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I am a total newbie to boatbuilding and I am constructing a Melanesia.

I have my panels cut out from the plywood sheets and I am about to glue the buttstraps, stringers, laminate the stem and stern posts. To do that, am I going to use the Epoxy resin + filler just like for the fillets?

Do I have to coat the surfaces to be glued previously? (In the booklet it says: "Endgrain has to be coated with pure resin first, as it sucks the resin out of the glue mixture..." I am not totally sure what endgrain means)

I am finding it difficult to find in my country microfibres, colloidal silica or microspheres... A surfboard shaper told me I could use fine sawdust as a filler... would you recommend that? Could I use it both for glueing the parts and for the fillets?


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Hi - short answer, no you don't use the fillet mix for gluing! I would suggest you check out some of the "how to" guides that are freely available online for example http://www.westsystem.com/ss/use-guides/ , there you will also find the link to download the "Gougeon brothers on boat construction" which is the classic (I think updated) text on the subject of using wood and epoxy for boat construction.

Endgrain is the part of the wood exposed when you cut across the grain - it is easy to see that it is more porous looking. The method is to coat these parts with pure epoxy (ie epoxy + hardner), then the glue mix has something to attach to. You do this also for the plywood surfaces to be joined. For gluing I usually use microfibres 403, and for fillets the "filleting blend" 405B (West system numbers). You can use additives like sawdust, but I don't have experience of using it for a whole project. Basically the additives give the epoxy something to attach to, to give the mass without being too brittle and allowing you to make fillets which would be impossible if it was just a runny liquid.

Good luck with your build!

Bonjour Christian,
I am myself a little confused, but here is what I understand.
There are three actions: coating, gluing, filletting.
1/Coating. You coat everything which will not be protected by a glass fabric, or glued. If you have to glue something that you have coated, you need to sand it for good adherence. You need two coats. Depending on your supplier, you will have to sand between the coats if you get a bad appearance (The wood fiber seems to "move up") These are made with resin and hardener only, and takes, in my case, a whole day to dry. Typical use is inside of the hull, mast...
2/Gluing: You glue with resin and hardener, well mixed, in which you had some fibers. I use West System 403, (since I do not know the real name of this fiber, I have to go for a brand recommended by Wharram. I beleive that with the real name, you find it cheaper). Put your fibers after you have mixed the resin and the hardener, and mix again. Aply on both faces and clamp or stich if necessary.
However, I have found a ready to use AB Epoxy glue. I made some trials, the joint I got was far stronger that the BS1080 iroko marine plywood I have. So I use it now, plus I have it for free. It dries faster than the resin with 403 fibers.
3/Filleting: I haven't tried yet, since there wasn't the West System 409 available at the shop, and didn't knew the real name of the product before Budget Boater and Chuck Valley kindly gave it to me. It is "hydrophilic fumed silica". It is nice to know a real name for a real thing... I have ordered it, and wait for, so I didn't tried it yet. It seems that, according to the technical (or cooking?) terms of Goujon Brothers, you may mixed it with the resin and get cream, peanut butter (never seen peanut butter in my life, I will go to a grocery store soon) mayonnaise (this I know) and others dellicacy. Don't eat all of these preparations, use them for your fillets, or to fill a gap, or to inject in some holes. I repeat, I haven't tried it yet, just like you I'm new on epoxy, which is dirty, tacky, and dangerous. But very efficient. On my opinion, do one thing at a time, follow the book and you will not find anything really difficult.
I wish you all the best,
Ah: You may or may not read the Goujon Brothers book, but don't read it as a novel, go to what you need, like in a dictionnary...

Sorry but for i'm most clear in french.
La resine est une base qui vas envelopper l'ensemble de ta construction. Donc lorsque tu doit protéger une surface résine avec ou non untissus de verre. Si tu doit coller deux pièce entre elle, ajoute à ta résine une chatge qui vas conbler les irrégularités plus une autre qui augmente la résistance de ton collage. Respectivement fibre de cellulose puis silice colloïdale ( fumed).les fameux filets joint congé sont fait avec les mêmes produits mais en plus grande proportion.
Personnellement, j'ai toujours assemblé avant de recouvrir de résine. Ce qu il faut éviter, c'est de sécher un collage, c'est à dire, ne pas mettre suffisamment de résine avec la charge.
Les vidéos de démonstration de collage, Westsystem montrent bien de commencer par imprégner de resine pure les deux faces à assembler, puis encoller au moins une face avec de la résine chargée. Donc, enduire les faces puis attendre la polymérisation puis poncer, c'est perdre du temps ,et surtout ne pas bénéficier de la liaison chimique. On peu même dans la foulée réaliser selon l'endroit, le fameux joint congé.
Pour la réalisation de ma pirogue double de voyage, j'ai utilisé cette méthode. J'ai réservé tous les endroits où je devais effectuer des collages, et j'ai enduit mes cloisons pour être prête à peindre.
Good luck and enjoy to build.

Sawdust is all but worthless as an epoxy filler in boat building. It adds nothing to the strength and is hard to sand. Its only possible use is as a coloring agent for cosmetics purposes.

Most wood to wood joints will benefit from the application of a straight epoxy mixture to "pre-wet" the wood before the thickened epoxy is introduced into the joint. Anywhere from 15 minutes to a couple of hours may be needed to provide sufficient time for the epoxy to soak into the wood.

Fillers are used to control and modify the consistency and final strength of the epoxy. They are always added, after the resin and hardener have been thoroughly mixed, in accordance with the manufacturers directions. The addition of cotton fibers help in wood to wood joints. Fumed silica (colloidal silica, Cabosil or Aerosil) helps control the amount of sag in the epoxy, but is extremely hard to sand. Other fillers, like micro-bubbles and talc, are used to make filleting and fairing compounds.

Combinations of additives may be premixed and stored for usage. I use a combination of 1 Part Cotton Fibers, 2 Parts Fumed Silica, and 3 Parts Micro Bubbles as a filleting compound. I use 1 Part Fumed Silica and 4 Parts Micro Bubbles as a fairing compound. These mixtures are based upon the work of others and I've found them to be very effective when properly mixed and applied.


Endgrain : in a ply sheet the width of the sheet (as opposed to the faces). In a length of wood the ends.

You can glue with resin and hardener, if the surface to glue is vertical and the epoxy mix will not stay put or if there are voids between the surfaces to be glued you can thicken the epoxy mix with sawdust or microfibers, even with silica. But don't overdo it, just thick enough.

Between coats of epoxy or before glueing something which is coated you must sand the surfaces, or you can apply the next coat (or glue) before the previous coat has cured (when it's still sticky but not wet, couple of hours) which will make an even better bond as there will be a chemical bond (as opposed to a mechanical bond when sanded) between the coats.

For fillets Wharram recommends : "Low density epoxy fillets are made of epoxy resin and hardener to which are added Microspheres (white) or Microballoons (brown) and some Colloidal Silica. The proportion of the fillers should be approximately 90% spheres/balloons to 10% Silica. However a higher percentage of Colloidal Silica is not detrimental and makes the fillets harder and stronger. You can make a dry blend of the two fillers in a large container, so that it can be directly added to the epoxy, but make sure that they are thoroughly mixed."

All is said, most clearly than me.
Jean Paul

Thank you all for your advice!

As you say, Ricardo, I think the best will be to glue just applying a coat that is not left to cure... just like the videos on West Systems show (http://www.westsystem.com/ss/basic-bonding-techniques/)

I will forget about sawdust and go for the proper stuff, as you say Omar.

Éric: nice to see that someone shares my confusion. Only a frenchman could have such a fine appreciation of the gastronomic qualities of the epoxy! I will tell you myself once I try the mayonnaise and the peanut butter.

oh y' m sorry ,epoxy be changing in butter!

French mans can't workink without gastronomic material.

catamaran creme

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