Dqx or acme prop

fiberglassmagic

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Still playing with prop due to slippage.I figured less slippage is speed and fuel economy if i keep the engine loaded the same.Who has experience with acme props?They offer props with more blade area than dqx by mishigan.Any help would be appreciated
 

backman

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I had Acme 18 X 26's on my Carolina Classic and loved and hated them. Loved them because of the mid range "bite" which combined w. a high torque common rail engine made for great acceleration as well as efficient cruise with less fuel burn than my old pair of mechnical engines + same sized Michigan Wheels. The manufacturer described them as 10-15% more efficient and less slip than the Michagan wheels.


I hated them because they were very thin at the tips and if you breathed on them, they bent....They also put enormous torque on undersized Carolina Classic shafts and in my mind and the manufacturers contributed to a rash of shaft snappage in that particular configuration.

Your milage may vary in a DE...
 

Brooksie

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Still playing with prop due to slippage.I figured less slippage is speed and fuel economy if i keep the engine loaded the same.Who has experience with acme props?They offer props with more blade area than dqx by mishigan.Any help would be appreciated

Sounds good and less slip is good but more blades (or blade area) also eats up power due to friction. So after a point, less slip can = less speed. What is your calculated slip now?
 

captainlarry84

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You cannot rob Peter to pay Paul……. If your slippage is .29 at cruising speed that i9n turns means that you are getting 71% current propeller efficiency. On a keeled hard chine Harris hull you and not doing to bad at all. The best way to decrease slippage is to increase diameter, however I am sure that you have already done that. Next we can increase blade area; however increasing blade area will reduce your pitch. The last thing which I am not a big fan of is to add some cup, however cupping is also not free and it may cost some drag.
Based on vessel & its current power I would not use either wheel. I would find a new Michigan
Dyna quad with max diameter, no cup & pitched to correct load with a full blueprinting to make sure every blade is working as a team.
Next I would address the shaft and make sure that your wheel is a far away from the keel as possible.
After all efforts I would est that the best efficiency you will ever get on your hull is at best 77%. Do the math and see what your increase is.
Lastly I would take a hard look at any possible weigh saving items, reduced weigh will also decrease slippage.
 

Brooksie

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slippage at cruise is .29 at full throttle .34

Those are good slips for a DE boat. That your cruise slip % is less than your WOT slip % is a little unusual and may indeed indicate that more area is needed to absorb the hp generated at WOT. Remember slip is not a measure of propeller efficiency. Rather, slip is the difference between actual and theoretical travel resulting from a necessary propeller blade angle of attack. If the blade had no angle of attack, there would be no slip; but, of course, there would be no positive and negative pressure created on the blades and, therefore, there would be no thrust. So don't confuse slip with efficiency, they are not the same.
 

fiberglassmagic

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prop

Going to try 1'' larger diameter with 2 pitch less and #3 cup,rpm should be the same just a little more prop area to work with....acme will exchange it or refund my money if it does not work...
 

Brooksie

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Given that (unless I missed something) you did not give us any details about your vessel, engine, prop, or speed and asked only if a reduction in slip could occur with a different prop; try what you want. I assume you gave some details to Acme and they think this will help you.
 

captainlarry84

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Before you buy anything give me the following:
Current wheel size
Current Tip Clearance
Reduction gear
HP & RPMs
Speed & RPMs at Cruise
Speed & RPM at WOT
 

fiberglassmagic

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Prop

Fighting with props ,acme is sending another thursday.When i get enough diameter and blade area for bite( .75 dar prop 24" diameter) i get too much transom lift .great thing about acme is that they will exchange props until you get it right.peformance is getting better in slow steps,most people would have left it alone.Have dealt with a few prop companys through the years but so far acme service is the best.slippage is down to .24 rpm is right just want to carry the bow higher for less drag.1" less diameter with more cup should do it.
 

captainlarry84

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Transom lift can be reduced by cupping the wheel. Once cupped the wheel throws the water away from the bottom of the boat allowing the bow to rise.
 
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