Sunday, January 11, 2009

S&G Night Heron Build Notes – Gluing the Coaming

Well this was a bit tricky! For the life of me I couldn’t get the cutout coaming risers to bend round the curve of the cockpit cutout. I tried kerfing every inch, I tried kerfing much less than an inch (bad idea), I tried a heat gun (good idea). In the end the result was a lot of fine line cracks at the points that I’d cut kerfs. I’m not too fussed. I can easily adjust the final strength by changing the amount of fibreglass I lay on; and now I’ve had success with fibreglassing the inside of the deck that doesn’t bother me one bit.

One thing I was a bit surprised about – how come I couldn’t get the two coaming risers to meet neatly? There was a 5mm gap that I had to plug with a bit of ply. Coaming risers didn't meet together exactly and a shim was needed. Hmm, I should've sanded it down a trifle...

Hmm, just looking at that photograph I can see I should’ve sanded the insert down a mm or two. Nevermind.

The surprising thing for me looking from the top down is how come the top of the coaming still fits neatly. Obviously the risers must have been cut out ok. No problem, it was easy to plug and actually I quite like the way it’s on an angle. I wonder what a riser would look like made of angled strips?

As for the final product see below. Obviously I’ve yet to fibreglass it. Currently I’ve just glued the pieces. I’m going to fillet tomorrow the fibreglass within the next day or so.

Coaming installed. THe cut out on the table was a (failed) idea to help me support a number of uprights to assist bending the coaming upriser.

A quick note here about the use of cyano-acrylate glue. I didn’t use it but I’m thinking perhaps I should’ve. I liked the idea that I could use the epoxy and it would give me time to set it up right whereas I was worried that with CA glue I’d fix into the wrong place too quickly. In retrospect it probably would’ve made the stitching and this coaming much faster.

Thursday, January 08, 2009

S&G Night Heron Build Notes – Fibreglassing

Well this was exciting. What amazing stuff fibreglass is. I read and re-read numerous fibreglassing guides from across the net; use a spatula, use a paintbrush, use a roller. I just came away quite confused.

So I’m going to recount my experiences for you, and probably it’ll just help to confuse you too. Probably main suggestion I have is to find your own way of doing it.

Anyhow, here’s my fibreglassing lessons gleaned from doing the inside of my hull and deck.

Firstly, I think it does make it easier to seal the wood with a thin coat of epoxy first. I ended up deciding that a bit of rag was as good as anything else at applying the epoxy. Wear two layers of gloves to be sure they don’t rip, then dab the rag in the epoxy and rub it on the wood. Worked fine for me and a lot cheaper than any other tool. Certainly means you can apply a very thin layer.

Secondly, for me, rollers suck. I’ve decided that a flat plastic spatula made from the lids of takeaway plastic food containers work great. They’re sufficiently flexible that they can get into funny internal corners easily and they don’t grab at the cloth. They especially good and removing excess epoxy and spreading it away from where it might otherwise pool.

Thirdly, and perhaps most importantly for me, on the internal sides of the deck and hull you should cut the cloth on the bias. This makes a huge difference. The pain with which I watched my first attempts to lay the fibreglass just pull away from the internal corners whenever I ever so slightly stretched the fabric was truly irritating.

Cutting the fabric on the bias (at an angle – 45 degrees seemed good to me) gives it much more stretch on those internal angles.

Here’s the result of my first attempt:

Yikes, how not to fibreglass

Compare that with this:

Wow, my fibreglassing is just sooo much better than my first attempt!

S&G Night Heron Build Notes – Attaching the Panels

This was an interesting exercise. Handling the long hull panels is a difficult task and getting them to fit well is not trivial.

There were a few lessons here.


Firstly, get a properly flat work surface to ensure the stations are positioned correctly.

Use a pencil to mark out a long straight edge down one side of the flat surface and mark out the perpendicular lines where the stations should sit.

In the S&G Night Heron instructions Nick suggests holding the stations vertical using a couple of quick clamps. I found that was painful as they’d move out of place whenever I pushed the kayak eg trying to knock an edge off; sand a bump off an edge or generally just touch it...

Instead, lock the stations into place using some scrap wood that’s wide enough to clamp securely into place. In the photo below you can see the deck on the stations and how they’re clamped to the table. (I wish I’d done this while building the hull:))Issues somewhat resolved, time to glue it up.


Next thing to remember is, bevel to the edge. Assuming you’ve cut the panels correctly this should ensure your boat stitches up as it is supposed to. Compare figure A to figure B… I naively would’ve thought that B was preferred to keep all fillets on the inside of the kayak, however, this might lead you to think differently.

bevel and station impact

Nick Schade’s instructions said to bevel so I worked on the idea it was figure B. Checking a station plan against the hull bottom confirms this, so, yes, you need to bevel completely to the outer edge (but not beyond). 001

The best way to ensure you don’t overdo it is to bevel most of the way with a plane or sanding block; loosely tie the panels together; then run a bit of sandpaper up and down the join until the panels close up together. Check the picture below.

How to get that bevel right. Run a bit of sandpaper up and down the connecting sheets to close up the gap.


What sort of wire do you use??? I tried copper wire and galvanised steel tie wire. The tie wire worked fine. After reading various messages on the different kayak building boards on the net I was quite confused about what to use. Once you try it you realise you can use just about anything. The important this is that you’ve cut the panels correctly and there is a consistent internal bevel.


I found this a bit confusing. Do you use plain epoxy or do you add an adhesive additive like West Systems 403. My current take on it is this: quickly wipe over plain epoxy because it will soak into the wood easily; then add a bit of the adhesive additive (made up of microfibres and colloidal silica I believe) and paint into the joint. You only want a minimal amount to actually glue the joint together. Don’t worry about forming a fillet during gluing.

If you have trouble removing stitches after the glue has set I found that the commonly repeated advice to use a soldering iron works great.


For the filleting I used a lightweight filler (from Epiglass I think) and masking tape. Masking tape is great.

I tried lots of methods to apply the fillets: a plastic spoon worked great, a wooden stirring stick shaped like a doctor’s tongue depressor worked great and I think I could easily have cut any bit of plastic to a round shape to form an applicator. So all in all, it wasn’t very hard.

Monday, January 05, 2009

Stitch and Glue Night Heron Build Notes – Cutting the Panels

There are a few important points here which I learn’t from the process.


I used the jig described in the One Ocean Kayaking building manual. It worked but my implementation of the jig wasn’t that great. In retrospect I think I might in future either do it by hand using a sharp plane, or use a router jig I’ve seen on the Kayak Forum.

Holding onto a circular saw and ensuring it cuts cleanly and evenly across the ply requires a fair bit of attention and a good horizontal guide with a clean, straight edge. The first piece I used was too thin and had a slight waiver in the middle. Better to make it nice and wide so it remains a true straight edge.

The ply sheets are thin with external veneers and an internal core; the saw is rough, so use a bit of waste material as the bottom and top layers. I ended up with the top and bottom sheets having some tatty edges (because of course I didn’t use the waste material top and bottom).

Clamp or weigh down the center of the sheets otherwise the middle has a habit of lifting.

Finally, check before you’ve finshed that the scarf is accurately square to the long edge of ply. Use a large builders square. If I had I would’ve seen I had a waiver in the middle of my scarfs.

Plywood scarfs with an unfortunate wobble in the middle

Scarf Gluing

This would’ve been a whole lot easier if I didn’t have that waiver in the scarf!

Having said that, the output hasn’t been that bad. There was some badly overlapping ply, and I really should have taken more time with the weighting down of the joint, and actually, in retrospect I went too light with the epoxy, but in the end it appears to have worked fine.

Just one note on the use of the epoxy. This was the first time I’d used the epoxy and if there’s one lesson with doing anything new – it’s give yourself time and opportunity to learn from your errors. I’ve tried a few different methods of application in the last 2 weeks and my current favourite is the nylon brush topped foam pads that are sold in the hardware stores as speed brushes. I can buy the pads for just a few dollars and they stick onto a plastic holder which, at least for me, is easier to work with than a roller.

I think the best approach is to mix up some epoxy, run a quick line of it up and down the scarf edges to allow it to soak in; then add an adhesive filler, give it a swirl and apply it to the edges before joining. This will help fill voids better than just epoxy itself.

Cutting the Panels

First discovery: positioning the paper patterns on the ply with spray on glue was a breeze. I was worried that I’d permanently stick the patterns on but it was surprisingly easy to apply a thin coat that would allow me to reposition a pattern. Having said that, I did end up using a couple of different spray glue brands. The 3M glue seemed to be far better to use.

I also used a string line for the main pattern that included the hull pieces. This is such a long paper pattern that I wanted to be sure that a center line drawn on the pattern actually ran straight down the table. Getting this wrong would be annoying as you’re cutting through two ply panels not just one.

I drilled the tie wire holes next and put little bits of wire in the lot of them to keep the panels from moving; then just for overkill I decided I’d hot glue round the edges of the two panels. I used a sharp hobby knife to cut round the pattern edges – surprisingly easy to do. Then I used a jigsaw to cut out each piece. The jig saw did a good job (I think) but the best method appeared to be to stay a mm or two away and use a block plane or sanding block to finish. That gave a very good finish. Just to give myself time to improve I purposefully cut the stations first.

Since cutting the main panels I’ve actually moved to using a fine point panel saw. It’s just less noisy, less dusty and more accurate for the straighter lines.

Lifting the cut pieces was alarming, They wobble a lot and by experimenting with offcuts I could tell the scarf joints could break at the point the ply starts to thin. There was often no epoxy at that point and when combined with a thinning (or complete lack) of external veneer, the ply was substantially weakened. My advice: don’t go too light on the epoxy round the scarf joint, and make sure in the positioning of the pieces that the inner ply layer isn’t left substantially exposed anywhere along the joint.

If you do get a dodgy joint just try a wood backing block. In the case of the photograph below I’d been a bit aggressive and planning away some badly overlapping ply on a scarf. The result was a weak point so I then thinned a piece of scrap ply down and glued that onto the joint. I later sanded this down so just a thin veneer was left covering the low points. It appears to have fixed my problem nicely. (Note that I decided to put a thin epoxy coat on panels but at the time I took the photo I hadn’t epoxied under the clamp.)

Backing block for a weak scarf

Stitch and Glue Night Heron

Over recent weeks I’ve been building a stitch and glue Night Heron kayak designed by Nick Schade from Guillemot Kayaks. There’s a lot I’ve learnt along the way so I thought it useful to post up some notes on the blog.

As a quick background to the project, the Night Heron family of kayaks are 5.5m ocean going sea kayaks available in plywood hard chin form or strip form. Check out the web site as there’s a lot more information there. Of special use when building is the Kayak Building Bulletin Board hosted by Guillemot. This is a great resource.