why don't more boats have v-drives?

[tcm]

why don\'t more boats have v-drives?

nick and coliholic were getting to this.

Background : a boat that has "V-drives" has the eangines mounted well back in the hull (like with an outdrive) but the angine are "wrong way round" - the engine crankshaft comes out at the bow end of the engine and points slightly downwards at an angle to reachj the gearbox. The gear box output reverses the direction (aft) and send it down wards again, out of the hull to the prop- hence the input and output to/from gearbox make the shape of a letter V, hence V-drives.

Now, the jolly good thing bout all this is that the arrangement has all the best aspects of outdrives (saves space) and all the good aspects of shaft drive (has rudders, easier to handle).

Even better, V drives actually cure the negative aspects of outdrives (no gearboxes out the back getting wrecked) and cures the negative aspects of shaft drive - needing a big engineroom for good access, or having to rip open cupboards beds etc in aft cabin to reach stern glands etc.

So, why don't more boats usem? Are they meg-expensive? or crap? yes, the leopard has them, but no I've never driven a leopard, yet.

Discuss

 

[Guest]

Re: why don\'t more boats have v-drives?

Hi TCM

I reckon the reason is probably a combination of cost and increased engineering complexity. Presumably, just as you need a gearbox to suit you engine/s you would need a V-box to suit them also, although ZF are now doing 2 and 3 speed V-gearboxes to kill these 2 birds with one stone. Also, one would have to align not just engine, shaft, stern gland and P-bracket but also the gearbox ( = increased installation work).

The main "plus"s are a) weight distribution, if you need to shift the C of G aft (beneficial only in certain cases) and mainly b) getting the engines nicely out of the way aft to free up accomodation space.

The benefits you describe are pretty much correct, but the V-box still leaves you with a similar downward shaft angle, which is inefficient. Also, the actual shaft exits the hull in a pretty much identical position to a conventional shaft so no benefit there.

I am just in the process of patenting an idea which I hope will prove more efficient than any of the above - especially in high performance boats - whilst allowing increased flexibility in positioning the engines.

I will of course tell you all about it once it is protected, and if it works I hope you will see it all over the place.

Nick



Nick

 

[burgundyben]

Re: why don\'t more boats have v-drives?

So wots the opinion of the transom drive a la Lancing Marine? Beneftis of both?

 

[tcm]

Re: explain transom drive?

new one on me...

 

[BarryD]

Re: explain transom drive?

Also interested - was going to ask but everytime I post BurgendyBen points out I'm an idiot (as per my profile) which is true for boating.

Barry D

 

[tcm]

Re: alignement

keep us posted about your mega idea when protected.

Wouldn't/doesn't any one them use some flexible coupling to avoid having to line up all of the componanets as you suggest? Or are flexy couplings a ton of money too?

 

[tcm]

Re: explain transom drive?

http://www.lancingmarine.com/lmtrans.html


but slightly different subject than v-drives...

 

[BarryD]

Looks very good...

Presumably with the rudder configuration then the boat would have more steerage when the gearbox is not engaged? Too expensive a conversion for MVII unless of course I rip the out-drive off during the summer <G>. Thanks for the pointer TCM.

Barry D

 

[Guest]

Re: alignement

They aren't so flexible as to remove the need for careful alignment, more to reduce bearing wear when the engine twists under torque etc.

Nick

Nick

 

[milltech]

Re: why don\'t more boats have v-drives?

Plus a significant reduction in wheelhouse engine noise. I first saw this arrangement on a JCL Mirage and very good it looked too. Made room for 2nd and 3rd cabin off forward stairwell and a big central lazarette. Well ahead of its time I thought.

Boat Junkie

 

[Guest]

Re: why don\'t more boats have v-drives?

Similar in principle to the Pulse Drive too, except with that one it is mounted under an extension "box" on the transom, similar to some Trimax surface-piercing prop installation, but in this case it also incorporates exhasts and the whole lot can be trimmed up and down. I guess the advantage is transom lift generated by the box itself.
Arneson drives similar but without the box. This Transom drive seems similar but lacks the trimming movement.

How did this discussion start life? Is someone seriously considering re-locating engines / new propulsion system?

Nick

Nick

 

[Guest]

You can\'t be Nick - I\'m Nick!

Interesting you have an idea which you would like to patent. I have had a few myself and, actually the ideal drive would be hydraulic so the engine would drive a hydraulic motor on the shafts. The engine(s) could then be positioned anywhere that suited, even transverse. However, every time I articulate these things I get shouted down as thick.

I also once had an idea about having an electric motor driving a central shaft with a folding yacht style prop, driven by the vessel's genny and used for extended low speed passages such as, for example, European waterway ventures. However, that one was also consigned to the fundamentally stupid bin by the panel.

I'll never be an inventor!

The real Nick

 

[paulineb]

Girly kitten-type question

Does my boat have v-drives ?

Pxx

 

[tcm]

Women: For Pity\'s Sake Know Your Place!

almost certainly not, most likely has shaft drives.

I agree, kittens are very fluffy and cute.

 

[jfm]

Re: why don\'t more boats have v-drives?

Guesswork, but I think it's because:

cost - a Vee gearbox is much more spesive to make than a straight thru. Bevelled gears, and handed. The straight thru reduction boxes on a regular boat have only about 100 components, pretty easy to make, and are not handed becuase they are indifferent whether run in forward or reverse. Also come preassembled onto engine whereas Vee has to be aligned and fitted sepratly

space - a Vee moves the 'gine right back, into the lazarette area. In a LS23 type boat that's good, because the space in the middle of the hull that is freed up has standing headroom. But in say a 40foot flybridge, the space under the saloon is too low, so nothing is gained by moving the 'gines back

The exception to the above is the sseeker manhattan 44, which had vees. I do not know what they did with the space under the saloon floor but no way was it standing headroom. Mind you, Peter Powell and Anthea Turner bort boat#1, and she was quite short I think.

Vees seem to suit the Italians, because they offer choice of Arnesons, KaMeWas and shafts on same boat sometimes. The Arnies and jets need the engine room right aft, and using Vees allows them to keep the engine room right aft for the shaft versions too

Let's ask the fairline boys at their next customer lunch

 

[Col]

Re: why don\'t more boats have v-drives?

Have you seen the MTT drives ?As fitted to speedturbine boats, lovely bit of kit, trimmable to !

http://n2speedturbineboats.com/

click on 2001 pics for close up.

 

[jfm]

Re MTT drives

These are the same in principle as Trimax, Arneson, SonnyLevis, etc. See the one tcm is sandpapering in the boatsontheweb/leopard2 pics. Strange thing is, the MTT ones steer with rudders instead of moving the whole drive left and right. Seems odd, the whole idea of a surface drive is to reduce appendage drag, then they go and attach a big rudder to drag thru the water. Wonder why?

 

[milltech]

Re: You can\'t be Nick - I\'m Nick!

I don't think that's an entirely new concept. Somewhere there is a converted Barnett lifeboat called The Lady Jane, actually come to think of it I know where she is, on the foreshore in one of those pretty creekside villages near Chichester. She was being refurbished, slowly, the last time I looked.

Anyway, back to the point, she has hydraulic drives so the two Gardners don't have to line up. It allowed the convertor to relocate the engines under a new MFV style wheelhouse so he could have two separate cabins forward. It worked well and was pretty. I'd buy her tomorrow but I think putting her back in reasonable condition would be more than a labour of love.

Boat Junkie

 

[Col]

Re: Re MTT drives

Yeh, I expect the rudder is to crispen up the steering, but on the other hand it does trim up and down with the drive.

 

[jfm]

Will the real Nick plse stand up!

The reason (original) Nick's hydraulic drive suggestion met wiv a bit of criticism was (a) whiney noise of hydraulics and (b) massive inefficiency in hydraulic pumps and motors. Hydraulics are suitable where you need to have distance between the power source and the power delivery, but efficiency doesn't matter. Eg a JCB. In a boat, much better to fix the engine directly to the shaft and save a bit of planet.