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I'm curious to hear what fellow builders are using for floorboards in their Bearhawks? The LSA plans show several different thicknesses of aluminum. I've seen plywood, carbon fiber, or aluminum used in cubs. I read in a forum that someone had used some small beads of silicone between the aluminum floorboards and 4130 tubing to successfully eliminate some of the noise and vibration. Each material seems to have it's own set of pros and cons. Thoughts?
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Some I gathered some facts about flooring for the Patrol (22.25 sq ft area), and considered 1/4" Baltic Birch, Composite Flooring, and Aluminum.
-A Baltic Birch floor would weigh 19.58 pounds.
-A composite Floor 1/4" 2 ply from Javeron would weigh 10.23 pounds
-An Aluminum floor of .032 weighed 10.26 pounds.
-An aluminum floor of .025 weighed 8.01 pounds
-Installing .020 under the rear seat between station D-E with .025 AL in the rest of the floor weighed 7.64 pounds.
-Istalling .016 between D-E would save another .3 pounds. over .020 AL.
I did not think of noise reduction with silicone, but I thought of Cork, which does not absorb water.
Some would argue that Aluminum is inferior due to noise and other factors. Cessna, Beech, and Piper used a lot of Aluminum and no one complains too much.
Aluminum does not make noise unless it vibrates, but neither will it suppress noise on its own. To add suppression of noise from other producers like exhaust would add .15 pounds per Sq Ft. if I used Sound Proofing Mat from www.supersoundproofing.org So, I thought that product was pretty light and will consider installing it.
It surprised me that I could save 12 pounds by not installing wood, and that Aluminum compares favorably with Composite Flooring for weight savings.
Brooks Cone
Patrol #303
Brooks Cone
Southeast Michigan
Patrol #303, Kit build -
An A&P I know does a lot of work on Pacers. On customers planes that are concerned about noise he will coat the bottom side of the aluminum floor with basically truck bed liner, something like roll on Rhino Liner. Says it works good to reduce noise.
I'm installing 0.032 aluminum flooring in my BH. Someday I'd like to replace it with carbon fiber but I'm not sure that will ever happen.Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.Comment
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It's tough to beat aluminum for floorboards. Like Whee I'd like to do mine in carbon fiber but for now I'm using the aluminum ones my kit came with. In all likelihood I'll never change them.Comment
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I have an 18.5' canoe made of Kevlar/resin. The entire canoe with seats and aluminum add-ons weighs only 48#
The Kevlar is tough, so thin you can almost see thru it,. I've thought of using something similar on my Patrol. And my canoe it is really quiet
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I've used .032 aluminum and it has held up well. The baggage compartment divider was noisy until I put that black, tar like, sticky back noise deadening material on it. You don't need to cover it, just apply small pieces in various places until it quiets down. The floor doesn't make noise when the rear seat is in. When the seat is out I lay a piece of egg crate foam on the floor which does the trick. It also serves as an emergency sleeping pad if I need to sleep in the plane.Comment
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I think if you can hear the floor boards rattling, then restarting your engine will be a higher priority. JK
I have aluminum flooring and its never crossed my mind that they could feasibly make enough noise to hear over the engine. You would need a lot of insulation and a great muffler... That said, I have a lightweight marine carpet over top. Even with a spartan interior like mine, bare alloy is a step too far. Carpet looks great and has lots of practical advantages.Comment
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wheeZzz I've also seriously considered using carbon fiber, but the additional cost and availability has me leaning towards aluminum.
​​​​​​​Well said, though my little C-85 probably doesn't quite match the sounds output of your 540Originally posted by Battson View Post Even though the engine produces the dominant noise, vibrating aluminum can still contribute to the noise level in the cabin. The post I read (can't remember where) said that adding the silcone between the tubing and aluminum produced a thud when impacting the floor, as opposed to a metalic rattle of aluminum vibrating against the steel. I'm interested in using some type of thin weather stripping tape stuck to the bottom of the aluminum floor, layed out on tubing centers.
Battson is your carpet fastened or glued down, or just laying on top of the aluminum floor?Comment
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Ouch! Do you know how much it hurts when you snort hot coffee through your nose? This made me laugh (and yell "Ow! Ow! Ow!") so much that my wife came to see what the heck was wrong with me...Originally posted by Battson View PostJim Parker
Farmersville, TX (NE of Dallas)
RANS S-6ES (E-LSA) with Rotax 912ULS (100 HP)Comment
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Yeah that is the difference, when the engine is at low idle on a steep approach, I used to hear some things rattle. To be specific, at certain RPMs I hit a natural frequency node of the alloy sheet I used for the aft bulkhead. If I don't have noise cancelling headphones on (which is never these day), then I can hear it rattling.Originally posted by lsa140 View PostWell said, though my little C-85 probably doesn't quite match the sounds output of your 540 Even though the engine produces the dominant noise, vibrating aluminum can still contribute to the noise level in the cabin. The post I read (can't remember where) said that adding the silcone between the tubing and aluminum produced a thud when impacting the floor, as opposed to a metalic rattle of aluminum vibrating against the steel. I'm interested in using some type of thin weather stripping tape stuck to the bottom of the aluminum floor, layed out on tubing centers.
Battson is your carpet fastened or glued down, or just laying on top of the aluminum floor?
The other thing I hear, particularly if I descent from up him down into a warm weather pocket near MSL, is the alloy panels which make up the wing tanks "popping out" (like drumming, except it only happens once!). It used to worry me, until I got used to it.
For the carpet, I used the same screws which hold down the floorboard to secure the carpet. Always looking for those little simplifications.
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That's the same thing I experienced. It can be quite loud but it certainly isn't louder than the engine. Because one of my kids is going to be sitting right next to the bulkhead I'd like to eliminate that noise.Originally posted by Battson
Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.Comment
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I bought 1/8" by 1" wide, 10' long felt. Cut 1/2" wide, applied spray adhesive to one side. Glued to all the tubing under the floor. 2024T3 .032" thick load bearing areas, .025" under the front seats.Originally posted by lsa140
Mark M.
Sent from my iPad using TapatalkLast edited by Mark Moyle; 10-07-2016, 02:10 AM.Comment
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Is that popping caused by the small fuel cap vents not being able to keep up with the outside air pressure change? Great idea using the floor fasteners to hold the carpet as well.Originally posted by Battson View PostComment
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Any good ideas on better materials for that bulkhead - weight saving materials which can't rattle are of most interest! Some kind of plastic maybe? A bare carbon fibre panel perhaps?? ($$$ Ching Ching)Originally posted by whee View PostComment
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I don't have any really good ideas. Plan A: Have my brother layup a carbon fiber sheet. He used to do carbon fiber work at Boeing and said it would be really easy but I know he is really busy with work and his family. Plan B: Layup and paint a fiberglass sheet. Plan C: Aluminum with some foam glued to the back. Think I'd use that foam all the guys on BCP are using on their Cessna rebuilds.
I wonder how Kydex would work. Mark M used it on his Pacer and the pics look great.Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.Comment
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