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Skid Plate Materials Testing
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Author:  Mike McCrea [ July 7th, 2019, 10:28 am ]
Post subject:  Re: Skid Plate Materials Testing

Recped, excellent write up and photo documentation.

When I got the part about cleaning the crater with acetone I let out an involuntary gasp. If acetone gets into the foam core it can dissolve the foam, and keep spreading and dissolving the foam core. Hopefully that did not happen, but I avoid acetone on any cracked Royalex hull.

The sterns on my rocky river canoes often see more damage than the bow. Like you I sometimes abrasion drag my boats, but I think most of the impact damage occurs from running a small ledge, when the hull drops before the stern is completely clear.

I had not seem G/flex in squeeze tubes before, what quantity comes in each tube? I lay a coat of G/flex thickly inside the tape & paper box, lay the Dynel atop that and then topcoat the Dynel with more epoxy. Having seen the undersides of some thick, thirsty cloth in the skid plate experiment inspection I think that even my heavy-hand with epoxy is barely enough.

The graphite powder makes it easier to see where the cloth still needs wetting out, and thickens the G/flex (or G/flex and epoxy mix) so it is less drippy.

Seriously, ain’t release treated peel ply wonderful stuff? The first time you wait overnight to pull the peel ply off a coat of resin is like a leap of faith. Like a damn magic trick.

About Step 16, I lay painter’s tape about ¼” away, then use a couple little pieces of scotch tape to put on the newspaper, spaced about half way up the first tape run. Then I run a second perimeter of painters tape half on the newpaper, half on the first run of tape. That way drips can’t run under the paper, and when I think the epoxy has stopped dripping I can pull the outer tape and paper, an still have a full perimeter of tape to double check for any nope-still-drippy epoxy.

No more creeping drips? Pull the inner tape, lay the peel ply down and compress.

Step 19, without (repeated) peel ply compression epoxied Dynel does swell, and gloved hand compression did the trick for me for years. Uncompressed Dynel also has a very rough surface. The roller is most helpful on glass tape, where the selvage edge swells tall and sharp.

About the “straight placement”. I try to remember to draw a line down the center of the skid plate material to help me eyeball where it goes on the center keelline. I forget sometimes and end up slightly crooked.

Looks good, and with multiple layers of S-glass underneath it should be multiply tough.

Terry Newcombe wrote:
I agree, the key to not having epoxy overflow when pressing the release fabric is applying just enough epoxy to soak the Dynel and not much more. That plus waiting until all drips are done, but not waiting too long! Out of curiousity, how long was that for you, between applying epoxy to the Dynel and applying/pressing the release fabric?

Terry, I dunno, how’s “It depends” for an answer?

It depends on the shop temperature, and if the epoxy is straight G/flex or 50/50 G/flex and 105/206, and if it is thickened with graphite powder, what materials I am using (thick E-glass tape under Dynel needs a lot of epoxy) and how thick I slop on the base and topcoats. I tend to use more than just enough.

30 minutes to an hour+ on average, depending.

I mostly go by when the drips running down the newspaper have stopped running. I Sharpie mark the bottom of the drips, repeatedly if they keep dripping past my mark. Once the epoxy stops running down the gravity-assist vertical newspaper I know it isn’t dripping down the crown on the skid plate.

ImagePC271495 by Mike McCrea, on Flickr

Then I pull the outer tape and taper and can watch the nice straight epoxy line on the 1st layer of tape as a second chance. Pull that tape, lay the peel ply, compress and walk away.

One more beautiful thing about release treated peel ply; I have a bad tendency to keep “playing” with uncovered epoxy, until I end up making it worse. Can’t do that once the release treated peel ply goes on.

Author:  Terry Newcombe [ July 9th, 2019, 2:55 pm ]
Post subject:  Re: Skid Plate Materials Testing

Wow, fierce documentation award competition between you two, recped and Mike. (And apologies, recped, for mistaking Mike for you on your July 7 post.) You two rock.

Author:  Mike McCrea [ July 10th, 2019, 1:21 pm ]
Post subject:  Re: Skid Plate Materials Testing

Terry Newcombe wrote:
Wow, fierce documentation award competition between you two, recped and Mike.

Terry, I cannot let Recped best me in Dynel skid plate documentation. Plus he is heading to Labrador on a trip and can’t respond.

One of the best multi-layer skid plates I have yet installed. Re-posted directly, sans the links to Canoe Tripping posts.

Using what I learned, and what I surmised, from the skid plate materials test it was time to lay up another skid plate, and I had one last RX canoe in the family fleet that needed stem protection, the Wenonah Wilderness.

I went with a 32” long Dynel top cover over a 29” long strip of 1 ½” wide bias woven tape (15oz, 12 ml thick). I have confidence that the peel ply compression will eliminate that tape thickness and selvage edge, and that the bias weave underlay will provide more impact resistance.

With an overlay of Dynel, and a piece of peel ply a couple inches larger all around, so I had plenty of perimeter overlap, just in case my peel ply placement was a bit off kilter.

ImageP4240027 by Mike McCrea, on Flickr

The blueish material is release treated peel ply from Jamestown Distributors, the other large whiteish piece is peel ply from a different vendor, both work equally well. At least I can’t mistake the blueish peel ply for 4oz fiberglass.

As always cutting the materials, taping the hull and staging all of epoxies and materials takes three times as long as actually laying the cloth and epoxy.

The narrow end of the Dynel pieces, which overlap the bias tape by a few inches, have a 2” slice up the centerline, so that end of the Dynel, laying atop the sharpest part of the stem curve, can be crossed atop itself to reduce fabric wrinkles and puckers. When crossed over a tiny triangle of X’ed Dynel can be cut off so the lapped ends still taper to a point.

ImageP4250031 by Mike McCrea, on Flickr

I laid out the thick bias weave tape and made a few marks on the hull so that my aim would be true while placing the tape along the stem vee and keel line.

ImageP4250034 by Mike McCrea, on Flickr

Time to set out the rest of the materials. Epoxy, G/flex, Graphite Powder, black pigment. Spoon to (slowly) dispense graphite powder into the epoxy mix. Acetone in case I have a boo boo. And multiples of things I’ll use several of, or want ready backups; gloves, mixing pots, brushes, stir sticks.

ImageP4250036 by Mike McCrea, on Flickr

Having seen how “thirsty” thicker materials were in the skid plate tests I epoxy the bejeepers out of that thick biaxial tape, a thick coat on the hull before laying the cloth, where the bottoms of thicker materials had experimentally proved to be thinly epoxied even with my heavy hand. Biaxial tape laid and generously top coated. And, as any visible weave appeared on the wetted tape, recoated in those areas just before the Dynel top layer went on.

The tape was easy to get aligned and perfectly emplaced. The longer/wider Dynel top layer went on with helping hands holding one end of the fabric while laying it evenly in place. I really didn’t want to do that part solo.

When the epoxy stopped dripping and (just) started to set up I pulled the tape and used the acetone to neaten up any wobbles along the epoxied edges. A little bit of acetone on a piece of folded paper towel works wonders. A little dab will you ya.

Peel ply laid on (I had helping hands for those pieces as well) I wanted a hard roller to help compress the thick tape and selvage edge under the Dynel. Had one, broke it a few years ago and need a replacement. Maybe one of these, except HD was sold out. ... /203809609

I have an assortment of squeegies, but that multilayer skid plate, or any skid plate, even a single fabric layer, lays down flattest along the transition edges, or tape selvage edge/thick raised underlayer, when firmly rolled down.

I still wanted/needed a roller to knock down that uber thick bias tape under the Dynel, and the Dynel itself from epoxy swelled thickness. I wasn’t running out to Lowes while the epoxy was setting up.

What have I got in the way of a DIY roller? AKA why did I save those horrible drilled dowel seat drops?

Now I know. So I could stick a 20 penny nail through them and use them as rollers.

ImageP4260039 by Mike McCrea, on Flickr

I still want a real roller, but dang that drilled dowel and nail worked very well at flattening out the selvage edge transitions and Dynel swell.

ImageP4260041 by Mike McCrea, on Flickr

Release treated peel ply removed

ImageP4260046 by Mike McCrea, on Flickr

Not too shabby* for an afternoons work. The thick bias weave tape disappeared under roller compression. I’ll neaten the edges when I put on a UV coat of black enamel paint, and round out the wide end angles into a semi-circle at the same time.

*Confession: In the 17 steps before actually mixing epoxy I neglected one important task, drawing a centerline up the Dynel. That visible keel line mark on the fabric helps immensely with alignment. The bow skid plate is misaligned by ¼” at the wide end. Something else to fix at least visually when the enamel paint top coat goes on

Until I find a source for (thick) S-glass bias weave tape I think I have my chosen skid plate materials.

That thick bias weave tape is from Sweet Composites. The Dynel as well. One caveat, Sweets does not carry release treated peel ply, just the (no thanks) green pull nylon stuff.

Best Skid Part II. In for a penny, in for a pound. I said this may be my best skid plate yet, and as such carried on after the epoxy had time to fully cure.

Taped the perimeter to prevent sanding oopsies and lightly RO sanded (220 and foam pad) the cured epoxy, G/Flex and graphite powder mix atop the Dynel to eliminate any high spots, wrinkles or creases. Most of which, from having used folded peel ply, are visibly but still near tactile flush.

ImageP4280001 by Mike McCrea, on Flickr

Pulled the tape, cleaned up the black graphite dust and retaped the skid plates for a coat of black-on-black enamel paint UV protection.

The first coat of black enamel Rustoleum was noticeably less successful at filling any remaining post-sanding peel ply weave than experienced in the past, and I needed to paint (and, again, re-tape) the skid plate for a second paint coat.

I attribute that to using the DIY dowel roller over the entire surface instead of simply compressing the peel ply under gloved hand as previously done. The hard roller pushed the faint peel ply weave deeply into the epoxy. I may go a little more gently on the non-transition edges of next ones, especially now that I have a serious roller to knock down that thick bias weave tape and Dynel edge.

ImageP5050015 by Mike McCrea, on Flickr

I am still amazed that the 12ml thick bias tape, centered along the keel line under the Dynel, vanished flush under roller compression. The swells-with-epoxy Dynel too, everything is flush and smooth.

A second coat of black enamel filled most (still not al) of the visible peel ply weave, and will have to do for now. Eventually I’ll retouch the black paint, but precisely re-taping that skid plate, especially the wide end semi-circle, was a PITA, and I’m already approaching an uncalled for Pblanc levels of exquisiteness in skid plate installation.

ImageP5050017 by Mike McCrea, on Flickr

I still need to install skid plates on three of the family composite decked canoes. Four boats if Joel ever gets his Loon up to the shop. Given the (90% freaking prep work) effort involved I’m gonna top coat those skid plates with black Pettit EZPoxy, and add a DougD Ocra-ish swirl from the black skid plate to the black trim line.

As soon as I get a couple work-in-progress canoes out of my shop I am moving on to our kevlar and glass & nylon decked canoes. My skid plate work gets better every time, and those boats deserve the best I can give.

Terry, the bar has been set. Please photograph and post your skid plate installation on your Swift Adirondack Pack.

BTW, simply stopping occasionally to take photos and think about next steps helps slow my roll and prevent overlooked procedure mistakes.

Author:  Terry Newcombe [ July 19th, 2019, 1:26 pm ]
Post subject:  Re: Skid Plate Materials Testing

Here's my own skid plate install, my first ever (and only my second fabric/epoxy project, the last one being 30 years ago). Below you can see paint scraped down to the Kevlar on the stern of my six-year-old Swift Adirondack 13.6 Pack Canoe:

I know it would be better to do a layer of fibreglass over the exposed Kevlar before applying a larger piece of Dynel as as skid plate, but I was nervous enough with one layer, and I figured I could add another layer later if needed. So here's my Dynel, before and after cutting to size. I used two side cut-outs rather than one down the middle, to avoid a weak spot in the most bump-likely place.

Next I taped, leaving 1/4-1/2" border, and lightly sanded:

Then I used masking tape over the green tape to apply the newspaper:

I took a deep breath and mixed the G/flex 650, adding 1/2 teaspoon of my graphite powder lock lubricant. I applied a layer to the canoe, applied the Dynel, pressed it down with my gloved hands and then rolled it for good measure:

My garage was warm so after only 15 minutes I wasn't seeing any more dripping, and I peeled back the masking tape and newspaper. Five more minutes of a slight drip onto the green tape, then I removed that too and applied the peel ply and rolled it down as well. Darn, I should have made side cut-outs on that too, as you can see the folds prevented full contact at the Dynel cut-out areas:

The next morning, I peeled back the peel ply (G/Flex Release Fabric), and was greatly relieved that it peeled off easily. I had been concerned that using the roller directly on the epoxied Dynel and then again on the peel ply would apply epoxy to the outside of the peel ply and possibly seal it on. Fortunately not.

The lighter coloured section by the cut-out is where the peel ply was folded over; the skid plate is rougher here, so I might touch it up with some epoxy when I do my bow skid plate. It's the same on the other side. Also, the roller had pushed excess epoxy into a puddle at the stern, and a smaller one at the cut-out, but I'm after function rather than appearance so I'm fine with that. (Y'think it can be carefully sanded away?) I haven't decided yet about painting (for aesthetics and UV protection) but am leaning against it out of laziness.

Overall I'm quite pleased. The surface is wonderfully smooth, and very thin. It's a bit bumpy/frayed at the cut-outs; I wonder if I should have cut less out so there would be an overlap there. I'll take the canoe out for a test run this weekend before doing the bow skid plate (which doesn't have exposed Kevlar, just scrapes).

Thanks a ton to Mike and recped for all your patience with my questions!

Author:  Mike McCrea [ August 16th, 2019, 3:10 pm ]
Post subject:  Re: Skid Plate Materials Testing

Terry, I hadn’t looked at this tread in a while, Yeah, that was more overlap than you needed with the peel ply. Two separate perimeter runs of tape would give you cleaner epoxy line when you pulled the tape. I have never rolled down the uncovered epoxy, but instead roll down the fabric once the peel ply is in place over top.

But, if you lightly sand down the folded peel ply lines, and then re-tape & paper and paint those Dynel slid plates, they will essentially disappear.

The half-teaspoon of graphite lock lubricant didn’t black-opaque the Dynel fabric anywhere close to the black achieved with West System graphite powder; that powder saturating the Dynel comes out black as midnight.

I’d paint them. The grey is light enough that a coat or two of white enamel paint will hide every smudge and wobbly edge and the skid plates will become near invisible. Or paint them black, which I think looks contrastingly sharp on a white scuff bottom.

Author:  Terry Newcombe [ August 16th, 2019, 6:56 pm ]
Post subject:  Re: Skid Plate Materials Testing

Thanks for the tips, Mike. They'll help for my bow skid plate next.

Author:  Mike McCrea [ August 17th, 2019, 7:34 am ]
Post subject:  Re: Skid Plate Materials Testing

Terry, for funsies, when you do the bow, take a small scrap of Dynel and epoxy it to something without using any peel ply. I think you’ll be surprised at how thick and rough it turns out in comparison.

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