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Wood prop

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25 Jun 2024 19:18 #7 by William McCormick
Replied by William McCormick on topic Wood prop
We'll just have to fly to Pandora and talk to the Na'vi and see what we can barter for some. Did not realize I'd start such a discussion! Not sure I want to increase my gph tho.

What I'd like to do is simply lose weight on Tweety and keep the climb performance better than standard but less than what it is now to possibly improve cruise a smidge if that could work out.

However from very good point Larry made, going to a lighter prop means the CG will be different now due to the lighter weight at that distance from the datum. At 6' in height I don't think I can scoot the seats forward to compensate without surgery! :)

The current prop Tweety has is pitched for climb and is a McCauley 1A90/CF7148 at 23.5 lbs. I read that as a 71" diameter with a pitch of 48" Warren suggests going to a 51" pitch new prop (metal? diameter?) after the carb change to C85.

Throwing more LL100 on the fire, Sensenich replied back to me that "we do have wood props for this aircraft but metal propellers will provide the best performance." Historically speaking from what I have read that would be more authentic to stay with metal. A bit of a newbie quandary to say the least.

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25 Jun 2024 18:27 #8 by Larry Snyder
Replied by Larry Snyder on topic Wood prop
In many cases it was a matter of finding a crankshaft. C85/75 crankshafts are now made of unobtainium. At least there’s a chance of finding an O-200 crank. Plus, the engine is still technically a C-85, so you can put a bigger prop on it - 71 inches. The biggest problem with an O-200 on an Ercoupe is the prop size restriction. You could get a lot more power with a bigger prop. I think the limit is somewhere around 68 inches. When I upgraded my C-75 to a C-85 (with the O-200 crank) I started using about a half gallon more fuel per hour. Of course I went from 2200 rpm cruise to 2500 rpm. Big difference in power! Went from a 73 inch prop to a 71 inch prop.

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25 Jun 2024 17:38 #9 by Warren Hampton
Replied by Warren Hampton on topic Wood prop
Thank for that, now we need a wood weight.

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25 Jun 2024 17:36 #10 by Warren Hampton
Replied by Warren Hampton on topic Wood prop
Just another Question Why are so many wanting more power using the 0-200 parts? The 0-200 engine itself needs to use the 150's 69-inch prop. An as long as I am asking questions, At a given RPM what is the dif in fuel burn between 75 and 85's

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25 Jun 2024 17:31 #11 by Charles Dicey
Replied by Charles Dicey on topic Wood prop
I have one sitting right here,a sensenich 72-48 weight is right at 9.5 lbs

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25 Jun 2024 17:18 - 25 Jun 2024 17:25 #12 by Warren Hampton
Replied by Warren Hampton on topic Wood prop
Who knows the dif in weight between Alum and wood props? If engine stoppage which would cause more drag? Larry you were talking about wings made me thing About 2000 there was a guy trying to get a new wing design going for Coupes wonder what ever became of that.
Last edit: 25 Jun 2024 17:25 by Warren Hampton. Reason: moe to add

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