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Hi,I am building a melanesia and am just about done with the main hull.  Next the outrigger ... recently I picked up a surf ski from a hard rubbish collection. It is very narrow perhaps 350 mm wide and 4.8m in length. The thing I a  wanting advice on is as I a  shortening the ski, should I use the front section or the rear. The bow is more full in shape and has an upswept skirt like a flared bow to prevent the ski conserving. The rear end is very fine, designed to leave a clean wake and provide long-distance to wavelengths the ski. So the full and flared bow to skip along the surface vs the fine stern section sleek and wave piercing ? I have n  experience sailing outweighed or proa, so have no leanings. Please feel free to comment  Tia.

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Hey there Terry,

I have no great depth of experience as yet with the outrigger float performance but the one I have recently built for my Tahiti Wayfarer followed the lines of a surf ski bow.

The reason for this was I figured that as speed and load increases when sailing with the float on the lee side it will push the float down into the water and the raised bow would help hold the whole boat as horizontal as possible through the lift created by the bow shape.

Not sure if this will pan out in reality but the theory of it makes sense to me.

If the rear of your ski gets removed you could consider fitting a reverse transom so the laminar flow is released at the trailing edge and not produce any squat at speed. Speeds will be relatively low of course but the effect could still be beneficial.

Google images of surf kayaks and check out the stern profiles, they are shaped that way for the same reasons, release laminar flow and prevent squatting.

Let us know what you decide and how it performs.

Cheers,
Shaun

My experience with outriggers is limited but my trials with a pvc pipe recommend a voluminous float. 

Check out the photos: the hull is a kayak, the float is a 2m tube with 10cm diameter so the volume is about 15 liters. This is nice to train your sailingskills and balance and any mistakes get an immidiate feedback (you really get a good sense for gusts).

But for real sailing the float is far too small. So next time i would take a considerably bigger one. So in your situation the fuller bow might be the better choice. ?

Note that the bow of the float is mounted higher than the stern, this arrangement worked very well.

 

I wish a lot of fun fiddling about

Pius

Hey Shaun and Pius,

Thanks for the ideas. Looks like 2 votes for the bow and lots of encouragement for experimenting/messing about. Sounds like fun.

Pius, your kayak outrigger looks very speedy :))

Cheers, Terry

Terry: Having sailed only once on a'Melanesia' but having many years experience building and sailing outrigger canoes,I feel qualified enough to chime in............it is not a bad idea to use the ski as an ama -- that is in order to save time in building and to get out on the water quicker, and in which case I dont see the point in modifications mentioned. You will have enough to do in creating attachment points for fixing to the connecting booms. This is of course if you intend primarily to sail the craft. Otherwise a lower volume ama will be way better for paddling, and in which case stick to the plans and make a low volume wooden ama.

If sailing is the main objective, then the 'duck billed bow' will not be bad at all, and the more volume in the ama the better.

You maybe need to be aware that a tacking double hull is essentially a catamaran when sailing, despite the unequal size hulls -- take a look at Hans Klaar's Ontong Java; which sails no differently to a catamaran.

Moving the rig to one hull, like a proa, is only going to make a small performance difference depending on whichever tack. Whereas a low volume ama needs to be kept to windward at all time to prevent it submarining.

'Melanesia' is possibly an unfortunate name for the Wharram designed craft, because Melanesian craft are on the whole unmistakeably double ended and designed for shunting rather than tacking. Tacking is the way that Polynesian craft come about, except of course for the Tuamotus Pahi, which is the only known Polynesian shunter.

Thanks Jeremy, there is a lot to this I understand now. I will be sailing and I am warming to the idea of proa sailing too which nobly confuses things further ...
I get that modifying the ski involves lots of work, may be not that much less than a simple timber Ama build.

Thanks for the reference, I'll check that out too.

Best, Terry

Typed on my kindle -apologies

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