angle as Ray built his Sky Scout. I imagine it is somewhere between those two values.

Can you guys tell I retired this summer and have way too much time on my hands?

Doug


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taildrags



Joined: 29 Dec 2009
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Location: Medford, OR

PostPosted: Thu Sep 07, 2017 8:53 pm    Post subject: Re: Sky Scout Plans Reply with quote

Doug; my seat back is not angled back any amount from stock, or at least I don't think so, but that makes me wonder even more! I shall put the angle finder on the pilot's seat back next time I'm at the hangar! Anyway, 11" forward of the seat back/bottom intersection sounds pretty good considering that in the last 10 years I have progressively lost sight of my "lower anatomy" behind the growing crest of a beer belly (a desk jockey belly, actually), and have gone from a 29" waist to a 33" waist at the belt line but considerably greater above that line. I don't know what has happened there.

Now let's see: if I were to calculate the center of mass of the bulge that is above my belt buckle, adjusted for the distance that my belt buckle has disappeared over the horizon, multiplied by 7" and divided by the wing area, multiplied again by the gross weight of the aircraft- the result (rounded to the nearest decimal place) might be the time in hours and minutes that I can fly at normal cruise between potty stops. Adjusted for headwind, of course.


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Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
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