Thick Fabrics and Epoxy Saturation?

[Guest]

Sanding the old kevlar felt and Twaron tape on the most recent skid plates made something (again) apparent. When I oopsie sanded far enough down there was some yellow felt or white Twaron visible inside/underneath, where the graphite powder and black pigment epoxy did not fully saturate the fabric.

With thick fabrics like kevlar felt or 10oz Twaron it is almost impossible to completely and thoroughly saturate the material (vacuum bagging excepted), and that was with my heavy handed undercoat to lay the material on, and an equally heavy (drippy) top coat allowed to seep in before repeated hard roller compression on the release treated peel ply.

I already knew that from peeling off test fabrics in the skid plate materials experiment.

http://www.canoetripping.net/forums/...stance-results

When I peeled off the test fabrics off in that experiment the thicker stuff, including the kevlar felt, kevlar tape, and thickly woven carbon fiber all showed that they were resin starved in places underneath.

Kevlar felt underside

P3200012 by Mike McCrea, on Flickr

Kevlar tape underside

P3290030 by Mike McCrea, on Flickr

Those were done using less viscous 100% West 105/206, a wasteful thick base and equally wasteful, drippy top coat. I suspect that kevlar as a felt or woven tape is hard (impossible?) to completely saturate by hand.

On a positive note the 5oz Dynel in that experiment did saturate thoroughly and completely on those peeled off bottom inspections.

P3290034 by Mike McCrea, on Flickr

Sanding the paint topcoat off the kevlar felt on the old skid plates, which had red pigment added to the epoxy, revealed considerable yellow (pink?) in the kevlar where I oopsie sanded all the way into the felt before installing the Dynel layer.


Same with sanding into the 14ml thick Twaron tape for a 2[SUP]nd[/SUP] epoxy coat, I got into some hints of still-white Twaron where the graphite and black pigmented epoxy didn’t full saturate.

PB110025 by Mike McCrea, on Flickr

That is a (typically) long way of saying I am unable to thoroughly epoxy-saturate thick fabrics, and I have a heavy hand with epoxy coats. Vacuum bagging is not in my future, but at least I know that a single layer of Dynel saturates thoroughly under peel ply compression.

 

[memaquay]

System three clear coat, warm it up a touch, it will saturate your mother-in-laws moustache.

 

[Guest]

System three clear coat, warm it up a touch, it will saturate your mother-in-laws moustache.

Ah, Mem, you never met my mother-in-lay. She was a trip; a “professional” Peace activist and American Friends Service Committee staffer. She was arrested numerous times and hauled away once with a suckling babe at breast. Jonah House/Berrigan Brothers, sundry commies, ect. She subscribed to the Workers World newspaper as well as the NYT and Washington Post.

https://www.workers.org/

I have often thought about Freedom of Information Act requesting her file; no doubt it would make an interesting read.

Twothreefour epoxy issue for me. I have gallon sized West 105 and pump, and 205, 206 and 207 hardeners with pumps. I can’t see switching horses this expensively deep mid-stream.

And, for skid plate application, I really like adding some bottom coat/top coat ratio of G/flex in the mix. I do warm up the epoxy, especially the viscous G/flex.

G/flex might mix well with System Three, but I dunno and will probably never try.

 

[memaquay]

well, i've used most epoxies, and clear coat is thin like water. It ain't cheap, but it's my favourite wet out stuff.

 

[Guest]

You stripper guys building Noah’s Ark sized square sterns go through a lot more epoxy than us dubbers using a couple ounces at a time.

 

[memaquay]

If I have any clear coat left from my next build, I'll mail you a couple of pill bottles in separate packages, lol.

 

[Cruiser]

Maybe the answer is is to cut the skid plate strips, mix a batch of epoxy and soak the strip first, then apply to the boat. I have looked at a couple of videos that presoak the strip and it seems it might eliminate your issue.


Brian

 

[Guest]

Maybe the answer is is to cut the skid plate strips, mix a batch of epoxy and soak the strip first, then apply to the boat. I have looked at a couple of videos that presoak the strip and it seems it might eliminate your issue.

Brian, I have done that with 16 foot long strips of glass tape when covering old screw holes on some glass canoes that had been regunwale twice previously. Think 70 old screw holes along each side.

I mixed up a pot of epoxy, poured it into a shallow rectangular plastic no-I-haven’t-seen-that-Tupperware-container-honey basin, laid the loosely coiled cloth in the epoxy and massaged it around for a spell.

Pulling one loose tape end out and allowing it to scrape along the flat edge of the container as I walked along and laid it in place squeegied off some of the excess epoxy, the remained in the pot got used to topcoat anywhere that looked a little thin.

I may try that method the next time I use the Dynel sleeve, even though I’ll only be cutting 3’ long strips as linear skid plates. If I were laying 16’ full keel line strip I would absolutely use that method; just getting very long strips to lay down straight without too much brush out helps.

 

[recped]

My first skid plate install (nearly 30 years ago) on a MR Explorer RX was done using the soaking method. I had no clue what I was doing, bought a piece of kevlar felt and way too much epoxy (it was still a lot cheaper than buying a "kit"). I mixed up the epoxy and soaked the felt to the point that it was dripping all over the place.

That skid plate install was my most successful ever in terms of saturation and maybe the longest lasting of any of the felt ones that I've done.

 

[Cruiser]

Mike,

I think I would tape off the area where the strips are going to lie, that gives a really solid reference as to what constitutes "straight". It also lets you squeeze out excess epoxy and just wipe it off the taped area without messing up the surrounding finish.

Once the epoxy kicks, just take up the tape to avoid sticking that as well ... it should be pretty simple to feather the edges and do the finish up stuff.

Brian

 

[Guest]

I think I would tape off the area where the strips are going to lie, that gives a really solid reference as to what constitutes "straight". It also lets you squeeze out excess epoxy and just wipe it off the taped area without messing up the surrounding finish.

Once the epoxy kicks, just take up the tape to avoid sticking that as well ... it should be pretty simple to feather the edges and do the finish up stuff.

Brian, I do tape out the perimeter where the fabric lies. The problem I have with aligning the material squarely inside that tape box is that, for skid plates, I’m using most often epoxy mixed with graphite powder. The epoxy/graphite mix is so opaque black that it is impossible to see where the tape edges are after the fabric is wetted out.

It doesn’t help that the tape box is only ¼” away from the edge of the fabric. I do pull the tape before the epoxy hardens, but if I ended up just a wee bit off-kilter with cut edge fabric that often pulls stray threads from the edge, which leaves a sloppy mess to deal with before the peel ply goes on.

I do like selvage edged tape for that reason, but none of the glass/Kevlar/Twaron tapes have the abrasion resistance of Dynel. I have never found Dynel tape, but the fine-weave Dynel sleeve seems to work very well and if I end up with the fabric a little over the tape edge there are no strays or frays to pulled free.

 

[Alan Gage]

I agree with Mem in that probably the easiest way to wet out thick fabric is to use a thinner resin that's made to wet out thicker fabric. I've used resins ranging from 200-1000 centipoise (measure of viscosity) and can say there's a big difference in how it flows and wets out cloth.

I looked quick and found these viscosity specs:
West 105 - 1000 centipoise
Raka - 600
System 3 clear coat - 380
Vinyl Ester - ~200

I've used a 1000cp resin before (Adtech ProBuild) in hopes it would lessen the number of fill coats but it certainly wouldn't be my first choice for wetting out thick or multiple layers of cloth. Seeing the vast differences in viscosity makes me realize why one person says wetting out multiple layers of cloth is no big deal while another person says they have difficulty with it.

Alan

 

[stripperguy]

Mike
Before you commit to all those dynel sleeve rub strips you might want to cut a sample sleeve section to be sure that both folded edges are tight against each other and the substrate

I know you need to know and all of us enjoy your experiments

 

[Guest]

Before you commit to all those dynel sleeve rub strips you might want to cut a sample sleeve section to be sure that both folded edges are tight against each other and the substrate

I know you need to know and all of us enjoy your experiments

I took an RO sander with 60 grit to one slightly raised end of the Dynel sleeve. Actually that worked so well to bevel down one raised end so well I did so on both stems.

The sleeve was tough as nails and seemed well adhered; on the underside (the sleeve was laid atop a thick bed of epoxy mix), on the top (covered with a coat of epoxy before the peel ply went on) and, where I was most curious/concerned, even well stuck together in the middle of the two-ply sleeve.

But, right you are, I need to know more, and of course love simple shop experiments. The next time I am mixing epoxy I plan to make a couple different batches and lay down short lengths of that sleeve several different ways.

I have some 12” squares of old Royalex to use as the substrate bed, and as a test will lay up pieces of Dynel sleeve. I have no less centipose (new vocabulary word) RAKA or System 3, and no desire to work with Vinylester, but I’m thinking something like:

Straight West 105/206, brushed under and atop
105/206 West mixed with G/flex, brushed under and atop
Same two done with graphite powder and black pigment
Same two done by submering the sleeve in a pot of epoxy and squishing it around to assure full saturation.

If I score some of the heavier Standard weight Dynel sleeve maybe some test strips of those as well.

Let it all set up for a week or three, and then replicate some of the original skid plate testing, grinding/sanding through the sleeve, maybe sawing cleanly through each test piece for a look at the insides before trying to pop or pry the test pieces off for a look at the undersides.

Oh goodie, more shop experiments.