W17 trimaran...What do ya think??

Randy
Might I suggest that you start your kit(s), with scarfed panels, sheathing, bulkheads, DB case etc all coated with epoxy and well stored for protection, before your leave in April. Then you'd have a head start in November. Just a thought.
If you have a large flat, formica covered table, you can create foam core panels using polyester and glass if that's easier for them - but they must be vacuum-bagged. Check out pic on KSS, as Derek (Kelsall) uses this for his system. There's also a little on this on my website under Construction Methods.
Exterior grade plywood can work for a small boat if selected, well checked, core gaps filled (I've used shish-ka-bob sticks for this) and all edges well sealed with epoxy. Can you get Lauan exterior grade in Mexico?
I think the only Marine ply made in the USA is of douglas fir (and perhaps birch) but both would be too heavy. Perhaps readers can help here.
BTW: While there's a simple 16'x2' build platform required, there are actually very few 'jigs & templates' required for the W17. A few ply brackets to hold the bulkheads up and one temporary bhd in the main hull.

mike
www.smalltrimarandesign.com

 

The two jigs I was thinking of were the scarfing jig and the aka end jig(s), plus one for the aka fairings. Once I have my plans in hand I'll have more pre-build questions ...

Vacuumed bagged panels with foam cores to replace marine ply also overcomes the initial resistance to the idea of a "wooden boat".

I'm measuring to see if I can hide a workshop on the property without my wife pitching a fit ...

R

 

Well ---It can be done-----and we did it.
With a helper, nine weeks from first cut to hitting the water.
482 man hours for a Buccaneer 24.
This was done with only hand tools, an electric planer, electric drill and a $99.00 Black&Decker "Radio Alarm" saw.
Admittedly, we did "Farm Out" the cutting and anodising of the crossbeams, swaging the rigging. and welding some of the mast fittings and pulpits, But all the rest was done "in house", in rented space, in a light industrial unit.

 

To my knowledge, no jigs were used or needed for the Aka ends and the Aka fairing sets up nicely over the flat ply template of the end beam. The first boats' fairing was done using stitch & glue though the plans show a method using tape.

And good for you 'OldSailor'. I know that takes lots of planning and foresight. An impressive achievement for a 3 hull trimaran. Using tube or extruded beams and waterstays is certainly a time saver (used on my W22 also).
Too low on a 17 footer though and we like the look of the W17 beams anyway ;-)

mike
www.smalltrimarandesign.com

 

Now that I've had a chance to glance at the plans (have not read it all yet), the aka fairings are #1 optional so you could put up with the boxy look. #2 the shape looks constrained by the material choice? If the sharp LE is to act more as a spray shield than an aero fairing, fine. However if one wanted to a LE with a larger radius you could build the fairing with a NACA section and close the "D" with the forward aka face as the shear web. Such a fairing would be a departure from the idea of a "One-Design" but a streamlined fairing could be lighter since the curved surface would not have to be as stiff as the flat sections (I think).

Yes, the W-17 beams set it apart from the others. They avoid the insect look of the WETA and the somewhat disjointed look of tubes and water stays. The look much more like ORMA 60 akas ... one of the features I love about the design!

I'll be looking at a trailing edge "V" for the tramps to mimic those on DZ-1, but probably stop short of the trailing edge bat wings.

The boat has to look sleek and fast at the dock after all.

R

 

Ama Fairing

Pleased you received the plans ok.
To be frank .. while the aka fairing is not required structural (hence presently marked optional) I'd be surprised (and disappointed) by anyone who leaves it off! The boat will be MUCH wetter without it and will certainly not look 'so cool'. I see no structural advantage to rounding it off and aerodynamics have little effect here as air speeds will be too low to ever show any difference. I personally think the hard line of the forward intersection not only looks better but is much easier to align straight & fair, than a rounded nose. I also wanted to slope the top edge down to discourage crew from sitting on it as its too light to take much of that. At the same time, I wanted the lower face to push water under rather than over the beam, so a roughly 1/2 height knuckle seam resulted, for what I feel are justified reasons.
In case you're wondering, most details of this boat have been worked through like this.

mike
www.smalltrimarandesign.com

 

A bit OT I know.
But can anyone tell me where to get my hands on the plans of a Piver "Frolic". A really hot little Tri which does not need any form of "Narrowing".

 

This is exactly what I thought when I saw the section!

I happen to be an anti drag nut from my RC glider design days. So some things just pop out for me.

Somewhere in the dark reaches of my now tequila soaked brain I think the bicycle guys figured out that 13 MPH was the crossover where air resistance was the major drag force to overcome, greater than tyre rolling resistance and mechanical losses combined. Cleaning up the aero even on a small tri should give a payback that can be measured.

The faired beams on the W-17 should have less drag than a tube and water stay. I've been soaked by spray off the lower strut of a folding system more than once and I know that round shapes like rigging wire are not low drag shapes. Any contact with water and it is just ugly from a drag standpoint, even though attractive from a strength/weight ratio view.

I'll not muck with your design for no reason.

 

From my background as an aircraft engineer I can only agree with RH.
When I was racing I used to make my crew lie on the deck or in the nets when the apparant wind was forward of the beam.
The average human being has at least 10 sq ft of "Negative Sail area" standing up.

 

No argument with that OS .. I'd do exactly the same. But the difference between a 2" and a 1/2" nose radius passing thro' the disturbed air of just a foot above the water surface at speeds of <15k, will not be measurable. Your human crew area is FAR more important and that effect becomes progressively greater as the distance above the water increases and apparent air speed increases. One reason I've designed a wing mast for this boat ;-)

mike
www.smalltrimarandesign.com

 

Why thank you. We used to "hike" on Stars by hugging the gun'l, crew facing aft with the water up your back keeping the skipper dry and the skipper looking forward over your shoulder.

I can see a W-17 crew riding the windward side of the cockpit like that or rolling out to the ama. At least they they could look forward and dodge the spray a bit.

Every degree of windward angle you can get at the same speed adds up to extra boat lengths you can use to recover from your mistakes!

R

 

And that gentle readers is another point for Mike.

 

Quote: I can see a W-17 crew riding the windward side of the cockpit like that or rolling out to the ama. At least they they could look forward and dodge the spray a bit.

You will discover that once sitting to windward on a trimaran and heeled enough to get the windward ama out of the water, that virtually all the spray goes to leeward and even the crew can stay pretty dry.
It's a wonderful new experience for most monohullers

 

You should post that one in the "Sailing Anarchy" forums.

 

If they were all as polite and courteous there, I might ;-(