# Layering various cloth weights for added strength?

Davo Detrick mentioned a little tip to me a while back and I haven’t had the time to follow up unitl now.

I believe he said that if you sandwich a different weight cloth (ie 6/4/6, or 8/7/8) you get a stronger board because the weave of one fills the void of the other. Or something like that.

Anybody have an expert opinion on this?

Actually, I’ll call Hank at Graphite Master and see if he will respond on Monday.

hm…not sure about that theory but…

comparing different FRP laminates in terms of total weight of glass…

say 6/6 vs 4/4/4, both being a total of 12…

the 4/4/4 is a stronger laminate do to

1. better glass/resin ratio

2. its a sandwich

HTH

Just for debating purposes, I thiink I could argue that 4/4/4 has more resin per weight of cloth, not less, than 6/6.

If I can get an answer out of Hank, I’ll post Monday or so. I’ll ask Hank for his opinion on the resin to glass ratio (because I am just not an expert).

it seems to me that 4,4,4 uses heaps less resin

if you glass carefully with modern epoxy layup methods

its just easier to fill the weave with a pretty dry lam

Four ounce cloth is easier to sand and gives a smoother final finish. I always try to do the last layer in four ounce.

You can talk all day long about layers and strength. Maybe some one can write a term paper about it.

What’s Herb have to say about the whole thing. I like Herb…

And Doc , that guy knows his stuff. I bet Doc has done some real world tests with layers of glass. Oh heck, It’s a surfboard. If it breaks I’ll build another one. …how strong does the thing need to be ???

So Cal got some swell this weekend. Go surfing !!!

Ray

not much of a debater these days but I’ll bite this time…

4oz is 0.006" thick

6oz is 0.0095" thick

4/4/4 is 0.018 thick

6/6 is 0.019 thick

for simplicities sake, lets assume both are the same thickness… 0.018"…

both have the same total weight of glass…12oz

So whats the diff?

The airspace/voids between the weaved strands. Each getting filled with tiny pool of resin…and they are (much) smaller in the 4oz weave.

As Silly said, HEAPS LESS.

No need for a science degree to figure this one out.

Very elementary stuff…if you want to get real fancy there’s hundreds of combinations when you consider weight, weaves, orientation, resin properties etc etc…a fun little micro world of opportunities.

Quote:

The airspace/voids between the weaved strands. Each getting filled with tiny pool of resin…and they are (much) smaller in the 4oz weave.

I’ll throw in hear. I’m just drinking coffee, watching NFL Countdown. Like Greg said “the airspace/voids between the weaved strands” get filled with resin. But really that just adds weight. I think the question was the strength, not weight. If we’re talking strength to weight ratio, then that resin comes into play.

Resin gets trapped in the cloth and between the lams. Maybe the most signifcant location in terms of this discussion is the space between the laps. Weave is weaved. Meaning it’s not flat. It also has some elasticity meaning it returns to it’s original shape which is undulated. So, the first lam, after layed up, has an undulated surface. The second layer has an undulated underside. The space between the lams that needs filling with resin is created by high points in the bottom lam and low points in the top lam.

If the question is strength to weight ratio, I’ll assume 12 oz. of glass is 12 oz. of glass in terms of strength, then you look at the resin in the cloth and between the lams. I would contend, with only a small amount of conviction, that even though the undulations in 4 oz. are smaller than those in 6 oz., that the total resin trapped between the lams is greater in the 4+4+4 system than the 6+6 system. That, would make the 6+6 a better strength to weight ratio. In regards to total strength, I don’t know.

There’s a huge number of variables and this, like many surfboard construction issues will probably come down to trial and error. Oh yah, don’t forget that manufacturing efficiency comes into play bigtime here. If there are only neglegible difference in strength here, no glass shop will want to do 3 lay-ups.

Okay, time another cup of coffee.

nah just weight

and more weight in the filler coat as well

this is my experience using careful layup on a 6ft shorty so far

(forget the bucket and squegee for minute)

6/6 eqauls 350 grams at least to fill the weave(pinholing and difficult to fill the weave with his amount of resin)

4/4/4 equals 320 grams no pinholing with a nice and easy filled weave(but way less for a nice filler coat)

say you were real careful and saved 60 to 100 grams (if you use a wetout table on the lam or other personal tecniques)

then saved another 75 to 100 grams on the filler coat

thats a lot of weight for the same strength!

thats getting close to half a pound

if you put the whole lot under vac u would prolly use 100 grams less again

or what about 2/2/2/2/2/2 even less weave to fill

btw these weights are relative to tecnique and board area of course

Quote:

6/6 eqauls 350 grams at least to fill the weave(pinholing and difficult to fill the weave with his amount of resin)

4/4/4 equals 320 grams no pinholing with a nice and easy filled weave(but way less for a nice filler coat)

That’s pretty interesting. Looks like considering how lean the 6 oz. was and how easily the 4 oz. filled, you might be talking a 10% reduction in resin weight which is wasted weight.

Variables are all over the place but on first glance it looks like 4x3 is a little better in weight than 6x2. Makes me think the 4 oz. is a little flatter and tighter, in other words more glass per unit of volume.

This is all fair enough. Why not stop using woven cloth and use unidirectional or biax cloths? More glass and less resin. You can really improve the resin/glass ratio using these cloths and vacuum infusion.

But how much of a gain do you want? Methinks on a short board the percentage weight saving is minimal. I’ve got the kit available, you tell me the laminate schedules you’re interested in and I’ll make samples, break them and post the results. My students love this kind of stuff!!

Yeah, but you end up sanding it all off anyways. Or you should be sanding it all off. I’ve seen some heavy 4 oz boards with thick hot coats. Anyhow a poly board in 6x4 is a pretty sturdy beast.

you all ran off and left me

Let me catch up. First 4/4/4 is not a sandwich of any consequence. Lacks a core. Just a simple matrix. Second, (I like the way Ryan put it) “I would have contended with only a small amount of conviction”, that with 4/4/4 you have 4 unavoidable small layers of resin between each layer of glass and foam instead of 3 for 6/6. Thus more resin for the 4/4/4. Based on a hand lam.

But you can have the last word because I’m just supposing. I’m just courious about the strength issue using different weight glass in layers. Is it just the number/area of fibers?

Rikds, great offer. You can weigh and break in a materials lab? Let me make a couple of calls in the morning and I’ll post a few suggested lam schedules for testing that I think would be enlightening. Others may want to do the same.

And Doc, where are you? And the boat people.

Just to stir your pot, how about the difference in flex due to the angle of one glass layer to another? I know the graphite panels we use at work are biased for flex and temperature characteristics by this. I currently ride a vacuum bagged epoxy that has one ~9 oz. glass layer, or so I’ve been told. The thing is tough as nails.

the core?

Sounds Great. I hope we can get some new insights. While you’re running tensile testing. Here’s a little jig I worked up for impact/ding resistence. Maybe you want to put your students to work on something like this too.

The trick is standardizing the foam and the layup with an area large enough to make enough strikes. When I worked this up in the past we were working with the traditional polyurethane/polyester system. Foam uniformity is non-existent. Now with EPS, it would be much easier. Quantifying results is a little rough too.

apart from the obvious hassles for the poor guy glassing the board, why not go to the extremes and use 2/2/2/2/2/2 ???

i’m thinking the resin that dries between the layers of glass (and not within the weave) would add thickness if not weight ?

Rikds

i’d love to know how 2x2oz compares to 1x4oz

Yeah, me too.

Maybe set up an envelope of lams to set some end points. say 2/2 and 2/2/2/2, and compare with 4/4 and so on. Of course the “so on” is going to get tedious with so many combiations. But we don’t need data for each one. Just some end points and indications about whether heading in a particular direction would be beneficial.

On the other hand, I’m guessing someone somewhere has already done this. Finding it is the problem.

Make some small hand sized samples of each and squeegee (same resin batch) on a plastic sheet…weigh everything before and after.

The stiffest laminate result is the winner.

How do you measure that you ask? Use your eyes, hands and brain…they are incredibly sophisticated and sensitive tools. A tip passed down to me by world class cardiovascular surgeons.

It would be nice to see the various combo’s to gain data and look for insight, but a lot depends on RiKds. Projects like this can get complicated pretty quick. His students are an X factor. Are they highschool, college, etc? How many are there, and how many hours do they have available? If the sky’s the limit, well, there are lots of options.

The sky’s rarely the limit, so it may be a program that needs to be minimized to create the shortest distance to meaningful information. Then the question is what’s meaningful? 4 oz. x 3 vs. 6 oz. x 2 is what started this. If they do a first round on those two it would be a good look at the relative perfomance of systems that are currently being used.

My brain hurts. It’s too early. I shouldn’t have check Sway’s before I started work.

to be fair

the cloth should be prewet and excess resin removed

then layered together so the cloth has minimum resin

epoxy resin should be used (becuase its better:) and im assuming no one cares with poly)

and the weave must be filled properly on both samples

cloth weights should be close to identical