ETpilot

I am building my first gas engine plane. It will be a tail dragger and I am at the point of making the LG assembly. This will be a grass runway flyer so how much prop clearance should I allow with AC in level attitude? Also what do you use for fuel proofing the firewall and fuel compartment?

Thanks.

raptureboy

Thinned epoxy, just like you would do for glow. I don't think there is a real formula for prop clearence. Depending on the plane and motor most of mine are 3-6 inchs off the ground.

Granpooba

My Feedback: (5)

Usually use Z-Poxy for the firewall & fuel compartment. Two parts, just mix them together and use a cheap brush to apply.

Never did use nor have heard of a formula for prop / ground clearance. Seems that if I built according to instructions and used the proper size prop for the sized engine required, that my models always had the proper ground clearance for hard and grass runways.

But, it will be interesting to see or hear if anybody does have a formula for prop / ground clearance ?

speedracerntrixie

My Feedback: (29)

Not really a formula but in all my designs I have the gear long enough so that at 15 degrees nose down the prop just hits.

av8tor1977

My Feedback: (6)

I would consider 2" prop clearance with the plane level to be a good minimum. More would be better especially if flying off dirt. I don't even fuel proof the fuel tank areas of gas planes; I generally mount the fuel tank on or near the center of gravity. On the firewall I just use either alcohol thinned epoxy, or brushed on Rustoleum paint. The nose of a gas plane doesn't get all "gloppy" covered with fuel and oil like glow planes...

"Gloppy" is a word. It stands for a disgusting sloppy mixture of glow fuel and oil.

AV8TOR

ETpilot

Thanks for the info. After I make the tailwheel assembly I will install the engine and make a wooden support for the LG assembly. I'm trying to stay with the recommended 17x6 prop. Will see how it looks. Most likely like the German Storch. Maybe nose higher. Will see. Thanks again.