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  #1  
Old 10-08-2010, 11:41 AM
Bigfork Bigfork is offline
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W17 trimaran...What do ya think??

I've been following the build of a very interesting ply tri...the W17. The web site is: http://www.smalltrim....com/index.html I have been very interested in a home-build for the last year or so. I would love to do a vacuum bag foam one-off, but lack the funds. I have loads of woodworking experience and a full range of tooling for such a ply boat. I've been all over Mike Waters's web site and found it to be extremely helpful on process, techniques, and all things tri related. It is really a comprehensive site dedicated to the Trimaran. There are comparisons of popular models, discussions with the designers, and various other informative viewpoints on tris.

There is a build on the website that is updated quite regularly with amazing detail and anecdotal info...loaded with "how to's" for those new to the build process. I don't think any have actually hit the water yet...that's where the proof is in the pudding. There are people out there who are far more nautical-numbers oriented than I am. I'm a 'sponger'...that is, I hover at the edge of this (and several others) forums trying to learn all I can without looking stupid. I've actually learned a lot in relation to boat building and design. I know that watching ski movies has the strange effect of making one a better skier. If you know what to look for and emulate, you can learn by observation. Sailing forum are a great for such passive pedagogy practice.

I'm interested in the opinions of those who have built more boats than I. what do you think?? I really like the looks of this boat. It's looks to be a cost effective build, fast, dryer than my H-16, containing larger payload ability, camp-abilty, and did I mention fast(?). There are other similar boats out there. For example, the Sea Clipper 20. There are design issues (imagined or otherwise) that I envision with the aforementioned and most other small day sailing tris. I hope this post can expose this boat for the sole reason to hear different opinions of it's potential. Check out the web site. It really looks interesting...! It seems like there is a market for the 16-22 foot "beach tri". It's really an underdeveloped genre. Of course there is the Weta and others, but I'm a recently graduated-with-debt student. 10,000$ foam build is too much...a 3-5,000$ ply boat is feasible.
(I posted this on the Sailing Anarchy site and got railed for advertising...I'm in no way affiliated with Mike Waters, I'm just interested in hearing the opinion of those in the "know". I want to make the right decision and value the opinion of others.)
Looking forward to hearing some chatter about this craft...thanks.
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  #2  
Old 10-08-2010, 11:53 AM
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Doug Lord Doug Lord is offline
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I think this is the link-the one above didn't work for me: http://www.smalltrimarandesign.com/index.html
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Old 10-08-2010, 12:01 PM
redreuben redreuben is offline
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Here's the link http://www.smalltrimarandesign.com/T...y-profile.html
For what it's worth the plan and profile look great and then you get to the sections, oh dear, boxy clunker very '60s. bit too far down the KISS path for me.
Check out http://www.teamscarab.com.au/index.html
Beautiful elegant, functional, practical, fast. But somewhat more work/skill required ply or foam.
Cheers,
RR.
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  #4  
Old 10-18-2010, 12:20 AM
W17 designer W17 designer is offline
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Hi guys
Have to say, I was pleased to see Bigfork's enthusiasm for the new W17. I have received numerous emails that read the same way, so I guess I got something right ;-)
Nearly 30 boats being built in the first 6 months is not a bad start after all.

I hope more sailors catch on to this thread and share their thoughts but meanwhile, I thought readers might appreciate my views on the comments to date.

As an experienced naval architect who has played around with many different shapes over nearly 60 years of designing, sailing and time spent in professional test tanks etc, I can tell you that you should not judge performance by looking at the cross section of a boat. What the water 'sees' is far better reflected in the plan and elevation views as the flow is then basically from one end to the other. 'Redreuben' may be right that the W17 appears boxy in one view, but there was a lot of thought behind that choice and the market it was for. A couple of years ago, before the W17 design was even started, I posted an article on my informational website (see below) in reply to a question I had received on 'what was the best way to use plywood for a small multihull?'
At the time, I briefly explained the pros and cons of various shapes and the shape that came out best is the one I finally chose for the W17 main hull. It's worth noting that two very well known designers who have worked with plywood for many years, have BOTH introduced new boats this year with this same general section - Jim Brown with his Seaclipper 20 and Richard Woods with this Strike 18. A 60's design? Are we all wrong? I don't think so, though this shape has to be correctly executed to work.
But if the sides are kept low up forward, the beam narrow and the sides not too flared, then this simple shape has surprisingly low wave making resistance. After posting a lot of tech info on the website, I had many write and ask for a design using plywood, a material that they were familiar with and was easy to find world wide. Some also wanted something to sit on an inexpensive flat trailer (that can be bought for as little as $300) or be happy on a sandy beach or a flat platform by the water. The W17 was designed to satisfy all these things and others, and this concept also makes the main hull, a very easy piece to put together, instead of being something quite intimidating for the first time builder. With so many already joining the class, its clear that this is what a lot of people want and the W17 will provide a major upgrade for those tired of getting wet on their H16's etc and having no dry space to carry anything for a camping weekend.
Despite the simple main hull, the W17 is very advanced in many other ways and those who know, will recognize these aspects by looking deeper into the design. This design was not just thrown together with a 'hope it works' attitude ... it was designed TO work and meet its designed objectives, right from its birth.
And to compare this boat in ANY way with the Scarabs is to miss the point I think.
All the Scarabs of this size that I've seen, cram a cabin on their short length. They also have hulls made with a huge number of parts and therefore take more manhours to build. Those of this size often use an old beach cat rig but while the W17 can do that if so preferred, it does have a very advanced wing mast rig of its own. And there's a major difference in the cost of plans too ... and if you actually BUILD a W17, you get plans for the Wing Mast free! And the Build Manual for the W17 is a course in itself ... with the new updated version now having over 85 pages of guiding text .... and I believe that all these aspects are the reason the boat has jumped off to a fast start.
I design boats for ALL-ROUND performance ... and that for me also includes handling, dryness, comfort and looks ... so please, don't just look at what first seems like a box section. After all, some of the worlds fastest planes and race boats have sections that have sharp chines and boxy looks when viewed in section. Its the flow lines and minimum displacement of waves that count far more.
thanks for 'listening' ... be happy to hear your comments.
mike of www.smalltrimarandesign.com

Last edited by W17 designer : 10-18-2010 at 12:26 AM. Reason: typo
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  #5  
Old 10-18-2010, 04:49 AM
jamez jamez is offline
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Mike, Your W17 certainly appears a great addition to the 'Beach tri' genre that has become more popular of late following a number of iterations by people such as Cross, Marples, and Hughes and later offerings by Chris Ostlind and Richard Woods among others.

I can't understand why people are down on dory (flat bottomed) hulls. IMO they are ideal for small multi's with a narrow waterplane. The difference in drag between a square bottom and and round bilge is likely to be less than that realised by poor sails, bad sailing technique etc. There are plenty of happy Wharram owners whose V hulls are even more drag inducing that a box-section. I personally think that for the average sailor the difference between hull forms of a similar W/L length to beam ratio is likely inconsequential.

I don't see the comparison with the similar sized Scarabs, which are designed for a different purpose (although there is an open option for the S16), with built in accomodation they are quite different boats and are arguably a more taxing compromise to get right than a simple day-sailer. There is more boat, hence more to build. While that style of boat may not appeal to everyone, Ian Farrier showed the niche existed with his highly successful TT18.

BTW, looking forward to the W22 coming to fruition. The 6.5-7 meter Sports tri market also seems to be coming into its own now.
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  #6  
Old 10-18-2010, 11:30 AM
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rayaldridge rayaldridge is offline
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Looks like a nice boat to me. One thing that wasn't clear from the literature (though maybe I missed it) is whether or not any boats have been finished and tested.

That's one thing I always look for, particularly if the designer does not have a well-established track record with this sort of boat. One of the reasons I greatly admire Richard Woods is that even though he does have an unimpeachable track record as a multihull designer, he still prototypes his boats.
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  #7  
Old 10-18-2010, 12:55 PM
W17 designer W17 designer is offline
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A perfectly valid point Ray. I would feel the same way.
Just that I've been designing and building small sailboats (mostly in England and the backwoods of Canada) for over 60 years but as a professional naval architect for larger ships etc, had no time to share what I had learnt until I retired a few years back.
During the last 30 years, I also sailed, studied and analysed many small tris and owned 3 of the best. So its not like I'm a casual woodworker who decided to make up a boat design. There's a lifetime of study and lots of sailing and analysis behind my boats.
The W17 was also prototyped but more indirectly. I was working on a W16 when I had occasion to sail (for a good week) a 12 footer with the basic hull form that I was considering. Although the W17 has developed considerably from there, that experience was an important encouragement and building block in the design cycle and I am confident that this boat will well achieve the initial design goals I had set for it.
But I fully understood anyone's concerns, so a report on the sailing of the first W17 will be coming up very
soon ;-) ... and thanks to everyone for their interest, enthusiasm and kind words.

mike
www.smalltrimarandesign.com
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Old 10-18-2010, 04:18 PM
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rayaldridge rayaldridge is offline
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Mike, I'll look forward to reading the sailing reports. It's a very interesting design. I don't think I've ever seen asymmetric float hulls like that on any other little tris. What was the thinking there? Looks like you'd get a very soft ride in light air, and then as the air gets heavier, the boat would firm up. Nice!

What's the waterline beam of the main hull?
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  #9  
Old 10-18-2010, 10:52 PM
W17 designer W17 designer is offline
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Thanks for your interest and intrigue Ray. I like to think that every twist and turn of this new design has a story and good reason for its existence and certainly the amas do.
While I will try to explain their unique shape, the best way is to look at photos of them and for that I suggest going briefly to www.smalltrimarandesign.com
where smack in the center of the HomePage, it says “Click Here for Latest News on Building the W17”. This will take you to a page called ‘The Waters Edge” and if you scroll down, you’ll see loads of pics … including those of several amas, that show the shape well.

I have tried to squeeze everything I can from these amas and here’s how. First of all they are very slim with a mid-depth beam of 240mm, giving a mid-depth L/B of about 19.
The sides have minimum flare (as does the main hull), as I want the displacement to be low down to reduce fluctuations of resistance from surface waves. To follow me on this, take the extreme of parallel sides, when surface waves just go up and down with minimum resistance and displacement (in a physical sense). But when you add a lot of flare, water is also forced outwards as it rises in a wave, and that extra effort shows on the hull as added resistance. If you compare that with a 90 deg Vee bottom hull (the typical shape of the 60’s) , the latter will have double the beam for just 5% less wetted surface and also be greatly disturbing the passing waves compared to a slinky square section with vertical sides. Ideally, I would in this case have the amas deep and narrow like the main hull (which BTW is ~500mm at max. beam) .. but it was found from the small prototype I tested (another builders experiment) that the flat sections forward, smacked the wave surfaces on the windward side in a most disturbing manner, so I came up with a twisted bottom that solved that by presenting a vee up forward when in the air, but become flatter when pressed down – all due to the change of heel. In addition, I have found it interesting and worthwhile to consider a slight toe-in for the amas relative to the main hull. If you consider that most amas viewed head-on are inclined in at the deck relative to the main hull, then a tri that is built parallel at the deck ( as most are), by projecting down, you will note that there is now actually a toe-out (!) at the waterline, due to the ama depth being greater at the bow than at the stern. I’ve not known anyone to address this before but the W17 is built to compensate for that and even give a slight positive toe-in to help handling and turning.
Although I favor deep hulls forward for speed and buoyancy, they can make turning a little more difficult, so the positive toe-in was built in to offset that. This boat also has an under-the-bottom spade rudder that is very effective and free from venting problems.

Now this is only a small part of a much larger design story, but I hope it answers your question and perhaps wets your interest for more. No one should claim that a square section hull will be faster than a semi-circular hull shape with clearly less wetted surface, but we must also not forget that wetted surface is not the only resistance there is, and that this hull was also designed to sit on an inexpensive flat deck trailer as well as on the flat beaches of ‘its birthplace’ (Polynesia) and also be very economical and easy to build. Everything in design is a compromise and a selection of priorities and choices. but I have tried to optimize all I can within the limits of the required design features and if we can build this boat light enough, that flat bottom may even offer some exciting surfing possibilities ;-)
Thank you for ‘staying with me’ on this one … and I hope I've not bored you back to a barge ....

mike
www.smalltrimarandesign.com
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  #10  
Old 10-19-2010, 09:18 AM
W17 designer W17 designer is offline
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I should have also mentioned that having the relief to the ama bottom on the outside also permits the boat to slide sideways in rough, survival conditions, with less tendency to trip and capsize the boat. While I can appreciate that a flat outside can theoretically provide a section that offers lift, in my experience these amas are too narrow relative to their speed for this to have much effect and too much asymmetry can add a lot of resistance too. I personally prefer to provide lateral resistance with a good, stiff daggerboard that can be lowered or raised according to ones needs, than to use ama keels or an exterior vertical sidewall that you cannot retract if needed.

mike
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Old 12-02-2010, 12:56 AM
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RHough RHough is offline
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Wow ... the design goals of the W17 are almost exactly what I listed in my SOR for a couple's daysailer! To say that I am very interested would be an understatement!

Quote:
Here is a basic SOR:
Easy to sail singlehanded or double handed
light air ability at high priority
boat that would be sailing (not drifting about) for an evening sail in 2-8 knots of breeze.
hard to capsize in under 16-18 knots of breeze
Sipping wine and relaxing in comfort.
relatively dry I like wild but not wet and wild
I'd race the boat for fun in even beercan races so it cannot be dull
No spinnaker required to sail off the wind but optional for the wild side.
No head required
No sleeping accommodations required
Enough cockpit space so another couple could join us
Trailerable from Canada to Mexico and back every year.
Boat and trailer absolutely less than 2500#
Would you like questions posted here or through your website?

Randy
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Old 12-02-2010, 04:10 PM
dstgean dstgean is offline
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It looks like the design used a Hobie 18 mast for the boat. Interesting...

This looks to be a nice addition to some fine small multihull offerings lately.

Dan
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Old 12-02-2010, 05:02 PM
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RHough RHough is offline
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Quote:
Originally Posted by dstgean View Post
It looks like the design used a Hobie 18 mast for the boat. Interesting...

This looks to be a nice addition to some fine small multihull offerings lately.

Dan
Prindle 16 or custom wing mast.

I have not read all the pages at the site yet, but capsize recovery might be an issue?

R
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Old 12-02-2010, 09:59 PM
dstgean dstgean is offline
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Quote:
Originally Posted by RHough View Post
Prindle 16 or custom wing mast.

I have not read all the pages at the site yet, but capsize recovery might be an issue?

R
I've seen the plan on his site...I was just looking at the three bails on his boom and thinking it looks exactly like my Hobie 18.

Dan
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  #15  
Old 12-03-2010, 12:00 AM
W17 designer W17 designer is offline
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Yes, I see that not much slips past you guys ;-)

The mast and boom for this particular boat, do indeed come from a Hobie 18, though the mast was shortened to suit the cruising rig chosen for this example and effectively make it act stiffer. I am sure the planned wingmast will follow at some point, but the owner was in a hurry to get the boat afloat and happened to have the mast available. It seems to work fine in this form and it might be worth mentioning that when using a mast from a cat, it's really necessary to use one from a slightly larger cat in the way we've done, as the loads from a tri will be higher than those generated while on the cat. Although the wider tri base reduces the relative compression, the lower stability of the cat relieves much of the ultimate sail pressure and the cat simply heels and ultimately capsizes, while the wider, more stable tri (with its heaviest hull always to windward;-), hangs in there, permits more drive and therefore, loads its mast more.

But can the boat still capsize one might ask? Of course, any boat can be capsized. But this is not something that will happen easily compared to a typical beach cat and in fact, there's a good chance that many W17's that are presently building will never ever experence that if sailed with some prudence and practical intelligence.
But some will add a racing rig and push this fun boat to and beyond its limit so sooner or later, of course someone will flip. And then what? Well unless we can change its basic characteristics in a major way, the boat will be as resistant to righting as it was to capsize, and like all larger multihulls, call for outside assistance. So the W17 has been designed to permit that 'character change' once this happens, and either the stern of the main hull or one full ama will be flooded to lower the boat in the water so that it's accessible and far less resistant to being rotated around its main hull. (Wing mast buoyancy will help too). Although it will take somewhat longer (for the flooding), the plan is to keep testing the options until we perfect the best system to make this happen and with a good number of boats building regardless, we will not be short of eager manpower to work this through.

And keep in mind, that even though beach cats capsize far more frequently, there are still some crews that cannot right them alone and need outside assistance, so the situation is really not that much different here.
Once the boat gets much bigger (over 18-19' perhaps ?) , then outside assistance typically becomes necessary anyway ... and ALL boats should be sailed and handled with the risks that apply to their particular boat always kept in mind, and no one should be foolhardy enough to 'push the limts' when there's not some potential help around. It just makes commonsense to learn progressively how to handle your boat, to always make SURE that sails can be quickly freed under load, and to reduce sail before excessive winds arrive.

Happy sailing!
mike
www.smalltrimarandesign.com

Last edited by W17 designer : 12-03-2010 at 12:04 AM. Reason: typo
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