Building a small trolling boat.

[Lurvio]

Hello

It's finally time to start collecting experience on boat building. I'm gonna build a two meter long speedboat(ish) hull, pedal and prop driven. I'm gonna use it for trolling on the lake I live by and maybe the neighbouring lakes also. For this use the hull has to be quite light, for me to be able to carry it on my shoulder for some lenght. The desing basis are better explaned in this older thread.

The plan after altering the prop and tunnel.


Originally I thought about using spruce, but seems pine is also gonna be used. I have both available, just not in the measurements I'd like.

This evening, after spending the day going over the birdhouses (made six new to replace the broken ones), I got around to actually start the build. I printed a pic of the keel and added offsets from the cad program. Then I drew it full size to a work table (thick plywood piece with legs) and screwed small wood blocks on the bottom side of the keel drawing.

I did an unsuccesfull try in bending 10x32mm pine sticks to ~500mm radius, so had to cut the wood to about 3mm strips, all 16 of them to make the 30mm wide and 60mm high piece. I didn't remove the saw marks (they weren't to bad) because I don't really have a suitable tool for it and I will use PU-glue for the build. After gathering the pressclamps close by I applied a liberal amount of the glue and covered the mess in packing plastic wrap and tightened the clamps.

The picture is taken about half an hour afterwards when the glue had started expanding and threatened to make a real mess of my work table.
Picture

Next thing in the morning I'll go check if I made anything usable. Should be interesting. Another thing I wanna check is if the glue works properly since its eight months over the 'best before'-date. What I've noticed in the past is that PU doesn't really go bad, it's drying just slows down. And besides, I've got about 15 0,75 liter bottles if it, got them for free.

Well, that's all folks for tonight, to be continued.

Lurvio

[Lurvio]

hoytedow
That would make my little duckling three meters long. Not really what I want.

There are a couple of points why two meters were chosen for LOA, first is that I wanted to build small, I have time to make a bigger one later(I have a strong suspicion, it'll be the Tiny Might, full scale). Second point is that one standard ply sheet is gonna be enough. I understand this aint gonna break any water speed records but that really wasn't the point.

Lurvio

[hoytedow]

Understood. Good luck with the project and post pictures as you progress.

[Lurvio]

Yes, I will post pics as I go.

I won't be able to work on the boat every day, I have a bit of construction work taking my time presently. Other thing that's probably gonna slow me down a bit is the temperature. Forecast for next few days is 5-10 deg. celsius daytime and below freesing on many nights. The keel lamination was still a bit tacky after 23 hours so I took it of the mold and brought it inside to dry.

I spent most of today shopping for building supplys and parts for the car. I also collected the ply sheet for the boat. Spruce or pine ply below 9mm would have been hard to get so I settled for 4mm 3-ply birch plywood. The sheet has a real lovely wave in it so it'll make a nice looking skin with a bit of staining and a good varnishing.

I have at least two weeks before the lake thaws enough to get on the water. I won't get the boat done that quick, but one can always dream.

Lurvio

[Lurvio]

Hello

The keel lamination turned out okay after all. Well, not exactly, the excess glue was a bitch to remove. The PU-glues I've used before hardens enough to be sanded, this one is like rubber, a real pain to work with any tool. I finally settled on an angle grinder with a paint removing sponge for the top and bottom edge and used the table saw for the sides.

The keel just unwrapped


Also today I got a start on the frames, transom is ready for glue and gussets. After an unsuccesful search around the premesis for scrap pieces of 5'' pine panel (would have been 18mm thick), I settled on nice looking sawn timber 5'' pine board (22mm thick) and cut the pieces from that. I stappled the pieces together to see what it looks like.

The transom frame


The frame needs to be smoothed a bit before assembly. A hand plane should do the trick. Tomorrow more frames.

Lurvio

[hoytedow]

Tomorrow more pics, I hope.

[Lurvio]

The camera tends to be forgotten when the saw dust flies, but I'll try.

[ancient kayaker]

I wonder if there is a problem with the glue. I've occasionally used Gorilla Glue which is a polyurethane glue and the squeeze out is a rigid foam that is very easy to remove with almost any cutting tool. A polyurethane glue needs a bit of humidity to set; I find it helps to lightly moisten the wood a few minutes before applying the glue in very dry weather. If the joint is a poor fit polyurethane glue will fill the gap but a lot of it escapes the joint and what is left is is too foamy to be strong; epoxy is a better choice for such joints. I'm keeping my fingers crossed that it turns out all right for you.

[Lurvio]

ancient kayaker
I'm not worried about the glue holding up. Elasticity I think is a good thing in such a glue lam. The 60mm keel lamination is stiffer than the 75mm board I cut the veneers from.

I will do a glue test in warm conditions to find out if the temperature is to blame for the rubbery excess or if it is just a feature of the glue.

By the way, if someone has used Essve PU-glue 926 somewhere, could you chime in to tell what it felt like.

Lurvio

[alan white]

I think not enough clamps were used. I got that from the first photo, not because the foaming occurred. Such a piece could have been wrapped with a steel wire tightly (spirally or with short pieces) to make up for not enough clamps, but you can never have enough clamps.
If there are gaps between the lams, you will get more foaming, but mostly I think your glue is fine and the problem is too much glue (which is okay too).
Lack of foaming would be a bigger problem, I think.
My guess is, once you belt-sand or whatever the stem down, you'll see some wide foam-filled gaps you could stick a pin into. Hopefully not, but if it were epoxy you could add more epoxy afterwards into the gaps.
Next time, hang around and tend the glue job if using PU by removing as much of the foam as possible. Use gloves and a putty knife or something to scrape off the majority of the goo. You'll thank yourself later. On the other hand, a good handsaw or a bandsaw can remove that foam if it's completely cured, so either way no worries, except removing right away, you can make sure the pieces are lined up flush or nearly so (good practice to make lams too wide to begin with, of course).

[Lurvio]

alan white
The keel lamination came out pretty good, only one void and most of it is going to be faired out. I've done glue lam before, in craft artisan studies I made my graduation work that way. Those pieses were done in a two piece mold made of chip board. I didn't wanna go to all that trouble in a one time piece.

My graduation work


I got a couple of hours work on the boat today, cut the rest of the frames and assembled them with staples.

Couple of photos






And the assembled frames


I cleaned the mating surfaces in a circular saw to get the accurate angles and a straight surface for the glue. Next time the gussets and the building form. I'm gonna use either 4 or 6 mm birch ply for the gussets glued and screwed on.

By the way that fluorescent lamp is one of the best things to have around. The hay barn doesn't have much lighting so the lamp really came in handy.

Lurvio

[Lurvio]

Hello

I have been a bit busy with the boiler center building. I've gotten little bits done on the boat also, the building form is done and straightened, the keel pieces are coming along and tonight I got the gussets glued to the frames. Also the glueing of the keel section around the tunnel is drying.

This is the latest pic of the day job, the paint is done in the last two days, mainly by the GF while I've been inside fitting gypsum board to make the firewalls needed.


I also got the glue test done. I had the wood pieces and the glue in the warm over night and then glued the pieces together. The excess is similar than before, it stays rubbery. Here's the test piece.


And then the boat, building form with frames attached.


The gussets.


And the keel section drying indoors.


Next is fairing the gussets and getting started on longitudal structures. I also have to find a suitable mold for the tunnel, I'll make it out of fiberglass. I'm thinking 8'' plastic pipes' 90-deg elbow might make a good mold when cut the right way. I have two opposing curves to achieve so there is some fitting to do. Also I'm not sure where I can get elbows that big. Ideas for the mold are welcome.

Lurvio

[hoytedow]

Maybe you can make a tunnel mold out of an appropriate piece of pvc pipe.

[hoytedow]

.... or perhaps a large oatmeal carton.

[Lurvio]

Well I have a good stock of almost 1mm thick cardboard lying around. It's just a pain to get that shape out of anything straight.

Lurvio