Building a skin on frame canoe

Bogwoppit

I made a start this evening on a new project building a skin on frame (sof) canoe.

the sof style originated from the Inuit of Canada and Greenland, a lightweight timber frame was built from driftwood and then skinned with sealskin, the original qajak (kayak).

The skins have now moved on with nylon or polyester woven cloth coated with a sealant of some type. The timber frames can be done in 2 ways, traditional style with steam bent ribs or a more modern style with plywood frames replacing the steam bent ribs.

Gunwales and chines (the timber that runs the length of the canoe) are usually made from western red cedar (wrc) which is very light and quite strong.

Luckily I had some wrc in the shed from another project as it’s not easy to get hold of in in “raw” planks, it’s common enough for decking but the size is not much use for this purpose.

The plywood I’m using is okoume marine ply which is made to a higher standard than regular marine ply and is built to a Lloyds of London standard.

First job today was to make the strongback, a length of 2x4 upon which the frame will be built.

Next I started ripping down the wrc for the gunwales, each gunwale will be 2 lengths laminated together for extra strength.

The canoe will be 17ft when finished so the gunwales need to be made to 18ft to allow for working them in at the bow and stern. My piece of wrc is only 12ft so I will need to scarf joint 2 pieces together to get the desired length.

Knots need to be taken out as they will crack when bending the pieces so I’ll place the scarf joints so as to keep the pieces knot free.

I cut 9 pieces off and immediately discarded 1 due to the knots. I have 4 full lengths that are knot free and 4 more that I’ll be able to use use to get the good ones up to the desired length.

I’ve made a jig for the table saw to allow me cut a 10/1 slope in the lengths, the joint will be glued with a thickened epoxy and will be very strong but a bit stiffer than the the rest of the length so I’ll have to make sure the joints are staggered to not have too many at one place on the canoe.

I don’t really have a timeframe on the build, I’ll do it as and when I get the chance.

The sof technique is not nearly as pretty or aesthetically pleasing as the strip built we had the pleasure of watching Fergal built recently but it is a lot simpler and should be lighter in weight. Target weight for the canoe is under 24kg so that it be loaded by one person, that’s a third the weight of a plastic or fibreglass canoe of the same length.

Bogwoppit

I scarf jointed the gunnels and the keel last night, boat builders say a 6:1 slope is fine for scarf joints with modern epoxy but I went with 10:1 to be safe.

I spread the epoxy evenly over both sides of the joint, the 2 pieces are then pushed together. I use a calliper to check the width a the joint so that the pieces are aligned correct.

The gunnels are made up of 2 lengths laminated together on the frame for extra strength.

Next I cut out and attached mounting brackets to the strongback. The slot in the brackets is to hold the keel, frames 1 and 6 are mounted to the bracket next.

Next I started on the plywood frames, okoume marine ply is pricey stuff so I’m trying to be as efficient as possible.

I got frames 3 and 4 cut out and sanded last night.

Bogwoppit

I’ve done some more of the internal frames when I’ve had 20 minutes to spare here and there.

I’m about to run up against an issue with my stock piece of cedar. I want to rip the chines off the piece before I cut the notches out of the frames so that I can get the size of the notches pretty close.

My cedar now has the grain in the wrong orientation though, it’s running at 45degrees, I need it vertical.

It’s a simple enough job with the right saw but my little table saw is not up to it as it only has a 3 inch cut, I need minimum 6.

I’m searching around for a bandsaw locally, I have a friend who can do it but he’s in waterford which is a bit of a trek.

Will give it another week of searching round here before I head south with it.

Bogwoppit

The local men’s shed have come up trumps with a good bandsaw.

Dropping in to them early next week to get some cuts done.

Bogwoppit

I got down to the Mens shed a few weeks ago to meet with the guys and have a look at the setup.

Hats off to everyone there, they have a great setup and were very welcoming, the saw was more than up to the job but a new blade had to be ordered. By the time we were ready to go it was another couple of weeks due to logistics.

There were plenty of hands there to help which was great as it’s a big piece of timber but it all went pretty well and the results couldn’t have been better.

Many thanks to all the lads that helped.

Once I got all the pieces back home it’s become clear that I only have just enough wood for what I need and can’t afford a single mistake so there has been a lot of measuring and measuring again, then I measured some more.

Then I measured it all again.

I ripped the pieces for the chines and after doing the scarf cuts I only have a few cm to spare on each chine.

I have just enough cedar left to cut inwales, spacers and rub strips if I’m careful.

I spent some time shaping the bow and stern pieces which are the marine ply, I have a bit more time to spend getting these right.

Bogwoppit

A lot of time has gone into ripping the chines and scarf jointing them to get the full length, cutting out the rest of the frames and sanding everything down.

I still have to rip down the inwales and spacers but these can be done at a later date.

I mounted frame 1 and 6 to the strong backs and slotted the keel piece into the bottoms of the frames. The keel

is then wedged at either end to produce bottom curve of the boat.

Next I will mount the stem to the front end of the keel followed by the stern to the back end of the keel. The gunnels will then be mounted but only secured at the stem and the stern, then I will start fitting the rest of the frames.

Bogwoppit

I was going to start adding the stem and the stern last night but then I noticed this knot in the keel piece, I thought it was worth cutting it out and putting a scarf joint in to remove the weak point.

I got the first scarf cut done but then the saw slowed down and died.

Took the brushes out and hopefully this is the culprit, a new pair ordered for next week and we can crack on.

Esel

If you cleaned/smoothed the existing brushes, would they work for a while until the new ones arrive?

Bogwoppit

https://www.boards.ie/discussion/comment/119882441#Comment_119882441

They might work, hadn’t thought of that.

New ones arriving Monday but I might try that out tonight if the kids go to bed on time.

Bogwoppit

Sanding down the old brushes got the saw going long enough to get the last cut for the keel done. Thanks for the suggestion @Esel

That’s glued now and waiting for it to set (24 hour minimum).

Bogwoppit

With the keel piece now ready to go and a lot more sanding done I made some nice progress this evening.

I screwed the stern piece onto the keel and moved the keel until the stern was the right distance from frame 6.

Offered up the stem at the front at the right distance from frame 1 and marked and cut the keel to length, the stem is just taped into place for now and will be glued and screwed later on.

I strapped the first gunnel pieces to frames 1 and 6 and then loosely put in frames 3 and 4. This gives the rough shape of the gunnel so I can mark the gunnel how it needs to be bevel cut at the ends to sit flush on the stem and stern.

^ Apologies for the orientation.

Starting to look like a canoe finally.

Bogwoppit

I cut the angles on the ends of the gunnels last night, the gunnels have to have a lot of curve put in them, so it’s going to be tricky to get them in place.

Unfortunately one of the scarf joints gave way last night, I think I must not have mixed the epoxy well enough. Will clean it up and glue it again today.

Bogwoppit

we finished the last 2 internal frames last night and the fully attached the gunnels.

The gunnel is attached by a single stainless screw and epoxy at each frame. The screw holes are pre drilled and countersunk.

The bend in the gunnels is really quite severe, they’re not far off breaking point I reckon as they are. Later on a second identical piece will be epoxied on top which will strengthen it right up.

There are 2 pieces across the top of the gunnels clamped in place, looking from the front of the canoe at these 2 pieces will show if there is any twist on the frame.

Bogwoppit

The cold weather has kept me out of the shed for a while but a return to (slightly) milder weather meant a couple of hours work over the last few days.

First job was to finish sanding the 6 remaining stringers.

I started mounting the lowest stringer first, it went into the middle frames fine but as I moved forward it became quite hard. There is a huge twist in this stringer between frames 1, 2 and 3, so much so that I’d thought I’d cut the frames wrong.

I messaged a guy on another forum who’d built this canoe a few years ago for advice, he said he had the same issue and broke a number of stringers trying to get them in. The twist is put into the bottom stringer to stiffen up the frame. Normal procedure to deal with this would be to build a steam chamber for bending to wood but I thought I’d try a towel wrapped around and then pour boiling water onto it before trying to bend it.

The heat gun was also used to keep the temperature up while I twisted the wood, I just about got enough twist on the first one. The opposite side actually proved to be a bit easier for some reason. I haven’t tried to twist them into frame 1 yet as I want to get them epoxied into frames 2, 3, 4, 5, 6 and the stern before i finish them at the front to minimize the chance of damage with further bending and twisting.

I fitted and finished the second gunnel layer on one side, the piece I have for the other side is a fraction short so I have to scarf joint an extra bit on the end before I can fit that one.

The 2 upper stringers fitted very easy and I have them in place on all frames and the bevel cut at the stem, I’ll cut them at the stern today. Screw holes are drilled and countersunk, I’m using stainless steel screws all round.

I want to epoxy all the joints on the stringers I’ve fitted so far before I do any more but unfortunately I’m limited by the temperature. I’ll have to wait until the temperature is consistently above 10 degrees and who knows when that might be?

homer911

Looks amazing, well done

Bogwoppit

Had enough of a rise in temperature last night to get some epoxy work done, all the completed joints have been fully done now and will need some time to set.

I’ll be able to get on with the rest of the stringers now, I don’t see any sign of another temperature window for a while so progress will remain slow.

Bogwoppit

Last 2 stringers dry fitted and one of the 2nd pair of gunnels dry fitted too.

I’ve put clamps on the lowest stringers to put in the twist they need, you can get an idea from the picture how much they’re twisting and hence the pressure they’re under. By the time the weather warms up enough to do some more epoxy work I’m hoping they’ll have relaxed into the twist a bit so that they can go into place without breaking.

nokiatom

nice job

Bogwoppit

I’ve had a couple of short temperature windows and I now have all the stringers finished, one of the gunnels in and the last gunnel scarf jointed and ready to be cut to length ( after cutting it too short previously!).

The bottom stringer with all the twist really was a right pain in the proverbial to get into place. Had to twist and push in 2 directions to get it where I wanted it. Judicious use of the epoxy gun will hopefully mean it will never shift again!

Should get the last gunnel in place this week and then I’ll be cutting out and shaping the breasthooks to fit.

Bogwoppit

Progress remains slow with the cold weather but I got the last piece of the gunnel in place this evening.

A lot of clamps are needed hence I’ve done one side at a time.

Next up is shaping and fitting the breasthooks for both ends from the marine ply.

fergal.b

Looking good , you can never have enough clamps, when you do then doubble the amount and you will be close 😉

Bogwoppit

https://www.boards.ie/discussion/comment/120189399#Comment_120189399

Thanks Fergal, good exercise for the grip strength!

Seeing Olds Cool again certainly provided a bit of motivation to get through the work on this.

If I do another project like this I’ll probably have to go down the bulk epoxy route, I’m going through the West epoxy tubes and mixers like they’re going out of fashion!

Bogwoppit

Stern breasthook

Probably the only concession to my (very limited) artistic flair on the canoe!

Bogwoppit

Both the inwales fitted now, there are additional spacer blocks to go between the inner and outer wales which is the next job.

fergal.b

Looking good, is there a bit of an S shape to her towards the bow or is an optical illusion on the right hand side you can sort of make it out but not on the left.

Bogwoppit

Thanks Fergal, yes there is. Hard to see it in the pics because of the angle, I’ll get a pic head on tomorrow which should show the curve. It’s a very pleasing shape.

fergal.b

Lovely I can see the finished boat in my head and can tell she will be a eye catching craft. Keep up the good work 👏

Bogwoppit

https://www.boards.ie/discussion/comment/120255510#Comment_120255510

I’m thinking ahead about what finish to put on the frame when complete. Not really an area I have any experience in.

The frame will be dry 99% of the time but I’d be grateful for any suggestions.

fergal.b

Probably 4 options , just varnish , you might have to do it every two years. Coat it in epoxy resin and varnish, more expensive but longer life span and less varnishing, just oill , needs to be done alot but easy to do and cheep. And last, if it's a wood with natural oil like teak just let it weather it will be fine for your life time 😀

Bogwoppit

It’s very hard to get a picture that shows the curves!

fergal.b

Sweet 😋