two 6 oz deck
single 6 oz bottom
free laps
any drawbacks to deck first?
Curing resin shrinks. The thicker, the more. Thus it (slightly) modifies the board’s rocker. That’s why you usually begin with the one layer bottom. This will “flatten” the rocker a little bit. Then the two layers of the deck will have the opposite effect and both distortions will tend to nullify each other. Besides it’s easier to sand the lap on the curved deck side than on the flat bottom without hitting the foam…
I always thought that you glassed the bottom first because of the weight issues. You would lose rocker with the weight of all that glass on the deck first because the weight would flatten it out. So you glass the bottom first to keep your rocker and give the blank stiffness to resist the flattening when you glass your deck.
But in general, you always want your strongest or overlapping layer on top, with weaker layers under neath to be protected by the stonger layer. Examples: When doing repair, you put on the small patch first, and the bigger patch over it…when glassing on fins, you use successively larger strips of cloth in the corner of the fin…
you’ve got that backwards. as the resin cures, it contracts. glassing the deck first will INCREASE rocker. weight has nothing to do with it. moreover, the only part that gets “protected” by another layer is the lap. and that all nets out to glass on top of glass. what does it matter whether it’s 2 layers of 6-oz from the deck over 1 layer of 6-oz from the bottom or 1 layer of 6-oz from the bottom lapped over 2 layers of 6-oz from the deck. the point is that it all bonds together. 3 layers of 6-oz glass is 3 layers of 6-oz glass. and the logic in your examples is not sound. larger pieces of glass does not mean stronger…it just keeps everything all sealed in nicely and allows for a better distribution of stress across multiple pieces of glass. it’s the fact that multiple layer of glass are used that gives it strength. making these layers successively larger is just common sense…making them successively smaller wouldn’t work, now, would it. whether deck or bottom is glassed first has absolutely nothing to do with the size of the cloth or the size of the lap.
EDIT: however, with epoxy resin, because it’s more elastic, lams do not noticeably change rocker. also, waaayyyyyy back in the day, i believe it was common to glass the deck first.
if curing resin shrinks, why dosen’t it pull away from the sides of the hole or container it’s in? What role does thermal expansion play?
If you do a 4+6 lam, don’t you put the 4 down first? Why?
I did a hot coat yesterday, (quite heavily catalysed) and it was a hot day, too. I tell you, the resin remaining in the pot did shrink off the sides. I believe the more heat, the more shrinkage (or the thicker, which does the same since heat goes up with resin thickness).
Also, I believe the reason for 4 oz first is the thinner weave will bond better to foam. Any other reason?
I was always under the impression that if you put a thinner cloth over a thicker cloth, any given impact would penetrate the thinner, upper layer easier than it would have if the top layer, which takes the impact directly, was thicker and stronger.
Can you explain why a thinner cloth would bond better to foam? I thought that coarser surfaces bond better than smoother surfaces, giving a better mechanical bond. That leads me to believe that heavier cloth would actually bond better because it’s a bigger, bulkier weave.
As for shrinkage… I mistakenly put too much hardener in a batch of epoxy once, and the stuff actually rose like bread in the oven… When things get hot, they expand. Resin has to get hot in order to turn from a liquid to a solid. So I can’t explain any significant shrinkage… Why does it shrink?
I don’t know about epoxy, I don’t use it. But I do know that polyester resin shrinks. I think the exact figures are between 2 and 7%, depending on resin types. As for bonding, I think I didn’t put it clearly enough: the thing is, the thinner the weave, the less resin is required between foam and glass. Less resin equals more flexibility of the resin film and thus less delamination. Delamination occurs when the foam flexes and the glass/resin combo doesn’t (or not as much).
I get it now… thanks for the info.
I just e-mailed GL to see if he has any specs on RR epoxy and shrinkage. Except for water, all solids are supposed to be more dense than liquids, which translates into reduced volume - shrinkage. I just don’t know about the effects of expansion as the resin heats up… Is it just temporary, before it solidifies? And epoxy has a really slow, steady cure… it dosen’t “kick” or jell…just gets more and more viscous. So I wonder what it’s doing… expanding or shrinking…
yea… I’m doing all epoxy stuff, and I don’t notice any rocker changes or shrinkage…
You mentioned the elasticity of epoxy… why do people always blame epoxy for being too stiff? Personally, I don’t have a problem with my boards being too stiff, but epoxy has come a long way…
Do you have any specs on elasticity or volume changes for poly vs. epoxy? I’m looking for that info…
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yea… I’m doing all epoxy stuff, and I don’t notice any rocker changes or shrinkage…
You mentioned the elasticity of epoxy… why do people always blame epoxy for being too stiff? Personally, I don’t have a problem with my boards being too stiff, but epoxy has come a long way…
Do you have any specs on elasticity or volume changes for poly vs. epoxy? I’m looking for that info…
hi…sorry, i’ve been out of town this last week…without internet. anyhow…
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i’m also using epoxy these days, and haven’t noticed any significant changes after glassing.
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people equate epoxy to surftech. they immediately write off a board glassed with epoxy resin as pop-out POS. it’s out of ignorance. i once thought the same thing, until i was enlightened by Swaylocks’ epoxy gurus.
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i’d venture to guess that greg would be your best bet for that kinda info.
hope you at least got some waves on your trip…
I shot Greg an e-mail but haven’t heard back from him. I’m sure he’s got a lot on his plate right now…
On thing I’ve recently discovered: I did two ding repairs recently where I laminated in a warm place (indoors) using fast hardener, then put the board in a cool place for about an hour, until the resin starts to get thick, then brought it back inside where it’s warm. The result is to get a little resin sucking into the foam just before it kicks, then warming it back up to speed up the cure and get a good bond without the risk of outgassing. Really saturates the foam in the immediate area of the ding without pulling too much resin out of the cloth.
I wonder how that would work for laminating a shaped blank…
Resin shrinks and gets hot in a bucket.If it is spread out over a board shrinkage and heat(exotherm) are less.I dont think it matters which side you glass first unless you are dealing with micrometer measurements.Have Fun. RB
I do know that west system epoxy shrinks away from the sides of the bucket to some extend, I would assume thar RR does as well.
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Curing resin shrinks. The thicker, the more. Thus it (slightly) modifies the board’s rocker. That’s why you usually begin with the one layer bottom. This will “flatten” the rocker a little bit. Then the two layers of the deck will have the opposite effect and both distortions will tend to nullify each other. Besides it’s easier to sand the lap on the curved deck side than on the flat bottom without hitting the foam…
If you glass the top 2nd aren’t you covering the bottom lap all of which is on the deck with your two deck layers. How does that make sanding the bottom lap easier.
Mark.
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hope you at least got some waves on your trip…
unfortunately, no. i was on spring break from law school, and went to a school in new york for some religious studies. wow…the mere notion of that just sounds horribly wrong…spending all of spring break studying something completely unrelated to the classes i’m taking when not on break. although, i do spend every morning at the beach (gettin’ a little morning sesh, if the ocean gives me just cause) before going to class. so i really can’t complain. besides i blew off class on monday (first day back from spring break) and got some fun waves. even managed to take a day off when i was up north and try snowboarding…although it would be more accurate to call it “me falling down a mountain on my A$$”. note to self…surfing and snowboarding are NOTHING alike.
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Quote:If you glass the top 2nd aren’t you covering the bottom lap all of which is on the deck with your two deck layers. How does that make sanding the bottom lap easier.
Mark.
When you glass the bottom first, the lap on the deck side is on foam. If you have some sanding to do on it before laminating the deck, the curve of the rail (on the deck side) makes it easier to sand (or surform) without hitting the foam. If you laminated the deck first, it would be harder since the bottom is usually rather flat. Besides, as far as laminating is concerned, it’s easier to stick the glass on the rails deck-side than bottom.