William Crawford wrote: > The wood prop already has a bored centre hole 2ΒΌ" and the whole thing > that fits quite well over the 5" extension with 6 bolts. The hole is > counter sunk about 3" deep, All the washer does is make this hole 2-7/8" > in other words the prop now remains about 1/8" from the cowling. You can > make a prop with a centre hole as deep or shallow as needed,
I hate to belabor this, but the only way I can picture this is that you are tightening the prop down against the 2.25" center hole, leaving a gap between the actual prop mounting flange and the extension where the six bolts pass through? If that's what you're doing, I'm not even going to wish you good luck with it. I'll loudly scream "don't do it!". That sounds like a press designed to punch the center of the prop out over time, or worse yet, split the prop around the flange instantly. Maybe I don't have the correct picture of this setup, but if it is as I just described, I wouldn't even run it up on the ground, much less fly with it that way! Now if you put the same spacers in those 6 gaps at each bolt hole location, that's considerably better, but still hoaky. But the easy and simple way to do it right is to cut out a 5" or 6" diameter spacer out of aluminum (whatever diameter the prop hub is), using the crush plate as a jig to drill the center hole and the six bolt holes. You can cut this out on a bandsaw if you are careful, but the center hole will problably require a lathe or a mill. If you do machine it, you might as well cut the outside diameter the same way and then match drill the six holes on a drill press. I wouldn't be surprised if Steve Bennett at sold something like this. See http://www.greatplainsas.com/scphub.html for something he calls a prop "face plate", and although it appears to be steel, it would certainly be easy and cheap, at 8 bucks! He might also sell one made out of aluminum. If not, it sounds like a manufacturing opportunity to me. Ken Brock probably used to sell these, but I believe the company met it's demise shortly after he did. I just checked your website at http://home.hiwaay.net/~langford/wcrawford/ and that is a gorgeous airplane! And since you are using a Continental, you need an SAE-1 crushplate. Aircraft Spruce sells these, but they are also steel. You just need to find an aluminum SAE-1 crush plate, and use it for a spacer... Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net
