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Old 01-05-2016, 12:16   #16
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Re: Quick Question - Time between fiberglass layers?

Objection your honour, not a good idea with the peel ply after each day.
As explained earlier, it creates a thin resin rich layers in the total laminate stack, which is not good for Interlaminar shear strength.

No objections to use it at the final layer.

If the area he deals with is not huge, it's better to sand before adding the next stack (only in case the previous layer is fully cured).
Wet in wet is best as it creates a chemical and not only mechanical bond.

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Old 01-05-2016, 12:36   #17
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Re: Quick Question - Time between fiberglass layers?

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Objection your honour, not a good idea with the peel ply after each day.
As explained earlier, it creates a thin resin rich layers in the total laminate stack, which is not good for Interlaminar shear strength.

No objections to use it at the final layer.

If the area he deals with is not huge, it's better to sand before adding the next stack (only in case the previous layer is fully cured).
Wet in wet is best as it creates a chemical and not only mechanical bond.

Welcome to the Woods Mira 35 - Catamaran Lady Rovers Website!
Hi Franziska,
With all due respect to your considerable knowledge, I think that the advantages of peel ply are worth exploiting in this case. The leading edge of a heavily layed up keel is not the sort of area that I would think will be negatively affected by a tiny extra thickness of resin. An inexperienced person is likely to create a resin rich lay-up simply by being unaware of how much resin you can remove with your squeegee. If the area being repaired is large the peel ply will reduce the amount of sanding required.
OTOH. If the repair area has complex curves ( like a corner), it may be a waste of time trying to apply peel ply.
It that case just sand very thoroughly.
Dave
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Old 01-05-2016, 13:07   #18
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Re: Quick Question - Time between fiberglass layers?

Dave,

I agree as long it's not a structurally loaded area. And yes, true a resin rich laminate is to be expected in a hand lay-up.

Franziska

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Old 01-05-2016, 13:09   #19
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Re: Quick Question - Time between fiberglass layers?

I believe there are epoxies that can be used wet-wet even after many hours in-between (you can stop working tonight, continue tomorrow). Similar to waxed / non-waxed poly resin.

If you have many layers remember there are benefits in mat / rowing / layering rather than using one style of glass for the whole job. Rowing is faster for thickness but rowing on rowing is not all that great for optimum wetting.

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Old 01-05-2016, 13:31   #20
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Re: Quick Question - Time between fiberglass layers?

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Dave,

I agree as long it's not a structurally loaded area. And yes, true a resin rich laminate is to be expected in a hand lay-up.

Franziska

Welcome to the Woods Mira 35 - Catamaran Lady Rovers Website!
👍 Franziska, that's a great web site you have put together, and a very nice little cat too
Dave
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Old 01-05-2016, 13:33   #21
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Re: Quick Question - Time between fiberglass layers?

Balnakeil,

mat has no value in an epoxy laminate.
What you say holds true for a polyester lay-up though.
Mat should never end up in any structurally loaded epoxy lay up.
It's just not the right material.

Have a lovely evening,

Franziska




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Old 01-05-2016, 13:48   #22
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Re: Quick Question - Time between fiberglass layers?

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Originally Posted by Dsanduril View Post
I'd look at all of the great guides on the West Systems site:

Applying Cloth & Tape

But, if you want the short version and are using epoxy then wet-on-wet is preferred, it gives you a chemical (rather than just a physical bond) between layers. Lay up as many layers as you can without worrying about it slumping/sliding. If it is going to get thick (>1/4"?) then you have to worry a bit about heat buildup as it cures, see what WEST has to say.

Once you get to a point where you have to stop (heat/slump/lunch) if you can dent it with a fingernail you can continue with a wet-on-wet application. If it gets much harder than that then you have to start looking at surface prep techniques between layers (peel ply, sanding, washing for amine blush).

Books could be written on this (and have), so spend a little time at the WEST site.

Totally agree. As long as you are using We$t you must deal with amine blush. Keeping at it aggressively and not letting it fully cure will let you carry a chemical bond without prep work. The advantage using the system you chose is that you can pre-cut a pile of glass and just keep it coming. I use a non-blush epoxy, US Composite 635 THIN 2:1 for all of my work. It does great work but is more fussy up-side-down. West is way higher viscosity so it can me made to stay put but wet-out is more difficult.

For what you are doing, I suggest application using Home Depot throw-away brushes. I use the brush to fully wet the prepped hull. Use the brush to wet the first patch layer; apply the patch; use the brush to get total wet out; Repeat on the next patch and so on. At some point, you will have a pile of patch that is resin rich. (too much resin and short on glass) At this point, I add dry layers to the mass and use the brush dry to pull resin into the top layers. I have done this using We$t for hull delamination blisters up to about 3/4 inch thick and usually about dinner plate size as one thick wet patch. When you have reached the last layer, apply a dry cleaner bag or very thin film trash bag of the crinkly type. Wrap it over and beyond the patch edge and tape it to the hull. Now use a roller or you hands to work from the bottom upwards and from the center outwards to exclude all air bubbles. The resin will ooze onto the hull beyond the patch. At this point, the epoxy mass is prevented from sagging or from pulling in air bubbles. The film will easily pull off when the epoxy hardens.
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Old 01-05-2016, 14:00   #23
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Re: Quick Question - Time between fiberglass layers?

Glass fibre construction is not new to me but I have not much experience with epoxy. So a question.

I have just made up a battery box cast over a mould I made, using epoxy and a combination of 3 layers of mat and two layers of woven cloth on either side. Whilst I know this not a "structural" application, it still needed to be strong as it contains 6 Trojan T105 batteries which are nice and heavy.

If I'm not going to use mat, how would I get any thickness in the walls of the box? The box I replaced (too small for my new battery bank) had walls probably 3mm thick and I wanted the new box the same. If I were to use only woven cloth I would need 20 layers!

As it happens the new box is made and installed so this question is rhetorical and BTW the box looks great and appears really strong.
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Old 01-05-2016, 14:05   #24
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Re: Quick Question - Time between fiberglass layers?

You can build up the same thickness with wovens or multiaxials.
There are also woven complexes which create thickness by expanding while curing.

Still what you describe sounds like a typical polyester application if weight is not of the highest importance.

Any complex 3D shape not highly structurally loaded, can be easily achieved with polyester.
As the binder breaks down the binder and the fibers are not orientated, they arrange easily to the desired shape.

Anything loaded use epoxy and cloth type materials if weight is of importance.


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Old 01-05-2016, 14:42   #25
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Re: Quick Question - Time between fiberglass layers?

Bonding resin is also an option. Used by many boatbuilders and recommended by a friend that's been a fishing boat surveyor for 40 years. It seemingly breaks down the blush to create a chemical bond. Big problem here is fishermen doing their own work but simply laying on top of existing fibreglass or gelcoat without as much as washing down with acetone. Not unusual to see outer layers peeling off once they have gone through ice and broken the tenuous bond.
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Old 01-05-2016, 14:48   #26
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Re: Quick Question - Time between fiberglass layers?

Btw. Gelcoat needs to be ground off before any substantial new laminate gets applied to a surface.
Otherwise it creates a weakspot as it contains no fibers.

The higher the glass component in a laminate the stronger it is from a structural standpoint. Aligned fibers of a certain length are stronger than chopped strands of a mat with random orientation.

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Old 01-05-2016, 14:52   #27
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Re: Quick Question - Time between fiberglass layers?

If your have slumping of your cloth in vertical or overhead areas, mix a little 407 in with resin to make a slurry and use wax paper to hold, it creates a little surface tension and the cloth doesn't slide, also helps a little with the fairing.
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Old 01-05-2016, 20:52   #28
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Re: Quick Question - Time between fiberglass layers?

Appreciate all the advice. It certainly helped the day go along.

I ended up having to do a little more work than expected. Basically, I felt that I should grind the hole back a little more to ensure that all the delam from the impact was ground out. I'm glad I did, it's more work but the piece of mind was worth it.

So, my hole was even bigger than before, about the size of a baseball. I started by sealing the hole with about 5/16" of matt and woven mix. I let that tack up nicely for about 4 or 5 hours, just until my finger nail could dent the surface. This sealed the hole nicely but did not have a good shape for the keel.

Next, I took a small length (3inch or so) of bluewater 20 board and shaped it so it would have a closer profile to the keel and used thickened epoxy to fasten that over the covered hole to give a little bit of shape the area.

After that had time to set in place, I used a mat/woven mix to apply another 1/4" to the area, this time with a much better shape.

I'm letting all that dry overnight and hopefully will be back at it tomorrow afternoon to finish the job. I feel it needs about 1/4" more to be thick enough to fair properly.

Lots of lessons learned... Mainly, make sure the area that is feathered is flat as possible. I was fighting quite a bit with "bumps" on the leading edge, which was making it difficult to lay the glass flat.
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Old 02-05-2016, 23:40   #29
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Re: Quick Question - Time between fiberglass layers?

Quote:
Originally Posted by Omatako View Post
Glass fibre construction is not new to me but I have not much experience with epoxy. So a question.

I have just made up a battery box cast over a mould I made, using epoxy and a combination of 3 layers of mat and two layers of woven cloth on either side. Whilst I know this not a "structural" application, it still needed to be strong as it contains 6 Trojan T105 batteries which are nice and heavy.

If I'm not going to use mat, how would I get any thickness in the walls of the box? The box I replaced (too small for my new battery bank) had walls probably 3mm thick and I wanted the new box the same. If I were to use only woven cloth I would need 20 layers!

As it happens the new box is made and installed so this question is rhetorical and BTW the box looks great and appears really strong.
Regarding your thickness question, have a look around on here, at some of their fabrics Fiberglass, Carbon Fiber, & Kevlar Reinforcements, Fabrics, Knits, and Uni
Note some of the cloth weights, & I mean the ones without mat, especially the "Knitted Fabrics" AKA Axials. http://fiberglasssupply.com/Product_...d_fabrics.html

It's not hard to find Axials (& Roving) in the 24oz range, or if you look, even double that. Though for things with corners, the latter, super thick fabrics are impractical. Or at least, complex, & thus not good "starter fabrics" to learn with.
Still, just one layer of 24oz, when wetted out, will give you 1mm of finished thickness. And such reinforcements are MUCH stronger than Anything with mat.
This thread Keel sump repair is an excellent read on these topics.

Keep in mind too, that mat soaks up Huge amounts of resin (without adding much relative strength). And as of last check, epoxy wasn't cheap. So, for the cost of all of that extra resin in your battery boxes, I could have built (stronger) ones out of carbon fiber, at the same cost.

You'll be doing yourself a favor, if you do some online study on the subject. And most any fiberglass/resin maker or supplier has Loads of; technical literature, how to's (text & video), project guides & examples. All for free.
Heck, you could literally download 10k pages of such from the WEST System site, & it's sister page by them www.Epoxyworks.com
The latter being a periodical put out by them, showing projects done by amateurs, with spectacular results. And also, there are search engines, as well as pull down menus on both sites.

Plus the Thousands of other sites out there online.
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Old 03-05-2016, 00:09   #30
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Re: Quick Question - Time between fiberglass layers?

For resin control, so that you get good ratios. In a DIY project, the simplest/best way, is to weigh each piece of cloth that's going into the layup, & weigh out the same amount of resin to use to wet it out with. And even then, work the fabric hard, & use peel ply, in order to get it as lean as you can.

Also, for some jobs, it's better to wet out the cloth before applying it. While again, using measured amounts of resin. As, thanks to gravity, it's tough to wet out cloth properly, without going to a resin rich layup otherwise.
However, even when you do this, you still, of course, work the layup hard, once it's in place, for the repair or construction. And if appropriate, use a layer or two of peel ply on top, to further "dry it out".

The other options are; Vacuum Bagging, Infusion. And then there are other advanced tools & techniques, prior to going to things like, Pre-Pregs or SP Systems SPRINT cloth/system. But usually they're tools that only bigger shops use, due to their expense. Plus the cost of getting them properly adjusted for the shop's resin(s) & cloth(s). For example, (semi) automated fabric resin impregnators.
Albeit when properly setup, they get the resin/fiber ratio down to about 40%/60%, consistently. Usually without vacuum bagging.
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