Affect of mast location on a Catamaran

[projectfiji]

A friend and I were having this discussion last night, and I've been unable to locate a good answer today. What affect does the location of the mast, from front to rear (bow to stern?) have on performance?

[sandy daugherty]

Not much. Total sail area matters, waterline and weight matter more.

[sandy daugherty]

Having just taken a look at your blog, I now interpret your question to be "Would an older Prout take care of us?" Now THERE is a meaty question. My short answer is yes. Try to find a well maintained 34. Not a race horse, but a sturdy, steady old war horse that will get you where you want to go safely. Mast forward vs mast aft questions miss the point when you are talking about a Prout. Invest in one of Charles Kanter's books, and study his opinion of these great catamarans.

[Southern Star]

Sandy, I agree with your assessment of the earlier Prout 34's. As to what is commonly called the 'Prout' rig (cutter rig with mast stepped well aft by the companionway bulkhead), there have already been discussions of the relative merits of the rig in another thread on this site - I suspect it was in relation to some of the new Broadblue cats where there was a choice of rigs.

My Solaris Sunstream has an identical rig and I firmly believe that, for the following reasons, it has serious merit in an offshore cat:

1. It steps the mast at the strongest point of the bridgedeck - over the companionway bulkhead.

2. All lines are automatically led to the cockpit without various turning blocks for the halyards, reefing lines etc.

3. It allows sail area to be maintained, but breaks it up into smaller, and hence easier to handle sails. This is particularly important with respect to the mainsail, which will not require electric winches etc. to facilitate hoisting.

4. It has a dedicated stay for a staysail/storm jib, which brings the center of effort both down and back in precisely the wind conditions which favour the same (witness the number of offshore monohulls that now have 'solent rigs', with a detachable inner forestay for the staysail/storm jib).

5. The additional stays provide additional strength to the rig.

6. A furling staysail/storm jib permits the use of much heavier weight dacron than would be appropriate for a genoa, and therefore ensures that the lighter genoa is not used (abused) in excessive wind conditions. Furthermore, sail shape is easier to maintain if one is only reefing a furling sail to about 30 percent of its overall size. Finally, it is easier and safer to unfurl/reef a dedicated staysail/stormsail from the comfort of the cockpit than having to go forward to raise a sleeved storm jib ( eg. galerider) over the furled genoa, or to remove the genoa from the slot in the extrusion and raise a dedicated storm sail in its place. (On the negative side, I will agree that higher aspect-ratio sails tend to peform better and, in particular, the new huge mainsails with significant roach and flat-tops provide much more sail area up higher, where the winds tend to be stronger).

7. Since the Prout rig spreads the sail area more fore and aft than the typical fractional sloop rig, it will tend to have a lower mast. This in turn lowers both the center of effort and center of gravity, important in a catamaran in terms of reducing the risk of capsize. Furthermore, the lack of a mainsail with significant roach allows much better sail shape when reefed, and permits the use of backstays - further strengthening the rig.

Although direct comparisons are impossible without sailing the same hull with each type of rig, I have found that the larger foretriangle aids in tacking; I do not, for example, need to depower the main, as is sometimes necessary with huge flat - top mains in order to come about cleanly.

Once again, different horses for different courses - but for offshore sailing with its greater potential of being caught out in heavy conditions, the 'Prout rig' made and continues to make a good deal of sense.

Brad

[roblanford]

I had a friend with a kantola trimaran that ran a mast aft rig. He was very happy with the way the boat sailed.

Here is a good article about them:
Sail Propulsion - Revisiting a Mast-Aft Sailing Rig

[sandy daugherty]

I have no objections whatsoever to the Prout rig, or cutters in general. One additional benefit is that a smaller main is easier to reef. About the only difference I can see is the location of the bulkhead that supports the mast: it might be said to limit the area of the bridgedeck, but it frees up the space that was cut up by a mast-supporting bulkhead at the front of the bridgedeck. I suspect that is the reason that Prouts used interior arrangements that were so different from others.