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David Staffeldt
IAC MemberVintage Aircraft Association MemberWarbirds of America MemberHomebuilder or Craftsman
39
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17
#1 Posted: 12/27/2009 16:54:58

I am looking for articles or websites that have detail specifically on building an aluminum I-beam spar, aluminum rib, fabric covered wing. I have the Tony Bingellis books, but they don't cover much if any of this. Any leads would be appreciated.

Thank you,

David



Joanne Palmer
Young Eagles Pilot or VolunteerHomebuilder or Craftsman
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68
#2 Posted: 12/28/2009 11:39:00 Modified: 12/28/2009 11:48:34

You need to look at the wood building book from EAA entitled "Wood Aircraft Building Techniques".  While not covering aluminum construction per se, it will give you techniques for building a wing suitable for fabric covering.   You also might want to look at the Bearhawk plans.

 

I do however, question the use of aluminum ribs.  These will tend to be heavy when built with the spacing required for fabric covering.  One option is to build the aluminum rib just like a wood truss rib.  The other option is to form the rib with a flange then use lightening holes.  These techniques will reduce the weight but they still will be heavy when compared to a wood rib construction.

 



Ried Jacobsen
194
Posts
26
#3 Posted: 12/28/2009 13:09:56

Joanne, thanks for this reply.  But it does raise a couple of questions in my mind.

You state the AL structure will be heavy is built with spacing for fabric covering.  Would the time savings of a formed rib with lightning holes offset the construction of wood ribs?

If you were designing a high aspect ratio wing from scratch, would you prefer wood and fabric, or aluminum structure and skin?  Or a composite of AL spars with wood ribs and fabric?

I appreciate your thoughts and opinions.  (and those of others at this forum!)



Joanne Palmer
Young Eagles Pilot or VolunteerHomebuilder or Craftsman
276
Posts
68
#4 Posted: 12/28/2009 22:05:49

Reid:

 

If I wer building a high aspect ratio wing, I think I would perfer to use aluminum spars and skin out of the choices mentioned.  However, sailplanes are now almost exclusively compostie construction and that is for a very simple reason.  Composites will be lighter than either of the two methods proposed for a high aspect ratio wing.  They will also be the most flexible, but that isn'e a bad thing necessarily.   Wood spars and ribs eventually run out of required strength as the span starts getting long.  In order to get the strength with wood the wing thickness starts to get high and you find it difficult to get and maintain a laminar flow.  Aluminum high aspect ratio wings can be built but then youstart to havve aeroelasticity issues in torsion. 

 

J



David Staffeldt
IAC MemberVintage Aircraft Association MemberWarbirds of America MemberHomebuilder or Craftsman
39
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17
#5 Posted: 12/29/2009 18:12:42

Hi Reid,

Harry Ribblett also said I should build my wing with wood, but I bought a wing kit that is all aluminum and fabric covered. I know I will sacrifice a little weight, but I prefer the aluminum construction. I was looking for a good source that would get in to detail in regards to compression strut spacing, drag and anti-drag wires etc. I have the wing kit manual, but am making a change in that I am clipping the wing a bit. My original wing was much like a Kitfox wing only much longer and I decided to put what I will call a conventional wing on instead of aluminum tube spars with wood ribs glued on and flaperons.

 I will look for the book you recommended though.

Thanks,

David

 



Ried Jacobsen
194
Posts
26
#6 Posted: 12/29/2009 22:16:38

Joanne and David, thanks for the comments!  What you are saying makes sense as avenues of some research.

My current dream is a two place tandem seating, motorglider.  I do not require anything high performance like some of the composite structures, I would be happy with something around 20 to 1 glide ratio.  I also think I would be more comfortable working with wood or aluminum than with composites.

My guesstimates are around 1000-1500 lbs,40-45 ft span, 125-150 SF wing area, maybe 75 to 100 HP engine.

I have found a couple of series of EAA Sport Aviation design articles, one by John Roncz in 1990-91, and the other by Neal Wilford around 2002-07.  There were some simple Excel type spreadsheets that should help determine some better numbers.  I do appreciate your suggestions for additional sources of information.

Ried



Ried Jacobsen
194
Posts
26
#7 Posted: 12/29/2009 22:21:35

David,

Which wing kit did you buy?  Just curious as to length, area, etc.

There is a July 1991 Sport Aviation beam design article by Ernest Jones that you might want to look up on this site.  It might be of interest to you for basic beam design info.  Do not let the title scare you off, read it first.

Ried



David Staffeldt
IAC MemberVintage Aircraft Association MemberWarbirds of America MemberHomebuilder or Craftsman
39
Posts
17
#8 Posted: 12/30/2009 11:19:54

Joanne,

Thank you for the information on the wood wing book. Apparently the edit function doesn't work well and I wasn't able to change my previous post.

Ried,  I am building a wing that came from D&E Aircraft based in Florida. It uses a Ribblett GAU613.5 airfoil with a 57 inch chord and is 15 feet long. They go on my Mountain Eagle project which originally had a 42 in chord Avid or kitfox style wing.

There is a Mountain Eagle flying in Canada with this same wing and the reports are quite good with much improved cruise speed and basically no loss in stall speed. I'll post some pictures in the next day or two.

Thanks,

David

 



Chase Balcom
Homebuilder or Craftsman
40
Posts
4
#9 Posted: 12/30/2009 13:48:02

   Hello ,.My name is Chase,...I just joined  Oshkosh365 today ,..

and this post interested me  because I am in the process of building my own design aircraft ,..I have 25 hours into the build ,..the fuselage is almost ready for primer ,..my  material of choice for my wing spars arrived yesterday,..which is 6061 T-6  2.5" OD .065 wall tubing,..I plan on installing an inner vertical  beam capped with HDPE, with supports that connect to my compression struts and cross bracing tubes thru the spar,. doing this gives me actually 2 spars in one per application,.each spar at 14' will weigh approximately 9 lbs,.and I'm using birch ribs,..to dampen wing twist in flight,..3 compression struts will be placed ,.1 between main fuel tank and main lift strut location and 2 in the outer section of the wing past the lift strut location,..these compression struts are omni mounted,..meaning they completely surround the spar at point of contact,..one could even call it an inner rib ,..with exception it does not have an airfoil top or bottom,..the idea is to keep the tortional loads in a more controllable enviroment ,.. a rectangle,.. such as a spanner truss design,..it can be built light and very strong,.. the reason for this is my wing will fold back to allow transport on a trailer,..same concept as a kitfox/avid with exception to the flaperon ,..I'm using a flap aeleron config. a 4 foot chord and 32 foot wing  span ,..the airfoil is also my own design,...having a folding wing  ,..the fueslage strut location is aft of the main spar ,.although proven in many designs to be sufficient,..it does allow excessive wing twist which is not good for wing tanks ,..it will eventually cause fractures in conventionally made tanks ,..and some composites in earlier recipe's.

thus the reasoning for the "inner Rib compression strut"

  This wing is going on a STOL aircraft TG ,.when completed should weigh in just short of 700 lbs and have a 1400 lb payload

since it is a prototype in every aspect ,..I will have to do the load testing myself ,..my goal is for a static 9G positive and 6G neg

 

Chase



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David Staffeldt
IAC MemberVintage Aircraft Association MemberWarbirds of America MemberHomebuilder or Craftsman
39
Posts
17
#10 Posted: 12/30/2009 15:07:43

Hi Chase,

Welcome to Osh 365. Your project sounds fun. My airplane was originally designed to have a folding wing with a wing similiar to your design. I never intended on folding my wings as I felt the design of the fittings was inadequate to support the weight of the wing with fuel in the tank and towing down the road. If you haven't already considered the fittings for supporting the wing for folding, look at the Glastar and it's fittings. It's the best designed folding wing structure I've seen so far.

Good Luck on your project,

David



Chase Balcom
Homebuilder or Craftsman
40
Posts
4
#11 Posted: 1/2/2010 00:04:20

Thanks for the welcome David ..your the first

  I plan on using the kitfox / avid concept for wing folding but I will look at the glastar,..

as for towing ,..I will have to put "transport braces" on the wing to limit twisting  while traveling down the road .

 

Chase



David Staffeldt
IAC MemberVintage Aircraft Association MemberWarbirds of America MemberHomebuilder or Craftsman
39
Posts
17
#12 Posted: 1/2/2010 16:17:43

I thought I would post a few pictures of my wing kit going together. I purchased both wings from someone else who had started to build them for a fantastic price. The previous builder had decided to metalize them and the rivet work was less than acceptable. I disassembled them and salvaged quite a few of the ribs, but decided to replace the spars. D&E Aircraft LLC in Florida supplies this kit. I'm doing some minor changes in an effort to save some weight. They will be fabric covered when I'm finished. Here's a couple of pictures from today after I installed the compression struts.

David



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