Epoxy and Cyanoacrylate (SuperGlue) on Plywood Boats

The flush joins on the Bow and Stern ends of strip planked boats don't lend themselves to epoxy joins. The planks edges are almost butt joins, so very little epoxy can be inserted into the joins prior to removing the wire 'staples'

Has anyone found that Superglue used as a temporary, non waterproof glue prior to epoxy covering, creates problems ?

 

In your example photo, I think you could brush on straight epoxy inside the hull and get enough capillary action to hold the joints during tie removal. It might take a couple or three coats spaced a few hours apart to build strength and offer some gap filling without resorting discoloring your epoxy with thickening agents.

Another options would be to chamfer the backside slightly to make a home for thickened epoxy "tacks".

 

Superglue is really designed for non porous surfaces and I doubt you would get enough of a bond to keep things together. I would take a very sharp utility knife or safety razor blade and bevel in a cut on the edge of each of the planks for about 6 inches... This is similar to Vee-ing the edges of thick steel to build up a weld. This will give some surface area for epoxy putty to bite into and you can smooth it level so it will be hidden under the tape with nothing showing. Being as the epoxy is stronger than the wood your joint won't suffer strength wise. Should only take a few minutes extra work. A chisel would work well too.

 

These are both good suggestions, and the reservations about the superglue not being strong enough when the ties are removed, is something to consider.

Putting in backing epoxy inside has the problem of access of course, and potential for gluing in some of the wire, especially in the very narrow stern (below)

I am getting an inclination to use a small V chisel ( like a linocutting tool ), and widening the tight joins as LP suggested. I have to lay epoxy with a syringe in the wide joins further up the hull anyway, so being able to just keep on going through to the ends seems efficient.

A lot of the build processes can be done with multi-step processes, but I am keen to streamline the manufacturing process, and reduce the 'bitsy' nature of the build if possible.

 

Superglue will work, but will also prevent epoxy from sealing the grain, which is pretty important.

On a very acute joint you can "back butter" (like laying tile) as you bring the panels together with wire, ties, whatever. I've all but stopped using this type of assembly for several reasons, but if you precoat the area with a roller or brush, then join (tie) the panels, you can use a pastry bag or my favorite a disposable, medium size syringe, say 60 cc or more. This gets the goo in the tight space, in and around the ties and can even be worked into the touching panels themselves. Of course you'll want to spread this out into a neat fillet to make the next steps easier.



This is a veterinary and dentistry syringe that I use often. This one isn't very big, but they are available in larger sizes. The tube can be cut and a vinyl hose used to extend it's reach.



This one has the tubing installed and a large capacity (3.4 oz), which is easy to load and clean.

A thin artist's palate knife is another tool I use in these situations.



They're very flexible, easy to trim to fit tight spaces and don't cost much, though not really disposable.

 

Thanks Par - the blocking effect of the superglue of the epoxy could be significant, especially as the superglue will be destroyed by moisture.

As it turns out, I invested in a syringe and tube last week to help in the bead application of the more obtuse hull joints - but the artists palette knife is a great idea I haven't thought of.

Earlier this afternoon, spurred by LP's suggestion, I went out and bought a Dremel woodworking bit, with a sharp V point.

I am hoping with a steady hand I can create a useful groove to create an epoxy bond at the ends.

 

I am planning to build a canoe, hope to collect the plywood next week and have been surfing for ideas to make the construction as simple as possible.
I came across this video which is one of many by this builder.

He uses Gelmagic a non sagging two part epoxy. http://www.systemthree.com/store/pc/SilverTip-GelMagic-c16.htm

http://www.youtube.com/watch?v=-cvBkBqWNhs&feature=relmfu

I am intending to bevel the plank edges (as per lewisboats diagram) where adjoining planks do not have enough angle. As well as the bow and stern, the canoe I am building is wider than normal and has the same problem at the mid section where the bottom plank and the adjacent ones are virtually butt joints.

 

The Gelmagic looks like an interesting product, though very expensive.

Bevelling the plank edges would be the ideal solution.

The next time I get the plywood CnC'd I might inquire about getting some of the edges done with a bevel cutter, but then I suppose it takes away the option to choose an inner and outer plywood side based on the wood grain.

I had half the wire holes drilled during kit production, and that was a time saver.

PS - sorry Steve, I failed to accurately thank you for your suggestion of the V groove method. Thanks.

 

They do not appear to market Gelmagic in the UK so I am looking for alternative products, hopefully cheaper.

The risk with the cnc bevelled cutter might be that it would open the joint up too much further down the canoe.

I have been looking into router bits to open up the joint but that Dremel bit looks much better. Let us know how you get on with it. I shall be painting the outside so the odd wobble will be hidden.

 

I would get a shallow groove cut only in the places at the ends, where the join is too "butt" angled.

Then I would have the standard router finish the cuts, as per usual.

I too am not optimistic about a quality clear finish, but I will do my best and see how it comes out.

To get a really quality clear finish, you have to use the really expensive epoxy, and wouldn't come at that.

I do enjoy a good wood finish, but the strain of keeping the 'look' after rock covered beaches, underwater sticks etc etc just leaves me unimpressed.

 

Instead of going nuts with machining bevels and stuff, just pull out the trusty pocket rasp. I have one that's always in my pocket and has 4 different rasp faces to work with. Spring open the area, run the course side of this rasp down each end to "back cut" it a bit, for a place where the goo can live and call it a done deal. The rather imprecise nature of these builds means you don't need to be neat, a hatchet will do in most cases, with lots of filler to cover the "ways" of the builder later.

I also think you're over thinking this issue. With a "tack welded" approach on the inside, you can pull you stitches, then finish up the fillets. With the inside of the corner (the most important one) completed, you can grind open the out side, as part of the round over process (which has to be done so fabric can lay down) and apply more goo into the voids, plus seal the newly exposed end grain. Fill and fair flush, then tape - all is well and protected.

 

I think you can get a decent bright finish most clear laminating epoxies. I've used several brands on my "budget list" and the results are worthy of looking at. Even filled tie holes that aren't perfectly matched to the wood don't attract that much attention. You may have to limit how much you radius/sand the chine edges to keep from revealing the underlying grain. Everybody loves to see a wooden boat and people that see your finished project are going to be way less critical than you will be.

I wouldn't worry too much about glueing your ties in. I little bit of heat from a plumbers torch on the end will travel down the tie and melt the epoxy for easy removal. The bigger concern would be the lump of epoxy that remains after the wire is gone. Tough sanding and grinding in a tight area. The tacking process is not quite so fiddly as it might sound. Just make sure the tacks are the shape of the final fill coat. Once they set and the ties are gone, you finish the fill and apply your glass tape in the same work session and you've not really added any steps.

 

Instead of using wire for the ties, you could use fiberglass rope/strands. It would just become part of the structure. Years ago I watched Hobie Alter use fiberglass rope to tie his foam panels to the molds when he was making prototypes of the Hobie 33. It was pretty amazing how fast he made the prototype hulls for the 33.
You can also use plastic wire tires and just grind off the ends after the epoxy cures. I used plastic wire ties when I made my dinghy. After stitching the dinghy together you can also epoxy 2"x4" or 2"x6" strips of cloth between the ties to hold the joint together. Then remove the ties and fill in the gaps if you are concerned about appearance or just proceed with your taping.
When I make my next dinghy, I will use the use the wire ties again with the tie ends to the inside. Put the dinghy upside down and tape/epoxy all the joints on the outside of the hull. Flip it right side up, remove the tie ends from the inside and fillet, tape & epoxy the inside of all the joints.
Good luck with your project.

 

There really is no such thing as fiberglass rope, and strands of rope or fibreglass are almost impossible to push through drilled holes.

I have used plastic ties on test builds, and they have the limitation of not being as rigid as wire. There are quite a few times that a quick twist of the pliers will hold a plank in place, whereas a plastic or flexible fastener would either need replacing or some other complicated adjustment.

As I mentioned before, there are lots of 'tricky steps' that will overcome most problems, but they all add up to wasted time. Its a matter of an hour or two to add lots of temporary tabs inside the hull, but then you lose a day as you wait for them to cure, another 2 hours sanding them back prior to the full fiberglass inner layer etc. so that's another day in the process.

 

Its all a matter of defining 'decent'. Most laminating epoxies leave the outlines of the glass fibres showing, which may be 'decent' for some people, but not for some super fussy buyers who have no idea of what goes into building boats. Its easier to apply an eyecatching design over the epoxy, and save all the hassle of having an entirely wood hull.

All of what you say is quite possible, but it adds a heap of fiddly steps, all of which takes time, especially when building two hulls.

I am hoping that a bit of a widening with a sharp Dremel will allow an easily applied run of epoxy in one easy run with a syringe, without all the problems of applying glass tabs.