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-   -   Prop Cup (https://www.offshoreonly.com/forums/prop-talk/339999-prop-cup.html)

bbladesprops 08-15-2016 04:47 PM


Originally Posted by ezrizer (Post 4471231)
Yeah, I'm with you on most of that Frick, If I didn't have props that were already dialed in I would probably just have mine bent up and that would be that, still might do it anyway... I just wish I could get an answer on what the negative impacts of cup might be.

Yes, I've been pretty busy. I'll try to call tomorrow.

Brett

bbladesprops 08-15-2016 04:49 PM


Originally Posted by frickstyle (Post 4471250)
Someone who knows alot more about it than me will chime in.

Just considering the physics of it, seems that it will reduce overall prop slippage, and bring down your RPM due to the fact you are "grabbing" more water. Not sure if you would actually lose much top end, and the prop should be more efficient, proving more thrust, in turn requiring more hp to turn it to max or target RPM. IE: you may lose upper RPM, but gain back a little because you reduced the slippage. maybe? :confused:

You are correct on your physics.
Also, cup affect the prop differently depending on where you add it. Very important....the amount of cup used and where. Additionally, different prop designs respond differently to cup too.

Brett

Brett

ICDEDPPL 10-12-2016 09:17 AM

Brett, 2 props with the same amount of cup and pitch if one is an 3/4 to and inch smaller diameter would the smaller prop be worse at planing??

Most props I`ve tried just burn a hole in the water and will not get this heavy beast on plane until my current new Mercury labbed 17 3/4 X 27 . gets up no issues.
Ive run out of pitch and need to move up but planing is a huge concern. I`ve been finding some smaller props hence my question.

bbladesprops 10-12-2016 11:56 AM


Originally Posted by ICDEDPPL (Post 4490734)
Brett, 2 props with the same amount of cup and pitch if one is an 3/4 to and inch smaller diameter would the smaller prop be worse at planing??

Most props I`ve tried just burn a hole in the water and will not get this heavy beast on plane until my current new Mercury labbed 17 3/4 X 27 . gets up no issues.
Ive run out of pitch and need to move up but planing is a huge concern. I`ve been finding some smaller props hence my question.

Yes the smaller diameter would be worse at planning if indeed you had the power to pull the larger diameter. More blade area will create more thrust.
It is harder to find propellers at 17.5 and above diameters.

Brett

ICDEDPPL 10-12-2016 05:13 PM

It is harder to find 17.5" + 4 blades.
I would imagine if I did go down to a 17" prop but went to a 5 blade instead of 4 that should help things? ( more blade area)

frickstyle 10-13-2016 06:53 AM

Dan, what pitch are you looking for? I have two sets, you're welcome to try one.

bbladesprops 10-13-2016 12:06 PM


Originally Posted by ICDEDPPL (Post 4490847)
It is harder to find 17.5" + 4 blades.
I would imagine if I did go down to a 17" prop but went to a 5 blade instead of 4 that should help things? ( more blade area)

Yes, 5 blades are still being made and do offer better planning in most cases.
I am supposed to be getting a number of 4 blade prop sets in for CR sales. Should be on the web site soon.

Brett

ICDEDPPL 10-13-2016 06:06 PM

Frickstyle , sent you a PM

MILD THUNDER 03-11-2017 10:51 AM


Originally Posted by bbladesprops (Post 4470251)
Grinding in the cup is a complete no-no! I almost laugh and then cringe when I see that. The water can't flow correctly when you grind out a hollow for the water to run into it. We add cup via heat, dies hammers and many moons of experience.
Call me and we can talk about your issues.

Brett

Is that how you add cup to a #6 style cleaver prop? I was always under the impression the blades on them were too thick to try and bend to shape, and thats why they grind out material on those style props? At least thats what mercury racing says regarding those cleaver style props.

bbladesprops 03-13-2017 06:32 PM


Originally Posted by MILD THUNDER (Post 4536502)
Is that how you add cup to a #6 style cleaver prop? I was always under the impression the blades on them were too thick to try and bend to shape, and thats why they grind out material on those style props? At least thats what mercury racing says regarding those cleaver style props.

Really, who at Mercury Racing told you that?
If Mercury Racing told you they grind out a hollow to add cup, Mercury Racing was mistaken in your question. I can promise you that unless something we developed over 2 decades ago has changed. And that is not the case.
You can bend and shape #3,4,5,6 drive propellers to some degree. It takes knowledge, background and talent. Some of that may have been lost or is being changed for easier production. But, it can be done.
Let's face it, the custom propeller ability is a fading art. Look at Mercury Racing, they don't offer custom propeller work anymore like when Dennis and I were managing the Laboratory. They offer one size fits all options now.

All the custom propellers we build at BBLADES come to you with 90 years of experience molding a handcrafted one off, if necessary, product.

Brett


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