Does back cutting a prop work on a mono v

[martin]

Running a small v hull on an Octura metal x435 at around 42000rpm for short straight runs. Ive recently de-tongued the prop which has let it unload more, Is back cutting advisable on a mono deep v hull or is that more suited to hydro use. Also would rounding the tips be benificial rather than the pointed tips or is that also more suited to hydros. Thanks Martin.

[TheShaughnessy]

spooning the tips and cupping them a bit will give the thrust a more direct path rather then sliding off the edge and creating more lift /prop walk. Spooning condenses the thrust cone. Back or bar cutting will further unload the prop and I don't believe it is suited to any one hull type.

[martin]

I have used bar cuts before & found it to be slower on electrics, Its probably better suited to ic motors. Martin

[TheShaughnessy]

I have used bar cuts before & found it to be slower on electrics, Its probably better suited to ic motors. Martin

I've only seen gas guys with the larger props using bar cuts.

[egneg]

Bar cut and back cut are 2 different types. Cupping the last 1/3 of the prop will help to narrow the thrust cone but add a bit more load - this is where the back cut comes in to help counter act this. You can also just back cut the prop to unload it a bit more as well. I have heard conflicting information about bar cuts for FE boats and have done it but it's not to the extent of the IC boats.

I hope this really muddies the water (pun intended).

[Diegoboy]

Thread moved

[TheShaughnessy]

they are a different style of cut, but essentially serve the same purpose.

[andym]

Back cut will increase rake and reduce lift, can be very good on a well set up mono. Bar cut does allow props to rev up a bit more, very use full if your prop is on the limit temp wise for your application.

[graill]

Back cut will increase rake and reduce lift, can be very good on a well set up mono. Bar cut does allow props to rev up a bit more, very use full if your prop is on the limit temp wise for your application.

Andy, your a prop god and i bow to you under 99% of the time but back cutting a prop WILL NOT change rake. I am with you on the reducing lift but rake is built into the prop from the moment its created and unless you cut the blades off and reweld them at different angles (sarcasm there) you wont change it. The only thing back cutting will do is change the exit angle.

Chasten me if you must.

[andym]

grail if blades where straight that would be correct, have a look at a large x4 prop and cut one blade then measure the rake, let me know what you find.

[graill]

grail if blades where straight that would be correct, have a look at a large x4 prop and cut one blade then measure the rake, let me know what you find.

If there is no rake originally built into the blade you will not create any rake if you back cut.

If any rake does exists and you back cut you will still not change the rake angle that was already there.

I wont post anymore on the subject, this was discussed three years ago too.

[Fluid]

Rake will not be changed by any form of cutting the blade - it is determined by the angle the blades are mounted to the hub:

http://www.propline.com/Propeller-General-Information/Propeller_Terminology.htm

Rake
Rake is the degree that the blades slant forward or backwards in relation to the hub. Rake can affect the flow of water through the propeller.

I strongly recommend NOT to Barr-cut the trailing edge of a prop. That is a fuel boat mod and does nothing for an FE boat. Every prop I have with the Barr cut - even those done by experts - has cracked at the bottom of the relief.






.

[martin]

Barr cuts on a FE boat does nothing at all except make it slower, Tried that on some carbon props just so as i didnt mess up expensive metal props. Will back cutting an x series prop add any thing on a small deep v mono. Ive already detongued & that made a very noticable difference in a positive way. Martin.

[Doug Smock]

I strongly recommend NOT to Barr-cut the trailing edge of a prop. That is a fuel boat mod and does nothing for an FE boat.
.

Interesting...................................

[egneg]

Interesting...................................

Very .....................

I have done it but 4mm is the most I have done for FE and as long as the radius continues back up the hub I don't see why it would crack.