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Cowl to FAB connection

kiwipete

Well Known Member
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KTDeCnfP8pqSpNLu9
https://photos.app.goo.gl/KTDeCnfP8pqSpNLu9

I’ve just about completed the FAB. I changed the front so that the filter box was the same shape at the inlet to the cowl. Hopefully this should give a uniform shape to allow for a good seal. (Since these photos I’ve now trimmed it to give a 1/2 - 5/8 gap)

Now I’m trying to decide what to make the sealing connector out of. Vans now suggest a softer silicone rubber. Sam James neoprene. If using neoprene how thick? And where are people getting it from? Old wetsuits?

Thanks

Peter
 
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Baffling material

I used this stuff:

https://www.aircraftspruce.com/pages/ap/baffling_0material/siliconecowlseals4.php



https://photos.app.goo.gl/KTDeCnfP8pqSpNLu9

I’ve just about completed the FAB. I changed the front so that the filter box was the same shape at the inlet to the cowl. Hopefully this should give a uniform shape to allow for a good seal. (Since these photos I’ve now trimmed it to give a 1/2 - 5/8 gap)

Now I’m trying to decide what to make the sealing connector out of. Vans now suggest a softer silicone rubber. Sam James neoprene. If using neoprene how thick? And where are people getting it from? Old wetsuits?

Thanks

Peter
 
15 years ago, I used the same rubber material that was provided in the firewall forward kit to do the baffling. It has lasted, shows no wear (just normal contact scuffing).
I don't recall what recommended gap is between the FAB and air intake extension but I can attest that it needs to be sufficient to allow the rubber to give way sufficiently when installing and removing the lower cowling.
 
Better Seal?

To try and get this to seal better I fabbed a flange onto the nose of the airbox, and filled the cowl inlet to be smooth as well. Then used closed cell rubber foam to make a 'doughnut' that sits between them. As the engine thrusts the seal should improve as the engine moves slightly forward.

Trying to get a decent seal using free hanging baffle material (or alternative is going to be pretty impossible.

The foam I used was about 3/4" thick.
 
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I used red silicon baffle seal.

On the FAB I put a piece on the top flat side.

On the cowl side I had a fiberglass tunnel from the air inlet. There was about 3/8 inch gap between the cowl tunnel and FAB.

I riveted on silicon baffle on the rounded side and bottom of the inlet tunnel on the cowl side.

So when you put bottom cowl on the top seal on the FAB overlaps to cowl inlet tunnel flat top side.

When you put a bottom cowl on the seal on the inlet tunnel pushes up and overlaps the FAB. At the corners the seals were thick and pushed against each other. The leakage was nil. This gives enough wiggle room to keep from cracking the FAB from engine vibration.

This makes putting on the lower cowl easy.

Be sure to put support strut on front of FAB to engine or you will crack the FAB mounting plate.
 
KTDeCnfP8pqSpNLu9
Thanks for all the suggestions.

Jimmy if I was in the US I’d just buy it from James Aircraft but the cost of postage and then import fees and taxes. Makes a cheap piece of neoprene very expensive.
Is it simply wetsuit type neoprene and roughly how thick?

I have reshaped the front of the FAB to the same shape as the cowl inlet so I have a uniform shape for about three inches over the area where the seal lies. So hopefully this will work better.


Thanks

Peter
 
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Wet suit material is just fine.

I used some with a fabric layer, that I put to the inside so it allowed a bit of movement with less surface friction than the rubber side.
 
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