FL14 "Robjack" update

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Steve_MA
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FL14 "Robjack" update

Post by Steve_MA »

I figured I would start a running post here on my progress. After all your help, I finally got my head straight and committed to glass the whole boat so as to minimize any chance of water getting to the bcx plywood.

I got my E-poxy Monday and mixed up 3oz of the gooey stuff do to the butt blocks on the sides. They have had 36 hrs to cure now so today I going to stitch the sides together, cut the bottom and do its butt block. Then Friday I will stitch the bottom in place, duct tape the chines, flip it over and start the fillets.

I have been using the Devlin book as a resource. He says to keep your stitch holes the thickness of the ply + 1/8 from the edges....seems reasonable. I dont know if I am going to use cable ties or drywall screws for the frames yet. 3/8 is a small target to hit plus I dont want to split the wood. If I predrill some guide holes, I think it might work OK. Others seem to have done it. I was also thinking of using a cable tie as a spacer between the wood sections to keep a gap. This way I will have no "wood on wood" which I understand is the objective for a composite boat. For the F14 probably doesnt matter much though.

On the fillets, Devlin says make them about thickness of the ply and about 2X up the sides. I was planning to shoot for 3/8 thickness and 3/4 to 1" up the sides. I think I can get my plastic spoons to do these nicely. The FL14 plans show 1/2 thickness in one place and 3/4 thickness in another, but I think those are just generic references, not specific to the FL14. Are my planned fillets big enough?

I also want to maintain wet-on-wet as much as possible to minimize sanding. When does wet become "dry"? They only guages I have been able to figure out are (a) the epoxy form some kind of amine blush (?) after about 48 hrs that should be sanded off before the next coat and (b) wet epoxy has more "teeth" for the next layer to bond to....but I will be the epoxy is pretty firm about about 6hrs (in my space which is about 60 deg F). If I do my fillets and then come back with the 4" tape about a couple hrs (ie. before it gets real firm), is that still wet-on-wet?

OK - off to build!



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Post by jacquesmm »

A note about the Devlin book: it is excellent but does not always apply exactly to our boats.
Remember that we were specifying biaxial and filleting techniques before the Devlin book was published.
We recommend the Devlin book but clearly say in our building notes that, if there is a conflict between his recommendations and ours, you must follow our specifications.
His specs work for his designs, not for ours.
The radius of the fillet has nothing to do with the plywood thickness. It is a function of the fiberglass type and weight.
In general, an amateur will not able able to properly laminate light fiberglass around any corner sharper than 1/2".
Some experienced builders will shape 6 oz. around a 3/8" radius but that's the max.

Use as few screws as possible on the frames. On a FL14, you should not need any screws in the frames.
If you do, you will have an unfair hull.

Blush depends on the resin. West System blushes a lot, our MarinEpoxy slow and our Silver Tip do not blush.
Wet on wet means wet. Wet enough for the resin to wet the next layer but there is very little of that in the FL14.
What you are thinking about is secondary bond: one to two days is fine depending on the temperature. That is for our resins, not for West or Mas. With those ones, you must wait for complete cure and remove the amine.
Jacques Mertens - Designer
http://boatbuildercentral.com

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FL14

Post by mpacek »

Steve,
I am builiding a FL14 in Woburn. Had similar plywood concerns and I am ready to glass the bottom. Between cold weather and kids have not had the time. Some progress pictures are in the gallery under MikesFL14

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Post by fishingdan »

Steve,

We have all been at the same stage. Once you get started, you'll quickly get the feel of these things.

- Fillets just need to be large enough to allow the fiberglass tape to transition from one panel to another without any air gaps.

- Wet-on-wet for simply means that you will lay the tape on the seam before the fillet cures. Apply a light coat of epoxy on the joint, apply/shape the fillet, clean up any excess, apply another thin layer of unthickened epoxy over the fillet and then lay down the fiberglass tape. Once the tape is down and push it into place with a disposable brush or glove coated hand. Let the glass absorb the available excess resin. Then complete the saturation of the tape (no white tape visible) by applying a little more unthickened epoxy.

- This time of year in New England, keep your epoxy at room temps and you can work through the winter without any problem.

Overall, take your time and pick a small area for your first attempt. When you are done, you will look back and say "what was I worried about, that was easy". I said that after every step of building my first boat.

Good luck and enjoy the build.
Dan

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Post by Steve_MA »

Thanks Jacques....I guess I will keep posting my planned method ahead of time to make sure I dont screw up too bad. I didnt think of the impact of trying to bend the cloth around a small radius.

I got the hull "framed". I used cable ties and its suprisingly tight. It would have been a nightmare using screws I can see now.

As far as getting this thing square.....hmm......the transom corner to the bow measures 153.5" from both corners of the transom. To frame 1, I can get the measurements to be 129.75". However, if I measure to frame 3 or frame 5 for example, I can be 1/2 or maybe even 1" different. .... Well I just went to check it looks good now! Maybe only 1/2" different at most.

I have the hull supported on a 2x4 at the bow and the same on each side by the transom. If I pick it up by the sides at the transom, wiggle it around, and set it down, I can get things to come out differently....get it out of square.

Now that I have it square. I will put the bottom ply on, mark it, cut and glue it...then Friday, stitch it together.
updated pics at: http://photos.yahoo.com/eabsjw

(I would use the bateau gallery, but first time I had a filesize problem, now I have a resolution problem, arghh..)

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Post by Steve_MA »

Wet-on-wet for simply means that you will lay the tape on the seam before the fillet cures. Apply a light coat of epoxy on the joint, apply/shape the fillet, clean up any excess, apply another thin layer of unthickened epoxy over the fillet and then lay down the fiberglass tape. Once the tape is down and push it into place with a disposable brush or glove coated hand. Let the glass absorb the available excess resin. Then complete the saturation of the tape (no white tape visible) by applying a little more unthickened epoxy.
This is pretty much what I was going to do. Should I try to serve the fillet mixture out of a ziplock bag like a cake decorator? I was thinking doing that then smoothing it with a spoon would be a good way to do it. I am not so sure the bag thing will work though.

I assume I am going to do corner to corner and not corner the tape at 90 degrees. I suppose it could be done but a couple scissor snips would be required to make it lay flat. Any guidelines on how much epoxy to mix at a time? How many pieces of tape can you lay with it? I only mixing 3oz batches now and it seems to firm up by the time to get to the end of it - may 5-10 minutes. This is with med hardner at 65 deg. Seems pretty fast. I think I should be able to get 15-30 minutes shouldn't I? Do I just need to mix more?

I am sure I will figure out a technique after a few trys, but I like hearing other peoples experience.

Lastly I was going to cover the fillets with some 4mil plastic after the tape is saturated and then roll it lightly with a clean roller. This I am hoping will give me a nice smooth fillet.

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Post by Steve_MA »

Blush depends on the resin. West System blushes a lot, our MarinEpoxy slow and our Silver Tip do not blush.
Wet on wet means wet. Wet enough for the resin to wet the next layer but there is very little of that in the FL14.
What you are thinking about is secondary bond: one to two days is fine depending on the temperature. That is for our resins, not for West or Mas. With those ones, you must wait for complete cure and remove the amine
So - if I epoxy seal the plywood, then come back a week later to apply a cloth covering to the plywood, can work right over the cured epoxy without sanding? (Using E-poxy)

I was going to do all the fillets first, then come back and cloth the large areas later (like several days later). I want to miniimize any epoxy I need to sand. If I dont have to sand it, I can just expoxy coat the large areas and not worry where the epoxy goes. If I *do* have to sand, I will confiine the expoy to the filllets.

Thanks for the help

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Post by ks8 »

Personally, I wanted the glass to be bonded to the wood with the same batch of epoxy. I wetout the cloth on the dry wood hull panels. Of course I had first taped the seams, let them cure, and sand prepped them all, without cutting too deep and avoiding cutting cloth.

If you epoxy all surfaces first, I would think it wise, if it cures, to first wash any potential blush off, then sand rough it up for a sheathing of glass and epoxy. After sand prep of such surfaces, I usually wipe it down with a couple of clean damp cloths after a light wash with a *damper* cloth, to get any fine dust out of the roughed up surface, since the next epoxy layer is relying on a mechanical bond instead of chemical. And I let it dry overnight and up to about noon the next day, in case I had sanded through the first cured coat and got the wood a little damp in those areas.

There will be, no doubt, several good opinions on the matter. Just remember that any epoxy coats after a preliminary coat has cured, will no longer be a total chemical continuous bond, but will rely on mechanical bond properties between the layers, which means it will, I believe, always help to rough it up a bit, even if a resin type boasts No blush at all.

sincerely,
ks

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Post by Steve_MA »

Thanks, ks....sounds like a prudent way to do it. I had forgot about dry time, especially for the wood. Your comment about the epoxy making a chemical bond with the wood got me thinking too.....I didn't realize that....it caused me to go do a bunch of reading on the forum and other places...

I picked up some tips on related items:
- let fillets cure up 30 min or so before applying tape
- dont mix more than about 15oz epoxy at once and try to apply to 15sq ft (Sys 3 epoxy book)
- you can wipe amine blush off with water
- "sanding" - if only for mechanical purposes - can be done with something like a damp scotchbrite pad - this will keep dust down immensely. Sounds like it might be worth a try
- if you cant get to a surface and want to avoid sanding - you can slip in a "skim" coat to give you an extra couple days

I am probably way over analyzing this, but heh....it beats work!

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Post by Mike Adams »

jacquesmm wrote:Use as few screws as possible on the frames. On a FL14, you should not need any screws in the frames.
If you do, you will have an unfair hull.
Jacques,

I've just started my FL14 (see separate post). I'm a bit confused by your comment on the use of screws. On page 2 of the building notes, under 'Assembly', it says: "Fasten the frame to the side panels. Fastening can be done with screws or staples. Stitching or taping are other acceptable methods."

I bought some bronze screws especially to do this job, and a special countersinking bit to ensure a straight and true pilot hole for the screws. Why will the use of screws result in an unfair hull? Should I forget about using them? :?
FL14 "Lake Dreamer" built.

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