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Carbon Fiber Rudder

ATango

Member
I've been working on making a carbon fiber rudder (RV-8 drop-in replacement) for a little while now and finally have a little bit of progress to share. I just fabricated the skins this past week while I was home from school for spring break. This project is primarily for my own education with designing/fabricating composite parts, and I'm quite happy with how the skins came out. The look is a bit different than the stock RV-8 rudder, with some influences from the GB1 Gamebird.

I'll try to include some pictures on here, but I have a lot more pictures and a fairly detailed write up on my website: https://sites.google.com/view/adamaviation/composite-rudder?authuser=0

Let me know what you think!

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Awesome project

Hi Adam,

What a great project to learn about design and manufacturing .

Liked the new shape of the trailing edge.

Great write up on your website.

Cheers,
 
Wow...that looks really nice!! I?m sure you could sell a lot of those if you ever decided to produce them.
 
Don't forget to flutter-qualify it!

And since the area looks reduced, be sure to run it through the full set of lateral-directional stability and control tests.

Dave
 
Ashley and Mark: Glad you guys like it. The mold is still in great condition due to many hours or prep time.. additional rudders may be something I would consider a bit in the future, but this one is for education and validation.

Dave: The area of the rudder is nearly identical to the stock RV-8 rudder. The rudder will be counter-balanced as well. When it comes time, flight test will be taken seriously. Thanks for your concern!
 
Nice!! Are you going to bond real ribs in there for stiffness? Any projection on a weight comparison with the stock 8 rudder?
 
Nice!! Are you going to bond real ribs in there for stiffness? Any projection on a weight comparison with the stock 8 rudder?

Bill, a spar and ribs (all carbon fiber) will be bonded into the structure. I do not have a precise weight estimate yet, but it will not be any heavier than the stock rudder. I am using fairly high factors of safety and over-engineering it a bit, so it will not be quite as light as it could be.
 
That looks cool!

My only comment is that there isn't a fitting for the rear light.

Can you make the entire trailing edge a combination position and strobe light with LED's?
 
That looks cool!

My only comment is that there isn't a fitting for the rear light.

Can you make the entire trailing edge a combination position and strobe light with LED's?

I have thought about this and have decided on two options. Preferably, I will leave the rudder as is, and add the appropriate lighting facing aft from the wingtips (maybe a custom wingtip as a future project). I believe the Aveo ziptips for instance would be a legal solution to the problem.

Otherwise, it will be pretty easy to 3D print a small mold to make a light housing that can be patched into the trailing edge, which would be much like the Van's solution.

An entire trailing edge light would be really cool, but it would likely come with a huge penalty to the torsional stiffness by not having the trailing edge bonded (if it's integrated into the T.E.). If it's possible to find a strip of LEDs that just adheres to the outside of the rudder and can conform to the T.E. radius as well without adding much thickness, that could be a really unique and effective solution. I think the FARs call for a specific viewing angle for those lights as well, which might be hard to comply with that way?

How does the torsional stiffness compare to the stock one?

Dave

The torsional stiffness will be significantly greater than the stock rudder.
 
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Adam, if you have access to vibration lab equipment at school, and you wish to make a project of measuring the torsional modes of a stock vs your carbon rudder, I can bring a stock one over for you to test. I would go a long way to understanding what we are flying with.

I think it will fit in the back of the 7, but driving to Lafayette is not so far either.
 
Adam, if you have access to vibration lab equipment at school, and you wish to make a project of measuring the torsional modes of a stock vs your carbon rudder, I can bring a stock one over for you to test. I would go a long way to understanding what we are flying with.

I think it will fit in the back of the 7, but driving to Lafayette is not so far either.

Bill, unfortunately aeroelasticity is more of a graduate level topic here at Purdue. I haven't done any lab work using (or know of any) vibration equipment around. I'm not sure the grad level aeroelasticity courses even have a lab component. I do have a stock rudder that I built, but I really appreciate the offer to bring one over. I do think it would be a great idea to do some vibration testing if it's possibly to get my hands on the equipment and someone that knows how to use it. Flutter isn't something I'm taking lightly.

I think we're all going to be proud to know you. Keep up the good work.

Dan, that means a lot, thanks!
 
Carbon

The Polen Special was designed and built by Dennis Polen in the mid 70's. It is claimed by some to be the worlds fastest 4 cylinder piston aircraft. It is now in the care of Dick Keyt in TX. After losing the entire metal rudder due to flutter, the rudder was replaced with a carbon fiber rudder.
The Polen was the Oshkosh Reserve Grand Champion in 1976. I believe it still holds a worlds record for speed over a 500 km course of well over 300 m/h. There is a lot of information available online about the Polen.
 
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