Cracked Folkboat Boom

[arigopulos]

Hi There,

This is my first post, so please let me know if I’m breaking any posting rules, posting in the wrong place, etc.

Two years ago I acquired a beautiful 1964 Nordic Folkboat in the Helsinki area. Much of the varnish needs to be brought back up to snuff, but she is mostly in good shape.

I was out over the weekend in 20 knot winds, and there was a rather rough accidental jibe. (Shouldn’t have happened in the first place, but it did... Fortunately, nobody was hurt.) After a couple minutes, I looked up to see that a crack had formed along the threading where the foot of the main attaches, starting at the seam where the end piece of the boom connects and running about 1.5 feet toward the mast.

I would like to take a whack at fixing it myself. Does anyone have experience repairing wooden booms? I am entirely new to wooden boat repair, and welcome any tips.

I can send photos if helpful.

Thanks!

[jackster]

Well welcome to the WBF, arigopulos.
Yes, the extent and location of the "crack" is important. Also, an idea of the construction method (solid, glued-up, box, birdsmouth...etc) if possible to detect.
Also if there is any hardware in the area
We like lots of pictures.

[Mark0]

I'm in the middle of making our spars at the moment... If it's a bad crack it might just be easier to build a new one. I had a folkboat a long time ago, it's not a big spar so materials shouldn't be too costly.

Cheers,
Mark

[Peerie Maa]

Hi, please post photos of the damage, that will make it easier for us to offer sound advice free of guess work. Look at the FAQ page for the how to.

[arigopulos]

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[arigopulos]

There’s a whole bunch of pics. Not sure why it changed the orientation on some of them, but I think you can get the idea. The links in the first post also include pics of the whole boom so you get an idea of where it is.

You can see that the crack originates where this small screw is attaching the back end of the boom, which is also where the glued seam runs. Seems like a natural weak point. I remember noticing shortly before this ceack opened up that the outhaul wasn’t sufficiently tightened for the wind speed, so I suspect that there was some undue strain on this threading (proper term?) that holds the foot of the sail on.

My feeling is that this should be an easy fix, and that I don’t need to replace the entire book. This crack only affects said “threading” and doesn’t seem to affect the overall structural integrity of the boom. Although maybe I’m wrong about this?

What would be recommended methods of closing this up? Screws? Some kind of glue?

Thanks for any tips!!

[arigopulos]

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[CundysHarbor]

For what it's worth, I would replace the boom. It has been repaired in the past and that was not done properly. Making a new boom is not very difficult and you have all the hardware. Maybe you could cobble a fix for this summer but I'd be careful.

[wizbang 13]

Ya, build a new. A house carpenter buggered that up some time ago.
Are "T" spars ever used on Folkboats for the boom?

[jackster]

It appears that you have a boltrope/slug slot arrangement for attaching the sail. And it split from the force of the jibe.
That is an important structural part of the boom. Simply gluing it back won't, IMO, be adequate.
Looks like that boom has been repaired before and the scarf is also in need of attention.
By the time you properly repair and re-finish, it will have been better, if not easier, to build a replacement.

I suppose you could glue it back together and lash the sail around the boom as an alternative.

[Ted Hoppe]

It appears that you have a boltrope/slug slot arrangement for attaching the sail. And it split from the force of the jibe.
That is an important structural part of the boom. Simply gluing it back won't, IMO, be adequate.
Looks like that boom has been repaired before and the scarf is also in need of attention.
By the time you properly repair and re-finish, it will have been better, if not easier, to build a replacement.

I suppose you could glue it back together and lash the sail around the boom as an alternative.

I believe this boom can be saved and in short order. if you drill out and clean up where the old screws were used, clean up the seams, use injected titebond or g-flex epoxy into cleaned split seams, use clamps and binding tape to bind the seams together for cure and then place dowels where screws were as well as several more down the boom along the potential boom fault lines, the strength would be near original. If you have no objections to epoxy and transparent cloths, you could consider using 2 wetted thin s-glass layers with high compression and tensile strength as you head to the gooseneck where the structural split happened thus being stronger than original. If you find the glass too clouded to match the varnished original look, you can paint the boom or section of the repair to match the hull and it will be class legal as well.

International folkboat class rules

The boom

The boom shall be made in accordance with the drawing and rule 6.3.2 of Aluminium alloy or of one kind of wood only.
6.3.1 Only European pine, Oregon pine or Sitka spruce are permitted when manufactured in wood. The cross section of the boom shall not be less than 105 x 40 mm nor more than 120 x 65 mm. The edges of the boom may be rounded off to a maximum radius of 12mm.

The boom shall incorporate a groove for the mainsail foot boltrope. The boom may be cut away to a maximum depth of 45 mm on the aft end and 25 mm on the fwd end or the groove opened out for not more than 200 mm forward of the boom measurement band for the insertion of a track, or other device, to control the clew of the mainsail; and for not more than 500 mm measured from the aft side of the mast, to permit the insertion of the mainsail foot bolt rope.


6.3.3 A measurement band (Boom Point) not less than 13mm wide and clearly discernible while racing shall be marked on the boom with its forward edge not more than 3380 mm from the line of the aft edge of the mast, projected if necessary and disregarding any local projections or cut outs


6.3.4 The Aluminium alloy boom shall be constructed of one continuously drawn extrusion with integrated fixed groove for the mainsail footrope. It may have an integrated fixed groove for the sheeting and the boom control arrangements.
6.3.5 The weight of the Aluminium alloy boom including all fixings and a device to control the clew of the mainsail shall not be less than 9 kg.


If the boom is found to be under weight a corrector weight shall be permanently fixed inside or outside the boom profile so as to bring the weight up to the required minimum. CG of the corrector weight shall be positioned not more than 1750mm in front of the Boom Point.


The position and weight of the corrector weight shall be noted on the measurement form.
6.3.6 A permanently bent boom is prohibited.


However, a permanent set not exceeding 50 mm between the forward end and the measurement band is not considered to contravene this rule.


6.3.7 The boom shall not be tapered or cut away except as permitted in rule 6.3.2


6.3.8 A stop shall be fitted, to prevent any part of the sail to move aft of the Boom Point.

[Peerie Maa]

^ What they said. That old repair has failed as well as the bolt rope grove splitting. It looks as though the repair was secured with iron screws that are staining and possibly rotting the wood, so that has to be sorted. All in all easier to glue up a new boom.
it looks like version "d" from jacksters post. Easy peasy to build if you have enough trestles and a flat floor so that it cramps up straight.

[skaraborgcraft]

My mainmast luff groove opened up in one spot, in a similar way to your boom, also a Folkboat. I ran a saw down the split and just glued it with some epoxy, being carefull to tape the inside of the groove to stop the epoxy getting everywhere. I had the same kind of boom, have seen some later boats with a track on top to take slides, though that might not be "class" approved.

[Jay Greer]

Yes, I must agree with the others here. While it could be repaired, I am of the belief that it would be more complicated than building a new boom. With the old repair, that appears to be failing, it makes more sense to build a new boom. We can coach you though the process. Not a big job if you are handy with tools! You will learn some useful skills in the process. And, it will save you a lot of money to boot!
Jay

[arigopulos]

Or rather, just d is a solid piece

[Peerie Maa]

Or rather, just d is a solid piece

It ends up solid rather than hollow. Start with two pieces, cut half of the luff groove in each piece either with a router, or with a circular saw to cut kerfs that can be cleaned out with chisels and sand paper, or what ever tools you have and are comfortable with. Then varnish the groove as it will be your only opportunity to do it well. Clean up and glue the two halves together, using the best waterproof glue that you can get.
Then you can shape the outside, dry fit the hardware, then varnish it all, then final fit the bits and go sailing.

[arigopulos]

Thank you to everyone for the rapid responses and advice!

It seems that there is a solid consensus that the boom should be replaced, and I am very happy to take it on as a project. Your offers of continued guidance are much appreciated and much needed! I have limited carpentry experience and virtually zero experience repairing wooden boats, apart from surface work.

Does anyone have suggestions for type of wood? Preliminary research shows that spruce is the go-to. I’d like to stick with the original material. Can anyone tell from the pictures? It looks like spruce to me, given my experience with string instruments, but I’m not positive.

Luckily, there’s a wood shop in the basement of my apartment complex, and I’ll be bringing the boom back there today. If anyone has insights on the construction methods, I’d be happy to hear them. When I look at the bottom side of the boom, it seems like it’s three separate pieces glued together. Is this standard?

I noticed in Jackster’s diagram, options c and d seem to be solid pieces. Pros and cons of solid vs gluing?


Thanks again for all the help! Feels good to finally be a participating member of this community, after having been a silent observer for some time.

[Jay Greer]

That old boom looks to be the color of spruce. Even so, fir can bleach out to that color as well and the summer wood grain looks like fir Running a plane over it and getting a few chips will allow you to smell the wood for identification which can be compared to a known sample. just taking a piece of the split to the lumber yard will allow you to compare. Also, weight is a give away as fir is much heavier than spruce. Fir will be a lot more reasonable in price and the weight is often a plus to keeping the boom from lifting in puffs while reaching off the wind.
Jay

[Jay Greer]

It should be obvious that, if the old boom does not fall within the parameters of the International Folk Boat Class Rules, that a new boom is the way to go! That is, if you are considering racing the boat. Even so, owning a boat that does not match the rule makes it difficult to market if you plan to sell it in the future!
Quite frankly, building a new spar will require less labor and futzing around in an attempt to save that old worn out patch work quilt! That scarf joint is all wrong and the rest of it is questionable!
Jay

[arigopulos]

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Hey all! I’ve been traveling for the last month, and didn’t have a chance to address this until now.

I’ve had a closer look at the scarfing job, and it is indeed a poor repair. The added piece on the aft end of the boom is very loosely attached, and the glue job along the inside of the seam is all gunked up. No wonder the wood split...

A new boom is definitely the way to go! However, I’d like to build it out of Sitka spruce, which may take a little bit for me to get my hands on here in Finland, so I decided to take a whack at Ted Hoppe’s suggested repair method so I can keep sailing in the meantime.

I cleaned up the seam and clamped it overnight with Titebond III. This morning I replaced the old rotten screw with a thicker and slightly longer stainless A4, which seems to be holding well. Then, along the length of the split, I reinforced it with these nifty Miller dowels I found at my local woodworking shop. This terraced screw design is great! They fit extremely snuggly after drilling out with the matching drill-bit. (Photos above)

Thanks again to everyone for the tips. I’ll be back for more hints as soon as I’m ready to start constructing the new boom.

Cheers!

[Phil Y]

One of those temporary repairs which will probably see you right forever. And probably a lot easier than building new!

Sent from my CPH1851 using Tapatalk

[J.Madison]

Varnish the dowels well, they are certainly not a rot resistant wood. Now you can take your time to source the right sticks of wood and make a new boom at your leisure.

The scarf at the end kind of scares me....