Ganging Outboards - Does it work?

Let me ruminate on this.

Maybe its just me but I don't like the idea of wells in the hull..extra work and more chance of trouble

 

I agree with WestVan - the existing tilt/trim doesn't give enough angle.

Bear in mind the extra force arising form the lengthened 'lever' also. Maybe replace the trim/tilt with a long hydraulic ram that attaches half way done the leg, and at the other end attaches forward of the powerhead to make a much larger triangle that can withstand both forward and reverse thrust from the props. The existing trim/tilt hydraulic pump could likely be used for the new ram.

 

I have not heard good yanmar diesel outboards.
Someone told me that they do more but I'm not sure.
Engine you want, is made in Italy, a few miles from me.

If I can give you an idea, since you already have an important generator on board, applie to an hydraulic motor a propeller.

Much less weight, no maintenance, low cost.

Only problem, pipes..
If you do not even want the pipes, you can use an electric motor more than IP67.
Here is beginning to be fashionable.

 

Well, that convenient seat in the corner of the stern platform is actually a box covering the powerhead. If you want to cover the leg as well (at least from the top) then have a shelf butted against the hull. The seat could then become a sun lounge.....

 

CatBuilder, are you going to mount the 60hp outboard at the end of one sponson and the 9.9 on the opposite side? If you have other thoughts how will you assure proper water flow to the props? Using 25" long shafts at the end of each sponson you should be able to tilt both engines up clear of the water surface in calm waters. I guess I'm not sure what you are trying to achieve. For sure they would dip in rolling seas but that is not like continuous drag.

 

Cat ..what is the distance from the calm water to the bottom of the aft beam? Two feet or so.

As an aside,I really had a thing for this cat 10 years ago....it was a distress sale and sold for $650k I think.

http://www.yachtsgreece.com/maia-180=pageid=1&ordervar=0

 

WestVanHan Post #151:

You get 71 degrees trim angle with the stock engine.

http://www.yamahaoutboards.com/outboards/High-Thrust/specifications

Plenty to take the props up out of the water. 90 isn't needed. I just need them out of the water and basically up enough that they don't drag on moderate seas. In crazy conditions, a little drag can be a good thing.

To be clear, these would no longer be in the hull. I agree. I don't like that ether, but wasn't finding a way to keep the power head dry while keeping the prop way down in the water (but still being able to retract it). These could now be mounted on the side of each hull, by the spot the bridgedeck joins the hull. Sort of like these outboards - see the prop under the bridgedeck? On this model, the put the outboards into a big box that lives in the bridgedeck tunnel area and use the built in trim/tilt to angle them up and down.



Brian Post #151:

Again, I agree. I had been thinking about that while I was out laser leveling my mold. There would be some considerable increases in the lever action on the mounting area as well as a bending load on the new leg extension. It would all have to be beefed up. I'd have to see what the stock trim/tilt could do as well as worry about reverse. Definitely.

Brian #154:

Yup. Just have to figure all that out. I already had the cockpit layout done, but I can probably change some things around a bit. I think if I paint the leg the same color as the hull it will blend in well, so the shelf may not be needed. I'll have to work through that.

Rasor#155:

No outboards at the end of each hull (extreme transom) for two reasons... 1) I have kickup rudders. They can't go there. 2) They would aerate and dunk all the time underway in any sort of sea. The absolute stern is the worst possible place to put an outboard, except maybe the absolute bow.

Yes, it's a high thrust 60 on one hull and a high thrust 9.9 on the other. They will both have clear water coming at them, being mounted under the bridgedeck. No issues there.

They don't make 25" long shaft high thrust outboards in anything but a 9.9. Kinda sucks but that's how it is.


WestVanHan #156:

Hey! What do you think, I'm building a piece of crap?!? It's over 3 feet from the water to the bridgedeck.

Re the link: She's a pretty boat. Nice curves! Nice slender hulls too

 

I also had a thing for the big shuttleworths...especially Bandaloop with the covered rear deck.

http://www.2hulls.com/usedcatamaran-2005/Bandaloop.html

 

The Choy cats (for example) used to use super extended outboard legs. There used to be a couple of firms that made them. Or you could buy leg inserts yourself and keep adding them.

IIRC David Oakely in the UK used to do it

http://www.outboards-direct.co.uk/home.html

He maybe able to give you some ideas, even if you got the mods done in the USA

One problem was the driveshafts became very long and could whip. I was on a cat once where the shaft snapped when the engine over-revved. I think the water pumps might struggle as well

When I was in the USSR we went on a 40ft cat that had a similar superlong outboard leg. The photo on my Biography page shows the boat, but unfortunately not the leg

We were moored next to Bandaloop in Guatemala about 6 years ago. I think it is still there

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

High thrust is a gearing of 2.33/1 so find a 25" (probably a 2 stroke) and require that gearing.

 

There has to be a way to build your own leg,or extend one.

 

Extended legs would be custom items < Big bucks .

Why not a simple sea saw , the outboard is on the end of a fancy plank and simply swung 90deg to clear the water.?

It would also seem less engineering to simply lift the OB straight up so the power head is at deck level under sail, and simply lowered to operate .

Either way the gear would be on the centerline .

Two engines one large one small, two sea saws or two jacking legs.

KISS!

FF

 

Good points, Fred. I woke up thinking the same thing. Modifying brand new outboards will void the warranty and I don't know if I can live with that.

Does anyone know of a 3 piece, telescoping slide type thing that I can attach to the bridgedeck and that will take a 60hp engine in forward and reverse?

I still think this is very, very close to an ideal outboard solution.

 

After tossing around ideas,I still think my fold up mechanism is the simplest way to store and lift

http://www.boatdesign.net/forums/at...s-does-work-screenhunter_02-jan.-29-15.34.jpg

 

What about having both outboards in one hull?

-the gas is in one area
-using one at a time anyways
-less hull work.
-other hull can be for the power/HVAC


I can envision a cassette that would pull both or one engine up...just some levers and a couple linkages.

I'll ponder this a day or two.