Newbie needs help with small DIY sail plan, trimaran setup.

[Chris249]

I think the fact that it won the fastest boat under 20’ in the R2AK is pretty good evidence. It might be a better boat for some people with bigger amas but it would need a bigger and more expensive rig to take advantage. You would also probably need to give up sliding seat rowing and the ability to store the amas in the boat. Given the limitations of what is essentially a rowboat hull it’s hard to imagine it would get much faster than the 11 knots it’s capable of in stock form. In other words it would be a different boat for a different purpose.

I hope I’m not derailing the conversation but I hope it’s helpful to point out that what works for a pure sailing boat doesn’t mean it works for a paddle and sail boat. I’ve beach cruised a Hobie Islander a fair amount in Lake Superior and would absolutely not want amas sized as if they were for a pure sailing trimaran. In addition to the drawbacks of handling in waves the extra outboard weight and windage would make paddling worse.

Its not a perfect model but I find it helpful to compare the psf of the wind on the sail as if it were a wall broadside to the wind with the volume of the amas. Given the CLCs ama displacement of 200# and a 60ft2 sail it would take a wind of 36 mph to put them under. Given that a sailing kayak can go at most 10 knots in perfect conditions bigger amas or sail doesn’t make a lot of sense.

But, with respect, placing in one race where the craft doesn't come up against any proven high performers of similar type doesn't prove that the type is optimised, does it? And the R2AK orders show that boatspeed is a pretty small factor in the race - look at the way the Montgomery 17, rated about 2 minutes per mile slower than the Seascape 18 in that class and race, beat the Seascape home by over two days.

I haven't really encountered the wave issue when sailing small tris, but I've only done it for a few days. Something like the Tri Fli or Supernova would definitely capsize in 36mph of wind at that sort of displacement and sail area despite the Supernova having much larger floats than the RC, as would a Laser with the sailor fully hiking (until the mast blew out :-) ).

I definitely acknowledge all your points about the rowing/paddling aspects, as there's no doubt you have plenty of experience in that area and I have not.

[Woxbox]

Some food for thought: Mead Gudgeon knew as much about making go-fast trimarans as anyone on the planet. In retirement, he developed this boat for the Everglades Challenge. Can be paddled, but it's designed to sail most of the time.

Some notable points: the amas are long and slender and designed to pivot so the bows can follow the wave form rather than get driven under. Also, the transom has some width to it so the boat doesn't squat as it accelerates. Note also the spray hood, which I believe was a later addition to the boat. He won in his class in 2014 and 2017 - and died later that same year.

And he co-wrote this book, which has become the hi-tech wood-boat bible for many.

[Lee.007]

And he co-wrote this book, which has become the hi-tech wood-boat bible for many.

That book is actually where I drew my inspiration for the design of the bow of my kayak a year ago. I read about how he was saying the amas on large racing trimarans were made with large volume up front, to force them up out of a wave instead of digging under the wave. So I put a lot of volume in the front of my kayak. Never thought I would be making a trimaran out of it though!

[Lee.007]

By the way, my clc plans finally showed up on the USPS tracker. Looks like they might be here tomorrow! Which is great because I am taking leave this week and should be able to get some building done! Cant wait! I haven't taken any leave since before the pandemic started in March!!

I am also slowly getting my bird's mouth mast and boom together. However, I have seen a lot of videos of the CLC rig without a boom. I plan to be flexible, but is it better with a boom or without? I would think the sail shape will hold together better with a boom, right?

[upchurchmr]

Sail shape is better with a boom, unless you have a circular main sheet track. And the shape needs to be correct for the sail.
Needless complication to be without a boom.

There are other methods beside a very full bow for trimarans.
Look at the boat in post #72, made by the author.
Full may be only in comparison to other long skinny amas of the time.

[Lee.007]

Tonight I built some fixturing to hold my bird's mouth mast and boom. I used the "manufactured 2 x 4 beam" that I made to use as a strong back for my kayak a year ago. (Cause there ain't no such thing as a straight and dimensionally correct 2 x 4 x 16 feet long board at lowes or homedepot. Trust me.) I made 16 nests and spaced them at 12" along the strong back. Worked out pretty good.

So lets start another fight, errr, debate:
Which glue is best for bird's mouth mast? Epoxy? Titebond II? Titebond III? I have all of these, and I used titebond III to glue my scarf joints together in the staves of my birdsmouth boom to get some big knots out.. Some it bonded very well. Others, not at all. I have never had these issues with titebond II. I bought the titebond III with the intention of using it on my mast because it is "waterproof". I am second guessing this idea now. I would like to use epoxy, but the short pot life has me worried, and it is so expensive to waste. I am foreseeing a lot of dripping from the bird's mouth mast and boom. What do you guys think?

Pics of my Nests and the mast dry fit. I realized after uploading the pics one of my nests is crooked... Just ignore it, I will fix it tomorrow. I plan to square them all to the strong back and then screw them down. I only left 1/64" of clearance in the notch so they would fit tight on the strong back. I cut the "U" at a 3" diameter. I am also planning on using 2"-4" hose clamps spaced 12 inches apart to hold the staves together, and then shrink wrap or tape the mast or boom to the strong back with the nests in between to keep the whole thing square and straight. Do y'all think it will keep it straight enough? I mean, how straight is straight when we are talking about a mast or boom?
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[Jfitzger]

The clc amas have a fair amount of rocker which will help prevent plowing into waves. It also won’t heel your boat as much when encountering waves as buoyancy forward would. You give up some top speed while sailing but gain better behavior in waves and better tacking. Drag will be less while paddling because only a small amount of the ama will occasionally be in the water. The Eldercare pivoting amas are very clever.

You might want to think about if you need to be able to reef or douse your sail while on the water. Since you plan on being on the ocean sailing between barrier islands it’s at least something to consider. The alternative is careful planning so you always have a beach to drive up on. It’s something I try to do in any case although I occasionally find myself 3 or 4 miles from anywhere to land.

This is the boom less rig I use,0ED67EE1-81C7-419D-B486-EA47C457442F.jpg


Because of the vertical battens it can furl or reef by spinning the mast. Close hauled trim is close to perfect. As you let it out it’s less so. Running the sail folds up on itself enough to be annoying in light winds. I’ve raced keelboats for the past 20 years and my instinct is to be constantly fine tuning trim. With this kind of sail it gives decent, but not great, performance no matter what you do. Now that I learned to let go I really enjoy it.

The CLC sails do have provisions for a boom if you want. The one thing I don’t like about the 2 smaller sails is that they have luff sleeves and horizontal battens which makes furling around the mast or dropping the sail on the water impossible.

[Lee.007]

Look at the boat in post #72, made by the author.
Full may be only in comparison to other long skinny amas of the time.

I was looking at that! So all that I learn in this boat, I will transfer as lessons learned to my next boat! (yes, i have already decided there will be more... maybe a retirement income after the Army???)
I have to wonder though, did he estimate the wave height he might encounter and adjust the pivot travel of the amas to meet the "worst case scenario" wave? Or did he just decide he was not going sail in certain weather conditions and built the "hinge" to allow only that amount of travel (up and down) of the amas? I have seen some really small amas attached with the same pivot-able mount type on the internet. I wondered if they worked good or not. Maybe thats how they get around not having larger amas?

I also noticed the very straight, almost vertical angle of the bow. I always thought you needed to have a long angle to "slide up on" the water as opposed to try and cut through it and break the surface tension.

And the spray hood is also a nice idea. I saw some videos on youtube of some guys getting pretty wet on a kayak tri. I don't mind getting wet, but I don't have a dry suit for winter time sailing...

[Lee.007]

You might want to think about if you need to be able to reef or douse your sail while on the water. Since you plan on being on the ocean sailing between barrier islands it’s at least something to consider. --- The one thing I don’t like about the 2 smaller sails is that they have luff sleeves and horizontal battens which makes furling around the mast or dropping the sail on the water impossible.

Yes Sir, i did think about that actually. I plan to sew those little straps into my sail so I can drop it at sea, and tie it down. To shorten it. Just in case I am out on the water and a storm blows up before I can get to land.

I was kayaking on the Savannah river one time, 3 miles from the Jeep. A huge thunder head was building behind me, and I couldn't see it until I hit my turn around point. When I made my turn, I realized I was in trouble had to really paddle like a one legged cat trying to cover up poop on a concrete floor to get back before the storm was on me. Luckily the return trip was downstream. I made it to the Jeep just as the rain started. Lucky. So yeah, I am still working on my sail rig design, but I plan on being able to flex to the weather conditions. I even thought of making two sails, in case one gets shredded, I will have a spare.

[Dusty Yevsky]

So lets start another fight, errr, debate:
Which glue is best for bird's mouth mast? Epoxy?


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Yes, epoxy is best. If you're using a medium speed epoxy you'll have plenty of time, which is why it's the best. TB2 and 3 set up much faster. pox also has gap filling qualities which TB's don't. I'd set up a string gauge to check for straightness. Straighter is better.

Also, how did you arrive at the measurements for your mast. It may be the perspective of the pics but it looks massive, especially the thickness of the staves. Kayak tris don't need or want heavy spars. Duckworks has a very good free bird's mouth stave calculator. https://www.duckworksmagazine.com/10/howto/birdsmouth/. If it's not to late I would consider tapering the staves. This is easily accomplished with a plywood template and a router with a pattern bit. A tapered mast will reduce weight aloft, which is a good thing. You do need to consider your sail attachment though.

I also noticed the very straight, almost vertical angle of the bow. I always thought you needed to have a long angle to "slide up on" the water

This is true, as long as the water is frozen. The long, shallow angle that you see on some kayaks is derived from "greenland style". Inuit hunters in kayaks favored that bow style because it allowed a kayak to easily slide up on a iceflow so the hunter could take a break, get out of the boat, smoke a bone, etc.

[upchurchmr]

Don't align your "nests" to the beam.
Align them to each other, using a tight string or a laser.
Straight is more important on your mast than anything else on the boat.

That looks like an incredibly large sized mast for a kayak.
What is the diameter? Will it be straight or tapered?

[Lee.007]

Also, how did you arrive at the measurements for your mast. It may be the perspective of the pics but it looks massive, especially the thickness of the staves. Kayak tris don't need or want heavy spars. Duckworks has a very good free bird's mouth stave calculator. https://www.duckworksmagazine.com/10/howto/birdsmouth/. If it's not to late I would consider tapering the staves. This is easily accomplished with a plywood template and a router with a pattern bit. A tapered mast will reduce weight aloft, which is a good thing. You do need to consider your sail attachment though.

So, I was worried about breakage. I didn't use any strength of materials calculus, I just figured I would use a 2.5 to 3 inch diameter mast and boom and hope for the best. Given the fact that it is virtually impossible to find lumber totally free of knots, and the fact that I want up to a 60 square foot sail, I figured wider diameter would be better.

Staves are 1 inch wide, 1/2 inch thick, 16 feet long. I can take another cut off the width if you think it is going to be too big? But if I reduce the thickness I will have to take a cut off both sides of the stave in order to keep my 45 deg notch centered. I don't have a router, all I have is a kobalt table saw from lowes. It did alright cutting the 45 deg notches. But a router would have been better I guess.

I also contemplated a taper, but I figured it would be too much hassle. I will look around the net and see if there is an easy way to jig up a table saw to cut a taper that is straight and repeatable from stave to stave. I don't trust myself to do it with hand held saws(jig saw, skil saw, saws all). There's no way I could keep it straight.

[Lee.007]

I just re-calculated some numbers on my bird's mouth mast. If I take 1/8 inch off the width of the staves, 1/8 inch off each side of the thickness, I will get about a 2 inch diameter mast. Right now, finished numbers give me a 2.5 inch diameter. Will 2 inches be enough to hold a 60 square foot sail in light to moderate winds? Also assuming I reef it when storms roll up.

[Lee.007]

I got my CLC plans today. They call for a 2" diameter 1/8" wall aluminum tube for a mast. Since that is what they call for to use with the 70 square foot sail, I am going to figure out what thickness of a wooden wall birdsmouth mast equals 1/8 wall of an aluminum mast. Unless somebody already knows?

[Dusty Yevsky]

I got my CLC plans today. They call for a 2" diameter 1/8" wall aluminum tube for a mast. Since that is what they call for to use with the 70 square foot sail, I am going to figure out what thickness of a wooden wall birdsmouth mast equals 1/8 wall of an aluminum mast. Unless somebody already knows?

Email CLC and ask what the equivalent scantlings for a wooden mast are. I've emailed them with similar questions. John Harris appears to like these kind of questions and has responded personally.

I'm pretty sure CLC is a boy's club masquerading as a business.

[Lee.007]

I'm pretty sure CLC is a boy's club masquerading as a business.

LOL, That's my kind of club! I will email them, thanks for the tip. I already emailed them about using cedar strip panels instead of plywood and Terry Otis said "No, I've never heard of anyone strip building the amas, but it would certainly be quite elegant." He suggested wiring the plywood, and measuring the result for dimensions to make the cedar panels, but that still means I have to build it up with plywood. Other option was to build the cedar strips over the plywood, then remove the plywood. Still means I have to get the plywood shaped up. The plans call for you to cut out 8 foot panels, 8" wide, and scarf it with a 4 foot panel.

If I use cedar strips, i may have to scarf some pieces together to get to 12 feet, but scarfing super thin plywood panels just sounds like a pain to me. So, what I plan to do is build flat 8 inch wide x 12 feet long cedar strip flat panels glued together. Then loft the hull panels from the plans to the the cedar panels, cut them out, wire them together, glue and build them as if they were plywood. If it all falls apart, I will just go get some luan plywood. Since I have so much cedar on the shelf, and a gallon of Titebond II, I might as well give it a go and see what happens. After I glue the strips together I am thinking about giving them one layer of fiberglass on the inside to hold them together while I stitch them. I plan to make the strips 1/8" ~ 3/16" thick or less so they will be nice and flexible when formed around the bulkheads. The plans call for 3mm plywood which is only a hair under 1/8", so I think it will be good.

[Lee.007]

Just heard back from Terry at CLC, he said my idea of cedar panels should work fine, and he wants pictures when I am done.

Also, he said they once had a bird's mouth mast that was 2" diameter, but it was too bendy. He said if I go down that small to be sure to use a fiberglass sleeve for re-enforcment. Since I don't want to buy more stuff, I will just stick with 2.5". If it becomes too bendy, then I will buy a fiberglass sleeve.

[Lee.007]

Don't align your "nests" to the beam.
Align them to each other, using a tight string or a laser.
Straight is more important on your mast than anything else on the boat.

I used the nests to get the thing together, then shimmed it on the ends to get it sitting straight. Reckon this is close enough? It is almost dead straight until you get to the left end in this pic. Then it is about 1/8" off center from the other end. Just enough for the laser(greenish blueish square in the foreground) to show on the back wall. I figure 1/8" over 16 feet is close enough for me.

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[upchurchmr]

If you can identify the ones that are not straight, I'd fix it.
Maybe I'm just too anal, but I don't think so.

I'm impressed with the work you get done.
It might inspire me in the near future.

[Woxbox]

These spars flex so much in use, you won't convince me that 1/8" matters. What does matter is having solid glue lines throughout.

[Lee.007]

I'm impressed with the work you get done.
It might inspire me in the near future.

Well, I do have the luxury of working one week on, and one week off due to COVID19. So What is a guy to do? Build Boats!!

[Lee.007]

What does matter is having solid glue lines throughout.

Yes indeed. I agree 100%. In order to check this to be sure, I plugged one end of the mast, and took it outside into the sun. I cupped the other end with my hands and pressed my eye to the end. I slowly rotated the mast to expose all sides(do circles have sides??) to the sun and I couldn't see any sunlight seeping through, so I am assuming I have decent glue adhesion and no cracks that go all the way from the outside to the inside. I sanded and faired it down, and noticed there are some cracks about 1/32" or less between the scantling edges, so last night I mixed some epoxy and some fine sanded wood flour and worked it into the crack until it started pushing back out. I will post some pics so you can see what I am talking about. But even before I did that, this thing feels so freaking rigid to me. I checked it again with the laser after the epoxy had set up and there is literally no flex from one end to the other when supported only on its ends. Of course that is only with gravity pulling on it. Maybe I will hang some dumbbells in the middle and see what happens.
I think it will do for the light to moderate conditions I plan to use it in. And like I have said before, If a squall blows up around me, I will just reef the sail all the way down to nothing if I have to.

[Lee.007]

I am at a good stopping point on the mast, time to work on some cedar panels for the ama's!!
So here is a pic of the mast with a 35 pound dumbbell hanging from a point close to the center. I opened the pic in MS Paint and drew a straight red line from the support points so you could see the flexing. Looks like it is flexing about 1 1/2" at the hang point. I am not sure how much torque a sail is going to put on it. Maybe that's a good math project for my teenage kids? Here are the details of the mast, just in case new people viewing this didn't read the whole post:
Scantling width: 1"
Scantling thickness: 1/2"
Number of scantlings: 8
Mast Length: 16 feet
Mast outside diameter: 2.66" (measured with digital calipers)
Mast_Flexion.jpg

Here is one of the edge cracks I was talking about that I filled with epoxy and wood flour:
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And here is an end view after sanding and fairing, I think it is round enough. I don't know of many lathes that could do much better on a 16 foot piece of hollow wood. In fact, I don't know many lathes for less than $40k that can handle a 16 foot piece of anything.
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[Lee.007]

Here is the first cedar panel I am making for the ama's. I will need 8 of these, but I have plenty of cedar. One 12 foot panel is taking about one 3/4" x 5" x 8' board cut into 1/8" thick strips. Scarfing out the big knots is kind of a pain. I have some 1" and 1.5" thick boards, so I am debating if I should make all the strips same size, or just save time and go with it. But it is going well otherwise.
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[upchurchmr]

Too late now, but your scarphs need to be 8/1 slope.
I tried 1/1 like you are making and they broke quick and easy.

It might work OK with you making a complete panel instead of a single strip.
If you can get the panel into place to form the hull without the scarphs breaking, everything will be just fine with glass/epoxy on both sides.
Then the scarf will not matter since the glass is the strength.

If you get some breakage of the scarph when you bend it, you might put a light glass patch on the inside so it survives being bent into the hull shape. Almost anything will do.

Again, nice progress.

[Lee.007]

Too late now, but your scarphs need to be 8/1 slope.
I tried 1/1 like you are making and they broke quick and easy.

It might work OK with you making a complete panel instead of a single strip.
If you can get the panel into place to form the hull without the scarphs breaking, everything will be just fine with glass/epoxy on both sides.
Then the scarf will not matter since the glass is the strength.

If you get some breakage of the scarph when you bend it, you might put a light glass patch on the inside so it survives being bent into the hull shape. Almost anything will do.

Again, nice progress.

Yeah, I was thinking about that. When I made my kayak, I put the scarfs in the thickness plan as opposed to the width plane. I got pretty good at cutting them and blending the joint with an oscillating tool with a saw attachment, but I don't think I ever had an 8/1 ratio. More like 4 to1 at best, and some maybe even 1 to 1. Never had any breaks as long as I let the glue cure over night(and I never lifted/handled the strip by itself). And since I am trying to hurry before winter and my back surgery arrives, I was just using my miter saw set on 45 degrees to cut them in the width plane. Since my strips are .75" wide, and my scarf is in the width plane, that gives me more like a 1 to 1.4 ratio of width to scarf length. I know that it is supposed to be more like 8 to 1, but I saw a post by Tom Bradshaw once about butt joints (just a straight end to end joint) instead of scarf joints on a canoe. He said he never had any issues.

But, with strips on both sides of the scarfs, as well as the fact that I intend to glass at least the inside before I assemble and stitch the hull pieces, I am betting that I will be ok. I expect the epoxy during glassing to seep through any cracks due to capillary action and make it even stronger.

I will definitely post pics after I assemble the hull pieces so y'all will know if I have any issues. If I do, I have plenty of cedar to make more, and I ordered twice the epoxy and fiberglass that I estimated I needed to cover both the inside and outside of the hulls. So if it breaks, I can fix it. Of course you are right and it should be 8 to 1, but I am using this whole project to experiment and develop my techniques so I can make my next boat with space shuttle precision.

I also started this panel out trying to matchbook the strips. But there were just too many knots to scarf out, and I have to make scarf joints to start with since the board I cut the strips from were only 8 feet long. I did do a dry fit and it looked freaking amazing matchbooked. Maybe I will spring for some 12 or 16 foot boards next time!

[upchurchmr]

Bradshaw is always right.

Rather than the 1/1 scarf I did as he suggested and made straight cuts. No issues at all but I was making the joints on the boat (single strip at a time) not as a panel.

When I tried to make them first and bend the strip around the forms, I got lots of breakage - so I stopped that quickly.

[Lee.007]

Holy flexibility Batman! Check this out. I came home from work today and checked my panel. I am super impressed with how flexible and strong this thing is. I clamped one end, put a 90 degree twist on the other, and there was no breakage, not even a whimper of a crack, from the entire panel. I was actually able to bend the thing into a U shape and it all held together. Now I am wondering if I need fiberglass on the inside after all. Maybe I will be ok with just a coat of epoxy on the inside to seal the wood. I think a layer of fiberglass and epoxy might reduce the flexibility some. What do you guys think?

But I am pissed about the two scarf joints that I laid right beside each other. I didn't notice that until today. I don't normally like having two joints right beside each other. I want my scarf joints to be sandwiched between two solid sides.
20200924_171617.jpg
This is a no-no in my book.

Look at this flexibility:
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[upchurchmr]

The panel looks great. Don't worry about the 2 scarfs together - I wouldn't want them that way either, BUT, the glass gives the strength of the strip plank system. If you don't want to glass the inside before assembling into the hull, it sure looks like you don't need it. Again, BUT, you need glass on both sides as a finished boat. If you get hit or hit something, the glass on the inside is what keeps the cedar from busting up. Looks good. No one will notice the 2 scarfs together - if they do just call them anal and smile. They didn't go to the trouble to make a boat!!!!! (probably)

[Lee.007]

If you don't want to glass the inside before assembling into the hull, it sure looks like you don't need it. Again, BUT, you need glass on both sides as a finished boat. If you get hit or hit something, the glass on the inside is what keeps the cedar from busting up.

Yep, you are right, I didn't think about that. An inward dent from a sharp object on the outside would be stretching fibers on the inside of the ama. Fiberglass on the inside is much harder to stretch into enough tension to break them than cedar is. I will go ahead and glass the insides before I assemble them. Then glass the outside all together as an assembled unit. I am still amazed that I could bend it so sharply without any cracking or breaking. I bet the fiberglass on the inside will give it just enough rigidity to make it nice and tight around the bulkheads. Next week is my "off" week. Hopefully I can get the panels all done and glassed by end of next week. after that its just a matter of lofting, cutting, stitching, and before I know it I will be done! With this one....

[oldnewsailor]

I'm new to this sailing stuff and have never posted anything. I started with a modified laser sail on my old wood canoe and have changed. The sail has some life left in it. I have no further use for it. It's yours if you want it. I don't do much internet stuff. I'm literally just a new old sailor. Send me a message if you want it.

[upchurchmr]

Oldnewsailor,

Why did you change from the laser sail?
Some info might provide interesting lessons learned.
Especially since I have a similar sail and mast!

How did you modify it also?

[Jfitzger]

In addition to impact resistance, glassing both sides of the panel will improve finished panel stiffness. Only doing one side is like cutting one flange off an I beam.

Out of curiosity I looked up finished weight of your panels with 6 oz fiberglass on both sides and it came out at 6.13 oz per ft2. 3mm okoume uncoated is 5.35.

[oldnewsailor]

It had too much power and I couldn't reef on the mast. So, I cut cut the foot above the window keeping the same profile and stitched it. Cut the sleeve, folded it inside and added additional 11 oz dacron to inside to reinforce the tack and stitched it. Stitched the luff to the head and installed spur grommets. Reinforced the clew and installed a new grommet. Added 2 reef points and then laced it to the mast (actually the spar because it is a gunter rig. The recut of the foot allowed me to shorten the boom too. It did pretty well overall. I'm currently making an ama to give it more stability. I pushed it and made 8.5 knots before I rolled it. At 70 I'm too restricted (old, feeble, arthritic, handicapped, or perhaps just crazy) and had to de-mast it to recover and barely got back in. I paddled to shore with two cushions supporting the rigging. "A man has got to know his limitations." I may turn it into a trimaran too.

[David G]

Welcome Lee! Nice boat. Stand by. Others will be along.

The old guys who know stuff go to bed at 8.

And, Tom, we know where you live (or can find out)... so watch yourself whippersnapper. <G>

Nice looking boat.