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Ribs and spar material

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Posted

just drumming up conversation and trying to learn a bit. I think Eurofox use aluminum ribs...but it doesn’t seem too popular. Neither does composite ribs and spars? I know belites are using carbon spars, just a thought. I’m always thinking these type of things.

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Posted

Yes, Eurofx/Aerotrek use aluminum ribs.

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Posted

How much heavier are the aluminum wings?

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Posted

Not so sure they are, in any event I never weighed any of my wings.

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Posted

Back when I was flying a Himax, I was talking to Wayne Ison who was the designer of the Mini Max, Himax, Airbike, and a couple of the Fisher aircraft.  He was telling me about how Hummul Aviation copied the mini max but did it out of aluminum, (at least the wings for sure) and it came in heavier than the wood built Mini max wing.  The wood was also easier to work with, and cheaper to build.  Hard to beat the design that Dean Wilson came up with, with the aluminum spars and wood ribs, probably for either cost, weight, or ease of building.  And as far as strength goes, Kitfox has run the same design with a better stiffener up to 1550 gross weight with no problems.  

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Posted

i guess the only benefit of going away from wood is rotting issues. i suppose a carbon spar and ribs would be lighter, but likely juice not worth the squeeze. just interesting thinking i suppose.

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Posted

Where can I get a sit of those wings?

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Posted

Has anyone ever made aluminum or fiberglass flap attachment tails. I would love to replace those with something other than wood.

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Posted

A couple of things I dont like about carbon fibre..

 

1) tiny slivers can get in your fingers and really cause problems.. ONLY a doc with a special magnifying glass can see the slivers and even then it is hard to get them out.

2) carbon fibre can be strong but it really needs to be engineered. I have read about  a few failurs of extra 300 wing spars made of carbon fibre and when the fail it is like bank and the wing is gone...

3) if you ever catch carbon fibre on fire, run.. .The particle floating in the air you will breath in have ever lasting respiratory problems...

The airline industry uses carbon fibre wet layups on the Boeing jets and lots of other aircraft, heavily engineered... I made some 1/8"plywood laminated with carbon fibre, floor boards for a super cub and they were super light. THose same floor boards are still going 14, 000 hrs later.... I also made a few tail skis out of carbon fibre, light weight and tough. Problem is carbon fibre is expensive.... so yeah its great stuff if you can make the part at minimum weight... Burt RUtan was an expert at this using fibreglass layups on the varieze....

ALuminum ribs, once you have the press molds made, and it takes a lot of work to make them, but once they are made and you can get hyour hands on pur soft aluminum, you can press out ribs fast as pressing coke bottle caps.... bet getting pure soft aluminum is not easy.. ALcoa will sell you a 5000# roll and companies like Univair can buy that much but you try  to get it..... I tried all kinds of aluminum 3003-1/4 hard was the best I could do. Univair Gave me a couple of square feet years ago because I used to buy lots of parts from them. I was trying to make aluminum blisters for a taylorcraft. IT took about 10 days to make the maple pressing  part which was pressed down into the aluminum which was bolted between two 1/2" steel plates with a template cutout of a blister. The aluminum had to be greased and the steel plates bolted together but not too tight and then a 20 ton press forced the maple form down into the plates which held the aluminum. You need to use .040 or thicker because it stretchs and work hardens also...you can tell when the aluminum has work hardened because the pressesure got way up while forming it.. stop, removed teh part, anneal it and then put it all back together and press on!! IT worked well. The guy who helped me demanded I give him the molds later on so I did an dnot sure what he did with them...but I learned how to do it

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Posted

I am currently working on composite ribs. The 1st attempt seems very promising. Longitudinal and vertical deflection is very similar to the wooden ribs. Weight  is a little better. 4.45 oz for wood and 3.40 oz for composite. These are only 1st impressions and it will need to be tested more extensively before I'll be able to make real claims. The rib tails for the flaperons are not done yet. They will be solid composite and will add that little weight again so I assume the weight overall may be the same or just marginally better than wood.

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Posted

I would say stick to what works, but if we did that, we'd all be flying the "Wright Flyer" still. One would probably be shocked to find out where some homebuilder ideas are being used today!  I can proudly say we homebuilders aren't satisfied with anything!

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Posted

Pictures, or it didn't happen :) I'm curious how you are building the ribs. I only have one wing to rebuild but if I were doing both I would have made composite ribs. 

You must be just weighing the main part of the rib between the spars without cap strips or tails. I am just finishing gluing my ribs up and they weigh 9.3oz with without the flaperon tail and 10.3oz for the long ribs with the tail. The short ribs behind the gas tank are 3.4oz and 4.1oz. Total weight is 6.35lbs in each wing. I'm using the 5mm 10-ply plywood for the main rib and 3mm 5-ply for the cap strips. I'm thinking composite ribs would easily save 25% in weight and similar cost vs buying the plywood from Aircraft Spruce. 

 

-Brett

 

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