The Melatelia: light wind dinghy

Beveling clamp strips

OK

This is what you do.

You install the clamp strips so the lowest edge is where it's supposed to be.

This, of course, will make the highest edge project too high. So it's going to need a haircut.

The trick is to do this accurately.

Once the clamp strips are installed around the inside perimeter of the tank, get a straight board that is long enough to extend across the tank.

Use this as a gauge, as you sand the high edges down.

The slower you go and the more patient yo are, the more accurate you are going to end up being.

Since you are probably going to have trim clamp strip edges on both sides, you should sand a little off one side then sand a little off the other.

When the board you used as a gauge sits flat on the outer tank edges and the clamp strips, you are done.

 

Okay, thanks for clearing this up. It seems a very logical procedure.

However, a problem I foresee with this approach - how do I keep this tank side at correct angle while I trim that timber piece (and also while I glue this plywood section to the bottom of the boat)?
In my previous screenshot you can see I thought of using three timber spacer beams which are pre-beveled to ensure that correct angle. But that isn't a good solution, these timber pieces would be very time consuming to make accurately.

If I could fit the tank surface (deck) on top, then it would act as a guide for that angle. But then I won't be able to access that timber piece for trimming like you described.

Also, this side deck will have to be held in place on the bottom of the boat while trimming is done. I plan to use a duck tape to hold it at the line, but I'm not entirely sure if that's going to work. I could use some temporary wood blocks, but then I'll have holes in my boat which will have to be filled with epoxy afterwards. Extra work.

Any ideas on how do I hold that tank side in place and at correct angle while I prepare that timber piece?

Yeah, they're weird right now. I'll try to make them perpendicular to keelson and move to the least supported places of the boat.

I think I know what you're talking about. I'll try and see if that's possible in this case.

Do you happen to have some photos of that bracket? How did you make it?

Makes sense. I will modify this.

I'm using SolidWorks software for this project (Delftship for hull shape), and it doesn't feature auto-nesting. That is only available with expensive plug-ins. Since my parts are far less complicated than yours, I nested them all manually. As long as I don't change my boat drastically, these parts still fit fine.

Well, in my country, they charge around 2.5$ per meter of cutting. It would be very, very expensive to have my parts cut this way.

 

Another quick question. How much epoxy should I order? The more I buy, the bigger the discount, so it would make sense to buy all the epoxy I'll need in one go.

As I've said, I won't be fiberglassing. But I will cover the hull with one epoxy coat for better rot protection and to act as a primer for painting.

I can buy 2.5kg, 5kg or 10kg packages. Some people here told me that 5kg should be enough. But I want to check again, just be sure.

 

I'm surprised you have not quite got to the deck solution something like the one in the attached link/pic. It is to my mind a little more elegant than a small step and is quite bendable, even if some CAD programs say it is not developable!.

http://www.solosailing.org.uk/images/rest-4.jpg

The ply join is on the c/l at the bow, with a small inset of matching or contrasting solid timber let in to cover it.

You will also find that how you tie the daggerboard box to the sides ie frame or thwart will massively affect the stiffness of the hull ie twisting etc. With a two man boat this is quite important as say 2 X 70-80 Kg (body weight) is a reasonable amount of potential righting load. The boat in the deck sample picture can be spread 50 - 100mm if the thwart (only) is removed.... and that's only a single hander.

I suspect you would also be better off using 2 per side floor battens around 12+mm high. To keep light, put a 2mm cap of hard timber over WR cedar. Personally I'd go for a 6mm floor and put some curvature in it for better shape/performance and stiffness. If your shape is sweet, floor battens can be clamped with weights and fit perfectly to the inside of the floor ie no screws/pins etc

Best of luck with the project.

 

One sure way to have the developments of the sheets without calculating and cutting computer is doing a 1:10 scale model with birch plywood 2 mm from which detect after all the exact measurements.
The x is meaningless. Removing the x and weight savings for a bottom to be 6 mm.
Also I remember the advice that I gave in another post: curving sligtly stern's panel, and forcing the bottom during assembly increases much rigidity.
Then if you look at all my drawings see that even the longitudinal line of the stringer is curved.

 

By elegant, you mean flush with bow deck? I can't see that done in my design because bow deck is very curved (has to be, to be high enough and give enough distance between mast step and partner).

I know, but as I've said numerous times before, any kind of thwart seriously limits the space in the cockpit. My boat is very small, and such piece will get in the way when crew is trimming. Also, if I make a thwart, I have to raise daggerboard height to an unacceptable level because of added weight. I posted screenshots of such design attempt several pages back in this thread and showed why it wouldn't work.

No such woods are available in my country, SukiSolo. We have pine and birch. That's about it. As for 6mm floor, it doesn't justify to buy whole 6mm ply sheet just for floor. And it adds so much weight that I can't compensate.

I have never ever seen 2mm ply in my country. Please remember, this is Far East, we don't have nearly such a variety of materials and tools as you do. I'll try to make a scale model from cardboard.

Removing X removes about 0.5kg. Changing to 6.5mm ply adds around 3kg. And as I've said before, I'd have to buy whole new sheet for it. And that stuff is very expensive here.

 

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If you use the method Stitch and Glue, i think 10 liters is right, because it is very difficult for the beginner don't waste a certain amount

 

I think it is very important that before you make the model. The cardboard is fine. What matters is that you make the boat that you want, not the one that wants the program of your PC.

The bottom : if you can not use 6mm then add a layer of fiberglass

 

Okay... That will be very expensive.

Again, as I've mentioned dozens of times now, fiberglass cloth is not available in my country I know, it's frustrating.

 

You asked about the sculling bracket I made. No, I did not take any photos, perhaps should have done, it was just a quick lash up for a one off fun race. I think some of the other competitors thought it was cheating so they did not let me get to the start line until another boat was about to cross the finish line (the meanies!). The bracket looked something like the first picture below - made from a few of bits of plywood and unidirectional wood (UDW). The two holes fitted the rudder pintles and the sides rested on the transom so it did not rock about when sculling. You could have a rowlock on the top rather than the notched plywood. I suppose you could also design it to pivot on the rudder pintles, then you would only need the oar to pivot one way at the top. If you try something like this you need to be sure your rudder pintles are strong, but then if you intend to sail on the sea you need strong rudder pintles anyway. I have really strong rudder fittings on my boat so no problem.

I also attach couple of pics of the row boat I have just started to make. It is intended to be suitable for rowing with or without a passenger and with either a fixed rowing seat, a sliding rowing seat or a sliding rigger system, although the sliding rigger system will only be possible without a passenger on board. My cutting files are complicated because I have included a lot of tiny parts, including parts for the rudder and a launching trolley. It seems to me that once you go to computer controlled plywood cutting you might as well cut all the parts you can think of at one go and including lots of small parts fills the gaps that there will inevitably be in between the large panels.

The middle picture shows the boat configured for carrying a passenger, the last one shows it as it would be without a passenger and without a rowing seat so that you can see how I am intending to strengthen the floor. I am proposing to have strips of UDW running lengthways along the floor and to secure these to cross members also of UDW, these being bonded through the sides of the bouyancy tanks. I have left clear spaces under the cross members so that bilge water can flow through to ease bailing and to avoid having lots of places that water can collect. Perhaps you could do something similar to this, and perhaps in your case the cross members could also be the supports for your dagger board case. However, I would add that my boat is not yet tested so there is no certainty whatsoever that anything shown in these pictures will actually work!

I would add that I like Sharpii's sugestion to have the grain of the outer plywood skins oriented athwartships for the bottom panel. The plywood I have purchased for this boat has three plys of equal thickness so it is quite a lot stronger in one direction than in the orthogonal direction. I think I will alter my cutting file to change the grain direction although with a roughly 16 foot long boat this means two extra joints in the bottom panel. I wonder about changing the grain direction in all the panels, not just the bottom, but probably not - longitudinal strength is also quite important in a long thin boat of this kind.

 

I hope no one told you that home boat building is a cheap hobby! If you want a cheap (or even free) boat these days you get a used one, you dont start custom designing and building!

 

That's an interesting boat you've got there. I'll see if I can transfer something from your design into mine. Thanks.

Rudder seems really tiny. Why's that?

Yeah, it's just that I thought 3m boat would need that much. After all, people seem to be able to build sounds boats of this size for the budget I will spend for the epoxy alone. Doesn't make sense.

 

if you want to spend less you have to use the old method and make the strips joining the corners.
in this case the epoxy may also be less than half

 

I'll use those strips in some places, but not everywhere.

Maybe I'll buy 5kg for starters and then see how much I need after I empty it.

P.S. Some say it's okay to substitute epoxy with simple wood glue in non-critical areas. I'm not sure if it's worth risking it.

 

For glues, don't use anything not marine. There are other types of marine adhesive which are extremely effective if your joints are tight, the tighter the better. Even marine ply is bonded without using epoxy - shock horror!.

Urea formaldehydes and resourcinols, and phenols are the main cheap alternatives. Mainly these are 2 part adhesives and some have quite nasty hardeners, others are OK. Do not use a product called Cascamite which is made from the whey in milk and dissolves over some years or crumbles! I'm not enamoured with PVA adhesives in a watery environment either, I often soften and release certain PVA glued parts with steam and a palette knife!. Traditional hide/pearl glues are just useless for any marine application.

Epoxy is the best currently for sheathing and sealing AFAIK.

BTW if you use even a 5mm 5 ply floor you will still need floor battens to stop it moving somewhere between 5 to 15mm vertically. Also the dagger board just needs a good frame, I did not say thwart although a deeply curved laminated one would give very good strength.