Mashup Trimaran (continued)

Spread the load, shed the water, increase reserve buoyancy, lighten the boat.
Make them out of foam and epoxyglass the s*#t out of them.

 

Greetings folks!
Still tootling along here. An hour here, an hour there, and then several hour blitzes where I can .
The first picture is the first time I've got to see the beam ends mocked onto the port float. I like the subtle curve of the front beam...gives it a slightly modern look. I can't wait to see what it looks like sitting in the water! The float will be at a 8* cant relative to plumb, which is why the beam ends appear to point upward at said degree. Currently, the float is sitting "plumb/level" to facilitate the joinery. One can envision the hinge point and the float folding up and over, a-la W17 style.

Once the beams are glassed, it will be time to mount the main beams to the H18 main hull. My garage won't let me do a full 14' wide assembly so it will have to happen in halves, ie main hull/beams fit to port float and then the mirror the process on the starboard side. The last step of the fit will be mounting the floats to the hinging beam end. I'll chalkline snap a layout grid on the ground (like doing log work) and use a 4' level and lasers to true, rack, and square the floats to the main hull (and then there's the thought of slight "toe-in".....how much?) I've also got to settle on a hinge design. I'd like to build my own glass hinges, 8 in total (two per joint). At any point, I could add water stays. I'd like to see it float with mock weight before I go that direction.

More than an update, I do have one silly question for the collective brain: A picture show the closeup of the aft beam. I managed to build in a slight gap (circled in red) here and there when I sheeted the top and bottom sides. I plan on putting a 1/4" roundover on all four corners to facilitate better glassing, but should I first fill the slight gaps with thickened (West 406 or 405, colloidal silica or filliting blend)? Or should I not worry about it and just round-over and glass fab.

Thanks for the thoughts!
cheers.

 

Oh yeah... one more silly question.
If I want to use any marine filler to fair or otherwise "smooth" transitions in sheeting (like where there is a joint between sheets but there not perfectly fair to eachother), should I do that before or after glass fabric.
thanks.

 

Before but at the same time so the cloth is going on over uncured filler.

 

If you use microballoons with a little silica you will easily be able to fair the joins before glassing, as blue bell says uncured is ideal, but before fully cured is 36 hours or so, just hard enough to remove excess with a blade and light sand could be 3 or so hours, your call. Don't use acetone to clean the extra, big risk of spoiling the bond with ply in that time frame.
Carbosil I haven't used but silica/resin is a lot harder than ply when cured.

I've had a go at nutting out hinges too a little different to you but perhaps my ideas will be helpful.

I think the easiest[ha] way is to do the lay ups of the hinges is with an ally tube that spans the distance between front and rear sets of hinges, to assure alignment. Mine would have 3 hinge parts 2 outside making a fork, 1 centre inside, the aluminium tube could be used as the shaft and the length inbetween cut out when everything is completed, especially main hull joins.
You can sleeve the tube at the hinge for strength but leaving the tube in place permanently means pretty thick walls/weight

I've left a few bits out like the what method secures the hinges when underway to stop them from flopping up and down, but that's easy compared to making and aligning hinges.

The last connections would be each lay up to the centre hull, held in place with enough adjustment in the support frame/jig to see whether the hinges/angles want to go.
I'm glad your doing it first, ha, I've shelved that concept for down the track, too much extra work so it can wait for a coupla years. Plus I get to see how yours works then,.
great stuff Big Fork

 

Cedar is as light as you are going to get for a wood piece.
What are you two talking about??????

 

Ya, cedar's pretty light for a piece of wood, especially if you drill holes in it.

Which "two" are you referring to?
Have you read or followed the thread?

 

Really ? What about Kiri/Paulownia?
Or Balsa. So what are you talking about ?

 

Hey there folks,
My mention of cedar was mostly just because that's what I have lying around...really it's just what was at hand. I realize there are lighter woods out there. My plan was to use a small 'block' of cedar oriented vertically (compressive strength) to fix the float arm to the hull. As this project is a learning experience and very fluid in its design, alas I have scuttled the idea in favor of shaving weight. Instead I am going to bond, glass, and brace the anchor point skipping the need for the permanent fixatives at these locations. I'll probably use a temporary stainless 1/4 to secure the float to the arm, then bed and glass/brace, then remove the steel.

Got a jug of West micro-balloons to fill/fair so that's the next treatment for the beams...then glass fabric. And there's the hinges....they'll take some time... then the pre-fit and alignment... then transom plugs and other odds and ends.... then, maybe by spring, a float test! The float test will tell a lot as far as dihedral, buoyancy, and float to main hull relativity. The whole lot could go in the bin at that point if it's deemed hopelessly heavy or otherwise frigged. Towards the beginning of this I'm quite sure I was overbuilding; now I think I'm on the edge of under-building. Without proper engineering sample tests, there's no telling how strong components like beams are...other than intuition (and there's been lots of that).

Cheers

 

Cover with 4 to 6 ounce, tape your joins avoid right angles with filler, lap your main beam /hull/ amas joins to increase load spread, don't sand through the mat.

 

Hey forum folks!
Well my folly is still alive. I just finished the hinges: 16 "paddles" or 8 hinge sets. Took me about 2 months of an hour here and there!! Very labor intensive but I became more efficient as the process moved along. Each paddle is 7 layers of 13oz uni with 1 layer of 10oz bi. I haven't weighed them yet, but I think they're much lighter than the equivalent in stainless.

I ordered the plans from Mike Waters based upon use for his W17. Frankly, I've sourced alot of info from his website and through emails with him. His site is an amazing resource for the DIY ply builder! He pointed out that my Hobie 18 main hull is under displacement for what I'm trying to achieve...related to dihedral. I sort of knew this... had a hunch. Obviously I don't want to be dragging 3 hulls through the water. I'm increasing dihedral so that when my (heavy) main hull is sitting at estimated waterline, the floats will be just touching. Means I need to add about 5" to my main beam mounting surface. And I need to do it with weight in mind.
(famous last words, but...) I hope to have a float test this fall. Fun Fun.

cheers folks,
bones

 

Hey Bigfork, I live up in Whitefish and sail often from my in-laws down in Somers. Can't for the life of me find an option to Private msg you on here, but would love to hear how this project is going and maybe connect someday. Found your thread while looking at W17 search results as they sure do look inviting to me.

 

Greetings MTcateran and others who contributed to this conversation

The mashup tri is due to float this Friday... It's the "make it or break it" float test. I'm aware that half of the cost of boat-building is the "building". The other half is the fitting out part. Ergo, I'm going to stick this thing in the water and decide if it's worth proceeding or getting out the saws-all. Worst case scenario I will cut the H18 center (vaca) out from under the cockpit coaming and beams, then buy real plans and build a new main hull that meets the displacement requirements better and nest my beams/floats into it in some way.

Any suggestions for the float test? I'm going to bring a 5 gal bucket with sand to simulate the rig weight.

Regardless of how the float test turns out, I will drop pictures in here. I'm a bit nervous as there's 3 years of garage piddling coming to a head. It could be glory or it could be landfill fodder. I've learned a ton about glass work and had many a beer whilst standing over my creation, pondering from scratch. I so far off the map...

stay tuned

 

Good luck, look forward to seeing how it goes!

 

Well well..So the float test went down last Friday...And I couldn't be more tickled with my folly!!!

This was the first main "make it or break it" moment. To see her in the water calmed my worries and reinforced my commitment to finish the thing. I was very concerned about where my laser lines of water level/displacement and dihedral would shake out. You can see the blue tape. My guess of waterline was 2.5" higher than the blue tape line. The main hull ended up sitting 2-3" higher in the water than I was expecting. The floats are just touching with less than an inch wet, the last two feet of the bows and transoms-dry. I'm in my ballpark range; no glaring issues. She is sitting slightly transom low but this is without rig. With 400lbs of adults on it, the waterline hardly moved. My beams felt stiff; the platform was rigid. I can always add water stays in the future if needed. Finishing the topcoats and sourcing/modifying a trailer will be easy enough. My educated guess all up finished (using a H18 rig for known weight) is somewhere from 550-600lbs.

The next big hurdle is the rig... So...while Hobie 18 sail/mast is readily available, I believe it would be anemic and under-powered.
With a 14.5 ' beam, I'll have the righting moment to carry a larger mast and sail. I'm open to ideas... One crazy idea I have is to build a 14" cord wing mast and still use a Hobie 18 sail (easily found used or bought new). Without doing the maths, I would gain a large amount of "sail area" via the wing mast.

I think I need to stay with a rotating mast if possible...or do I ?? Thoughts? Ideas? What fixed mast work? I have the Solcat boom, 6/1 main sheet, stays, and other bits n bobs. I have a 39' Frankenstein mast that came with it. The single spread-ered mast is 3 aluminum sections welded with gussets riveted between. I have the Solcat main and jib. That said, it's just about the same sail area as the H18 main and likely not enough canvas.

As far as downward appendages, I'll likely just use the H18 daggerboard and rudder assembly. (looking way into the future) If I find I'm flying the main hull with relative ease, I can use the trunks in the floats and hang rudders off their transoms.

Just this float test has been a long time coming, 3 years of garage piddling to be exact. The consensus from the armchair observers who helped me carry it to the water was "holy **** dude, you made this?" Everyone had positive things to say. Several folks have some experience with wood boat building and they told me to keep going

So... thoughts on rig? Anyone have any criticism, constructive or otherwise?

cheers.


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