10 foot oars

[GreenLake]

clever!

[tomodda]

Thanks for the photo and the explanation. I want to share some thoughts and questions when I have time/energy but I'm a bit worn out from a session on my local lake. I LOVE those rare days when we have good summertime wind here, but rigging the boat in 95F heat is no fun! Worth it once out on the water.

[tomodda]

Thanks again. I've thought of those rollers before as additional flotation + megafenders + beaching tools. $75 a pop, a bit under 138lbs of flotation each, not bad (4.5*pi*60 cubic inches, convert to liters, math, math, convert to pounds). I'm a bit concerned about the D rings though, you're potentially hanging 138lbs on two glassed in nylon straps. If I go this route, I think I'd feel safer with two Drings for each position (4 total), but that's just me. Not worried about the epoxy to gelcoat adherence, I'd worry about the gelcoat/fiberglass interface (seen it fail in one spot on my DS1 already).

Question: do you inflate the rollers 100% or leave some slack for heat expansion?

And we're getting well away from the subject of oars. Yours a beautiful, I love the layup in the oarblades.

Tom

[GreenLake]

138# isn't all that much. It's in the range of what you can exert by pulling. Not sure you can rip out that D ring bare handed

[Slim]

I’m not so sure about the strength of the D ring connection either. Pulling on them they seem pretty solid but I haven’t given them a hard yank. I scraped off any of the gelcoat before epoxying them on so they are attached to raw fiberglass. Also since there is other flotation in the boat I don’t think the full 138 pounds would be pulling on the D rings. That would only be if they were fully submerged, right? At some point this summer I’d really like to do some capsize testing to see how it all works out. I’ve made some other flotation improvements on my boat that maybe I’ll bring up in another thread.
As far as the inflation pressure goes, they definitely get super hard when left out in the sun if they were inflated in cooler weather. With the air pump I use or just blowing them up the old fashion way they don’t get super tight. They definitely fit a little better if they have a little slack in them.

[GreenLake]

Epoxy bonding strength is in the thousands of PSI. So a one square inch tab should easily hold half of 138#. However, if you lift only one edge of the tab, you may be limited by "peel strength". That's said to be > 50# per linear inch. In your D ring fixture, you'd see a mixture of both. It should be stronger than if you had wrapped a single U around the ring and tabbed only to one side. The reason is that the two opposite sides are connected, so each isn't held only by peel strength - in ripping it out you also have to overcome the tensile strength along the tab.

Even allowing for less than ideal conditions, as long as you've cleaned the surface of contaminants I'd wager it will be plenty strong.

Always better to have one fastening that you engage reliably than too many that you may opt to skip in a hurry.

[tomodda]

GL and Slim: Agreed re: Epoxy strength, and thanks for all the input. As I wrote, my issue with epoxy has not been the epoxy adherence, it's been gelcoat. To be specific, I installed a cheekblock on the side of my centerboard to route my vang line to a swivel/tube setup on top of the trunk.

Anyway, I screwed the cheek block to a bit of teak that I had, then epoxied the teak to the CB trunk. I roughed up the surface a bit with coarse sandpaper and figured that would be good enough. NOPE! First real gust and the cheek block mount (the teak) came off, along with the underlying paint. So I carefully cleaned the whole area to bare gelcoat and reepoxied. Bang! The gelcoat came off the raw fiberglass. Now I'm going to clean around the area and try to epoxy direct to fiberglass, but if that doesn't work then I'll need to put down some bias tape (fiberglass tape) to hold down the block and spread the load over a greater area of CB case. Sigh. At least the walls of the CB case are pretty thick, so no worries there (I think).

Anyway, you've confirmed that I need to epoxy to raw fiberglass, thank you!

Tom

[GreenLake]

The lack of gelcoat bonding may also not be typical. I'm thinking that a check block at 90 degrees will see 141% of the force on the line. In a gust, how much do you think that would exceed the force you can apply? Unless your teak added a bit of a lever arm, that should all have been well enough within the range of what an epoxy bond can hold. Clearly your paint wasn't going to be strong enough, but I wonder whether gelcoat should have come off that easily. Don't know figures,

[tomodda]

I hear (read) you on the math. Remember, mine is a 1958 boat, class number 37, so Marston Plastics was still figuring things out. Add 63 years of the Centerboard trunk flexing around and I'm not surprised that my teak block (. 25 inch thick) pulled off a hunk of gelcoat.

Do you think I should go straight to "strapping" my teak clock on with bias tape, or give epoxying to raw fiberglass a try first?

Man, I'm so off topic. Want to move this to another thread? Let's go back to admiring Slim's handsome oars....

[GreenLake]

I'm game to making a new thread, if I can see a "clean break" in the contents. This one's tough because you started discussing something that was also present in a photo. Let's not worry about it. I suggest you try just bonding and if it comes off again try tabbing it. You've nearly done the complete series of clean experiments, why skip a step?


Once you've found something that holds, why not then start a new thread that discusses how to mount blocks using epoxy.

Good luck with the lobster poisoning.