bond stregenth question

[pescaloco]

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

[tinhorn]

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?

[the1much]

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.

[SamSam]

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.

[pescaloco]

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

[ondarvr]

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.

[the1much]

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 ;)

[Jimbo1490]

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.

[tinhorn]

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.

[Landlubber]

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.

[pescaloco]

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 ??

[the1much]

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

[tinhorn]

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.

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.

[the1much]

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.

[tinhorn]

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

[the1much]

Gotcha. Instead of typing "to avoid obvious overlaps" I should have typed "to make your overlaps less obvious".
ooo,,,,o.k. ;)

[pescaloco]

Much and others thanks, for the replies that is discourging, but i think i read in Ken Hankinson, fiber Glass Boat Building for Amatures that a butt joint had "almost" equal stregenth to a over lap.

any way to give you a little better picture the glass schedule is 1.5 oz mat over core cell 3/4 in foam the matt has the edges torn / feathered the 18oz biax cloth "has been butted" then the final will be of course 1.5 oz matt, this will be inside and out.

now any dry layup / resin drain out (my error - one small section in the whole scheme ) or non continious lay up (my error) these things aside, would this not be considered a sound layup ??

I can fix what isn't right, but wanna do it right

mark

[pescaloco]

here are some pictures

[ondarvr]

Nice project.

With only one layer of Biax a butt joint will be very weak, it will only have the strength of the two layers of mat covering the joint and hopefully the mat joints aren't in the same place. For less fairing you could have recessed the surface of the foam where the over lap will be, this way you would get full strength.

[tinhorn]

I'll leave it to the boat guys to pass judgement on the strength of the part - my background is in car bodies and industrial products. Am I reading correctly that your layup is mat, biax, mat, foam, mat, biax, mat?

There isn't any danger of water getting onto your rolls of glass, is there? Water removes the sizing from the glass fibers that the resin needs in order to adhere to them, creating dry, white spots when you try to wet it out.

[the1much]

well if,,Ken Hankinson, fiber Glass Boat Building for Amatures ,,said it,,it must be right,,,i cant imagine anyone writing a book full of idiot ideas,,,,,,my opinion is the dude is an amateur,and doesnt know much about fiberglass,,,i dont claim to be a fiberglass king,,,but theres a few things i KNOW,,,,and 1 of those things are that ANY butt joint , made out of anything,,glass,metal,,wood,,ANYTHING,,,is weaker then EVERTHING around it.
i would take that book,,and burn it,,,,then find that idiots address and ask him if he'll sign a contract, that you'll follow his instructions,, and he'll stand behind his words and pay all bill,medical bills, and replacement of ya boat,,,,and insure the boat from,,,freakin falling apart.

[TollyWally]

LOL 1,

Tell us what you really think! :)

[pescaloco]

Wooooow, now I would probably not call this a crtitical lay up where life and limb were at stake REMEMBER this is not a hull, I bought that from a professional builder. Any way that aside this way too much work and money to piss away.
just for the sake of saying it I will give you a little excert (foam panels / using 3 or more layers of laminate

"While it would seem that lapped joints would be much stronger than butted joints, this is really true only if joints are considered in a SINGLE layer of laminate. But when considered in the TOTAL laminte, there is very little loss of strength in the laminate as long as all butt joints do NOT occur at the same point. Tests show that the difference in strength characteristics between butted and lapped joints in laminates can be discounted for all practical purposes in the majority of most boats that an amateur would be involved in when using conventional materials in the laminate. For example, flexural strength remains virtually the same, as does innerlaminar strength, while tensile strength decreases only about 10% and compressive strength by only about 7%." (KEN HANKINSON, NAVAL ARCHITECT)

[pescaloco]

Any way, for what its worth Much there is a little read for ya, and still appreciate the feedback. :cool:

tin horn - yes the glass has been stored inside my enclosure under a tarp and it has rained a lot, it is possible the glass has absorbed moisture from the air but deffinetly no direct exposure. whats the scoop on moisture test or dry out period? I think I am about ready to go buy a roll of nytex instead of this straight cloth any way, the mat backer will make life easier for me

thanks, mark

[the1much]

still horse pucky,,,ive seen it happen too many times to let some book learned dude tell me any different,,,,most times i say,,"my opinion" few things i say i KNOW,,,,,,well,,i dont believe everything i read,,,in fact i dont believe half of what i read,,( and i read VERY little hehe),,,and i dont point people to books,,,but i do point to what i have seen myself many many times,,,i KNOW this dude aint crap of a F.G. dude,,,no matter what his little pieces of paper on the wall says....if done correctly,,and in 1 lay-up,,,an overlap joint will ALWAYS be stronger,,,,,do the simple common sense math,,,,more surface area to bond together = more of a bonding strength,,,,< was more saying that to diploma dude ,,heh,,not you pescaloco ;)
and this..(be discounted for all practical purposes in the majority of most boats that an amateur would be involved in when using conventional materials in the laminate),,,WTF is that suppose to mean?,,,to me it means a damn canoe,,or row boat,,,,if you plan on taking ya boat out farther then you can swim,,,,ya better not be thinking like an amateur,,unless ya life aint worth crap,,,just because you are an amateur,, doesnt mean ya shouldnt be smart enough to ask people that know,,and do a better job,,or care about it more,,,then just what 1 would call "amateur",,,,and ANY part of your boat that you walk on,,lean on,,hang on,,or depend on should be considered "life and limb" at stake,,,,,magine a wave hitting,,you grab a fiddle head,,it breaks,,you fall,,,hit head,,drop cig,,knock yaself out,,burn to the water line,,,magine walking cross ya deck,,,ya leg goes through that butt joint,,ya brake 1 leg..ya other went ta ya side so bad ya hip got displaced,,your stuck there,,,,,,all sound stupid or way overboard??,,,i can give HUNDREDS more examples,,,,,,,,how many can navy dude give ya.
heh,,,,o.k.,,,,,before ya even say it kapt.,,,,im taking my meds and going to bed ;)
and loco,,,,,stop reading books,,,hahahaa ;)

[pescaloco]

na, it's cool, the real world, engineers and books I get it

I don't do anything half ass and have a pretty fair amount of mechanical appitude and common sense.

But I know to consider and apply the advise of those that are professionals in their field, (like guys that build / repair boats) you do that don't ya ;)

thanks, look forward to alot more itche / scratchy grinding :eek: & nicely overlaped joints :D

[ondarvr]

If you look back at my responce to butt joints, you will see I said "with one layer of biax", If you had multiple layers of Biax it wouldn't be as important. Currently you will be relying on that one layer for most of your strength, that strength stops at the butt joint, the two layers of mat are carrying the load at this point and they're not cabable of even coming close to being as strong as Biax. Will it fail, maybe, maybe not, but if it's stressed severely it will fail at the weakest link and that weak link will be the butt joint.

[tinhorn]

whats the scoop on moisture test or dry out period?

I've never had a wetout problem that I could blame on humidity, but I live in high desert country where periods of high humidity last maybe two or three days. My concern, seeing your rolls of glass at the very end of your "shop", was that perhaps rain could drip onto them.

[the1much]

i forgot the humidity thing hehe,,,,i built boats in maine,,,,90% humidity on the dry days,,,,,,and same as tin.,,,,,we never had a problem with it,,,,even glass thats been rained on a time or 2,,as long as its been dried,,,and isnt wet when ta use it should be o.k.

[pescaloco]

Thanks guys.

overlaps it is, why take a change, it's not so far along that it can't be corrected. :D :D :D