PocketShip.net

I've been reading all of the Pocketship blogs and forum postings in preparation for my upcoming build. (I have to finish my current paddleboard project first.). One question that I have that is relevant now is in regards to fiberglass. I've used e-glass on all of my projects to date, but I was reading about other options on the Fiberglass Supply website. Have any of you worked with S-glass? For a project like Pocketship, would the stronger glass be beneficial? To an extreme, what about carbon fiber?

I have not seen the mast glassed in any of the builds. This would create a regular varnishing requirement, I know, but after watching my friend's 53' wood mast snap at a rotten joint, I'm a little worried about waterproofing and extra strength.

Many thanks,
Erich Schneider

One thing to consider is that maybe different fiberglass types would require more epoxy to wet out and fill the weave, adding weight and cost. If not, then I guess there's no disadvantage? I've never used anything except for e-glass since I read that e-glass is what is traditionally used for these types of boats. If you get a different kind, make sure it wets out clear if you intend to varnish.

The mast in pocketship is supposed to be epoxied and varnished. I guess you could fiberglass it if you want. Would add weight though. Hard to sand. Come to think of it, I've read that most of the forces on a mast are at the pivot point. If you wanted to add more strength without a lot of effort or weight, you could just reinforce that area.

As Craig points out, the mast is epoxied, so if properly done there should be no worries about water infiltration. (Any holes drilled in the mast should be sealed with 3M 5200; or drilled larger, filled with thickened epoxy, and re-drilled within the epoxy fill.) The mast should not be fiberglassed as this would add too much weight at a high moment-arm. Craig's idea about reinforcing at the pivot point seems logical though, and wouldn't add that much weight--also not at a very high point of moment.

But I've been wondering for a while about mast strength.

And that brings me to my question. I have a Skerry (still building the Pocketship) and on the Skerry the mast partner is an extension of the seat, about 13 or 14 inches above the step (the boat is all sealed up for the winter, so I'm not going out there and measure). There are no stays or shrouds, so obviously there is tremendous pressure at the point it goes through the partner and down to the step. So Craig's comment about most of the pressure being at the pivot point makes sense, except for the fact that the mast has shrouds and the jib stay serves as a forestay. There is not backstay, but the shrouds are angled back a bit. So to my mind this relieves a lot of the pressure on the pivot point, provided the stay and shrouds are adjusted properly. Am I correct about this? Wouldn't most of the pressure on the mast now be distributed more-or-less evenly along the length of the mast from pivot point to head? As long as the chain plates and bowsprit eyes hold, the mast should be pretty safe. Please let me know where I'm missing the point.

Hmmm, I don't want to admit that I'm wrong, but....

You may have a point. For an UNSTAYED mast there is a lot of pressure at that point, but now I'm not so sure about a stayed mast. I guess you're right, and the stays would put the entire mast in compression and reduce pressure at that point. I would still bet the forces would be higher there than elsewhere though. The mast seems very solid, but from all the creaks and groans I've heard, it's the tabernacle I'm worried about. I've already rebuilt the thing once and wish I had upgraded to 1" material. Or fiberglass it.

Maybe to the heart of the matter, PocketShip is plenty strong with the fiberglass schedule specified by the designer. I can't see a compelling reason to monkey with it.

JonLee is correct. And, replying to my own earlier post, the shrouds, jibstay, or chain plates could fail, and if they do it would of course be at the worst possible time. When that happens a strong tabernacle might buy you enough time to douse the sails. And making the mast too strong could cause damage to other, more difficult to repair, components--better to sacrifice the mast.

Here's a little insight from three years of experience. First, the stock fiberglass schedule is more then strong enough in most areas. The two places I would recommend some extra layers in are the bow to reinforce the bow eye when winching the boat onto the trailer and the cabin roof to bulkhead joint since this one will break pretty easy if the stays are even slightly loose and the jib halyard pulled on. I added several layers about 6" wide under the bow eye and haven't had any issues in that area but I do need to repair the cabin roof joint this spring. This is also the boat that suffered a trailer rollover at the launch with only minor damage near one rub rail. The structure is more then strong enough as designed and s-glass would really just be adding cost with little benefit.
As for fiberglassing the mast, you're going to add weight in the worst possible place by doing so. A rough guess would be about three pounds of ballast to counteract every pound added towards the top of the mast. In reality the mast seems to be the one that needs the least attention maintenance wise. I pull the spars off and refinish them each winter and the boom and crutch always have the worst wear on them from rubbing together taking the sail up and down. It also gets dinged up by the hardware on the gaff when they're strapped together for storage and trailering. While fiberglassing the boom might help some it's so overbuilt that it would take a lot of rot before any safety issue ever arose. As long as it's not painted you'll be able to see any problems starting. It only takes a light sanding and a couple coats of varnish to fix them between refinishing.

Chris