I've been trying to read up about this online but there are clearly mixed views.
What kind of finish gives the best results on a prop? some people say polished but others say its best when you used 120-grit sandpaper
I've been trying to read up about this online but there are clearly mixed views.
What kind of finish gives the best results on a prop? some people say polished but others say its best when you used 120-grit sandpaper
Here is an interesting link on the subject, site owner Ron Hill is in it
http://www.screamandfly.com/showthre...sh-prop-or-not
interesting read, not a very definitive answer though
I'll add my thoughts here. Over the years, in kneeldown boats I've never seen a satin finished prop in the inspection area of the finals at an APBA Nationals. Usually, the props are thin as hell and sharp as a razor.
BUT, I used to make OPC props like that and they usually broke after not much use and that was in the 150 HP days.
I my onw testing, I believe a satin finished bottom is in fact faster than a polished bottom. Jay Smith said 400, but I like almost 80 grit...sanded long ways, which brings us to the question of satin finished propellers. I would not want the satin to go across the blade. I try to make the satin lines follow the rotation of the blade, not exactly but in that motion. I am convinced that Speed coat is slower.
The trailing edge is very important in how a props really runs. We, family relgion, always took a very sharp knife and ran it across the trailing edge of a blade to where there was a slight burr, just before a Kilo run or a Nationals final heat.
The slightest "EDGE" is what you are looking for in racing. Polishing, under a microscope, tends to roll off the back edge. But this can be sharpened back..
Bottomline, if the prop works, keep it...Polishing a satin finished prop could ruin it. Same as satin finishing of a polished props could ruin it. I take a machine polished Mercury Bravo One, thin it, balance it, sharpen the edges, and satin finish it and it picks up three mph and gets on plane faster. Nothing I did SHOULD make it plane faster, I wouldn't think anyway, except the satin finish.
Sand blasting or glass beading the trailing edges, to me, was done to cause the cup to "Slip". See, I believe cups slow props down......Anyone want to go there??
DeWald seems to own Formula One, his props are polished. Most Formual One dudes don't use Merc Props, but I've heard it is a customer service (He loans you several to buy one). I've heard Mercury sells you one or several. When I've reworked DeWalds, the winningest one I did was satin finished.
Jim Boo has built some damn fast props over the years. His polishing is close to perfect.
All the above are my opinions. I guess that is what makes "HORSE RACE".
Bottom line: I don't know that there is an answer...maybe, I should run for politics!!!
Ron let me axe sumpin. Is it not easier to see stress cracks and would be trouble areas with a polished prop?
Don Hendrich would polish my props and then sharpen the edges so you would get a mirror finished prop and then about 1/4" of the edges ground sharp. I even smeared a little shaving cream on my left arm and sliced the hair off one night when I had a few too many Heilemans Old Style beers to show my buddies.... You could see the machine marks running the same direction as the edges parallel along the curves if that's the correct term.
Bill Schwab
Dirty Deck Brewing
Company
All my props from Pinner were satin, I never polished them out and they ran well in 25ssh. If they were polished I doubt that any cost effective measuring device could detect the difference under controlled real world test conditions because of the many variables that would be hard to keep constant. No doubt controlled lab conditions could detect a difference in drag (interesting test for a ventilated surface piercing prop) but not the same as real world running.
As for bottom finish tried gloss varnish and sanded flat black with 400 in long direction and sanded was better feel with my SOTP Buttmaster (patent pending). BTW Bob Wartinger, Bob 110 records as of 11/04 and read he uses sanded bottoms.
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