Does back cutting a prop work on a mono v

[martno1fan]

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.






.

Hmmm care to elaborate on this ?,it doesnt make sense to me

[andym]

Ask Paddy if back cut and bar cut do anything, each application is different but it can makee a large difference.

[andym]

Fluid look at your posted links picture, if I was to back cut that blade it would change the rake angle, thanks for the pics it confirms what I have been measuring.
On bar cut;I have seen a prop gain 4mph from bar cut, this prop is now over two years old and gets ran allot, no cracking
But as I said each set up is different,

[wparsons]

How exactly do you measure the rake angle? If it's based on a line drawn halfway between the leading and trailing edge, then back cutting would change the rake. If it's based on a fixed point on the blade (certain part of the curvature, etc) then that point wouldn't move with back cutting, and rake would be un-effected.

To me it would be like thinking that trimming the trailing edge of a plane wing would change the sweep of the wing, which IMO isn't the case.

[martin]

My personal experience on Barr cut on FE was running my boat then barr cutting that same prop at the lake & running again so running conditions were exactally the same . The boat was noticably slower & you could hear the prop had much less bite in the water. Where as de tonguing i found worked really well on X props. Martin.

[martno1fan]

My personal experience on Barr cut on FE was running my boat then barr cutting that same prop at the lake & running again so running conditions were exactally the same . The boat was noticably slower & you could hear the prop had much less bite in the water. Where as de tonguing i found worked really well on X props. Martin.

That doesnt prove anything,fact is theres too many variables involved to say it doesnt work,each setup is different so to just say bar cuts dont work at all is just silly in my opinion.Just because it didnt work on your prop doesnt mean it wont work on many others.
Mart

[wparsons]

IMO the big difference between FE and IC boats and bar cuts is that if you over prop by a bit an IC boat it won't rev out enough, and potentially won't even get onto the pipe. A FE boat (as long as it isn't WAY over propped) will just draw more current but still hit the RPM.

You may not get more speed with a bar cut on a FE boat, but I bet the amp draw would go down a bit.

[martin]

It proved to me on my boat with my set up which is all i was interested in when testing that the Barr cut prop was slower on my FE boat. Thats not to say it wont run better on another boat with a particular set up. But for me personally de tonguing & cupping a FE prop worked much better. Martin.

[martno1fan]

Someone posted that bar cuts dont work on fe and hes yet to reply and explain to me why.It doesnt make any sense whatsoever to me and as the last poster stated even if it gets the amp draw down then its a well worthwhile prop mod.As far as i know this was the main reason for doing such mods to props,not to gain more speed as such but to help unload the motor easier.While it might not be needed as much in fe every little helps,even if it just makes everything run cooler sureley its well worth it.
Mart

[martin]

I agree 100% if your getting to high on amp draw & high temps then Barr cuts will make a difference because of the noticable prop slip that i got when testing. I wasnt suffering from to high amp draw or high temps so certainly wasnt looking for more prop slip & lower speeds. This was just one of many mods i tried along with de-tonguing & cupping & found the latter 2 to be what i was looking for ie more speed. The reason i tried Barr cuts was perhaps even with a bit more prop slip taken into account i hoped i might of got more rpm at the top end & increased my speed because of the higher rpm making up for loss in prop slip. But as i said it didnt work for me & ran slower which is not what i was looking for. Martin.

[NativePaul]

Have you tried doing away with the barr cut by back cutting it to the same point? depending on the size of the barr it would be an extreme back cut but it might work and of the barr wrecked the prop you have nothing to lose by trying, I've back cut many props but never tried a bar cut because it seems weak and I've folded or broken enough blades as it is.

[martno1fan]

Hey Paul nice website,very informative ,i too prefer back cuts to barr cuts.
Mart