Bearhawk - Carbon Fiber Seats

[@rileysmith8980]

Looks good and functional

[@Nicky.Stiles]

Great video! Thanks for posting the update!

[@brettgerber795]

I picked up a pair of electric Black & Decker scissors on clearance for less than $10 about 15 years ago when I was finishing up my Long Ez. I didn’t have high expectations of it and went through a few sets of jaws but well worth it! I think it finally gave up on me at the end of the Velocity build. I probably will find another set of electric scissors as we get into our BH5 build when our kit comes in.

[@barnbuiltbearhawk7267]

Good luck with your BH5!!

[@Max_Janszen]

Doubt youll ever see this, but if you leave the top plastic on and use the spreader to push air out, you'll be able to see the air coming up and end up with a great pre-preg and better bond.

[@barnbuiltbearhawk7267]

Thank for the tip!!

[@Max_Janszen]

@@barnbuiltbearhawk7267 keep the kids coming, I'm wanting to build a bearhawk 4 seater when sport pilot rule opens up here soonish

[@2freedomworks]

So I'm curious about not using a Kevlar layer to keep the carbon fiber from splintering and having thousands of needles running you through in an emergency situation?

[@barnbuiltbearhawk7267]

Well....good point. I did actually put a thin layer of kevlar in after the video for that reason. At the time I thought...if my seat pan is that badly damaged....the person in it is not likely going to fair to well. All my other parts do have kevlar in the layup

[@psgflier]

I am going to steal your super glue on the brush trick next time I do some fabric work, nothing worse than finding a bristle under a wrap of glued down fabric.

[@e28powerm30]

Do you know how much weight the carbon added? How much weight is saved over the standard seat pan?

[@barnbuiltbearhawk7267]

The typical setup is an aluminum pan riveted or screwed into the frame tube. Off the top of my head carbon saves around 20% compared to Aluminum. I do not have the exact numbers

[@rickswanberg4995]

Is there any concern with the carbon fiber applied directly to steel causing electrolysis and decaying the steel?

[@barnbuiltbearhawk7267]

Not at all for two reasons. First, the steel has a solid coat of paint on it. So no steel to carbon contact. Second, it is a dry environment. Being the inside of the plane, it wont have water to aid in a corrosive process

[@AviationWP]

What does the foam inside of the carbon fiber do for strength?

[@barnbuiltbearhawk7267]

The lower back area was quite flimsy prior to adding the foam. It helped a lot. Also it gave me a curved feature to wrap my seat covers around.

[@newdeathscope]

It's a light weight filler that makes the carbon more efficient. Think about how a truss is stronger per pound than a solid block. Look into the statics use of moment of inertia for more info

[@PDZ1122]

Just hope you'll never have to weld a crack in any of the seat frames.

[@newdeathscope]

Are the seats comfortable?

[@barnbuiltbearhawk7267]

I'm having cushions made right now. Will keep you bbn posted

[@stevebrown5819]

Good comment below on the stiffness of carbon fiber. Was that considered? The engineering episode seems to be is missing. The internet is full of un-engineered carbon fiber videos. People tend to think that carbon fiber is stronger than anything it's replacing so there is no engineering required. Maybe that's OK. Maybe not. There should be NO maybes in aviation. It would be lovely to have that Oratex fail in a crash and have a steel tube break your back.

[@barnbuiltbearhawk7267]

You bring up good points. Yes stiffness was considered. I try to keep the videos short so i might not dive into the engineering on every choice. Whether carbon fiber is stronger or not depends on the material you are comparing it to. I 100% agree with no maybe in aviation, we have zero tolerance for that in the Aerospace industry. I have seen a few methods to do the back. All with pros and cons. What approach would you have chosen?

[@PDZ1122]

@@barnbuiltbearhawk7267 You could proof load the seats. To at least 5 G. The rear seat frame alone seems pretty flimsy to me. 2 hefty, a hard landing and I can see those tubes getting bent.

[@kylegoldston]

Carbon is not going to absorb energy in the way you might want in a crash.

[@stevebrown5819]

Good question that went unanswered.

[@barnbuiltbearhawk7267]

@@stevebrown5819 it is a statement. But, the bearhawk does come with a nice suspension setup and will have larger than typical soft bush tires on it. I did consider an energy absorbing system similar to fall arrest gear but chose not to. It would take time to engineer that setup. I will ride this through the test phase and reserve the right to change it later if I feel uncomfortable with the setup.