Resin choice

[mcdc]

Question, the fuel section stringer glass was around 4mm and the engine stringer glass was 5 to 9 mm at the bottom and top......thinner on the sides, around 5mm. how many layers will i need to match the same strength or thickness with epoxy. Also will I need to tab then cover or run the full section out 6 inches on the first layer then start cutting back on the rest as i go? Also do I need to lay all wet or wait until the first tacks up thne add......had someone say the lay and dry then lay was the best. Thanks

[PAR]

Who ever said the "lay and dry then lay was best" shouldn't be listened to anymore, because they don't have a clue. Wet on wet is best, period, no debate, no rational discussion other wise.

Laminate thickness is dependent on a few factors, resin/;glass ratio, fabric type and fabric weight. A single layer, wetted out and hand squeegeed down, 10 ounce regular cloth, set in epoxy is about .02" of an inch (.51 mm). Thicker fabrics and construction (biax, unidia, etc.) will change this.

Yes, stagger the tabbing so the edges don't stack up over each other. I prefer the biggest pieces first, with the cut down pieces on top, but some folks do it the other way around with the short pieces first, being covered by progressively larger. There's advantages and disadvantages to both methods. I find the big to small approach is easier to fair and less prone to air pockets.

[mcdc]

Thanks Par!! What cloth sould I use. I was thinking about 1708 but have learned the CSM on it may not be a good idea........I was looking for a little bulk since the glass/resin was so thick

[Sheetbender]

Originally Posted by Steve W

Sure the 1708 will wet out ok with epoxy,(ive used it in a pinch myself when its all i had on hand) even if the binders dont dissolve, because the mat is very light but why would you want to on a big job where you are ordering speciffically for the project? its not needed with epoxy and is as i said wasted weight, not just the weight of the mat but also the resin used to wet it out, its not insignificant. (its a mindset,take care of the ounces and the pounds will take care of themselves) I dont know for sure but i suspect that the mat on 1708 still has the styrene soluble binder.

Steve

1708 of course will use more resin than straight biax. A laminate of straight biax will be more flexible than a 1708 laminate. In my case, my main aim was to gain stiffness being that the hull was so deeply peeled and epoxy being more flexible than polyester.

Stiffnes is a function of resin content and thickness. Thickness is acheived with fewer layers with mat in the laminate and the since resin weighs less than glass the stiffer laminate will also be lighter than straight biax. Laminates of equal thickness, straight biax vs 1708, 1708 will be lighter and stiffer, not necessarily stronger though.

This is the principle behind Coremat. Basicly, Coremat is a polyester sponge that soaks up resin resulting in a stiff core material, the stiffnes comes from the high resin content.

It really comes down to what your trying to acheive. If your going for pure strength, than yes, pure biax is the way to go.

[tunnels]

This is the principle behind Coremat. Basicly, Coremat is a polyester sponge that soaks up resin resulting in a stiff core material, the stiffnes comes from the high resin content.

Core matt absorbs resin yes but the amount of resin is far less not more than what a solid glass lay up would be of the same thickness and thats where it gets its stiffness from not the other way round old chap !!. !!And its not a sponge its a fine glass matt impregnated with Qcells that are there to displace the resin not to soak it up as you put it !! .
Time you had a closer look at the products you use and got to know them better !!!

[Sheetbender]

Originally Posted by tunnels

This is the principle behind Coremat. Basicly, Coremat is a polyester sponge that soaks up resin resulting in a stiff core material, the stiffnes comes from the high resin content.

Core matt absorbs resin yes but the amount of resin is far less not more than what a solid glass lay up would be of the same thickness and thats where it gets its stiffness from not the other way round old chap !!. !!And its not a sponge its a fine glass matt impregnated with Qcells that are there to displace the resin not to soak it up as you put it !! .
Time you had a closer look at the products you use and got to know them better !!!

I stand corrected on the principle behind Coremat, bad example I guess. I do stand behind all else in my post. Epoxy and 1708 are a good match for many but not all marine fiberglass projects. After 35 years of fiberglassing, I've "gotten to know" FRP pretty well, but you learn something new everyday. Thanks for the heads up.

[tunnels]

Originally Posted by Sheetbender

I stand corrected on the principle behind Coremat, bad example I guess. I do stand behind all else in my post. Epoxy and 1708 are a good match for many but not all marine fiberglass projects. After 35 years of fiberglassing, I've "gotten to know" FRP pretty well, but you learn something new everyday. Thanks for the heads up.

Core matt is a miss leading material and i am even after 25 years plus amased at the amount of factories i beento that have the completely wrong attatude to using core matt . like all others i had the same thoughts its blotting paper and why use it!!, so i sat one day and ripped a piece to shreads and saw first hand what it was made from and a while later saw the process of its manufacture , then the penny finally dropped , its an amazing material to use but like everything we use in the glassing industry there are limitations and places where i should not be used , like i always say quite often recently ,understand the materials you work with and hand on what you learn to others ! its what we are all here for, the exchange if ideas, information and learning for all !!

[Sheetbender]

After more research, it appears the consensus is that 1708 does not use binders in the mat and is stitched only. I took a bit of 1708 and pulled the glass stitches out of the mat and it has no cohesion without it's stitching. I have noticed when handling 1708 where you have some missing or ripped up stitching the mat falls apart easily. The standard 1 1/2 oz. mat I've used in the past with poly is much stiffer, obviously full of chemical binder. I have gotten some mat from US Composites that was much less stiff and wet out with epoxy quite well. Hope this helps.

[tunnels]

Originally Posted by Sheetbender

After more research, it appears the consensus is that 1708 does not use binders in the mat and is stitched only. I took a bit of 1708 and pulled the glass stitches out of the mat and it has no cohesion without it's stitching. I have noticed when handling 1708 where you have some missing or ripped up stitching the mat falls apart easily. The standard 1 1/2 oz. mat I've used in the past with poly is much stiffer, obviously full of chemical binder. I have gotten some mat from US Composites that was much less stiff and wet out with epoxy quite well. Hope this helps.

Its good to see people not taking things at face value . 1708 as you call it will not made by just one glass manufacture !
i am living working in china and the glass we were using was just plain 820 gram woven roving equal in both dirrections but after asking around looking for a better wider material and during the process we discovered and 100% better combination woven of which we immediatly swooped on . its beautiful stuff to use !, wets out as quick as the resin is applyed with a saturater gun and is really easy to roll .
So yes the 1708 thats supplied from various manufactures is not the same as what your neighbours have and the guy on the otherside of the road could have 1708 or so its called but could be differant yet again .
Something else no one ever takes any notice of is the actual weight of the glass used to make the 1708! oh yes overall its the same weight but on the 0 plane maynot be the same glass weight as the glass weight as on the 90 plane so check you may get a pleasent or unpleasent surprise when you do some digging below the surface at what youve actually bought !!. like ive said many times never take things at face value !!!,know and understand the materials you have to work with most times the supplyer will not say anything or he dosent know either !!

Yes the csm used on a cloth is stitched and no it dosent have any binder .
The stiff csm you exsperianced will be E matt and the softer csm will be P matt !! do you understand the differance between the E and the P matts ??








.

[mcdc]

Can I tab a vey layers of 1708 and then finish with 1700 so I can gain some thickness and still be strong

[PAR]

If you're using epoxy, you're wasting epoxy and making a weaker laminate with 1708. Topping it off with straight biax will not fix anything. Mat doesn't absorb anything, but does provide lots of space for resin (regardless of type) to live. Even a bagged laminate will have a modest 'glass to resin ratio, which sucks (read costs more), in both materials used and effort to produce. So, if you have no problem using twice as much resin as a straight biax laminate and aren't especially in need of a strong, light, skinny layup, than go for it. A lot of boats are built like this, with massive amounts of resin, thick, heavy and relatively weak laminates. They just build them thick enough for the strength requirements. Ever seen a chopper gun laminate?

[rick carr]

Hi guys you will have to watch the temp during the day you live north carolina make sure it stays over 10 degrees C for epoxy or it will stop setting we dont have that problem in darwin we think its cold when its 20 degrees C and reach for the woolies happy glassing.

[Steve W]

Par has it right,there is no up side to choosing 1708 instead of a straight double bias if your resin choice is epoxy, all stitched fabrics are low profile fabrics so produce thinner laminates for a given weight of fiber so if you need the stiffness of a thicker laminate you just add extra layers of double bias, not mat, this way you consume less resin and pack in more structural glass for a given thickness. If you insist on using 1708 use polyester or preferably vinylester. Typically you use a core to achieve panel stiffness with high strength low profile fabrics, not extra laminate thickness.
Rick, if you think its a challenge getting enough temperature for epoxy to cure properly in North Carolina try Minnesota.

Steve.

[mcdc]

Thanks guys!!. this is a chopper gun boat so the glass is really really thick in the tab areas. What do you guys think of three layers of tabbing and two to three cover layers with each cover layer over lapping the top of the stringer.... and over the tabbing.........or is this over kill. I am not really worried about making it any lighter at this point

[PAR]

Post some photos Mcdc, so we can see what you're working with and trying to do.