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View Full Version : Labbed Prop? What do they do??



Greg Maier
08-25-2002, 08:52 PM
I'm trying to understand the labbing of a prop. What is involved with labbing a prop? Why does it perform better? I've heard that the blades are thinned, does this weaken the prop?

HyperDonzi
08-25-2002, 09:13 PM
lab finish means not polished, polishing will weaken the blades in areas that DO NOT need to be weakend.

well, that is how i always read.

G - FORCE 88
08-25-2002, 09:46 PM
Greg
My .02 Labbed props are thinned at the blades to make themn sharper and to lighter to make them spin faster and more efficiently through the water giving on avg. a 2-3 mph increase in speed as well 100- 400 gain in rpm's. They of course become more fragile but they wont just break under normal use.. if you hit soemthing they will stand less of a chance. Labbed props should only be done by a reputable place...it is tricky and around $175 per blade..try a place called "Throttle Up" they do all the labbing for Donzi Racing..look them up on the net and ask for Julie (very very knowledgeable) :D :D

oldLenny
08-25-2002, 09:48 PM
Something I found from Hydomotive Engineering

"As a company, we are often asked about the benefits of lab finishing or blueprinting propellers. We offer the following information in an effort to enable you to weigh the advantages and disadvantages for yourself and make an informed decision.

Both lab finishing and blueprinting refer to the process used to insure the accuracy of the propeller rake angle, pitch, progression, pitch variation and cup. This hand process involves thinning the blades and sharpening the leading edges.

The advantage of blueprinting is that it reduces the horsepower required to turn the propeller and generates more usable horsepower for thrust. On an accurate, well-built propeller the speed gain may be 2-3 miles per hour. On a lesser quality propeller, the increase may be 3-4 miles per hour.

The disadvantages of this same thinning and sharpening are greatly reduced blade strength, fatigue resistance, and being more subjective to stress risers occurring at the sharpened leading edge. A sharp leading edge is very prone to minute nicks which create stress risers. These stress risers often propagate cracks that originate from the nick at the leading edge and work their way through the blade. The same thing is true for any nicks at the trailing edge. It is for this reason that we at Hydromotive grind our trailing edges from hub to tip rather than across the blade, thus eliminating any potential stress risers. Reducing the blade thickness from a 1/4" to a 1/8" (1/2 the original thickness) does not reduce the strength by 50%, but actually reduces the blade strength to 12% of the original. Consequently, we can not warrant any propeller that has been lab finished or blueprinted.

Cost is yet another factor to consider. Hydromotive Engineering offers blueprinting to our own propellers as well as those of our competitors. Some of our competitors are currently charging 50% more than Hydromotive charges for the service.

No matter which source you choose, we encourage you to carefully weigh all the factors when deciding whether to have this enhancement performed. Keep in mind that blueprinting, no matter by whom it’s performed, voids the warranty of any propeller."

If you decide to proceed with blueprinting by Hydromotive Engineering, it’s as simple as shipping us your propeller via UPS, or whatever means is most convenient for you. Please expect approximately a two to three-week turnaround, with seasonal delays possible.

blackhawk
08-26-2002, 12:09 AM
Greg, I have been doing some homework on this myself. After loosing a blade last year I too do not want my blades thinned too much. I was told that "proper" labbing only the leading edge is thinned and it should not weaken the blades.

Also, on a blackhawk drive there are 6 blades spinning instead of 3 or 4 and they are spinning in opposite directions so blueprinting them can yield even better results than a single prop. I am going to bite the bullet and get mine done this winter. I just need to decide on who I am going to have do it.

Greg Maier
08-26-2002, 05:41 AM
Thanks for the info. I have first hand experience with nicks in the blade and stress risers. I might leave the props alone for now. On another note, I put on my 31's this weekend, replacing the 29's that had developed a crack. The 31's make the Blackhawk much easier to handle. I'm not sure why there is a difference. Plus, she throws a much nicer roostertail with the 31's !

Forrest
08-26-2002, 10:51 AM
If you think your prop will ever hit anything other than water, then don't get it labbed. Even a small nick on the leading edge of a thinned blade can cause just enough of a stress riser to start a crack which will render the prop useless. Scuff the bottom with that expensive labbed prop, even a sandy bottom, and it will most likely suffer damage requiring repair or replacement.

blackhawk
08-26-2002, 12:44 PM
Greg, the boat probably handles better because you are probably trimming a little higher to get your rpms. Which would also explain the "better" roostertail. If I remember right, you were bouncing off the limiter with the 29's so you didn't have as much positive trim. What kind of speed and RPM's are you turning with the 31's?

Back to the labbing. One of the place I talked to also stated they could do a blueprint and balance only which may be good for a couple mph.

Greg Maier
08-26-2002, 01:38 PM
I hit about 71 mph, but I was in an enclosed inlet and I didn't really have time to play with the trim and planes. It was 90 degrees with a full tank also. I was running about 4600 at 71 mph. I think it had a lot more but I didn't have any more room. But, in general, it felt much more controllable.