Cat prop size and pitch

[captlloyd]

Can someone tell me what the prop size and pitch would be for a 38-40ft. catamaran running approx. 30 hp diesels. I understand there are variables but would appreciate a ball-park idea or what you are running. Gracias.

[jdazey]

You're right, there are a lot of variables, weight and hull shape among them. If you have a specific model in mind, you'll get a better answer.

[captlloyd]

Originally Posted by jdazey

You're right, there are a lot of variables, weight and hull shape among them. If you have a specific model in mind, you'll get a better answer.

OK, how about 38FT Lagoon? Thanks for your reply.

[44'cruisingcat]

There's bound to be someone with a 38 ft Lagoon who can help you. Maybe ask the question in the Lagoon forum?

[akprb]

Yes a lot of variables. Ours was severely over pitched when purchased (1800RPM max). We had a 3 blade max prop that allowed adjusting the pitch (not a straight forward task but doable).

We found Yanmar's specs for max rpm for our 3J series engines (27hp each) then adjusted pitch accordingly until we reached it. Actually did this over three seasons. First year we took 4 degrees out then two degrees each subsequent haul out until happy.

Pretty sure there are faster ways to get closer but we were a bit lazy on this one and got the job done eventually.

Catamaran Storm Tactics | sailingohana

[duefocena]

Originally Posted by captlloyd

Can someone tell me what the prop size and pitch would be for a 38-40ft. catamaran running approx. 30 hp diesels. I understand there are variables but would appreciate a ball-park idea or what you are running. Gracias.

I have Autoprops on a 42' Lagoon and am very pleased. Replacing two blade props, these have the same thrust in fwd and rev. Really handy when backing down on a following breeze or current. Never had them "hang up" like other feathering props I've owned. Loaded in no current @ 1,800 revs I move at 7kts-8kts.
Ab Marine has a good website and they are knowledgable to Lagoon props.
ABmarine.com
From their web site:
"The Autoprop is an automatically self-pitching feathering propeller that maintains maximum efficiency at all times. It has a higher efficiency over a wider range of RPM settings, producing higher speeds with lower engine RPMs."

[Aqualibrium]

You really should make a decision re folding or feathering props.

I prefer feathering as you get 100% astern propulsion though many owners of folding props seem happy with astern performance but folding props should be 3 bladed.

From my research the Autoprop isnt recommended if your boat will sail above 14knots.

Won't be a problem with a Lagoon

[yeloya]

For L 380 and 30 HP, 17X12 or 13 (folding 3 blades) would do the job.


Cheers


Yeloya

[takeabow40]

send kiwi props an email or fill out calculator form on their website I like the fact they are composite and you can buy spare blades , not possible with some other brands

[EWOL Props]

Hi captlloyd, you can run your own calculation at this link: http://www.ewoltech.it/index.php?rou...ory&path=65_66

If it doesn't work directly, just copy and paste on your browser.

Enjoy !

Originally Posted by captlloyd

Can someone tell me what the prop size and pitch would be for a 38-40ft. catamaran running approx. 30 hp diesels. I understand there are variables but would appreciate a ball-park idea or what you are running. Gracias.

[atoll]

prout elite 37 ft ,single engine use
for 32 hp 14x14 with 2.6:1 gear box
or 14x10-11 with 2:1gear box
or 13x8 with 1.6:1 box

[captlloyd]

Thanks for all the great replies.

[Fast Cat]

What work well is setting pitch so at RPM of about 2700-2800 the point at which the fuel to power stops going up so steep on the fuel to RPM graph .
This give good power to fuel consumption and engine will still go up in Rpm but takes a while and gets to about 3000 Rpm.
Has worked well for me ,I have had a Privelege 49', Catana 471 and now an Outremer 55.
Just a sugestion