GIS - Epoxy question

[Tomahawk J]

Hello all, I'm brand new to this forum. By trade I'm a cabinet and furniture maker, but this is my first attempt at boatbuilding. I started building my GIS about a month ago and am just about ready to put the hull together. My question is, which is better, build the hull, then epoxy coat the interior, or coat the panels, then assemble? If I pre-coat the panels, how important is it that I mask all the glueing surfaces for the bulkheads and other framing timbers?


Thanks,
J

[jmk89]

J

My reading of Michael's FAQ (http://www.storerboatplans.com/Faq/faqindex.html) on his website leads me to believe that you can do it either of the following ways:

you mask off the areas that you are going to glue and remove the masking before the epoxy has gone fully off or
without masking you use the same kind of epoxy (with thickener) for the adhesive and you rub off any waxy surface that the epoxy has (I believe that some epoxies are better at not having this than others) before gluing.A third alternative is to use the all at once system that Mik describes:
One Hit coating and gluing
An extension of wet on wet epoxying is a method for coating areas that are easy to get at now (plain plywood compenents) may be hard to get at a bit later when other parts are attached. A couple of examples are fitting the bottom, fitting the side decks and fitting framing to the bulkheads.
For example if gluing the bottom panel in place it is easy to coat the inside of the bottom at the same time. For major gluing processes like this it is important to make sure that everything will work smoothly – do a DRY RUN without the epoxy to make sure that you have enough screws etc to hold the bottom on OK – you can use the same holes again when you are putting the bottom on permanently.This is the method (put on your disposable gloves!!!).
1/ get all the framing that the bottom will be attached to bevelled and ready to accept glue
2/ put three coats of epoxy “wet on wet” on the inside of the bottom as per the mehod in the appendix above.
3/ immediately put glue (epoxy plus the gluing thickening powder – make up to a peanut paste thickness) on all the framing of the hull that the inside of the bottom will be glued to – spread it out ready to take the bottom.
4/ drop the bottom on with its wet face in contact with the glue in the previous step and screw the bottom in place.
5/ clean up any excess glue that has squeezed out of the joints about 20 minutes after the assembly. If you wait till tomorrow you will be sanding forever. Use a flat piece of timber sharpened to a chisel edge on the end with a sander.

The same method can be used when putting the framing on the bulkheads. Coat one side of the bulkhead immediately before gluing the framing on that side.





But I am sure that Mik will be along and will give you the correct answer

[Boatmik]

Perfect and elegant explanation JMK - that's how the system is supposed to work!!!!

the precoating methods without masking do rely on either your epoxy not waxing much or being easy to dewax. This is critical for reliable secondary bonding.

Doing the epoxy once the boat is assembled is to be avoided at all costs. It is soooooo labourious - so messy - and wasteful of materials which then just add weight to the boat.

The one shot method above is particularly suitable to items that have only one side being coated at a time.

The three coats wet on wet are recommended. Wet on wet is the biggest key to get the amount of labour down.

Thanks again JMK and good luck Thomas Hawk - we can help with any other questions

MIK

[Daddles]

Even with a square sectioned boat full of flat surfaces like the GIS, coating once the boat has been assembled is tricky. For starters, you won't be able to use a roller for much of the work and believe me, using a brush instead of a roller is messier, harder, more frustrating and uses a heap more epoxy. Do it first if you can :2tsup:

That isn't to say you can't coat a partly completed boat (eg, do the floatation tanks BEFORE gluing the tops on :wink:). I have to do the inside of Sixpence and she's lapstrake with side tanks :cool: I'm not looking forward to it and it'll be brush all the way :( (yes, I've experimented with a dry roller - filling the tanks with poxy then bailing them out would be easier in a couple of spot).

Mik's 'All in one' effort sounds scary if you haven't done it. While I haven't put a hull together that way, I have coated plenty of decks then glued them to the boat while wet, which is pretty much the same deal - it's not hard in real life. Unless you're working in very high temperatures, the poxy is pretty forgiving stuff. Buy the SLOW hardener if you've got the chance eg West Systems - you don't need the extra working time often but it's nice when it's there.

One tip - when coating with a roller, DON'T put your roller down in the tray. Usually you won't have a problem, but with my recent laminating effort, doing so concentrated the heat in one spot and the next thing I knew, the pot of poxy was smoking and I had epoxy instant glue to work with :oo: New roller, new tray and a new mix solved the problem but ...
Similarly, don't mix up too much in one hit or store it in a deep pot with a small cross section - you can get the same sort of heat build up. It's not a problem, you know it's happening because of all the heat, but you do have to chuck the mix and have another go.

Dry fit everything first and do it as many times as needed. There is ALWAYS and easy way of clamping things together, often so easy you can't see it, so experiment. Once you're ready, take a deep breath, pull on some gloves and got for it :2tsup:

Richard

[Boatmik]

Hi Daddles ... it is the deck method I was talking about with the "one hit" method and sometimes it is extendable to other bits like centreboard cases and rudder boxes.

Slow hardener is available for most brands of epoxy - but it is only a slight amount of comfort. Whatever the hardener it can be a smoking mess in 5 minutes or you can have half an hour or more of trouble free playing.

The things that really give you comfort are
1/ getting everthing ready and organised BEFORE you mix the epoxy. If it is a complex setup DO A DRY RUN
2/ mix the epoxy and get it out on the surfaces quickly - this way the heat can dissipate and the epoxy goes off more slowly. Use plastic snap lock bags as piping bags for mixed glue - pipe onto the surface and spread after it is all piped out.
With glassing mix a tin and then get it out on the surface - spread roughly with a squeegee then finish with a roller - don't rush rolling too much or you will introduce too much air into the resin. Happily with glass you can work progressively along the hull or preferably from the middle towards the ends mixing up enough epozy for you to handle each time and finishing applying it to a section before moving on.

If you leave slow or fast hardened epoxy in a mass - in a bag or tin or tray - on a reasonably warm day it will be a smoking mass in 15 minutes and would have been disastrous to apply to a hull as a quickly hardening mess after even 5 minutes in a tin.

AFTER MIXING PROPERLY - Get it out on the surface and in most conditions you will have a half hour or more. If your dry run tells you that you need more than a half hour for a gluing process then break it up into smaller bits. Like with a bottom made up of lots of sheets mix enough glue for one sheet - get it on - then move to the next sheet - etc.

If you are planning to glass and recoat using hte wet on wet method and you think you won't have enough time - get someone to mix the epoxy and then hand it to you.

Happily - while all of this sounds highly dramatic, the bigger jobs tend toward the end of the building process so you have plenty of experience by the time you get to the bigger ones.

There are only very occasional problems where this type of advice has been followed whchever hardener has been available.

Best wishes
Michael

Oh and don't work in the direct sunlight on a warm or hot day unless the job is simple gluing of a smallish area. Direct sunlight when glassing or coating usually results in thousands of tiny bubbles as the air in the timber expands.

[Daddles]

Oh and don't work in the direct sunlight on a warm or hot day unless the job is simple gluing of a smallish area. Direct sunlight when glassing or coating usually results in thousands of tiny bubbles as the air in the timber expands.

Oh yeah. Working in the shed in high summer can be like working with super glue :oo:

Just reiterating though, using epoxy sounds scary but is really quite benign ... just don't get it on your skin (some people become alergic to the muck).

Richard

[Boatmik]

clean off skin with vinegar - but don't get any vinegar near epoxy that you hope will cure.

Sensitisation as Daddles points out - is an allergic reaction and can build up over time for some people.

I'm allergic to horses, but not epoxy.

You can also become sensitised working in confined spaces with poor ventilation.

Michael

[Tomahawk J]

Thanks for the Info. I started coating the inside of the hull sides and the bulkheads day before yesterday. Not as smooth as I'd like it, but I expect It'll come with practice. By the way, how thick should each coat be?

J

[Daddles]

By the way, how thick should each coat be?

J

As thin as you can make them. It's obvious if it needs another coat, in which case you just roll on another thin one until done. But if you whack a thick coat on, you just wind up with lumps and puddles and runs and usually put on too much epoxy. Guess how I know this stuff :-

Richard

[Boatmik]

Good info Daddles!!!

Use a thin foam roller for as much as possible and have a disposable brush as backup.

With the brush cut the bristles down to around an inch in length. Prevents the brush overloading with epoxy and allows you to get a lot more pressure to spread the stuff.

With the roller you can get a nicer surface if you hold the roller directly and gently and slowly slide it over the surface of the epoxy and it will puncture any bubbles and get rid of the stipple for a very nice surface.

BTW - the only rational way to epoxy seal a boat is to do all the coats you need (typically three) wet on wet. Wait for the first one to become quite tacky, then go over again - then wait for that to go tacky - then the final coat.

MIK