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Wood prop

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25 Jun 2024 17:00 #13 by Warren Hampton
Replied by Warren Hampton on topic Wood prop
Well not being an Engineer. I cannot believe ERCO would want to loose anything using a small engine like C85. Wood props were less used by general aviation... Pitch and RPM has more to do with pulling than how long the prop is. And there is an efficiency dif between wood and Alum props also thin vs a club.

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25 Jun 2024 10:27 #14 by Ronald Raty
Replied by Ronald Raty on topic Wood prop
I have seen some arguments that upgrading the engine C-75 to C-85 doesn't gain you much if you have to change to a shorter propeller. The C-75 allows a larger diameter propeller (73, I think), so going to a C-85 may give more HP, but a smaller propeller (71 inch) with less lift area doesn't give much additional thrust. A wood propeller can be as large as 74" diameter.

This all assuming I am reading the Type Cert correctly.

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24 Jun 2024 21:19 - 24 Jun 2024 21:24 #15 by Warren Hampton
Replied by Warren Hampton on topic Wood prop
larger jets require a larger venti + more fuel more air. Just basic stuff Contact Vern see if he has an C85 carb. Mac, I am going to look see if I have a good 71 with a 51 pitch. I know I have 48 and 49  there is no change in weigh...
Last edit: 24 Jun 2024 21:24 by Warren Hampton. Reason: more to say

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24 Jun 2024 20:33 #16 by Larry Snyder
Replied by Larry Snyder on topic Wood prop
The carb change assumes a Stromberg. I’m not sure you can make the coupe light enough to make a noticeable difference in its glide. The fat wing pretty much precludes “soaring”. My best glide is 80. Basically, you just have to get used to that green circle around your plane in ForeFlight being real close…

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24 Jun 2024 18:20 #17 by William McCormick
Replied by William McCormick on topic Wood prop
Thank you Larry, very helpful. So if I understand you correctly 75 to 85 is essentially a carb change so weight change N/A but more power and a requirement to change the prop ($3,500 - $5,500) - ish and while wood lightens the overall empty weight it also changes the weight and balance a good bit. What I'd like to do is to lighten as much as possible in order to improve glide rate if at all possible without messing with the W&B. I probably am spoiled by the 150's 70mph glide when doing "power out" and with Tweety it is more like 80 mph to maintain the same 700 fpm descent.

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24 Jun 2024 17:17 #18 by Larry Snyder
Replied by Larry Snyder on topic Wood prop
Upgrading a C75 to a C85 requires different carb jets and a new prop. You’ll have to go to a shorter prop. I have a 71-49 on my C85 and it cruises at 110 and climbs great. But I have the O200 crank STC. It’s pretty easy to make a 75 an 85 but the prop change is expensive nowadays.
I’m not too crazy about wood props. You’re losing weight but it’s really far forward of the datum.
But to each his own.

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