For Sale

I replaced my 4-blade prop with a 5-blade prop. My old 4-blade is now for sale.

4-blade

ZF - FPS

Bronze

D38 x P28.5 Left Hand

EAR: 08 KCA

#18245

3" Tapered Shaft

PropSpeed applied

Back from Mukilteo Prop Shop: no dings, properly balanced, and tuned.

This was my spare, but I'm losing my storage and it has to go! Please help me free-up space!!!

A new prop is $15k. Asking $500.

Located in Anacortes, WA

Safe Adventuring,

Peter C. Adams

m/v Blue Redd 5726

To answer a few questions.

Blue Redd has a QSM-11 535 engine.

I’ve been on a mission to eliminate vibration and noise. Switching from the 4-blade to the 5-blade prop was part of that. The 5-blade is smoother and quieter. But interestingly (at least to me), it has turned out to be slightly less fuel efficient than my 4-blade.

I surmised that on the 4-blade, when 2 of the blades were vertical they were being shadowed by the keel and experienced lower pressures, while the other two were perpendicular to the keel and experienced lower pressures higher pressure. That caused a thrust differential, hence vibration at every 1/4 revolution. It’s only theory, as I never measured the actual pressures (not even sure how I would do that). On the 5-blade prop, only 1 of the 5 blades would be shadowed by the keel at any one time…

Anyway, that was the reason for the change and I’m satisfied with the results. Was it worth the $15k? No way! But it is what it is…

Safe Adventuring,

Peter C. Adams

m/v Blue Redd 5726

I a

Should add a comment about thruster in reverse too. That was a very noticeable improvement over the 4-blade. I don’t know about your boating, but I don’t drive around backwards much, so that wasn’t something I was after. I suppose if I ever have to get unstuck from something shallow I may change my mind on that one.

Safe Adventuring,

Peter C. Adams

m/v Blue Redd 5726

I will try to sneak in my useless comments about number of blades. I was surprised to find the aircraft that switched from the old two blade 1970s propellers to a modern 3 blade would loose top end speed. They gained climb rate, and lowered vibration, but gave up what airplanes are always looking for. Speed and efficiency.

My understanding in aircraft at least is adding blades is a function of harnessing increased horsepower. With our slow speeds and low horsepower, I would assume a move back to 3 blades would have done the same thing for you as going to 5 blades. Either way would have cost you so it’s an intellectual exercise, not a recommendation. Given the choice I’d have 5 blades too because it looks cool.

The Iowa battleships have different blade counts inboard vs outboard. That was to solve a vibration problem that was discovered after the build. So it’s certainly an idea to try.

If nobody buys your prop, I will. I’d hang it on the wall for that price. Better to go to a user first though so someone has a spare or replacement.

Dan and Bethany Moore

Blue Phoenix - 2008 Selene 59-17

Because of the many long days we ran/run, we were equally invested in minimizing vibration. In 2008, we hired Eg Hagemann, a prominent marine architect, to study our hull and prop solution. His recommendation included a 5-blade prop with the caveat that this could reduce vibration by ~20%. Further, to maintain efficiency, we needed to match the DAR as closely as possible or to reduce it slightly to possibly improve efficiency - all else being equal. “Different prop vendor designs differ in power absorption and thrust, given the same spec in diameter and pitch.” We reduced the DAR from .7 to .65, which in the scope of such an effort is negligible, and no real change in efficiency was noted. We could feel the improvement in vibration, but it wasn’t remarkable. Our original 4-blade Hung-Shen makes a great yard ornament and is not for sale.

Carl & Melody

MV Ellipsis 5906