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akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Mon Jul 30, 2007 3:32 pm Post subject: need engineer type to run a calculation

I am looking for an engineer type to run the calcs on a set of floats and tell me the displacement.  The floats in question are a set of Northaire copies, but they were scaled down a tad from the 1200# floats.



  Any takers?  I can supply all the measurements you need.

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

kirkhull(at)kc.rr.com
Guest

Posted: Mon Jul 30, 2007 4:55 pm Post subject: need engineer type to run a calculation

As I am better at picking up the pieces and figuring out how they got there

I would not be the guy to run those calcs.  However maybe I could stear you

toward some info to help you do them your self. In the Dec issue of Sport

Aviation on pg 46 there is an article on seaplane design that might help and

I seem to remember a while back an article in Sport Aviation about how to

size floats

--

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Mon Jul 30, 2007 8:31 pm Post subject: Re: need engineer type to run a calculation

Leonard,



How accurate do you want the figure?  The reason I ask is that some floats have complex curves particularly in the hull area and the calculations would be fairly involved to find exact displacement.  If you are looking for a ballpark number, say plus or minus 5% to 10%, you could simply divide the float into sections and approximate the sections using a series of varing sizes of cubes (the more sections, the greater the accuracy)...find the volume of the cubes and then you would have your displacement.  Keep in mind that the float will displace more water the further under water it is (i.e. a float that is partially submerged displaces less water than a float that is completely submerged).  If your wondering about my credentials, I am one of those engineer types...a civil engineer.



This may be a dumb question as I am not up to speed on the various floats offered but wouldn't the manufacturer have that information for you (they would have to figure displacement to determine the capacity of the float).  If you are using a scaled down version, simply scale down the displacement the manufacturer has by the amount your floats are scaled.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Jul 31, 2007 5:21 am Post subject: need engineer type to run a calculation

Mark a line on the outside of your float where  you want the waterline to be at full load.  Place your floats on a  set  of scales absconded form the local highways dept. and zero the  scales.  Next, fill them to the line.  The weight of the water will be  your displacement. 



You can also fill the floats to your line with a  1Litre milk bottle ( metric is a lot easier here there is no U.S. litre )  Count the number of litres to fill the float to the line and multiply by 1 this  will give you your displacement in Kilograms to your useful water line. You can  multiply the number of Kilograms by 2.205 to get the number of pounds.



If  you really want to fool with U.S. gallons ( 4 qt. to the gal ) the weight of a  U.S. gallon is about 8.36 lb.



The weight of a "real"   Imperial  Gallon of water is around 10 lb. 

These weights are approximations as the density of  water changes with temperature.  they should be close enough for  "Government Work".



Consider filling the float on a beach where sand will  help support the float and there is less chance to damage the float. And pump  the float dry before moving it.  Be sure your float isn't leaking the water  out or your capacity will be high.  

 You could ask the float designer what the  operational displacement is.  That saves time, sand  and a day at the  beach!

 

 

[img]cid:552331813(at)31072007-2E42[/img]  

 Noel Loveys, RPP, AME intern

 Campbellton, Newfoundland, 

 Canada

 Kitfox Mod III-A, 582, B box, Ivo IFA

 Aerocet 1100s

 noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)

 

 

 Do not archive

 

 

 

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Tue Jul 31, 2007 6:52 am Post subject: Re: need engineer type to run a calculation

the floats are a scaled down version of the northaires that were made of fiberglass.  They are foam filled with no hatches or pump outs.. I am not fond of the foam filling or no pump outs, but they are on my brothers plane not mine!  I have a set of the northaire drawings, and will copy them in autocad, then scale them to the dimensions he has.  After that it will be easy to find the volume... now I just need time to model them in cad.



I installed the floats on his plane last week and did the test flying.  solo it was great, but with 2 200+ guys, a full nose tank and 7 gallns in the wing, it was a bit of a slug to get off the water.  she sat a little low for my liking, but most beaver drivers up here will tell you that any float left sticking out of the water is wasted revenue (only partialy kidding here).

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Jul 31, 2007 2:25 pm Post subject: need engineer type to run a calculation

That shoots my idea of filling the floats with water... Oh well.



The idea of filling the floats with foam is a good one if you are planning

on landing in questionable places.  If you rip the bottom out of a float you

can just keep on going. Something like Full Lotus on steroids  I guess.



Sure wish I knew how to do the 3D modelling in AutoCAD.  When you get it

done post it so we can learn how you did it.  2D I'm ok at.  When it comes

to the 3D and filling....



Noel

[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Tue Jul 31, 2007 4:09 pm Post subject: Re: need engineer type to run a calculation

I just did the 2D to the correct scale and sent it off to my kid so he can do it in 3D....The only class in highschool he likes or bothers to apply himself in is the Acad Drafting class.. Staight A's in that class.



One of these days I will learn how to do the 3D.  I will post it up when he gets it done.

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Jul 31, 2007 4:49 pm Post subject: need engineer type to run a calculation

Thanks... I'll be watching for it.

When he draws it up tell him to put in a water line (X) inches below the

deck.  You decide the value of X.  Then he will be able to get a volume

below that line and from that you can calculate the displacement in lb.



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Wed Aug 01, 2007 7:03 am Post subject: Re: need engineer type to run a calculation

well I had a brain cramp yesterday.. I have a whole dang engineering wing one hallway over..I got one of them to model the floats and run the calcs.  It was a nice break for him from the hohum everday work.  The model is not perfect as the cad software hit a wall for meging the compond curves (without getting the co to spring for the addons) but it is very darn close to perfect.



At the end of the day, the numbers are pretty close to my W.A.G. Each float is 12.874 square feet.  At 62.4# per square feet that makes them 803.33 pounds (each)  I was actually guessing around 700# each.  They are still a goodbit undersize for the KFII at 950 gross (1050 on floats).



With these floats he has a good single place plane..



for those of you who like to see numbers I will attach a word doc to look at.



It wont let me attach the 3D model.. I guess the forum software does not allow the .dwg attachments...

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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Aug 01, 2007 9:30 am Post subject: need engineer type to run a calculation

Where did you get the 1050 figure on  floats???  I ask because I have a mod III-A which is for all intents a late  model II.  It's on Aerocet 1100s and if possible I could sure use the extra  100lb. On floats.



 

[img]cid:056342617(at)01082007-2E5E[/img]  

 Noel Loveys, RPP, AME intern

 Campbellton, Newfoundland, 

 Canada

 Kitfox Mod III-A, 582, B box, Ivo IFA

 Aerocet 1100s

 noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)

 

 

 

 

 

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Wed Aug 01, 2007 1:08 pm Post subject: Re: need engineer type to run a calculation

well... the faa allows 100# gross increase when on floats.. The gross on all my certified aircraft were more on floats than wheels or skis.  Look up the rules for sport AC.. on floats it is 1430 not 1320..



for a full story and the 3D cad drawing you can go here

http://avidfoxflyers.com/index.php?topic=68.0

jdmcbean(at)kitfoxaircraf
Guest

Posted: Thu Aug 02, 2007 6:02 pm Post subject: need engineer type to run a calculation

Interesting... I have never been able to find an AC or a Reg that makes that

allocation... Please forward that to me if you have it.  I understand it to

be accepted behavior in Alaska but it is not endorsed by the FAA.. I have

heard 10% not the 100 #



Regarding LSA's  If you are flying an aircraft that has a max gross weight

of 1320.. it does not get to increase the gross when you put floats on it to

the 1430 allowed...

Fly Safe !!

John & Debra McBean

208.337.5111

www.kitfoxaircraft.com

"It's not how Fast... It's how Fun!"



--

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Thu Aug 02, 2007 6:08 pm Post subject: Re: need engineer type to run a calculation

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 1, 21, 43, 45, 61, 65, and

91

[Docket No. FAAâ€“2001â€“11133; Amendment

No. 1â€“53; 21â€“85; 43â€“39; 45â€“24; 61â€“110; 65â€“

45; 91â€“282]

RIN 2120â€”AH19

Certification of Aircraft and Airmen for

the Operation of Light-Sport Aircraft

AGENCY: Federal Aviation

Administration (FAA), DOT.

ACTION: Final rule.



SUMMARY: The FAA is creating a new

rule for the manufacture, certification,

operation, and maintenance of lightsport

aircraft. Light-sport aircraft weigh

less than 1,320 pounds (1,430 pounds

for aircraft intended for operation on

water) and are heavier and faster than

ultralight vehicles and include

airplanes, gliders, balloons, powered

parachutes, weight-shift-control aircraft,

and gyroplanes. This action is necessary

to address advances in sport and

recreational aviation technology, lack of

appropriate regulations for existing

aircraft, several petitions for

rulemaking, and petitions for

exemptions from existing regulations.

The intended effect of this action is to

provide for the manufacture of safe and

economical certificated aircraft that

exceed the limits currently allowed by

ultralight regulation, and to allow

operation of these aircraft by certificated

pilots for sport and recreation, to carry

a passenger, and to conduct flight

training and towing in a safe manner.



This is a copy and paste from the final rule... it does indeed alow for 1430 on floats...

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Thu Aug 02, 2007 8:04 pm Post subject: need engineer type to run a calculation

John:



Like yourself  I have heard this for quite a while and I believer there are

a few manufacturers who actually certify their planes differently for

floats.  The reason, as I under stand it, is that in the water the floats do

not stress the airframe in any way.  In the air, once past 60 mph., the

floats actually fly their own weight again removing the stress of the

additional weight, which for small planes is around 100Lb.



Also like yourself if there is anything written on this I'm interested!  An

extra hundred lb. (to 1050) would make my float plane a two passenger

machine even with my considerable mass aboard.  In the meantime I have come

close to 950lb....Full fuel and camping gear.



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Thu Aug 02, 2007 8:41 pm Post subject: Re: need engineer type to run a calculation

http://forum.full-lotus.com/viewtopic.php?t=20



the float manufacture seems to be under the impression that FAA allows a 100# increase when you go on floats also...



Every certified AC I have had allowed the 100# gross increase when on floats.. the ruling says you get an extra 110#.  I may be confused, but if so then everyone who has a floatplane here is too.  

Bottom line for 99% of the guys here is if they can get it in the plane, then get the plane in the air, they will swear that they are just under gross and could have safely hauled another 50 pounds..if they could not get it off the water, the passenger lied about thier weight..

akanka(at)kiamichiwb.org
Guest

Posted: Fri Aug 03, 2007 4:57 am Post subject: need engineer type to run a calculation

For what it's worth, FAR 1.1, General definitions, Light Sport Aircraft, is

quoted below:



Light-sport aircraft means an aircraft, other than a helicopter or

powered-lift that, since its original certification, has continued to meet

the following:



(1) A maximum takeoff weight of not more than—



(i) 1,320 pounds (600 kilograms) for aircraft not intended for operation on

water; or



(ii) 1,430 pounds (650 kilograms) for an aircraft intended for operation on

water.



(2) A maximum airspeed in level flight with maximum continuous power (VH) of

not more than 120 knots CAS under standard atmospheric conditions at sea

level.



(3) A maximum never-exceed speed (VNE) of not more than 120 knots CAS for a

glider.



(4) A maximum stalling speed or minimum steady flight speed without the use

of lift-enhancing devices (VS1) of not more than 45 knots CAS at the

aircraft's maximum certificated takeoff weight and most critical center of

gravity.



(5) A maximum seating capacity of no more than two persons, including the

pilot.



(6) A single, reciprocating engine, if powered.



(7) A fixed or ground-adjustable propeller if a powered aircraft other than

a powered glider.



( A fixed or autofeathering propeller system if a powered glider.



(9) A fixed-pitch, semi-rigid, teetering, two-blade rotor system, if a

gyroplane.



(10) A nonpressurized cabin, if equipped with a cabin.



(11) Fixed landing gear, except for an aircraft intended for operation on

water or a glider.



(12) Fixed or retractable landing gear, or a hull, for an aircraft intended

for operation on water.



(13) Fixed or retractable landing gear for a glider.



John Hart



--

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Fri Aug 03, 2007 7:37 am Post subject: Re: need engineer type to run a calculation

I think the issue here is the float manufacture, when going through STC process for installing the floats on certain planes, did the math and figured the floats will "fly" atleast a 100# at a very moderate airspeed (fullotus being one of the best for producing lift).  Part of the STC on the float install is a gross increase of 100#.  I figure if it is good enough for them it is good enough for me, and if there is not a 100# safety factor involved in the manufactures gross weight calculations then something is terribly wrong.. I know in my line of work we deal with a minumum 2 times safety factor.  I bet there is a pretty good bit of fudge in the actual weight a plane can safely carry.  Worst case, you can go through the flight testing again and bump it up if you think you are going to be getting ramp checked.

jdmcbean(at)kitfoxaircraf
Guest

Posted: Fri Aug 03, 2007 10:12 am Post subject: need engineer type to run a calculation

Not to be a burr....On type certified aircraft it is actually part of the TC

(type certificate) it is not automatic and it is specific to the float and

the install...



On SLSA it would need to be an approved float and install by the manufacture

of the SLSA and the manufacture has to approve the gross increase and has to

have the documentation to support the increase in testing.. not

mathematical. It is not an automatic increase. The ruling does not say you

automatically get another 110 lbs.. What they have done is make an allowance

for the manufacture to build the aircraft to support the increased gross

weight allowed.



On AB aircraft... You can install whatever float you desire and make

whatever increase you want.. however, it is a major change and needs to be

submitted to the local FSDO and that will require an inspection and the

inspector will have to sign off on the increase.. He may do so without any

requirement or he may have you document the testing to substantiate the

increase.. really depends on the inspector..



The safety margin you refer to is technically 150%... IF (big if) the

manufacture built to the guidelines of FAR part 23.  In other words the

current Kitfox Super Sport for example was built to sustain +3.8 and -1.52

G's at 1550 gross. Therefore it was tested to approximately +6 and -3 G's.



While there may be some merit to the floats carrying some load in flight at

a given airspeed I wonder how the loading is applied to other parts of the

airframe when landing on choppy water or even on land with amphibs

considering that most amphibs do not have any shock absorbtion other then

the tires themselves.



Above all just be safe !!  don't become a test pilot inadvertently.



Fly Safe !!

John & Debra McBean

208.337.5111

www.kitfoxaircraft.com

"It's not how Fast... It's how Fun!"



--

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Fri Aug 03, 2007 10:22 am Post subject: Re: need engineer type to run a calculation

you are right.. the manufacture gets to determine the gross.. in our case that would be the builder.  I know that experimental does not require STC's.  to make the kitfox a 2 place float plane is pretty much up to the individual.

lcfitt(at)sbcglobal.net
Guest

Posted: Fri Aug 03, 2007 12:05 pm Post subject: need engineer type to run a calculation

First, I am not a float flyer - sometimes wishing I was - but the 100# is 

mystifying me.  With a Beaver 100# would add a fairly small  increment to 

it's max gross wt.  With a Model I Kitfox it would be a bunch.  Are you 

suggesting that the 100# is for all aircraft?  For me, at least, Johns 10% 

sounds more realistic.



Lowell



---

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