Resecuring fasteners in wood mast

[Kristian]

Hi all,

Figure this might be a good place to learn about things I'm not familiar with.

I'm bidding on doing some repair work to a spruce mast, made in a hollow box section. A few of the fasteners have pulled out where a mainsail track let go. They left small craters/splinters. The fasteners will have to be reattached, and it will be a much easier job to reattach in the same locations for about 5 wood screws.

My initial thought is to clean up the holes, and fill flush with a 404 thickened epoxy, and drill/tap mchine screws into that. Could also just use wood screws again I suppose.

What are the thoughts around here? As much as I like wood masts, I don't know a whole lot about them.

Thanks
Kristian

[CharlieJ]

no need to drill/tap. Fill the holes with thickened epoxy, and set the machine screw while the epoxy is wet. Let it cure, then heat the head slightly with a soldering gun and back it out. That'll leave exact threads cast into the epoxy. Don't over heat- doesn't take a whole lot.

Or you can do that while installing the track and just leave the screws epoxied in there.

OR you can over drill, glue a wooden plug in and use a regular wood screw in that, also wet with epoxy when driven.

Personally I'd go the second route.

By the way, my boat has it's original 46 year old wooden mast

[Ceasar Choppy]

Using a mold release on the screws might be easier. PAM (that cooking non-stick stuff) works pretty good for this actually.

[David]

Using a mold release on the screws might be easier. PAM (that cooking non-stick stuff) works pretty good for this actually.

I agree with using a release agent versus heating the screw to remove it. Cooking oil or Pam works very well. If the mast is painted, over boring the holes, filling with thickened epoxy and drilling and tapping would be my approach.

David

[CharlieJ]

A mold release would also work. Absolutely nothing wrong with heating the fastener though. Works really well.

Since he's reinstalling a sail track I'd think over drilling then filling would work anyway- it's gonna be hidden under the track and it doesn't have to be over drilled THAT big.

But again, as I said- no need to remove them- just set the track after the epoxy is in the holes, insert the screws and let it cure. Then you don't need Pam OR heat.

Drilling and tapping will work of course- just seems like extra work to me though.

On the last two masts I built, I just set the admittedly new screws in wet epoxy and drove 'em home.

[David]

A mold release would also work. Absolutely nothing wrong with heating the fastener though. Works really well.

Since he's reinstalling a sail track I'd think over drilling then filling would work anyway- it's gonna be hidden under the track and it doesn't have to be over drilled THAT big.

But again, as I said- no need to remove them- just set the track after the epoxy is in the holes, insert the screws and let it cure. Then you don't need Pam OR heat.

Drilling and tapping will work of course- just seems like extra work to me though.

On the last two masts I built, I just set the admittedly new screws in wet epoxy and drove 'em home.

The overboring should be twice the diameter of the fastener.

David

[Quetzalsailor]

I've been worrying the 'best' solution for this problem for years. And there's no method that I haven't used (that I know of anyway).

Laziest methods (best for cheap furniture and lots of wood) to more-better methods:
Carefully use a larger/longer screw (root dia of new screw is OA dia of old screw)
Matchsticks or similar (loose or glued; you're screwing into end grain so not nearly as strong as new. Usually good enough, even using epoxy and teak matchsticks)
Bond w/filled epoxy (use the mold release {Teflon slip spray, wax, etc}; I have limited faith in the heat-to-release method because you can't reliably control the heat - too much destroys the epoxy and adjacent finish, too little doesn't do the job, you need the right temperature all the way down the fastening. The epoxy is waterproof so it does not change size with the wood: adds stress. The epoxy is non-compliant: subsequent tightening splits the epoxy 'sleeve'.
Tapping an epoxy sleeve (works fine but is labor intensive and tapping to the bottom is problematical and w/o tapping deep enough is prone to splitting, too.
Drilling and plugging and redrilling for the screws (not pretty, the plugs are often small and prone to split out, just like you remove bungs)
Fitting and gluing in a Dutchman. (gotta be better than most, labor intensive, gives you a new piece of wood where you need it.)
Make a new piece. (honestly, recommended for player piano and organ work where structure and airtightness across the joint is important)

Project at hand is repairing all the 'pulled through' holes for finish nails in my face-nailed Oak flooring. I don't want new holes; I don't intend to totally refinish the floor when re-laid (just fill the set nails, sand and recoat). Thinking about trying sawdust and carpenters' glue as a compliant filler to nail through.

[Hirilondë]

Lots of good ideas mentioned already. I will add my choice of method.

I like filling the hole with solid wood glued in. Dowel has often been used for this method, but as pointed out you now have end grain instead of face grain where you will be drilling and fastening. I would drill out the jagged hole large enough to remove all splintered wood, but no larger than necessary. It would also be the size of a bung cutter I possessed (we have almost every size conceivable, so this isn't an issue). If possible do not break through with the hole into the cavity inside the box. I would then wet out the inside of the hole and the outside of my newly cut spruce bungs of the same size with slightly thickened epoxy, and tamp them into the hole on top off each other until the hole is filled solid. Let the epoxy cure and dress off the surface. You now have new wood to drill into, it is the same species (most dowel available is maple), and it is face grain. Spruce is a great wood for holding fasteners by the way. The sinewy grain is part of what makes it a fine choice for spars.

[CharlieJ]

A quote from "the Gougeon Brothers on Boat Construction"

The WEST system folks.

"Heat fasteners which you cannot remove with normal force with a soldering gun using a knife type tip which fits into the screw slot---- You can usually force larger fasteners with more root diameter without breaking the fastener itself. But applying heat of around 300 degrees F softens the resin TEMPORARILY and always makes the job easier"

I've built boats with epoxy since 1976 and I've used the technique for years.

[Kristian]

Thanks all for the solid information.

I like the sound of the overdrill/fill method. Sounds very similar to what's used on fastener holes in glass decks, and I've got more time doing that than I'd like to think about.

Did a more extensive quote on this boat today and am recommending a whole new track due to damage from top to bottom.

The boat is some sort of one off wood boat from the 50's. Current owner bought it acouple years ago and is slowly but surely making it better. like that!

[David]

If i were fastening a mainsail track to a wood mast I would take the time to overbore and drill and tap. It gives an insurance that the track is stronger than the wood and will simply never pull out.

David

[Quetzalsailor]

It was suggested above that boring though to the inside of the mast would be undesirable. Quite true: you don't want splinters catching your halyards, you don't want to glue the halyards in. I repaired my mid 50's FD mast where the hound bolts had begun to pull down the mast where there also was compression failure crumpled wood and also where the spreaders were screwed on. I scooped out each face of the mast and only approached the hollow interior; the interior wood was discolored by its nearness to the air inside the mast, so it was easy to see. I then laid in a dutchman of new spruce (actually, old spruce out of a piano soundboard) using epoxy. Got two seasons of use before the rest of the boat was laid up; I'm now in the fourth summer of a pretty thorough rebuild.

I think that, if I had 4-5 bad screws in a row, at the 2 1/2" centers I could imagine for light track, I'd rout a groove and lay a dutchman in to repair them all in one swell foop. I'd make a jig to control depth and straightness. The jig would be arranged to allow the groove to deepen at 1:10-12 so as to scarpf the new wood into the mast, and would be only 2x the thread dia of the screws, or about 1/4".

I think that, if I had the same count or more of screws, but spread all along, I'd build a jig to locate the mast on a radial arm saw table and plunge cut using the 'wobble' dadoe blade. I'd accept a 1:8 scarpf due to the dia of the blade and the depth of cut.

Obviously, neither a router nor a radial arm saw is the perfect tool, but not all of us have all the toys!

I'd hate to have a row of 3/8" dia plugs with the attendant stress concentration and the original longitudinal wood interrupted.

[Hirilondë]

Many people find it very hard to use the heat method to release screws from epoxy. It is just so against common sense. But as Charlie has explained it is really very simple and works well.

I'd hate to have a row of 3/8" dia plugs with the attendant stress concentration and the original longitudinal wood interrupted.

There will be no significant compromise in the structural integrity of the mast.

I think that, if I had the same count or more of screws, but spread all along, I'd build a jig to locate the mast on a radial arm saw table and plunge cut using the 'wobble' dadoe blade. I'd accept a 1:8 scarpf due to the dia of the blade and the depth of cut.

I think this a slight over-engineering of the repair and I can't imagine anyone controlling a radial arm saw depth and feed simultaneously. I don't use radial arm saws for anything. They wobble too much. Most marine carpenters don't even scarf the seem repair spline, never mind screw holes. A straight spline repair would be a good way to make this repair, but I wouldn't suggest anyone attempt this type without great confidence in their ability. A slip of the router or saw and serious damage is done. It is so much easier and safer to control a drill and repair each hole individually.

Here are a few pics of a mast seem repair I did last spring.











The routed slot and spline make a great repair, but even after 35 years of woodworking I still cringe as I plunge my router into a very expensive to replace spar.

[CharlieJ]

Nice job- that mast could almost be a twin of mine. What boat was it?

Oh- and I agree with you on the radial arm saw. I used to use mine just for rough cut offs, before I trimmed to exact length. Just could not rely on it staying adjusted precisely. When I built my new shop and moved tools, I gave the thing away.

[Tim]

Oh- and I agree with you on the radial arm saw. I used to use mine just for rough cut offs, before I trimmed to exact length. Just could not rely on it staying adjusted precisely. When I built my new shop and moved tools, I gave the thing away.

When I moved last year, I just left my old radial arm right in the garage at the old place--a bonus for the new owners (or something). I hated that tool.

[Hirilondë]

Nice job- that mast could almost be a twin of mine. What boat was it?

Thanks Charlie. This one:





Its a 1939 Concordia 31. She is one of 3 that were built before WW2 and one of the last Concordias built in the USA. A few more 31s were built after WW2 and then negotiations with Abeking and Rasmussen began for what would become one of the most famous lines of wooden boats (39s and 41s) built.

[CharlieJ]

what a fine cruising boat that makes- outboard rudder, tiller steering, full keel

Lovely boat AND comfortable at sea.

[Quetzalsailor]

Yup, a radial arm saw is a pretty iffy tool. Rather like a Shopsmith, it can do lots of tricks, but never as well as a purpose-made tool. When I use the radial arm saw for 'serious' work, I jig the daylights out of it to control it. I've got two (one was free...); neither my basement shop nor the two-horse barn with the three FD are big enough for multiple saws. Both are honkin' heavy old tools with lots of cast iron but neither can be trusted to stay in adjustment. Too many loose parts, and adjustments, tracks, etc.

The application I suggested would have the work locked in place and simply crank the saw down to plunge cut a dadoe. Even so, the dutchman would have to be fitted to the slightly out-of-parallel and out-of-flat shape that a wobble dadoe blade would produce.

Ditto the router. Again, I have or build jigs for the application du jour since there's no holding them accurately.

I get to devise a new method to fix stripped screw threads. A switch box was cut into our dining room paneling back in about 1927. Roughly 8" x 8" x 1" panel of pine sitting in a frame of stiles and rails with the 2" x 4" box opening cut through the center. It's probably been cracked since 1927 but in replacing the box and wiring, it fell to pieces. Working in place, I gotta affix all the pieces and then fix the threads. Thinking I'll locate the pieces correctly with aliphatic, and then dowel with pine each break along the grain from within the box opening: I'll thus get a spline joint at each of the breaks and the spline will serve as the new wood for the screws.

You're quite right, 3/8" plugs in the Concordias' mast won't matter; the wood mast in my mind is 19lbs, 26', 3" in dia, hollow with 3/8" wall thickness. Every cell counts.

[keelbolts]

No need to tap the holes for mounting a mast track. You don't tap for wood screws and you don't screw things to wood with machine screws. In many situations, sheet metal screws will hold as well or better than wood screws, but machine screws belong in machines. Wood screws belong in wood. Drill out the old holes, glue in dowels, drill, and screw. If the idea of fastening your track into end grain bothers you, route out a groove and glue in a spline. Remember, while there's some force on your track, each screw just holds a little bit of that force.

And most importantly, it won't last forever. When I first started working on wood boats, I thought in terms of forever. Twenty years later, I think in more realistic terms. Wood 'dies', things break. As your body survives by constantly replacing dead cells, your boat will survive if you commit to replacing 'dead' wood. Fix it and go sailing. There is no perfection in this world and attempts at it just piss off the gods.