bond stregenth question

hey guys,

Question, with polyester resin standard mat / biax fabrics non continious lay up, what kind of results would you expect.

example first layer mat sat for a couple weeks hit it with the grinder to rough up vacuumed surface off applied cloth and wet out, left a completely dry outer edge on the cloth, after cure I came back and started to pull / yank off, there is resistance but the cloth pulls off almost completely in tact.

not what I would expect, seems as though a good portion of the cloth should be bonded to the base more tenaciously, and not come off in a sheet.

it was on a large verticle surface and had some smallish air / white patches.

I am not happy with the results but wonder what is the point where a person has to be concerned and what would be acceptable.

I know it kinda hard when you can't see / touch for your self, but if you have some input it would be appreciated.

thanks, Mark

 

ALL of the cloth should bond more tenaciously. I'm going to make two guesses about your project:

The rough surface of the cured mat allowed a thick layer of resin between the old mat and the new layer of cloth. I never added cloth without a layer of mat beneath it (and on top, too - even if it's just 1.5 oz mat).

The air/white patches give me a clue that perhaps the layup was not wetted out properly, or more likely, rolled out properly. Since it was on a vertical surface, was the resin draining from the upper part of the layup?

 

old glass ( week) should be more called sanded,, then ground,,,almost like you was putting another coat of paint on an old coat.,,and ya should be using 36 grit if thick enough for it,,,but nothing finer then 80 grit,,,but thats for fine thin work. after sanding,,wet you work area, lay ya glass,,and roll out all air,.,, them white bubbles you see could be 1 of 2 things,,,,air bubbles,,,,or where your resin "sagged",,,flowed out.

 

Since the first layer of mat was set up, after grinding, etc, you should have put another layer of mat first and then the cloth, wet on wet.

 

layup

I, think all points are valid. (probably / draining and no matt to cloth issue)

I am a full time worker and a week end boat builder, so it has been hard or impossible to have a continious lay up.

my mat is 1.5 oz over foam panel - I usually have sanded the matt with 8in DA sander and 80 grit paper (its the roughest I can find)

Yes the the cured matt is hard to lay up over, deffinetly not the same as a mat/clotch application - to boot my clotch is a 0/90 biax fabric with "no" mat backer.

Would a thickened resing mix w/cabosil help as far as the bond stregenth goes ?? It is hard for me to get a good wet out with the thickened resin mixture, I have tried both ways.

thanks Mark

 

Why are you doing only one layer at a time? Just do the mat and DB or Biax whichever you have at the same time, it's the only way to get good results. Don't use a thickend mix, it will only be weaker, the only solution is to do a layer of mat with with your fabric. For normal hand laid application with ployesters a layer of mat is needed for a good bond, it actually helps to elimnate the resin rich layer between the new roving, cloth, BD or Biax type product and the old surface. The resin bond is the same in both cases, it's actually the resin rich layer that fails.

 

my OPINION is thickened resin with cab. wont matter a bit,,in fact i would think it would make it weaker.,,it may help with drainage, but for that you trade for it being harder to get all the air out.,,what we ( all these other guys heh) need to do is figure out your "original" problem,,,or i should say, the root of your delaminating problem,,,,because until we figure out why ( and what your using and the material is o.k.) you cant bond your layers,,, nothing (thickened,cabosil) will bond and be "safe" or useful.
,,,and now i see ondarvr's comment,,,heh ( im a little slow heh) he's right on,,,,,it actually will take you say an hour ( remember we're working against kick time) to lay-up half of a 30" boat with 6 layers,,,o.k.,,,,maybe 2 hours,,,,,you just need a weekend to pre-cut and lay-out ya cloth and get it ready,,,,then on 1 saturday lay up half a boat.,,,o.k.,,,time to feed my snake ,,heh

 

One of the problems with these kind of 'interrupted' layups is that mechanical adhesion is never really as good as chemical bond adhesion that you get from laying it all up at one time. When you rough up a cured surface, you really only get mechanical adhesion from the new resin you put on top. If you insist on building one layer at a time, then using a rough 'peel ply' release like Ceconte helps a lot since it leaves a nearly perfect texture for maximum adhesion later with no sanding.

Much is right about the resin thickened with cab being weaker. For sure it makes the layup brittle.

 

If the resin is draining on your vertical surfaces, you NEED to mix in a little Cabosil. It doesn't take much - I used a "quart" or two of Cabosil to a five-gallon pail of vinyl ester to give it enough hang time to kick. I can't imagine that the part would be weakened as much as it will with dry spots.

 

I am assuming that you are not using a waxed laminate resin?

White patches are definately dry areas, use a roller for the resin, roll out with a bristle brush roller, that will penetrate the cloth and assist removal of the air, and finally ise a paddle metal roller to squash the laminate into place. Running over again with the bristle roller if need be, it works wonders at soakin up and out excess resin whilst still maintaining enough resin to make the laminate go clear.
Roll resin onto the old job before you lay on the csm/cloth layer. It will assist absorption, seal the last layer and aid general flow.

 

lay up reply

you guys are right, my problem is the working time and not good enough prep (meaning having everthing pre cut) also my work area sucks because it is tight/ cramped & part of the area is subject to direct afternoon sun which can be a serious challange (problem).

I will go back and grind all the matt surfaces I have and apply and continious application, my fear has been in the joints, my fabric is 36 inches wide, that is why I have tried to cover a complete section with matt then come back with the cloth using butt joints to elimate high spots from overlaps.

the good news is this is a pilot house on a male mold, other wise I would, never had tried a non continues layup (knowing it is weaker) just thought I could make it work. My main concern has been on a super fair surface to keep finish work to a minimum.

thanks, for the help
wanna see some pictures ??

 

we got a "pic tease",,,,damn just show us,,hahaa
to make ya overlaps not get thick,,,,off set em,,,,just like shingling a roof
and im not im getting ya right,,,,but are you saying your putting the cloth against each other and not overlapping?,,if thats what your doing , then you wont need to worry about the bonds,,,,,,everything will fall apart so there wont be a question on bonding hehehe.,,,,never EVER butt up glass,,,,,,think bout what size material is keepin ya togather,,,1/4 if glass held to the next piece down the line by a 1/4 bond of mostly just resin,,,,cut everything out man and start over,,,,,o.k.,,maybe thats going to far ,,,but butt joints in glass is like having no glass at all

 

He's right.

You've GOT to have all your glass ready to go in advance. To avoid obvious overlaps, tear the mat instead of cutting it. The edges just disappear.

 

you have to have overlaps,,,,theres no way of doing it right and not overlaping,and thats what they made 36 grit for hehe ,and he's not using much mat,,,,so tearing dont help.,,and i really dont think theres a way to make "butt joints" bond,,,even if you lay it up the same time,,,is like holding 2 pieces of glass a 1/2" from each other butt end to butt end,,with JUST resin between.

 

Gotcha. Instead of typing "to avoid obvious overlaps" I should have typed "to make your overlaps less obvious".