Drop half a pound by minimizing fill coat

General Discussion
1

 

I posted some of this earlier in another thread that was widely ignored.  I thought I would trim the content  back a little, drop the Xglass discussion and see if anyone had an idea about this.

I have glassed two boards in the last week or so as an experiment.  Both 6-5 round tails pretty much the same. One regular, one asymmetrical.  Both stringerless.  I got a small roll of 56 inch wide 2.3 oz glass plain weave from Thayercraft .  I was interested to see how much I could reduce the amount of fill coat needed to get a smooth finish when I used  2.3 oz on the outside instead of a heavier weight cloth.  I have previously found that by putting the finer weave lighter cloth on the outside of a lamination, you can reduce by 1/3 or more the amount of resin used for the fill coat. And in place of the resin, which adds no strength to the lamination, you add more fiber, which does add strength.  Mike Daniel is saying amen.

On the other board, I used 4 oz warp on the outside.

 I had a few problems handling the 2.3 oz.  I thought it would be good to share a bit.  Actually, over all, it turned out well.  I am definitely liking where this is going, but I have a few kinks to work out.    See what you think.

1.     I am still convinced that a multi layer lam is the way to go.  Three layers of 4 oz is better that one layer of 12 oz or two layers of 6.  Just like G10.  Inter-laminar bonding, and better glass to resin ratio.

2.     Using smaller weave cloth on the outer lam to minimize fill coat and weight seems like a smart thing to do.  Exchange the worthless weight of resin with some fiber and reduce the amount of resin needed to fill the weave.  On the board with 2.3 oz on the outside, instead of using 7 oz of fill coat resin per side I used 3 oz.  I used the squeegee to move it around and cover the board, then the brush to smooth it out and get the needed finish.  On one board, I saved a half pound of weight (total both sides), and didn’t have to sand the excess off.    The problem was that the light cloth moved around as I laminated and it was really hard to avoid bunching at the curves.  As I tried to pull it tight, it just bunched up locally.  It didn’t wrap the sharper curves on the round tail very well and left me with a lot of sanding on the wrapped laps.   I found on the curves that you needed lots of relief cuts to get it to wrap well.  This particular 2.3 oz plain weave was just hard to work with.

6.     In spite of all the trouble I had during lamination with the 2.3 oz,  I really did save a lot of resin on the fill coat.  That 2.3 oz cloth almost didn’t need a fill coat.  (see Pic).  I would have normally used 7 oz of fill on a 4 oz cloth but instead used only 3 oz.  Actually, I could have used less and been fine.

7.     Weight diff:  I saved 8 oz of resin for both sides on the fill coat but added about 8 sq ft times two of 2.3 oz cloth, so the weight saved was 8 oz resin minus about 4 oz of cloth.  And the board ought to be stronger.  Ought to be.

8.      I used rail channels on both boards.  Using the 2.3 oz made this a big pain. I couldn’t run my finger in the slot to push it down and pull out resin without bunching and moving.   No problem with the 4 oz.

 

Anyone have any ideas for making the 2.3 easier to work with?

 

Here is the board with the 2.3 oz on the outside.  Very slick.  I used 3 oz, but could have gotten by with less, maybe none for the deck.

 

 

for comparison, here is the 4 oz outer lam on the other board.  Obviously, some fill is needed.  You can see the x glass underneath.

 

 

So, I saved a half a pound of weight on a 6-5 SB, and strengthened it as well.  Or did I?  Actually, my before and after weights bear this out exactly.

 

 

 

2

I don’t see how this can be…

whether on top or inside, you still have to fill the weave of both layers, right?

 

3

If you wan’t to save more weight, vacuumbag your board after glassing.

 

Your resin to fibre ratio will be much lower AND you won’t have the troubles with your 2.3oz weave anymore!

4

It's not me saying ''amen'', it's Eric and Kirk Brasington. Viva la fiber!!!

5

Amen to more layers of lighter glass and ditto what Hans has said above…

Why not trim the 2.3 oz right to the edge of the rail and not try to wrap it at all… I’ve got the same cloth probably, but I mostly use it for under skin applications…

6

It just takes a lot less fill resin to fill the weave on a finer weave.  That is where the savings comes from.  On a 6 oz weave, I’d need 7 oz of resin minimum or I’d be sanding off the tops of the yarns in the weave.

7

Kite, good idea.  I have not yet been brave enough to bag the lam yet, but I think I may need to go there next.  On the other hand, when you bag any weave, you will compress the weave which should reduce the need for filling the weave. 

 

I hand intially wanted to use the 2.3 in an X pattern as X glass.  I could do that under a layer of say 4 oz,  then bag the lam and be fairly light.  hmmm.  thx for the idea.

8

Hey Greg.

I hope I didn’t lead up up the wrong tree with my usage of  2.3oz. under skins. Skins as in bamboo and core-cell bottom skins is what I was refering to…

I’d stick with the light weight stuff as a final layer to do what you originally intended ,reduce weight due to the smooth surface already provided by the final fine weave…

I used to do this on twin-tip kiteboards  for the same reasons and results you achieved… They were still vac. bagged for the compression of the weave of multiple layers of 4oz. s-glass  I use for the general construction…

I use multiple layers of 3.2oz on my kite surfboards now, it seems to be a nice mid ground for the results I’m  looking for… I did put an added butterfly  capping patch of 2.3oz over my last Pro-Box installation with great results…

The problem I think you might encounter putting the fine / tightly woven cloth against the foam core is  the increased possibility  of delamination due th the lack of “keying” between the bond of foam and glass…  I’ve done test panels using different weights/weaves of cloth, and the lightest .  75, 1oz  and 2 oz. all pulled off the foam  progressively easier the lighter they were…   Of course you’re not going to get “peeling  away”   forces on a board, but it does see shear forces which may have a similar effect at times…

That last paragraph reminds me, I’ve used quite a bit of 3/4 oz and 1oz. as a final finishing layer in the past with good result…Very smooth finish… Easy to mess up the cloth though when applying  as it’s so light …

I used to laminate the board with multiple layers of 3oz. to 4oz. then lay on the 3/4 to 1oz. and squeegee it down without applying any epoxy… It would soak up any excess resin much like a nylon peel ply when vacuumed down, and would fully wet out… Kind of a permanent peel ply that you don’t peel off…lol

I might be way off with the “keying” thing, but the 4oz. does seem to stick to the core materials better than far lighter cloth, and this is the only conclusion I can come up with as to why…

The twin tip board shown here was glassed with  one layer of 5oz .carbon / kevlar twill, 3 layers of 4oz. s-glass ,and a " finishing glass"  layer of 2oz.E…

9

Hi Greg, I’m a bit confused.  

Did you use 2.3 to substitute the hot coat?  Or did you use 2.3 over a 4 oz outer glass?  Or did you use 2.3 for the outer glass?  If you used 2.3 for the outer glass how much glass did use use inside the (bamboo?) skin?   What was the overall glass schedule?  2.3 is pretty light unless you have 6 oz inner glass.  If you used 4 oz inner, bamboo skin and 2.3 oz outer, then you have a pretty light glass job, pretty prone to denting, no?  How much glass is on the rail?

Also, with 2.3 and, as you said, bunched up laps and what not, didn’t you sand through really quick?

I have often thought of using 2 oz as a sacrificial sanding layer under the hotcoat, given my propensity for sand throughs, but I always figured it would add too much weight.

Do you have a link to the first thread?

10

I get that…I’m just saying that the only way this makes a difference is if you have not filled the weave on the lower layer…for the sake of argument.

11

is half a pound about 250 grams eh. i find the micro fibers trap air and are harder to glass . also you say are refering it to the FILL coat which is ok but i kinda see it as a SANDING coat . so most of it gets sanded off and so the board is nice and perfect ready for the gloss. i made at least 20 or 30 boards where i was chasing lite weight but found that the boards were far more durable with a good sanding coat and finish coat… people always talk about the resin being useless but in fact it does have point load damage resistance . this protects the board from small dings and dents that can seep in water.

i think it has been proven beyond a doubt that boards with finish coats are more durable . a compsand board is by its nature far stronger then any other construction types so  requires less glass for strength but IMO the more coats of sealer/paint or resin you finish it with the better the board will be. also 2 oz has very little strength in itself so its doubful a layer of it that has been sanded through has any more strength then say a single layer of 4 that has been well laminated. i discarded 2 oz . it has problems with delam and tears very easily. it has SFA peel strength on foam and almost no compression strength. you could improve overall strength far more effectively by increasing the thickness of the sandwich core .5mm

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Great  points  Paul…  !

I have to admit ,  I’ve used  2 oz as a somewhat sacrificial “sanding” layer on some boards in the past… I had so much “good stuff” under the 2oz. it didn’t matter if a little got sanded off, and the boards were getting  2 pack poly paint anyway…

 I totally agree with the “SFA peel strenght on the foam” as well, as I’ve seen this on test samples I’ve made…

I do like it sometimes on the inside of bamboo  or balsa if I need to make the veneer a little less fragile, and it does make for nice butterfly patches just to seal the top of Pro -boxes… but I could do this just as well with scrap 3.2…

 I’m having good results with  3.2oz and 3.6oz. and think thats as low as you’d need / want to go

 The sanding /gloss coat does help prevent scratches and dings, no doubt…

 Greg just want’s to experiment, and mess around with the light weight glass, and that’s OK  too…

Hell, I’ve got landscape fabric (poor- mans innegra) in one of my boards, It’s all part of the fun… I’ve got rolls of 6oz Volan S , 4oz.S . 2.3oz ., 3.2 ,pieces of carbon .kevlar etc… etc…   I mix it up simply because it would be boring to just use 4 or 6oz E for the rest of my life… And I think that’s why Greg’s asking the question, although I could be wrong…

13

hi kiterider 3oz cloth is fine to use  but would defeat gregs purpose i guess. i now use only 3 or 4 oz on the insides of skin laminates. mostif not  all failures and and early compsand problems were eliminated when i stop using the 2 oz microfibre glass

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i tried the method greg suggests on board number 3 and used the 2oz and it traped lots and lots of air in a handlayup. i think that you could explore other areas to reduce weight. one thought would be to TOPHAT your skins and keep with the .75pound foam and use a decent 3 oz glass inside and maybe 1mm paulownia(or super dense balsa) with tophat bracing and extra glass where your foot traffiic is. then glass the outside with a 3 oz bottom and 4 oz deck. very light fill coat and sand into the weave a touch if you feel the need then use a 2pac finish coat. this would make a very light strong and durable surfboard @ around 4pounds for a 6 1

15

been doing lots of polys and am pretty well over it so thinking to tool up for a few superlights

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geez, I hadn't heard your term "tophat" in years.

I think I still have your picture you posted years ago when Sabs and everyone was still here.

but those were the days..

I thought you went over to the dark side and gave up on the extra labor stuff.

 

All you NZ folk doing okay?

surprised no one here said anything about that big rocker you folks had.

 

I was told by the FBH guru's to use the 2 oz over Carbonfiber, and S glass layups to smooth things out not to reduce the weight..

I also used to use the 2.5 oz under my 1/8" skins, but now I just epoxy them on and put the glass on outside.

Paul didn;t you say to make a paste and brush on the epoxy to the wood and then lay the dry glass over that and dampen with a brush to reduce weight?

I though I saw a video of you dointg that awhile back 

17

My larger plan was to incorporate the 2.3 oz as X glass and rotate it 45 degrees. So it was a given that the deck would be a layer of 4 oz and 2.3 oz.   I have always put the lighter cloth on the outside anyway and saw this as a way to really reduce a chunk of weight.  I could have put it under the layer of 4 oz but choose not to.  And had some trouble with it as I said.  But I didn’t sand off the 2.3 oz.  I used RR Kwik Kick for the fill coat and it gives a bit of advantage in that it doesn’t drain off as much.

I had a layer of 2.3 under the bamboo as well.  And I had some foot patches under the glass using 6 oz knitted Xglass from Graphite Master.

Paul, you make some good points about finish and strength and Kite as well.  You can increase strength more effectively with a thicker sandwich, but you still have to glass it and put a fill coat over that. 

Paul, didn’t you do some vac bagged laminations?  Kite, I know you have.  I’m thinking that is a two man job, but I am ready to try it.

Yes, 2 oz isn’t very strong.  About half as strong as 4 oz.  (sorry to be a smart ass).  I’m just putting it out there that instead of using 7 oz of fill (or call it sanding coat) per side, replace some of that resin weight with light cloth and in the process you will need less fill coat because the weave size is smaller.  And with additional fiber the board should be stronger.  If you don’t sand it off.  As intuitive proof, consider using some 10 volan cloth and imagine the weave that would need to be filled.  Now look at the pic of the 2.3 oz cloth and it seems pretty obvious that less fill coat is needed. 

On my next board, i am going to pay more attention to weighing it in between stages and measure whether I am right.  Probably should have done that first, but I just thought I’d engage the experts here first.  I’ll do one side of a board with 4/2 and the other 2/4 and weigh it at each step.

 

18

yeah big quake bernie lot of homeless people down there in middle of winter . no water. everyones getting together and helping each other out in kiwi fashion. no i never nade a paste i just used straight resin. i found that this way and i still do it with compsands is that all little gaps and cracks in the wood will not trap air bubbles if you put resin down first rather then try and push the epoxy though the cloth.

 

19

ah i hear you greg. i dont think 2 oz is half as strong as 4 oz, i think its way less than that actually.  i think you would get similar results(weight wise) if you just heat up your resin and put on a thinner hotcoat so as you can still see some weave and perhaps just knock the top off the weave when you sand it. or leave it slightly textured on the deck. it would be definately superior cosmetically. i mean you will basically sand away what little strenght the two oz has anyway. i was doing fill coats like this for light boards  maybe 75 grams or something like that 2 or 3 oz . i was doing the lam with 150 and the fill with 75 or 80 on a 6 1 shortboard or something like that. by heating the resin and using a brush or roller

20

Hey Greg,

While I haven’t been using 2.3 oz, I have had good success with 3.2 oz from thayercraft.  I laminate a shortboard in 4 oz like normal then go over it with 3.2 oz and like you I use way less resin in the fill coat.  The 3.2 oz is sort of difficult warp, but not terrible.  I also switched to a slower epoxy to give myself enough time to chase out air bubble and wrinkles.  I am glad to see that you are having success with the 2.3oz. 

Cheers,

Mike