Epoxy filets or wooden cleats?

[John Blackhall]

Starting to install the bulkheads into the interior of the 23’ cold molded cutter. Bulkheads are 6mm plywood with a 3/4” by 2” laminated Doug Fir frame. I am having a mental debate on how best to attached the bunk fronts, counters, etc. to the bulkheads. The plans call for 3/4” triangular cleats, glued and nailed, all the books on the subject tend to suggest epoxy filets are the way to go. Personally I leaning towards the epoxy filets, the cleats will be finicky to install and I question the strength.

Thoughts, suggestions, comment?

[NormMessinger]

I'm sort of partial to Sam Devlin's construction methods if the boat fits. Epoxy fillets with glass tape to spread the load. Some like to be able to take things apart, however.

--Norm

[Wayne Jeffers]

If the plans call for wooden cleats, I see no reason to doubt their strength.

I think it's mostly a matter of personal preference. Which do you prefer to work with? I would choose cleats because I don't care much for working with Googe. But some people prefer Googe. Either one is okay, I'm sure.

Wayne

[Bayboat]

As Norm suggests, the main difference between the wood cleats and epoxy fillets is that you can dismantle easily if the members are screwed to wood cleats, but with epoxy you are stuck :rolleyes: with it.

[Leon Steyns]

I don't know where the idea comes from that epoxy irreversably turns into granite after curing. When 'tortured' by a hot air gun (or similar), the epoxy softens and can be removed using (sharp!) chisels and/or a planer. No more trouble than removing glued and screwed cleats.

Greets, Leon Steyns.

[The Schooner Etain]

Exactly Leon, which is why I won't use epoxy for any of my structural bits. The sun is just one huge heat gun waiting to make my epoxy weak and breakable. That's a whole other subject though. smile.gif

Chris

[kng]

hi !! Chris what did you said ?? sun as a huge heat gun ?? i´m building the Grey Seal plywood lapstrake bonded with epoxy...... please tell me that is just a joke !! or i will have to refresh the deck with water on sunny days ?? smile.gif
about the problem of john i would put cleats if i understand what his saying... strips of wood instead of epoxy fillets. i think they will look better.

bye !!
Emiliano.

[capt jake]

Poxy!

[Meerkat]

Kng; don't worry - just paint everything a light color - and most fillets are below decks anyway. Standard epoxy starts to soften at about 140F and a dark paint can build up that much heat, but a light color won't. Sam Devlin reports that all the boats he's painted dark (per customer request) end up showing "print through" where the weave of the glass cloth starts showing through the epoxy coating when it's gotten soft from the sun/high heat, but doesn't see it often in light colors.

If it really bothers you, you can use special epoxies, but those require a high-heat (oven) cure. Then you're good up to about 300F.

[kng]

Meerkat: i would like to build a bright deck, but when i read what you said, the joints between the deck planks may be will be dark and may be there will happen what you say..... any advice ??

bye !!

Emiliano

[Meerkat]

kng; They're not structural, so they won't cause the boat to sink. Come to think of it, bright deck seams aren't typically paid (filled) with epoxy either - it's a flexible silicone caulk to the best of my knowledge (some 3M product or similar, the name/number of which I don't recall offhand). Silicone is pretty heat resistant and as long as it doesn't crack and pull away from the deck planks, it shouldn't leak. If you epoxy the planks to the subdeck, I've read that there are limits on the plank dimensions because the planks will work (expand/contract) from environmental factors (heating, cooling, humidity changes) and the epoxy isn't elastic enough to cope if the wood is "too big" (real technical term there ;) ). I think the WEST System epoxy website has info on that issue.

Meanwhile, back at the fillet vs. cleat question: I think a taped fillet is going to make a much stronger bond then a glued 'n screwed cleat. Devlin uses them as structural components in lieu of frames etc. in most areas on his boats. Sort of like the difference between welding and crimping.

[Leon Steyns]

The big guys in the epoxy-industry (West, SystemThree, SP Systems, etc.) also offer specialized epoxy systems that are less prone to solar heat. They are more expensive, but not un-affordable when you consider the total cost of your boat and the amounts required. It would be overkill to use the special products on all fillets. Unless you want a black boat, the 'standard' epoxies are sufficient. If possible, SP Systems recommends elevated temperatures during the curing process for most of its epoxy systems, because it increases the strenght and makes the cured epoxy better resistant against high surface temperatures.
If you feel insecure, check with your epoxy manufacturer. I've yet to see the first case of a structural failure due to solar heat build-up.

Greets, Leon Steyns.

PS - I'm not opposed to traditional boat building, but I am opposed to people that ignore progress and development of new materials and construction methods. Choose what you like, but respect someone else's choice.

[ 10-26-2002, 05:37 AM: Message edited by: Leon Steyns ]

[wolfietuk]

Even Devlin uses cleats and screws to hold the seats on Nancys China. I cant speak for other designs. I am sure part of the reason is ease of use. The cleats are more than adequate for the job and a lot easier than working upside down to put epoxy in. If these are structural parts then the fillets may be called for. If not then it is overkill and a lot of work.

Rick

[On Vacation]

In cold moulded boats, many cases we use starboard cleats in place of wood on the inside area and tape fillets on the outside. Predrill and couterbore bulkheads. Nice alternative.

As far as take aparts, you will experience less take aparts in cold mould glass building then you will have in traditional wood craft. Just a point of note.

[ 10-26-2002, 07:04 AM: Message edited by: oyster ]

[NormMessinger]

My two cents as well. Epoxy (normal epoxy, chemist, just to remain technically correct) begins to soften at around 140 F. It does not fail at that temp. If it is heated to that temp or a little higher, it will not again soften until the higher temp is exceeded. In home build aircraft, some post-cure the googue just for that reason. "Not Normal" epoxy must be heated to cure.

Also, consider that wood is a pretty good insulator. So hot to the touch outside may will be comfortable for goop inside.

Is the fear of using epoxy for boats that will be used in the tropics based on true life experience or speculation? I'm _guessing_ the latter.

--Norm

[stan v]

I've had to remove epoxy (3 to 1) before, required a propane torch, then after heating while moving the flame, had to pry the part loose. Manufacturer suggested temp needs to be about 200 degrees to break bond between parts. That's a lot of sunshine. Epoxy must be removed with a grinder, or heat. Amazing stuff. Once put where you want it, forget about it.

[JimConlin]

For a 23' cold-molded boat where weight is an issue, I'd lean a lot toward liquid joinery, epoxy fillets. By varying size. fillet material, consistency of the bog and glass or no-glass, you have a lot of control over the strength and weight of the joint. The appearance can be pretty good, too. The one case I can think of where i'd use applied cleats is where I couldn't get to the back side of the joint after assembly. The outboard edge of a berth flat might be like this. Then, all you can do is apply a cleat, touch up its bevel, bond down the panel and temporarily secure it with weights, staples, or whatever works.