Skid Plate Test Materials Impact Resistance Results

[Guest]

Bottom inspection of skid plate test patches.

There is no sense in trying to weigh the individual pieces now that I have cracked, broken and abraded sections away. But after seeing the undersides of the peeled-off kevlar felt and S-glass/Dynel patches, I did want a look at the bottoms of the other 2-ply sandwiches.

#4, carbon fiber under Dynel. Fully saturated on the bottom, the twill weave is visible. It is carbon fiber black with black tinted epoxy (the white is flash glare) but is smooth to the touch and seems well saturated. Still, black on black, who knows?

P3290027 by Mike McCrea, on Flickr

#6, kevlar tape under Dynel. That is the one I was most curious about, after seeing the poor bottom saturation on the kevlar felt pieces. There was one still kevlar-yellow area near the molded bend angle in the siding.

P3290030 by Mike McCrea, on Flickr

#7, E-glass under Dynel. There is a small crescent of white E-glass showing through, again at the siding angle. Those under saturated angles atop the vinyl siding may be indicative of unseen issues with hand laid cloth and epoxy skid plates on stem areas curves where it is more difficult to maintain a layer of epoxy while laying cloth.

P3290032 by Mike McCrea, on Flickr

#8, single layer Dynel. Smooth and fully epoxy saturated, with a (very) few champagne-bubble sized pock marks.

P3290034 by Mike McCrea, on Flickr

I have always thought that I was too-heavy-hand with epoxy; painting an uber thick coat, laying fabric, painting a thick coat of epoxy on top and then peel ply hand compressing. But I’ve never had a good look at the bottoms of fabrics I have hand laid before. Not something you usually get to see.

I was not heavy enough with any of the kevlar felts, and it makes me reconsider the “lighter epoxied is better” theory; although that more lightly epoxied kevlar felt does seem to perform better under impact. I was closer to full saturation with the kevlar tape and closer still with the 8oz E-glass.

Those bottom saturation differences would not have been as visible without the graphite powder and black pigment, showing the under-saturated kevlar yellow and E-glass white fabric colors.

I already recognized the weight difference achievable with vacuum bagged boats; I now have a better appreciation of the more thorough epoxy saturation with vacuum bagging, in the layers you don’t usually get to see.

With all of the skid plate materials removed I have one more torture test to perform.

 

[alsg]

The unsaturated areas surprise me considering the test was done on a bed of vinyl siding which I assume absorbed zero epoxy. On a cedar strip hull, the starvation issue would be worse as the epoxy would be absorbed into the cedar (unless the cedar was previously sealed with epoxy).

 

[Odyssey]

Is it wrong to assume the flexibility of the vinyl siding might have also played a role in eventual adhesion failure? (Unlike the rigid stem ends where these patches would otherwise be installed might be the least flexible areas of a canoe.) But this is by no means a critical opinion, just a wandering thought. I'm more focused on the wear and tear results of the patches themselves. Good experiment Mike. Now we just have to interpret the results. I'll need help with that.

For the Skid Plate Test Part Deux:
Heat the vinyl siding enough to bend around and fastened to a wooden board with eased edges (to mimic a canoe stem).
I'd like to see a belt sander with 60 grit employed just lightly to mimic sandy gravel rash seen on canoes dragged at takeouts.

ps . Oh, and your lab attire is seriously lacking any pole danceability. No dance chaps from you, no hand claps from me.
You know what they say ,if you got it flaunt it. If you don't, try harder.

 

[Guest]

Is it wrong to assume the flexibility of the vinyl siding might have also played a role in eventual adhesion failure? (Unlike the rigid stem ends where these patches would otherwise be installed might be the least flexible areas of a canoe.)

Not wrong at all, nor when inspecting impact damage with such a thin, flexible substrate. But sometimes skid plate material extends beyond the vee thickness at the stems. I have no idea if more flexible or more rigid would be helpful the bendier parts of, say a UL hull. I suspect the former with off-center strike deflection impacts.

When bent even a little the kevlar felts each released a wide flap edge or lifted corner, which I could grab and peel off cloth-intact. In that regard any corners or angles on a skid plate are not a good thing.

The other non-felt materials were the thinner and harder to get an edge lifted and (subjectively, as I clawed at them with straight edge and fingernails), better adhered.

For the Skid Plate Test Part Deux

Nope, no part Deux. I am still hoping to convince West Systems/Epoxyworks to do this test with different epoxy mixes and materials, and actual measured scientific data.

Oh, and your lab attire is seriously lacking any pole danceability.
If you don't, try harder.

My go-to PPE over-garment is one of my (many) old lab coats, kept laundered and un-dusted in a sealed shop box for just that purpose. I had 35 years to get comfortable in a lab coat. Love the big deep side pockets, and the breast pocket for glasses and pen.

I have one lab coat specifically for pole dancing. 8 x 10 photo glossies on request.

I won’t try harder with this peculiar experiment, but at least I tried.

https://www.youtube.com/watch?v=Cxx8RC4iQvI

 

[Guest]

Bend ‘til it breaks test

Some of those test patches were a PITA to get even a corner or edge lifted to peel free, even when bending the vinyl siding into a curve. That pliability vs stiffness in bend may be useful on more flexible hull or longer/wider skid plates that extend further past the more rigid center of the stems.

I have impact smashed and ground down through the substrate on those pieces, but I can at least bend-until-they-snap the remains, all bent along intact areas. I want my thick gloves for this test, and a full face shield.

None of the kevlar felts bend, they crack and shatter.

P3290038 by Mike McCrea, on Flickr

The carbon fiber under Dynel bent and folded into a right angle edge. In retrospect one of the best stil held together when bent to extremes.

P3290040 by Mike McCrea, on Flickr

The (unabraded) S-glass was intact was not impacted or abrasion tested, so not a fair test. It bent to some extremity before snapping, but even then the woven fibers held it together.

P3290042 by Mike McCrea, on Flickr

The kevlar tape. Hard to say; it took a lot to snap it at the under saturated still-yellow bit, the rest of it bent dang near in half. I am now suspicious of my ability to thoroughly saturate any thick kevlar material.

P3290045 by Mike McCrea, on Flickr

E-glass. Hard to bend to the breaking point, and even broken it hangs together well. I am impressed with E-glass as an underlay, in a combination of impact, through-abrasion and flexibility testing. The least expensive and most availabile of any of the fabrics, and using E-glass tape would make the underlayment easier, without frays and strays coming off the edges during the fill coat before the Dynel cover was applied. I think I have my material choice underlayment with a Dynel top cover, and really wish I had tried the bias weave E-glass tape as an underlayer.

P3290047 by Mike McCrea, on Flickr

Single layer Dynel. Easier than any of the two-ply sandwiches to bend; being thinner the single layer of Dynel was the most pliable and had the fewest broken strands visible when forced to snap.

P3290048 by Mike McCrea, on Flickr

Just because I am gloved, visored and breaking stuff, #’s 9 and 10, the pigmented kevlar felts on which I managed to accidentally epoxy the peel ply on top. I don’t think the wee dab of color agent pigment made any difference, both pieces snapped like the unpigmented kev felts. But at least I finally had a free peel ply edge to lift off before resnapping.

P3290050 by Mike McCrea, on Flickr

 

[Guest]

Part of the reason for the bend-‘til-it-snaps test was that I know I would end up keeping the intact test pieces as a shop demo collection. Now that they are busted all to heck, I really don’t care,

Broken into pieces they would make a nice gift for DougD. He needs some abused skid plate samples. Plus I have the new BMO hat he requested, which would make a handy receptacle for the (loose, unbagged) shards.

P3290054 by Mike McCrea, on Flickr

With luck his head will itch for the next 20 years.

 

[dougd]

Hmmmm, you can keep the whole kit and kaboddle thank ya very much!