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This is the place to post your ideas, thoughts, questions and comments as relates to general boatbuilding and reconstruction techniques and procedures (i.e. recoring, epoxy, fiberglass, wood, etc.)
Finally started the recore job today. I thought that removal of the top skin would be a little easier than it was. Some parts of the core were totally melted and the top skin fell away easily, but other sections were still tightly adhered. After an hour with prybar, chisel, scraper, screwdriver, etc. I broke down and went to HD and got the Dremel Multimax. Terrible tool, but it did the job (barely). With many breaks to allow the machine to cool down enough to hold it, I finally got all the core material out. The Dremel POS will be going back to HD tomorrow, hopefully to replaced by something more robust (Multimaster?!?). There's no way I am taking down the other side deck and the foredeck out by hand!
And now for my question. On the photo below, the bottom skin on the cabin side of dotted line is literally paper thin in some places, and painfully thin in most places. In some areas you can see through the open weave to the liner sitting about a half an inch below. The other side of the dotted line is much more solid (probably from the glassed in hull-deck joint). Since its so flimsy and flexible, should I glass another piece of cloth (6 or 10 oz fabric) before I put in the core material? Or just go for the core material?
Thanks for any and all advice.
Doug
Good core, bad core. All saturated, though.
The thin part of the bottom skin is on the cabin side to the left of the photo.
The Dremel POS will be going back to HD tomorrow, hopefully to replaced by something more robust (Multimaster?!?).
Skilsaw. Cuts like butter just as fast as you want to go.
Since its so flimsy and flexible, should I glass another piece of cloth (6 or 10 oz fabric) before I put in the core material?
I think I would. Putting some pressure on the core while you glue it in really gets it into the epoxy well. If the skin wasn't strong enough to do that I would build up the skin a bit. Matter of fact, I think I have on occasion.
-Britton
Work is overrated.
Most everything you read on the Internet is wrong.
What you are showing is not unlike most boats of similar nature. The inner skins tend to be very, very thin. Structurally speaking, when the cored deck is all put together and well bonded to both sides, the thin inner skin does not pose a problem. However, it does pose some problems during repair.
Use your judgment about whether to, and/or how much to, reinforce it. You don't need to do so in terms of the strength of the cored deck, but you may need to simply for practicality and the ability to adequately work in the area.
One thing to keep in mind is that if you add material to the inner skin and then reapply the same thickness of core, it will stand taller than the original construction. This can lead to issues if you're reusing the top skin, as it may sit proud of the surrounding surfaces when you reinstall it. This can be a frustrating situation to correct.
You can avoid this problem if you laminate new fiberglass on top rather than re-use the old skin, which I'd recommend anyway (the new material, that is). It sounds as if you had enough trouble removing the top skin that it may have been destroyed anyway, but you didn't say whether you planned to use new material or reuse the top skin.
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Thanks for the advice guys. I did use a circular saw to cut the outline of the area, hoping the top skin would come up intact. It did not, so I will be using all new material. I think I will just go ahead and install the core material without reinforcing the bottom skin, since its not a very wide expanse. It should hold its shape, and if it deflects a little bit I can build it back up on top. If I encounter a similar situation in the foredeck, I will definitely be adding a layer though. I can't really add bracing from inside due to the liner, which only supports the foredeck in the middle.
My circular saw(s) worked great for zipping through the top skin, it was picking out the core material that was still adhered to the bottom skin which gave me fits yesterday and prompted the purchase of the Dremel MultiMax. I kind of though it might not be up to the job, but HD was close by and I didn't want to spend all day trying to find a better one. It did do the job, reluctantly, but I didn't realize it would be quite that bad. Good tools are worth every penny!
I've been finding (and am about to go out and continue) that using the circular saw to cut the top skin into little pieces (1"x1" where it's really adhered) makes it pretty easy to get it out. I then stick a 1" chisel into the saw kerf and lever it, most of the pieces have been popping right out that way.
How were you using your Dremel MultiMax? I just bought a Fein Multimaster and thought it would be the cat's meow for this job, but the things I thought it would be good for it's not quite working out on. It's great (with the scraper blade) for cleaning up left over bits of polyester resin and balsa once the bulk of the top skin and core have been removed, but it's slow to cut the top skin (and has such a narrow kerf that I can't use it as a place to put my chisel) and the scraper doesn't want to dig into the still-bonded core to remove the chunks of core & top skin. Since I'm new to using these vibrating tools if there is something else I can use the MM for I'd love to know what it is!
I've posted pictures of my efforts on my site (link in signature below) which show some of what I've mentioned here. I'll post more later - I'm hoping to be done with removing the top skin and core by the end of the day (may turn out to be wishful thinking).
Oh - and I've got the same incredibly thin bottom skin as you, and have had some holes created in it by the removal of the core (nothing since I started cutting it into smaller chunks, knock on wood), so I know what you're talking about in that regard. I believe that the very skinny bottom skin is possible because the interior liner is intended to be bonded directly to it. In my boat, at any rate, the liner is mostly bonded to the bottom skin - but there are voids in places, and the thickness of the bonding varies. I figure that the places where it has disappeared will be filled with thickened epoxy before I start laying the balsa core (in less thick (yoghurt-consistency) epoxy), and that'll help to complete the structural attachment of the liner as a beefing up of the bottom skin. My understanding of the way beams work, though, requires that the bottom skin be strong enough to hold things together, so having it be 1/32" thick or whatever it is probably isn't adequate without taking the liner into account. The top skin, on the other hand, is considerably thicker than it needs to be - presumably to have it better resist having winch handles and bottles of rum dropped on it. Since you're laying up your own new top skin if your situation is like mine with a top skin that's thicker than it needs to be you can always add a layer of cloth to the bottom skin and make the top skin correspondingly thinner.
Thanks for sharing some pictures! Good luck with it - it's nice to know there is someone else out there doing the same kind of annoying work that I am!
Someone may have said this, but for removing the balsa that is not rotten enough to scoop out with a putty knife I am using a real nasty flat wire wheel on an angle grinder. "Grooms" the balsa right down, and with the right touch stops at the inner (or in my case outer) fiberglass layer.
Update on the core replacement- I purchased the cheapest (least expensive!!) version of the Fein Multimaster. What a difference! At full power it blasted right through the balsa. Probably took less than half the time of the Dremel. I can tell i am going to find a ton of uses for the tool. My wife who is sick of my tool habit has even said it was worth every penny!
Its been awhile since I have worked with epoxy and I should have used slow hardener when filling in the gap on the sides of where the new core will go. But I didn't have any available so we went for it. It was midday about 80 degrees and the epoxy kicked too fast and heated the deck up. Only a few little curls of smoke though, so I am hoping its ok! My wife and I had to frantically shovel epoxy around for an hour for fear of it kicking in the pot. So could there be any structural issues from it kicking too fast?
