Catamarans: better with an engine in each hull, or a retractable sail-drive?

[geem]

I have owned both. Frankly the sillette legs are a bunch of **** engineering wise. They are always in need of service regarding pivot points and locking mechanism and are very very noisy. The only advantage of the damn things is that you can raise them when not sailing and if you get a rope around the prop. However, be warned that I once got a rope around a prop and it tore the leg completely off its yoke. The castings are very poor and pourus and break easily! Twin engines are far better but like all sail drives you need to be assured that the rubber gaskets are in good condition and there is no water getting in the engine bay because it can corrode the sump and cause big oil leaks. For manouvering the twin engine configuration is also far better and you dont need contra rotating props with them that far apart. The ideal set up IMHO is twin engines with brunton autoprops. Perfect!!

I owned a Prout Snowgoose 37 for 11 years and dont view those drive legs in quite the same way as you. Yes they are agricultural but like anything in a marine environment, they need to be maintained. When we bought our Prout she was in pretty poor condition, including the drive leg. We stripped the leg and refurbished it including shimming bearings etc. With regular oil changes and greasing I came to really appreciate the benefits of that leg. With a little practise we could manoeuvre that Prout in and out of marine berths in strong winds to the suprise on many. The benifits in an old catamaran design like the Prout of minimising weight by only having a single engine cant be over emphasised. I suspect 90% of those cats spend their life overloaded and performance suffers horribly.
Knowing what I know now, I wouldnt consider buying a Prout Snowgoose with twin engines unless I was happy with a motorsailer. They are simply not large enough, in my opinion, to bear the weight of twin engines in such a small vessel.
I suspect we had the fastest Prout Snowgoose afloat with her extra tall rig and lightened set up.

 

[brian eiland]

I owned a Prout Snowgoose 37 for 11 years.....

.....Knowing what I know now, I wouldnt consider buying a Prout Snowgoose with twin engines unless I was happy with a motorsailer. They are simply not large enough, in my opinion, to bear the weight of twin engines in such a small vessel.
I suspect we had the fastest Prout Snowgoose afloat with her extra tall rig and lightened set up.

Do you have some photos of that extra tall rig Prout? Would like to see them.

Early on in my boating career I was favorable influenced by the Prout catamaran design, particularly the rig. It had a lot of influence in my pursuing my own aft-mast design. But I did find problems with that rig when I began to design my own.



[url]http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623.html#post23390[/URL]
...a few excerpts...

Most of the mast-aft rig experiments I can find thus far, have all moved the mast to the very stern of the vessel. Thus they are unable to maintain adequate headstay tension. Without this tension our headstays sag with increasing winds, our sails become fuller rather than flatter, which is exactly what we do not want, and thus the poor performance of previous experiments. With sag they all had to continually re-adjust their sails, and thus they were all seen as problematic. I think I have solved this problem. The key to proper forestay tension is proper backstay tension! First look at my masthead. The single backstay at this location is actually pulling aft at a more favorable angle than on most all other sloop rigs. This might suggest that we could decrease the tension load of this stay, but wait, lets keep it tight in order to maintain the mizzen’s leading edge shape as well. Hard to see on the website drawings, but the bottom end of this backstay is attached to the frame member of the vessel that supports the mast…the backstay’s tension upward is countered by the mast’s compression load downward…….less strength required from the frame structure, and it cancels out the dependency of this backstay’s tension on the stiffness of the aft sections of the hull structure. (The frame structure itself is also a major bulkhead of the vessel)

At the hounds is where we really load things up. We have the inner forestay tension we wish to maintain, and we have the significant forward push of the aft jumper as well. Lets employ two quasi-conventional pieces of rigging: 1) the two forward facing ‘baby’ jumper struts are rigged in such a manner that both jumper stays are always sharing the load rather than allowing one to go slack, 2) the lower backstay from this hound location is split into two legs in a geometry that promotes both legs are always sharing the load rather than the normal situation with a slack leeward stay. All the rigging is working full time, which imposes less load to any single member and less load to their attachment points. Note I have 3 backstays working full time. The x-wide staying base of a multihull allows for x-wide spreaders (note no overlapping genoa) thus lower compression loads from the shrouds…..and they in turn are anchored to this same cross frame member that supports the mast.

For a moment look at the profile drawing of my rig and picture it as though the mast was standing straight up vertically with its masthead in the same location as mine now is. Contrary to Tom’s statement, my forestays are really no longer than a conventional sloop rig, in fact they are likely shorter. And his comments about the angles between the backstay & the mast and the forestay & the mast are not quite correct. In reality it’s the horizontal (not vertical) component of the tension forces in these two stays that determines the ability of the rig to resist sag in the forestay……my masthead backstay has a more advantageous (rearward pulling) angle than does my forestay pulling forward. Interestingly, this phenomenon was probably most detrimental to the Prout mast-aft rig. Their short vertical mast at the aft position resulted in a highly sloped forestay that was both too long for the rig’s overall height, and it could over-exert a forward pulling force on the masthead that was indefensible by the shallow-angled backstays…..result, big time sag, sails too full. This rig had other problems as well…the very open spacious interior structure was less advantageous in providing an ideal base structure for the rig to be anchored to.