Attaching rub strip under water line?

[Ed]

Hello All,
I need to install a rub strip on the bottom of my wood dingy. My dink is coated in epoxy with varnish over the area where I want to install the strip. I’ve heard that people drill an oversized hole and fill with epoxy. I’ve done that with deck hardware but in this case I'm not thru bolting, just wood screws. So my question is how to do this epoxy trick without the screws becoming a permanent part of the epoxy.
Thanks

[Rachel]

Whoa! Work of Art!

Is that an Eastport pram?

I'm going to let someone else tell you how to drill holes in that baby, but... wow. Really gorgeous.

Rachel

[rshowarth]

Here is a link to the West System site: http://www.westsystem.com/


In an article entitled:

Varnish over epoxy
A look at the benefits of undercoating with epoxy



It includes this advice:

Keep the moisture out: sealing screws with epoxy
It is important to eliminate places where moisture can find its way into the wood. This includes applying epoxy to screw holes prior to running the screw in place. If you will need to remove the screw in the future, you can apply a wax or mold release to the screws. If you forget to apply mold release to the fasteners, you can use a soldering iron to heat the fastener head for removal.

Beautiful Pram!

[Bluenose]

Whoa! Work of Art!

Is that an Eastport pram?

I'm going to let someone else tell you how to drill holes in that baby, but... wow. Really gorgeous.

Rachel

Ditto!

[Peter]

That looks familiar ... definately a big (nesting) brother to this one, and a beauty, too!!
(Rachel, you're right on the money,as always)


On my East Port Pram I attached the bottom rub strips with bronze screws and a layer of thickened epoxy. I left the screws in.
Where did you get the nice plastic wing nuts that hold the two halves together? I'd like to pick one up to clamp my fold-up rudder.

[Quetzalsailor]

Gorgeous!

I've used Teflon slip spray for mould release: easy and clean.

As for your rubstrip, I'll have the same problem on my Flying Dutchman rebuild. It, too, is coated out in WEST epoxy and will be varnished bright. FD are required to have rubstrips of a specified dimension, 3/8" wide and 1/8" thick. The old wood boats had brass/bronze with heaps of little screws; the plastic boats have the shape moulded in. I've got the bronze strips that came off the boat, but I'm loathe to drill all those holes and have to seal 'em, bed the strips and so on. The screws caused 'nail sickness' in the wood, and I just resist the whole idea! My latest 'brilliant' idea is to buy fiberglass rod and saw it to extract the correct shape off the faces. Easy to get two. Unfortunately, I have not found brass-colored fiberglass rod. I'd simply epoxy the fiberglass rub strip on and varnish over.

You can see pictures of my FD at: http://www.oudzeilendhout.nl/page11.html
(veneering; repair of lamina; interior; interior)

Again! What a gorgeous dink!

[keelbolts]

I give. Don't you usually put a rubbing strake at the widest point on the hull?

[bcooke]

I think the critical detail is the description "Rub strip".

Skeg just doesn't seem right when it is not providing directional stability.

I am not sure if there really is a traditional name for these. I think most of the old-time boats had false bottoms or replaceable skegs or maybe just replaceable metal strips on the skegs.

I had a dory with wide strips but they didn't help much. Some people have actually suggested to me that they channel the grit into a line creating more pronounced local areas of wear. On an Eastport pram I wouldn't be too worried though.

Edit: on a second look, I bet some half round brass strips screwed onto those rub strips would be very effective and easily replaced. I have one on the skeg of my nutshell. When I get to it tomorrow I will try and take a picture.

-Britton

[keelbolts]

Boy, do I feel special. I really can read. No, really...

In any case, I think the oversized hole with an epoxy 'liner' is more used in FG boat construction than wood. I don't know why you don't see that technique used on many wood boats as it seems like it might be helpful in keeping water from seeping in around fastenings. I'd guess that it's either unnecessary or too labor intensive for general fastening. I know that it is done when gluing fasteners into wood boats.

Also, I've set silicon-bronze screws in epoxy many times and unscrewed them without any trouble. If one gets difficult, just put the tip of a soldering iron on it and heat it up a bit. It will come right out for you.

I agree that half-round brass strips, properly bedded, would do it just fine.

[Hirilondë]

I think what Ed is talking about is the chafe strip on the keel. I have one on my dinghy and it is essential as I see it to protect the keel from wearing when the boat is hauled out or beached.

First off, she looks great Ed. The East Port ran a close second choice to the Spindrift I ended up building for myself.

Epoxy is great stuff. But I think it is over used. Not everything needs to be saturated/coated/infused with the stuff. Screws in wood is a fastening that has been used for many years before epoxy, and when done well last a loooooong time. Over drilling then filling with epoxy for screws is very weak. I definitely would not do that.

Lay out your chafe strip, mark and drill the pilot holes. Dry assemble the whole thing. Remove all the screws and carefully apply a good smear of bedding to both the chafe strip and the keel. Guess what brand I like? ;<) (hint: Sikaflex 291) By working the goo onto both surfaces you break the surface tension and significantly reduce the chance for bubbles, hence voids. Now when you fit it back on you are bedding goo to goo. Secure the screws again. Clean up.

This double coating method is how I bed everything. If I don't see ooze all around my bedded piece I can't be sure there are no voids.

[Ed]

Thanks, that’s exactly what I needed. My dink is a Chesapeake Light Craft Passage Maker Kit. Big brother of the Eastport. I love it but unfortunately when the decision to buy/build came we had a much bigger mother ship, not having learned the small is beautiful message yet. So the dink doesn’t fit real well now.
This is the area I’m specifically talking about.

[Rachel]

I like the sound of Dave's recommendation.

Do I see correctly that the skeg is plywood? Does that change anything in the way one would fasten the wear strip?

Again, lovely dinghy!

R.

[Ed]

Yes it's two layers of okume(sp?) that were epoxied together then screwed and epoxied two the boat bottom. It's a very strong piece. We grab and flip the boat using that hand hold without a second thought.

[Peter]

Ed,
That handhold cutout looks like a great idea. It wasn't on my plans, but after seeing yours I'm going to make a cutout on mine.
My old dinghy has twin skegs about 15" apart and they are cut out to act as grab rails when the dinghy is lashed on deck. Very handy when going forward, and it allows you to sit between the skegs when working at the mast.

On my Eastport I've laminated three layers of 9 oz. cloth over the edge of the skeg, but I know it won't last. I'm looking for something plastic to cover it. I had brass on the other dinghy but took them off because they dragged over the gunwhale of the mother ship when I hauled it aboard. I went back to unprotected wood. As it's old growth fir it'll probably last forever, but the Eastport plywood skeg will delaminate if it's scraped bare.

MY next dinghy won't be a problem to lift out because it'll only weight 28 lbs :-)

[Rachel]

My 1984 7' Fatty Knees has a molded in fiberglass skeg, that has worn down over the years (mostly before my ownership).

I'd been thinking of screwing a Starboard strip or a Glyde-Slik strip (http://tinyurl.com/22woxr) to it, but that was before I realized that these products don't take caulk very well, and so water might get past and into the void of the hollow skeg.

My current thoughts are as follows:

1)I've seen self-adhesive "bow protector strips" (like a soft version of a "grunch pad") in a Cabela's type catalog, although I can't find them now. I thought I could perhaps use one of those.

2)Epoxy on a sacrificial strip of pre-made fiberglass board (such as from McMaster Carr).

3) Just add layers of fiberglass, in sacrificial mode.

For #1 don't like self-adhesive factor.

For #2, I'm not sure whether the strip would stay on without mechanical fasteners, and I'm also not sure what happens when that stuff wears from abrasion; does it get "itchy" or fibrously disagreeable?

I'm not keen on a bronze strip for the reason Peter mentions - it just seems like it could be too rough on the mother-ship.

Maybe a strip of teak is best, after all!

[Peter]

Maybe a strip of teak is best, after all!

How about a strip of some type of ironwood? We had one in Argentina called "quebracho" which means "axe-breaker".

[Tony]

Rachel,
I have an old glass dinghy that's been around a while. The PO made an epoxy-rich strip about an inch deep all the way down the center line on the bottom. Dragging it over rocks and concrete does wear it down, but I've not noticed it getting fibrousy or anything and I've never gotten any fiber slivers from it. Next year I'll probably give it a couple layers to beef up the worn down areas. I think (and as always, correct me if I'm wrong, oh guru of the glass Lackey :-0 ) it doesn't matter too much as long as the initial layup gets good fiber penetration by the resin.