Prop modification question

[DevonG]

Hey guys quick question. Can I trim what I suspect to be a cruiser prop into more of a performance prop? I have all the necessary tools to do it accurately. The reason I ask is one was givin to me and I just destroyed my prop on the jetties. The cruiser prop is correct size and pitch it just cavitates at about 3500 rpm. Big round fins on it ya know. Thanks for the help!

 

[Frank Acampora]

Re: Prop modification question

Based on older Chrysler props that used the same blank casting for a regular cruising prop and were cut to a different blade profile for a cleaver prop I would say (qualified) yes, it is possible. HOWEVER-- a little knowledge is a dangerous thing and the design engineers put in a lot of hours tweaking any prop. More than likely, the possibility is that you will ruin the prop.

 

[tazrig]

Re: Prop modification question

+1^^^ I wouldn't try it.

 

[jimmbo]

Re: Prop modification question

Like trying to turn a sows ear into a silk purse.

 

[DevonG]

Re: Prop modification question

Lol. Thanks. I may try amd trim it.. it was free after all.. if it is a failure I guess im buying a prop.

 

[Ned L]

Re: Prop modification question

Uhm, ..... This is one place where I would say that if you have to ask the question you do not have the tools or knowledge for the job. (I suppose you could change the diameter on something like a machining center without really understanding what you are doing, but you would probably not end up with an optimal re-profiled blade tip shape. If you ask the question I'll bet you don't have the equipment to change the pitch.) But, if as you said its a free prop you can try anything.

 

[airshot]

Re: Prop modification question

If you get it to far out of shape and balance it may be more than the prop that gets trashed. Slight trimming for nicks etc is one thing but reshapping blades is another.

 

[jestor68]

Re: Prop modification question

Hey guys quick question. Can I trim what I suspect to be a cruiser prop into more of a performance prop

Not unless you have the correct pitch block for the particular propeller that you're trying to turn it into.

Props are cast with a particular progression of pitch across the blade.

If you think that you can duplicate that precision by hand, have at it.

Let us know how it turns out. :facepalm:

 

[tazrig]

Re: Prop modification question

Lol. Thanks. I may try amd trim it.. it was free after all.. if it is a failure I guess im buying a prop.

And quite possibly lower end seals and what ever else you damage or shake loose in the lower end from putting on an out of balance prop. :facepalm::facepalm::facepalm:

 

[DevonG]

Re: Prop modification question

Thanks for all of the positive input guys. And yes I have zero knowledge of any prop modifications. I have been doing metal fabrication for the last 15 years though. Anywho, I trimmed it into the desired shape. checked Balance at +/- 1/10th oz. it runs great but still cavitates at high rpm. Through a lot of research I have come to the conclusion that this is because of the trailing edge of the fins not having a slight curve at the end, not the shape of the fins as I originally thought. Im assuming they are just losing "traction" at high rpms due to lack of this curve. I will play with it soon and check back here.

 

[Frank Acampora]

Re: Prop modification question

You are most likely experiencing ventilation, not cavitation. Bending the trailing edge of the blades is called cupping and it does increase the props resistance to both ventilation and cavitation. the cup should have a sharp edge for best performance.

The degree of cup and the amount of blade cupped both influence performance.