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Twill · 19-08-2015, 08:44

I want to replace my prop on my Ticon 30 with a folding prop. It has a 2 blade on it at the moment. Will a 3 blade help my boat speed under power?

Cheechako · 19-08-2015, 08:59

a prop of proper size and pitch should get you to hull speed. If you are not getting there now you are not propped properly. A folding prop will likely be less efficient than your fixed 2 blade. (There may be some exceptions now days.) A feathering prop may be more efficient than your 2 blade.

exMaggieDrum · 19-08-2015, 11:14

Read the other thread about folding versus feathering props and read the article about them by Yacht Monthly that is linked there. According to Flexofold, and the article backs this up, their two bladed prop can push the boat faster for a given rpm but the three bladed can give better acceleration and quicker stopping. Go figure.

**a64pilot** · 19-08-2015, 11:56

I know you can't always compare airplane and boat props, but in aircraft, the more the blades, the smoother the prop vibration wise, but also it's slower and less efficient.
More blades = more drag.
I think with very few exceptions, a feathering prop is actually a pretty inefficient prop, because it's blades are flat, no airfoil. You may can overcome this inefficiency by being able to precisely match the pitch to your boat as many are adjustable pitch wise, but it is an inherently inefficient blade profile.

**Jim Cate** · 19-08-2015, 13:01

Quote:

Originally Posted by Cheechako

a prop of proper size and pitch should get you to hull speed. If you are not getting there now you are not propped properly. A folding prop will likely be less efficient than your fixed 2 blade. (There may be some exceptions now days.) A feathering prop may be more efficient than your 2 blade.

Cheech, you have this quite backwards: a feathering prop is LESS efficient than either a folding or fixed prop (assuming decent design for all three types). this is inherently true due to the lack of twist in the feathering prop's blades. We've been over this effect many times here on CF... I'm surprised it keeps coming up.

Jim

Twill · 20-08-2015, 09:55

I would like to use a fixed prop. I don't really care about the slight lose of speed under sail. I need more speed under power. I can only get about 4 knots at the moment (5) with a clean bottom (maybe). The prop on my T30 is about 12 inches across. Will a three bladed prop give me another knot? or not...(ha ha). I do like the idea of smoother ride with the three blades. What is the best way to proceed? Thanks, you guys sure make this fun. I appreciate all the feed back.

leftbrainstuff · 20-08-2015, 10:02

It would help if you can describe your current prop in terms of the technical specs.

Its not as simple,as just comparing props. There are tradeoffs. The system comprises hull, engine torque curve, drive reduction, prop specs and hull type and hydronamic dimensions.

Of course you can just try props as long as you're prepared for many haulouts and power tests.

If you're lucky enough to find someone with the exact combination you can learn from them.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

fstbttms · 20-08-2015, 10:03

Quote:

Originally Posted by leftbrainstuff

Of course you can just try props as long as you're prepared for many haulouts and powerntests.

Why would you haul out simply to swap a prop?

leftbrainstuff · 20-08-2015, 10:05

Quote:

Originally Posted by fstbttms

Why would you haul out simply to swap a prop?

You can change props in the water if you like.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

fstbttms · 20-08-2015, 10:06

Quote:

Originally Posted by leftbrainstuff

You can change props in the water if you like.

Yes, I know. I do it for a living. And I guarantee it is faster, cheaper and more convenient than hauling out to do it.

Cheechako · 20-08-2015, 10:08

Quote:

Originally Posted by Jim Cate

Cheech, you have this quite backwards: a feathering prop is LESS efficient than either a folding or fixed prop (assuming decent design for all three types). this is inherently true due to the lack of twist in the feathering prop's blades. We've been over this effect many times here on CF... I'm surprised it keeps coming up.

Jim

It depends. The old Gori folding used on many racing boats were terrible and did not push the boat thru chop or work in reverse hardly at all.
A feathering Max Prop does both better than a fixed blade. The devil is in the details. You theory may be right but your reality isn't! just sayin....

Twill · 20-08-2015, 10:20

I will be hauling out in the fall to do some other bottom work anyway> Can I get a consensus...Will a three blade make me faster ?? if not I will save myself the trouble and stay with the old prop. My boat is 9800 pounds a 4'11' fin and spade rudder. The prop shaft is old school one support strut. I have a slight vibration at moderate RPM very little at idle and very little at full power. My engine is a Yanmar 2 cylinder 16 hp. Thanks

deblen · 20-08-2015, 10:31

Quote:

Originally Posted by Twill

I would like to use a fixed prop. I don't really care about the slight lose of speed under sail. I need more speed under power. I can only get about 4 knots at the moment (5) with a clean bottom (maybe). The prop on my T30 is about 12 inches across. Will a three bladed prop give me another knot? or not...(ha ha). I do like the idea of smoother ride with the three blades. What is the best way to proceed? Thanks, you guys sure make this fun. I appreciate all the feed back.

A 3 blade will give you quicker acceleration & stopping/reversing.That is worth a lot in maneuvering.
Hull speed limits your top speed,unless you have more HP than the avg sailboat of similar length. You can push a knot or so beyond hull speed with enough HP,but you pay in fuel,etc.

My 28Ft pilothouse motorsailer has a hull speed of 6.2 kts. The sails will drive it that fast,with enough wind,etc,etc.
So would a 12-15HP diesel with 2 blade-the standard for 30 ft. sailboats.It would take awhile to reach hull speed,but it would get there.

I have 28HP 2.x reduction & 17D x 14P 3 blade & can reach 7.3kts at W.O.T., & get up there fairly quick.
Lots of squatting & extra fuel & the engine probably wouldn't last as long.
On the other hand,I can cruise at hull speed at 60% throttle/RPMs,so fuel consumption is excellent-1.5 Ltr/hr

It's a trade-off. 3 blades will cut your sailing speed by 1/2 + kts.,but you will be able to accelerate,dock,stop & maneuver with a lot more confidence.

If you go 3 blade,you will have to calculate a new dia. & pitch based on HP & reduction gear ratio.
Find a well respected prop shop & google for info/feedback on your boat model with 3 blade.

Cheers/Len