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Canoe Outfitting Attachment Weight Bearing Experiment

Glenn MacGrady

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Next up, Vynabond and epoxied D-rings.

Good. I think this will be the most real world practical experiment. That is, I don't think many canoeists pop rivet through hulls, which I've only seen for foot braces, or expect much force to be put on gunwale attachments. Stringing float bags or gear doesn't put much force on gunwale lashes, even when a canoe is upside down in the water.

On the other hand, many whitewater canoeists fasten thigh straps and saddles to the bottom of the hull with glued D-ring patches of vinyl or hard plastic. Significant force can be put on these D-rings when heeling, bracing and rolling a canoe. On flat water, I also lash non-floating gear to hull bottom D-rings, such as a my heavy chair and canoe cart.
 
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I think this will be the most real world practical experiment. That is, I don't think many canoeists pop rivet through hulls, which I've only seen for foot braces, or expect much force to be put on gunwale attachments. Stringing float bags or gear doesn't put much force on gunwale lashes, even when a canoe is upside down in the water.

Snap rivet attached spray covers have studs pop riveted through the hull. Most of the derelict canoes I have worked on have had attachments, or long gone past attachments somewhere on the hull or inwales. Most often through-hull lacing, typically with cord so old and UV degraded that I didn’t need to unlace it, or even cut it. A simple tug and most of it fell apart in my hands. Even in decayed short strands not that easy to pull the frayed cord through the lacing holes.

I do not like leaving through-hull lacing in place when paddling without float bags, it is a PITA to thread through the hole, pull, thread through the next hole and pull to install or remove. I have a single solo canoe that lives year round with lacing; the most whitewater-ish canoe we own, and it came that way. When that (apparently high quality) lacing cord gives up the ghost I will consider easier attachments.

Other DIY shadetree outfitting has run the gauntlet from rusty eye screws to pop riveted stuff to WTF were you thinking bits installed on or under the gunwales, and I have tried to include as many of those possibilities as I had on hand.


On the other hand, many whitewater canoeists fasten thigh straps and saddles to the bottom of the hull with glued D-ring patches of vinyl or hard plastic. Significant force can be put on these D-rings when heeling, bracing and rolling a canoe. On flat water, I also lash non-floating gear to hull bottom D-rings, such as a my heavy chair and canoe cart.

Well Glenn, I am bound to disappoint you. And me. The Vynabond and G/flex experiments with hard plastic pad D-rings and DIY epoxied webbing & glass D-rings were not encouraging in weight bearing limits, at least in comparison to some winky gunwale attachments or through hull doohickies.

Much as I would like to test vinyl pad D-rings busting those at $8 a pop is too pricey for me. Some whitewater aficionado really should test vinyl adhesive, G/flex and etc on thigh strap pads where the adhesion really matters for life and limb.

I am back to thinking that if, I have a heavy gear bag (or my precious drinking water supply on tidal trips) tied or strapped to a D-ring on the floor I might still want a line or strap across the top near the sheerline, for some belt & suspenders action. Especially if both tie downs/straps, top and bottom, are easy to access, undo and retighten.

I expect I know now why those hard plastic D-ring plates fell out of favor. Think the flexibility of the hull vs the rigidity of that hard plastic pad. That differential rigidity failure became obvious. Are those old-school hard plastic D-ring pads even sold today?

Glenn, “Better than Netflix”? I don’t do Netflix, but understand that this now is a meme catchphrase - Are you still watching?

More to come.
 
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Time to split hairs. Think tent pegs. Tarp stakes. Boat cleats. Etc. One wouldn't test these by trying to pull them straight up and out as is being tested here, especially as their strength or "purchase" is (at least) perpendicular to the direction of force. Is this not the gunnel fastener situation for example? In real world situations the force applied would be unlikely to come straight up from the fastener but more likely at an angle by perhaps as much as 90 degrees. That's where the real strength comes from IMHO (in my humble opinion). Thus the purchase of said screw or rivet would be more than the thread or flange but the design of said anchoring device. So in a way you are testing these at their least effective weakest position. As for the hull attachments, think how you'd most easily pull a bandaid from your skin, and what would the least effective method and direction be. There's a reason we pull a bandaid at a sharp angle away from skin, in order to most easily break the adhesive strength. No less than a 90 degree angle direction of force. I think I've made salient points but have in no way negated your work. Maybe just added a chapter 2 is all.
I am not a naysayer nor an engineer. If you saw how I hold up my pants some days you'd see that. I am just pondering the difference between direction of force and their possible results. These fasteners might in fact be stronger than tested here. However, you are putting these gunnel and hull fasteners through their paces so to speak, and once again providing answers to questions some paddlers are asking themselves when they're hovering over a parts buy wondering "Just how strong is this? Can I trust it?"

And wondering what season 2 will be like.
 
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...I have a heavy gear bag (or my precious drinking water supply on tidal trips) tied or strapped to a D-ring on the floor I might still want a line or strap across the top near the sheerline, for some belt & suspenders action. Especially if both tie downs/straps, top and bottom, are easy to access, undo and retighten.

I have a hunch that a water supply container, heavy as it may be on land, doesn't actually need to be tied in because it is not going to sink in the event of a dump. If the concern is other than sinking, i.e. it's going to float/blow away and get lost, that's another issue entirely. But I wouldn't think that'd be an issue on a tidal trip.

Water is neutrally buoyant in water, so the water weight in the container is irrelevant -- a wash (pun intended) if you will. (Actually, the fresh water in the container is less dense than the salt water on your tidal trips). And while the plastic of the container is more dense than water and would sink if you could fill 100% of the container's volume with water, that's not possible on the water containers I'm familiar with -- all of which have a hollow handle set somewhere above the fill/dispenser opening and the air relief valve. So, even when the container is filled to it's upmost capacity, there's an air pocket in the sealed container. If the volume of trapped air provides enough buoyancy to at least offset the weight of the plastic alone, I think that water container is going to stay at the surface rather than visiting Davy Jones' Locker.

As soon as the weather permits and my pool is open, up and running, I'll fill up my big water storage container to capacity and do an experiment (in the shallow end)! Then we will know if my hunch about it floating is right or if I'm all wet.
 
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As soon as the weather permits and my pool is open, up and running, I'll fill up my big water storage container to capacity and do an experiment (in the shallow end)! Then we will know if my hunch about it floating is right or if I'm all wet.

Why worry? If it sinks like a hollow water filled stone then just swim down, tip it upside down to empty it and carry it back up.
 
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Time to split hairs. Think tent pegs. Tarp stakes. Boat cleats. Etc. One wouldn't test these by trying to pull them straight up and out as is being tested here, especially as their strength or "purchase" is (at least) perpendicular to the direction of force. Is this not the gunnel fastener situation for example? In real world situations the force applied would be unlikely to come straight up from the fastener but more likely at an angle by perhaps as much as 90 degrees. That's where the real strength comes from IMHO (in my humble opinion).
So in a way you are testing these at their least effective weakest position.

Brad, all true about the orientation of the weight pull. Dan Cooke made the same observation

The direction of force applied I believe should mimic the use.
Fun exercise in trying to understand strengths of attachments. So many variables and small scale samples of testing that I doubt anything more than general conclusions in the end will be attained; but a fun exercise non the less.

My rationalizations in testing with direct force were several fold, mostly for the sake of simplicity.

I was attaching the test pieces of various gunwale stock to the 4x4 dozens of times, and opted to use cam straps instead of somehow screwing or bolting each one in place. The cam strap use immediately proved problematic; with the weights pulling sideways the piece of gunwale would rotate a little no matter how tight the cam straps. I could have used ratchet straps but I don’t own any.

With the really heavy weight loads the poly Thule cam straps, tight as I could get them, would stretch out a bit, so the gunwale piece was no longer held tight against the 4x4 and would slip around to where it was facing straight down.

At least nothing slipped with a sudden jerk, another weight bearing factor not tested, ie what happens when I drop the 52LB cinder block on the platform instead of placing it gently centered? Probably nothing good. BTW, gently placing 52lb cinder blocks and 30lb barbells dozens and dozens of times, and retrieving them off the mess on the floor after failure is a great workout for your abs.

Trying to figure out a way to hold the gunwale piece vertically, so the suspended weighs were pulling sideways, would have required a different test apparatus and required bolting the gunwale pieces in place.

No doubt there is a better, more scientific testing method; some kind of scale that records the highest weight load before failure combined with a come along or motor drive that could apply increasing force. My simple shop isn’t Underwriters Laboratories or JPL.

I did end up testing the grommet strap with weights pulling sideways (for specific outfitting use reasons), and should probably replicate that test with the weight pulling straight down in the weaker fashion. That re-test isn’t happening any time soon, I already put all the cinder blocks away and cleaned the shop.

So my rationalization is that the weight bearing numbers pulling straight down are a weakest position/likeliest failure/worst case scenario. The sturdiest of them held 300+ lbs, gawd only knows how much weight I would have needed to fail that one if pulling sideways.

As Dan pointed out, so many variables and such small scale testing provide nothing but general conclusions. But even with those variables I learned a few things and found some surprises. It was worth the couple of bucks in screws, pop rivets, attachment doohickies and adhesives.

I have a hunch that a water supply container, heavy as it may be on land, doesn't actually need to be tied in because it is not going to sink in the event of a dump. If the concern is other than sinking, i.e. it's going to float/blow away and get lost, that's another issue entirely. But I wouldn't think that'd be an issue on a tidal trip.

The large water containers will not sink. The only water container that went to Davey Jones locker was a full to the brim stainless steel Kleen canteen that sunk like a rock. I learned to leave a little floatation headspace in those canteens.

The dromedary bags are insulated, so more than neutrally buoyant. The 5 gallon carboy has a piece of exercise flooring glued to the bottom, to protect the plastic against sharp rocks and abrasion in camp, so it too would float.

My concern, admittedly very minor is that if I dumped in the wind the boat might blow away a lot faster than the mostly under the surface water container. It was evident when recovering stuff from past yard sales that some things move along faster than others. Crocs are like little sailboats.

Or, you know

About a half mile later, things calmed down and we began to retrieve our gear, which was spread out over another half mile or so of river. Never found the tent.

Smileyface thingee.

I don’t always tie gear in, and almost never lash everydamnthing in place, but all of our canoes have both D-rings on the floors and attachments up near the sheerline, including webbing loops & washers on the bottom of thwart and yoke machine screws; already have a machine screw, washer and nut there, no pop rivet to break.
 
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Wasn't meaning to be critical, and sorry I missed Dan's post. Thanks for your level headed reply to a guy who skim reads. As you were gentlemen.
 
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Wasn't meaning to be critical, and sorry I missed Dan's post. Thanks for your level headed reply to a guy who skim reads.

Brad, no worries. I have been thinking about this experiment for years, and cogitating how I could most easily accomplish it. That “most easily” part was important to me.

That cogitation part I never imagined placing a cumulative (I just added it up) 2800lbs of weights on the platform.

Actually at least twice that total weight if you include taking off 30lb barbells and 38 lb cinder blocks and restacking starting with the 52 cinder block. Er, maybe three times that if you include retrieving the fallen mess from the floor. See my self-published “8,000LB Shop Experiments and Five days to Rock Hard Abs”

I am far more critical of my own methodologies in these experiments than anyone else might hope to be. I spent 35 years in and around research labs; I know better, I just can’t do better.

Well, I could do better. At least no one suggested that I buy a $2000 Shimpo load tester.

For skim readers (OK, OK, I know, this experiment is already 7,000 words, and I’m not done yet) I will post a summary of what failed at what weight, how, and my best guess at why.

The testing is all done, at least for now. The only question is how much longer do I torment Glenn with the absence of (hard plastic) D-ring testing results.
 
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Oddly, the last thing I found after that yard sale was my camera, which was inside a small pelican case roughly 5" x 9" x 1.5". Only one small corner of the pelican case was above water and somehow I spotted it from about 100 feet away and yet the tent bag, which was 15" x 29" x 8", disappeared.
 
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Another shelter-in-place day of cinderblock hositing. The rigid plastic pad D-rings, one adhered with Vynabond and the other with G/flex, have had a week to cure, and the horribly sloppy DIY webbing, glass tape and epoxy D-ring likewise.

49762348711_314b158992_c.jpg
P4100016 by Mike McCrea, on Flickr

That DIY D-ring attachment would have looked much neater had I just tape boxed a perimeter a bit beyond the fiberglass tape instead of just smearing the epoxy on. And not used old (not even that old), already getting dark 205 Fast hardener. The pump was cleaned and replaced 4/19, and the can of 205 isn’t much older.

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P4100017 by Mike McCrea, on Flickr

Those DIY D-rings need not look as ugly

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P4110041 by Mike McCrea, on Flickr

My resins and hardeners are kept relatively temperature-stable, typically between a low of 50-55f and max of 75-80F. I have no use for West System Fast hardener anymore; I’m slow in the shop, and that stuff goes dark too fast.

The Vynabond pad failed faster that I would have thought, popping off the Royalex sheet pad fully intact at 127.5lbs. With zero wait time, add the last weight, jump-back-Jack and watch your toes, so maybe less weight. I’m guessing that the hard plastic pad is not vinyl. Nylon maybe? Vynabond on that hard plastic pad sucked, and I never like that pad style D-ring in any case.

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P4100028 by Mike McCrea, on Flickr

Next, the G/flexed hard plastic D-ring pad.

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P4100019 by Mike McCrea, on Flickr

Eeek, something made a sharp CRACK sound at 119 lbs. That is a sheet of probably brittle Royalex from an ancient Dagger Caper. Something cracked, but it is still hanging together.

It was not, as I suspected, cracked RX; some underside inspection showed that the rigid plastic D-ring pad had started to separate from the Royalex at one end. That RX sheet had a slight arch to it, and with 119lb on the RX went decidedly flat between the two 4x4s. The rigid plastic pad, which had been weighted down to the slight curve as the epoxy cured, did not like that action.

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P4100022 by Mike McCrea, on Flickr

Still holding on at 187.5lbs

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P4100024 by Mike McCrea, on Flickr

The pad finally failed at 226lbs. Actually the pad didn’t fail; the Royalex sheet didn’t break in half between the 4x4’s and the D-ring was still perfect; the hard plastic pad again popped free, taking a bit of Royalex skin with it

Those hard plastic pads were bought decades ago when the Keelhauler’s outfitter went out of business. I actually had those installed in a canoe which I later rebuilt. I don’t recall what adhesive I originally used, probably Vynabond, but on the rebuild those hard pad D-rings popped off when I have them a good hard tug.

I ran the bottoms of those old plastic pads on a 4x36 tabletop sander to take off any adhesive residue, so they were actually a bit thinner and more flexible than original plastic pads. I again kept them, and may sand of the new residue, but I’ll never use them in a boat again.

I could sand the residue off the bottom of the surprisingly clean Vynabond pad and try it with contact cement, but I know (ok, I think, at this point half the stuff I thought I knew I now know better) that contact cement would provide a much weaker bond.

I am left thinking that the flexibility of vinyl pad D-rings has distinct advantages over the rigid plastic pads when the hull flexes. I do still wonder about how much weight the stitching in those sewn D-ring pads will support, but that is another we’ll never know.

Last test piece, the fugly FIY D-ring with webbing, glass tape and epoxy.

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P4100029 by Mike McCrea, on Flickr

The DIY D-ring made a couple of faint crack sounds at 119lbs as the arched RX sheet flattened out and I left it to hang for a while. A long while, getting really tired of re-positioning cinderblocks, which I now refer to as F%#&@*! cinder blocks, and it was time for a beer.

More cracking sounds at 157.5lb, and the occasional snap-crackle-pop resounded through the shop for a few minutes. More weight added, still holding, but making near constant cracking sounds for 10 minutes later before quieting down.

Er, no, as I finished my beer it started cracking, even more loudly and more frequently. It’s gonna break any minute now. Scotty, we need more power!

“She can’t take much more Captain”.

She could, but at 187.5lbs the cracking sounds got louder and louder, and more frequent, and I kept my distance.

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P4110031 by Mike McCrea, on Flickr

Still held for a few minutes of snap-crackle-pop before the 187.5lb crash.

The West 105/205 saturated poly webbing and glass tape pulled cleanly off the hull. The metal D-ring itself is still fine and I cut it off for (?) future use.

49762672487_b6acf674b1_c.jpg
P4110038 by Mike McCrea, on Flickr

That DIY D-ring might have held better had I propane torch flamed the RX first. Almost certainly would have held better had I used G/flex (note “flex” in the description) as the epoxy.

Dammit, I really want to try a vinyl pad D-ring. Or vinyl pad D-rings plural, one with installed with Vynabond and one with Gflex. Or plural X4, vinyl pads with stainless steel vs nylon D rings. Or X6 if I test vinyl pads with sewn in webbing loops instead of D-rings.

Maybe after I hit the Lotto and can blow my winnings on an assortment of vinyl D-ring pads. I really like Northwater’s nylon double D’s for running two straps in different directions, and have those in most canoes. I would like to know what fails how at what weight.

I’m moving all the weight testing folderol back outside today – oh boy, more F%#&@*! cinder blocks to carry around – and cleaning the busted pieces off the shop floor. But somehow I’m not sure I’m done with this experiment just yet.
 
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About the shop cleanup, the tall horses and 4x4’s are outside the shop, but still nearby, awaiting future funny business, and the shop floor has been leaf blowered clean of busted parts and fallen cinder block dust.

Side note for Conk: The wheeled shop chair screeches to a fingernails-on-blackboard halt when it runs into a busted chip of concrete block. Just sayin’

I even learned a thing or two during the shop clean up. The sundry washers and broken pop rivet parts didn’t travel very far, falling out directly under the sawhorses.

The brass spray cover studs were the only parts that ended up a long damn ways away. Like 20 feet away, against the distant shop walls. It’s a wonder some of those aren’t stuck in the sheetrock like Bond villain Odd Job’s hat. Yes, I wore safety glasses. And steel toed Crocs.

More importantly I learned that, while dabbing G/flex in the screw holes made absolutely no weight bearing failure difference – I had thought it likely the smaller screws would pull out, that’s a nope on every screw - it made a big difference in trying to back out the screws to remove the broken attachments. I broke the heads off half of the epoxied-in-place SS screws trying to remove them. I will not be epoxying screws in anything I might ever need to remove or replace. Bad idea.

About the loud failure crash clangs, eh, my wife’s office is directly above my shop. I made sure she was not on the phone or some video conference skype whatever before adding weights, but I suspect the once an hour crashes, especially the horseshoes clanging on the concrete floor, may have become tiresome.

She professed not to share my fascination for such thoroughness in discovering what fails and how, especially after a couple dozen crashes over the course a week. I won’t repeat what she said.

I tried to explain, and wanted to reply “It’s a canoe thing, you wouldn’t understand”, but knew better.
 
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For skim readers (OK, OK, I know, this experiment is already 7,000 words, and I’m not done yet) I will post a summary of what failed at what weight, how, and my best guess at why.

As promised (still a lot of descriptive words)
Attachments, Failure Weights, How Failed and Suppositions as to why things failed.

Nylon webbing pop riveted through vinyl gunwale, 30lbs
Webbing pulled through 3/16” rivet head

Nylon webbing with fender washer pop riveted through vinyl gunwale, 60 lbs
3/16” Rivet pulled out of vinyl gunwale

Poly webbing pop riveted through vinyl gunwale, 70 lbs
Webbing pulled through 3/16” rivet head

Poly webbing with fender washer pop riveted through vinyl gunwale, 80 lbs
3/16” rivet pulled out of vinyl gunwale

Thoughts and suppositions:
Webbing loops need a washer under the pop rivet. OK, I already knew that.
Thin nylon webbing will pull through a washer more easily than thick poly webbing. No surprise there either.
3/16” pop rivets through thin (1/16” thick) vinyl gunwale will pull through the gunwale between 60 and 80lbs. The thicker/sturdier the webbing the more weight it held, perhaps because the weight was less likely to pull sideways, bending and sheering the pop rivet.

Grommet strap pop riveted through vinyl gunwale, 114 lbs
3/16” rivet pulled out of gunwale

Thoughts and suppositions:
OK, not a fair comparative test, the weights were pulling on the grommet strap sideways, not straight down. It definitely takes more weight to pull a pop rivet from a vinyl gunwale in that orientation. I am still impressed that the grommet strap itself held 114lbs

Nylon pad eye with dual pop rivets through vinyl gunwale, 163lbs
One of two 3/16” rivet pulled out of gunwale.

Thoughts and suppositions:
Two pop rivets are better than one. And I’m more a fan of those nylon pad eyes than ever; those are where my swivel snap Surf to Summit back bands are attached.

Weird plastic webbing connector (no pop rivet, hung via webbing), 95 lbs
Plastic broke

Thoughts and suppositions:
I dunno, whatever that skinny thingamadoodle was made of it held an impressive amount of weight. I only used it because I had one in the parts box. The type of plastic, nylon, derlin, etc obviously makes a strength difference.

Plastic Cable clamp pop riveted through vinyl gunwale with 3/16” pop rivet, 41.4lbs
Plastic clamp broke

Thoughts and suppositions:
Way more weight than I thought one of those would hold. The elongation before failure should have been no surprise.

Spray cover stud and mini SS D-ring pop riveted through Royalex sheet with 1/8” pop rivet, 124.5lbs
Rivet broke

Spray cover stud and webbing loop with 1/8” pop rivet on Royalex sheet, 171.5lbs
Rivet broke

Thoughts and suppositions:
Wow! A lot more weight than I would have predicted using a 1/8” pop rivet. Backing up spray cover studs is now a given.

Mini SS D-ring with 1/8” pop rivet affixed to aluminum gunwale, 82.5 lbs
Rivet broke

Webbing loop with 3/16” pop rivet on aluminum gunwale, 55 lbs
Rivet broke

Thoughts and suppositions:
Note the reduction pop rivet failure weights. I believe the aluminum gunwale helped sheer the aluminum pop rivet. And that was pulling straight down; pulling sideways might be even worse.

I tried using 3/16” steel pop rivets once. That was a nope with my hand pop rivet gun; I couldn’t even begin to squeeze them closed. I have a box of 24 left, 3/16” dia X 3/8” long, large flange steel. Free to good home.

Under-inwale D ring plastic tab with 3/16” pop rivet, 151lbs
Plastic tab tore.

Thoughts and suppositions:
Again, seriously stronger than I would have thought. A decent solution for under aluminum gunwales.

Eye screw in wood gunwale, 76.5lbs
Eye screw hole straightened out (long before weight limit was reached)

Thoughts and suppositions:
The eye screw loop straighten out, probably starting at 50lbs or so. Kinda predictable.

Cable clamp screwed in wood gunwale, 51.5 lbs
Plastic clamp broke

Thoughts and suppositions:
The elongation was comical to behold, but even those winky attachments held more weight than I anticipated.

Webbing loop screwed in wood gunwale with cup washer, 282.5 lbs
Webbing tore through cup washer

Webbing loop screwed in wood gunwale with flange washer, 320 lbs
Webbing tore through flange washer

Thoughts and suppositions:
Those both held a lot of weight. Flange washers helps. Better webbing would have helped as well. Dabbing epoxy in the screw holes made no difference, except that I couldn’t back the screws out when done.

Pad eyes screwed in wood gunwale (with smaller screw heads), 146 to 157 lbs
Screw heads pulled through nylon pad eyes

Pad eye screwed in wood gunwale (with larger screw heads), 300+ lbs
Nothing failed, I just gave up, although that pad eye was bent like crazy.

Thoughts and suppositions:
Size does matter, at least when it comes to screw heads in nylon pad eyes. Again, nylon pad eyes, with two pop rivets or screws, will hold a tremendous amount of weight. Also Mike will give up at 300lbs weight and call it good.

Vynabond and hard plastic D-ring on Royalex sheet, 127.5 lbs
Hard plastic pad popped off cleanly

G/flexed hard plastic pad D-ring on Royalex sheet, 226 lbs
Hard plastic pad broke free, taking some vinyl RX skin with it.

Thoughts and suppositions:
Hard, rigid plastic pads adhered to flexible Royalex do not make for a good combination. I’m thinking there is a reason those hard plastic D-ring pads fell out of use in favor of more flexible vinyl pad R-rings


Edit: Precluding the ask, I can already hear ALSG requesting this is chart form. And have faith in his abilities to turn it into an Excel spreadsheet with macros ;-)

Next fall I mean to have at this again. I’ve thought of more things that need to be tested, starting with side release and other buckles.
 
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Glenn MacGrady

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I expect I know now why those hard plastic D-ring plates fell out of favor. Think the flexibility of the hull vs the rigidity of that hard plastic pad. That differential rigidity failure became obvious. Are those old-school hard plastic D-ring pads even sold today?

The hard plastic D-ring pads are still sold by Western Canoeing as part of their wilderness lashing kit, but you can buy the individual D-ring pads for about a dollar each.

Wilderness_Lashing_System_Kit__69815.1473378468.jpg


There's little doubt that a vinyl pad D-ring with a much larger surface area should adhere better than the plastic pads, especially on a noodle flexy plastic hull or a raft. However, I much prefer the small plastic pads with plastic D-rings for a composite canoe or kayak. I think they look better; big vinyl D-ring pads are really ugly in an expensive composite hull. In addition, most vinyl pads have metal D-rings, and I've seen too many of those encrusted with rust after a few years.
 
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Growing out of McCrae's dry bag-making thread and me wanting to equip my bag for the 14-lb Alps chair with grommets, I present a dry bag / grommet test.

What's it take to make a grommet rip out of a dry bag? I ironed up a scrap of the dry bag pack cloth and installed a grommet an inch from all edges. The hole for the grommet had been burned, which leaves a theoretically stronger, sealed edge around the hole. This was the first grommet I ever installed, so user-error should not be discounted. The grommet was a 1/2" Bostich brand bought at Lowes.

I started off hanging 20 pounds from the grommet.
Grommet - 1.jpeg

No sweat, no strain at all. I let each weight hang for at least an hour as I worked up through 30 and 40 to 50 pounds. After half hour with 50 pounds hanging, I could see a glimmer of light at the top edge of the grommet. Apparently the fabric opening was stretching.

Grommet - 2.jpeg

Well, that's not really failure, but it was beyond a comfortable weight for this trial. What would happen if the 50 lbs was applied dynamically? I picked up the weights about six inches and let 'em drop--straight to the floor.

Grommet - 3.jpeg

The grommet was only slightly distorted, and it never really pulled out of the fabric. So, I guess it was more of a fabric failure than a grommet failure. Regardless, I satisfied my curiosity about whether a grommet in a dry bag could support the weight of an Alps chair. I believe it can, several times over. I think this was less than a scientific test, but like I said, it answered my question.
 
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