Mast Delaminating

[LakeErieSailor]

O.k., forumites, I need help. This morning, sailing on Lake Erie in a moderately brisk breeze with my wife, we had the unsettling experience of hearing a loud crack, and on closer investigation, seeing a crack open (you could see daylight through it) between the laminated sections of the mast, near the partners. Fortunately, we were in shallow water, close to shore, so we beached the boat and towed her back to the house, about a 1/4 mile away.

The mast is construction grade Douglas fir, longitudinally laminated in three sections, using MAS epoxy.

The question is: how do I fix it? I thought of running a circular saw into the seam, on both sides of the mast, and then filling the gap with thickened epoxy. The problem with that is that the mast is round and the shoe of the saw is flat, so one bad move and I've got real trouble.

The other idea is to run a thin saw, like a keyhole saw, maybe Japanese type, in the seam and then filling it with epoxy.

The boat is Reuel Parker's Maryland Crabbing Skiff, 20', the mast is abt 20' long, unstayed, 20" or so is buried.

Any and all constructive suggestions are welcome.

[John B]

You can put some blocks alongside the spar to create a flat surface for the circular saw, make a temporary wider shoe from some scrap if you need to.

edit, but I like the japanese backsaw idea better on thinking about it.

And then , because I wouldn't want a repeat( why has that glue failed?) I'd plane some flats perpendicular to the existing join and past the delamination some,and glue some new timber in across the join.

[Banjo]

I would cut the seams with a hand saw to clean them out,
then tape the seams lengthwise on one side and align them vertically
and fill them with straight epoxy (not thickened) using a syringe,
keep filling until you get it oozing out the top of the seams so you know
there are no air pockets in there.
Would probably help if you warm up that end of the mast first in front of a heater for a while, then remove the heat source just before you start injecting the epoxy.
Once filled wrap the area with plastic and clamp with large hose clamps.

[Thorne]

You might want to consider making some structural changes to the mast, or rebuilding it.

Think about it -- what if the epoxy you used is fine, not poorly-mixed or whatever. That means that the problem is the construction of the mast, not the glue. So gluing it back together will fix that joint for awhile -- but what of the other joints?

And if the glue IS failing due to being poorly mixed or applied, same problem with the other joints.

Perhaps it is time to build another mast of higher-quality DF, possibly making it thicker up past the partner? You'd just need three good 20' 2x4's, right? And according to numerous posts here, you want to use thickened epoxy to avoid having a glue-starved joint.

After breaking two smaller-diameter unstayed masts on my dory skiff, I built a thicker one from good-quality DF. After having Weldwood glueline failure (failed to meet Weldwood's temp or clamping requirements, or both), I sawed out the joints in the lower part of my mast and reglued with epoxy - no problems since. Unstayed masts on small boats may be one of the most extreme uses of epoxy -- they REALLY flex!

[Bob Smalser]

Why'd it break?

Worth some investigation and thought, otherwise your repair might simply break again.

[LakeErieSailor]

Thanks to all for your suggestions.

Banjo, when you mention taping on one side, I have to assume that you mean strapping tape or something similar, not fiberglass tape? Also, are you suggesting running the saw up the length of the mast, effectively disassembling it, or just through the separated areas? And why not thickened epoxy?

Thorne, I've thought about rebuilding the mast. I have an e-mail in to L.L. Johnson lumber in Charlotte, MI, at this time re a solid piece of DF; they have it in a 4x 8, rough-sawn, it's $168, but I only need a 4 x 4 piece. Re the reason for failure, I suspect that I may have at least partially starved the glue joints due to over-clamping.

I can get DF 1 x 's at Lowe's, but they're expensive as hell, and would take multiple laminations since their 1 x 's are actually 5/8" (I'm not making this up). Also, your point about increasing mast diameter is well-taken, since the designer specified solid lumber. But he did say that laminating a mast would work just as well.

Bob S. - see my response to Thorne, above.

[Thorne]

Why not build it from 3 20' 2x4's, glued two wideside and one narrowside?

If that doesn't meet your dimensional requirements, you can also build from 4 2x4's, split 'em all in half and glue them up in three rows of three 2x2's.

20' DF 2x4's should be under $20 each.

[Jay Greer]

Yours is a problem that has, always, made me shy away from epoxy as an adhesive for making up a mast. Some people get lucky and others end up with delamination problems. So far as repair of your spar is concerned, I would approach it using a Japanese rip bladed saw a "Kataba". These saws are available as rip bladed only, as opposed to the combination bladed "Ryoba" and are disposible. Having a blade that can be easily replaced can be an advantage when the tool will be cutting out hard material such as old glue. Using epoxy again might seem like asking for problems. But, West System does offer adhesives that are formulated with more flex in the mix which, should suffice for the time being. The spars on my H28 were repaired by the former owner for just the same reason, epoxy joint failure. There are several reasons for this which I will not go into. I am planning to build a new set of spars for "Bright Star" using resourcinol glue which is not known to fail when correctly used for mast lay up.
Jay

[Bob Smalser]

I've always suspected with epoxy failures on masts and other major structures on boats bigger than canoes, that it isn't the epoxy, it's the wood.

Epoxy can't stand very much clamping pressure. Yet the thicker and/or longer the stick of wood, the more likely it has a tad of twist or cup requiring it be pulled in fairly hard in spots. And tighter than the epoxy can stand. Clamping up 30' stock, you can starve the joint of glue in places without even knowing it.

Using resorcinol you don't have to be as fussy, because you can't apply enough clamping pressure by hand to starve the joint.

[MiddleAgesMan]

Why'd it break?

Worth some investigation and thought, otherwise your repair might simply break again.

Twenty foot mast with twenty inch bury?

[kc8pql]

I've thought about rebuilding the mast. I have an e-mail in to L.L. Johnson lumber in Charlotte, MI, at this time re a solid piece of DF;

I can get DF 1 x 's at Lowe's, but they're expensive as hell, and would take multiple laminations since their 1 x 's are actually 5/8" (I'm not making this up).

May be worth calling Public Lumber in Detroit. They stock very nice VG Sitka and D. Fir in both 4/4 and 8/4. They supplied me with 22' to 24' lengths of Sitka for my mast.

http://www.publiclumber.com/index.html

[Bob Smalser]

Twenty foot mast with twenty inch bury?

Even the weakest or cheapest of glues is stronger than the wood it adheres to. If it's the glue and not the wood giving way first, there's a problem with the glue or gluing technique.

http://pic20.picturetrail.com/VOL12/1104763/7738131/103956073.jpg

http://pic20.picturetrail.com/VOL12/1104763/7738131/103956083.jpg

[Banjo]

Thanks to all for your suggestions.
Banjo, when you mention taping on one side, I have to assume that you mean strapping tape or something similar, not fiberglass tape? Also, are you suggesting running the saw up the length of the mast, effectively disassembling it, or just through the separated areas? And why not thickened epoxy?


Yes masking tape or duct tape, just to form a barrier to stop the epoxy from running out of the gaps.
Ripping only in the glue lines that are of concern.
Un thickened epoxy will flow and fill the small cut section easier, it will also wick into the wood better, besides trying to get thick goop in there would be a lesson in futility to the n'th degree :)

[Jay Greer]

I've always suspected with epoxy failures on masts and other major structures on boats bigger than canoes, that it isn't the epoxy, it's the wood.

Epoxy can't stand very much clamping pressure. Yet the thicker and/or longer the stick of wood, the more likely it has a tad of twist or cup requiring it be pulled in fairly hard in spots. And tighter than the epoxy can stand. Clamping up 30' stock, you can starve the joint of glue in places without even knowing it.

Using resorcinol you don't have to be as fussy, because you can't apply enough clamping pressure by hand to starve the joint.

The phenominom of glue joint delamination in nearly all instances is caused by the joining of two materials of a different modulus of elasticity; the glue which is inflexible and the wood that is. In a marine invironment where wood constantly swells and contracts as it is effected by moisture absorbtion and loss, the wood mechanicaly tears itself away from the adhesive, leaving a thin layer of fibers attached to the glue line. Examples of this can be found in cases where plywood has undergone this frustrating and maddening process.
Jay

[LakeErieSailor]

Thanks again to all of you.

I think that you're all on the right track regarding the reasons for failure, Bob Smalser and Jay Greer in particular.

I think what I'm going to do as a short-range solution for this summer is to saw out the failed portion of the seams and refill them with epoxy. I'm also thinking about wrapping the bottom 4' of the mast with 6 oz. fiberglass, saturated with epoxy. The long-term solution is to build a new mast using resourcinol.

Comments?

kc8qpl, I checked Public Lumber's website and they don't show 20' lenghts of DF; I guess I'll need to call. BTW, I was down in your neck of the woods Sat. evening at the Mon Ami Winery on Catawba island.

[Aed]

LakeErieSailor, it's been my brief experience with Public Lumber that they don't update their website on a regular basis. You definitely need to call them.

[kc8pql]

LakeErieSailor, it's been my brief experience with Public Lumber that they don't update their website on a regular basis. You definitely need to call them.

I agree. Stock changes all the time. They didn't show the long lengths I got on the web either.

[Thorne]

Don't think anyone will like the fiberglass wrap on the lower mast -- if the stick flexes too much for you to consider thickened epoxy a permanent solution, it will certainly flex too much for the glass wrap to do anything but crack and hold water against the wood.

Why not try it in steps and see what fails, or if it fails? Many small boat masts have been glued up with epoxy and hold together fine -- and I suspect that's what will happen with yours. My unstayed 16' mast flexes a lot, but I've seen no glueline failures from re-gluing with epoxy after cleaning out the failed Weldwood glue.

As strange as it may seem, you want to use thickened epoxy in this application -- the thickeners (cabosil) help fill the gap and reduce the starvation effect. Pre-coating with CPES or thinned epoxy may also help avoid excessive glue loss into the wood.

[LakeErieSailor]

O.k., so I reefed out the joints a bit and tried to fill them with slightly thickened epoxy - a bit of a mess; took me two tries to fill some of them. They were obviously quite deep, even in places where they didn't go all the way through. Used a plastic syringe. I'm going to do the other side of the mast today.

This may old news to some of you, but when I ran out of the "boaty" syringes, I checked around and found some at Tractor Supply - used for farm applications - much, much cheaper than those at West Marine. The only difference is that they don't have nozzles, but have needles. I used the 16 ga. needles which put an adequate amount of epoxy into the smaller cracks, and shot the larger cracks with no nozzle attached to the syringe at all. If you do have to have a nozzle, some small-diameter plastic tubing should serve.