Finn Wooden Boom Repair

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UCanoe_2
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Finn Wooden Boom Repair

Post by UCanoe_2 » Wed Feb 27, 2008 2:14 am

Last summer I became the owner of an old (mid- to late-1960s?) Finn dinghy with a fiberglass hull and wooden spars. Elvstrom Finn made by Bermuda Plastics, US 547. This is my first "real" sailboat after a couple years of attempting to sail a Grumman aluminum canoe. What an amazing difference!

The Finn is basically sound, but like any boat of this age has a few "issues." One problem is the boom. It was made in two halves that are glued together along the centerline. Each half is mostly softwood (spruce?) with about 12" of hardwood (oak?) scarfed onto the forward end. There is no conventional gooseneck. Instead the boom fits into a mortise in the mast, and is held in place by a wooden wedge.

Now the glue joint at the forward end of the boom is coming unstuck. In addition, the boom is badly abraded at the points of contact with the mast.

I'm thinking of making the repair by first using a strip sander to remove the old glue from the split part of the joint, then gluing it back together. Then I will saw off the abraded areas and glue on small pieces of hardwood to return the end of the boom to its original shape.

Do you guys have any thoughts about how to accomplish this repair? Should I try to duplicate the original unknown adhesive, or would epoxy work? Any recommendations for brand and type? Can I just glue the repair pieces to the boom, or would some kind of joinery make it stronger?

Thanks for your advice. Here, I hope, are links to some photos:

Forward end of boom showing split and abraded areas:

http://www.picturetrail.com/gallery/vie ... 2&offset=0

Side view of boom:

http://www.picturetrail.com/gallery/vie ... 9&offset=0

Scarf between hardwood and softwood parts of boom:

http://www.picturetrail.com/gallery/vie ... 7&offset=0

Aft side of mast showing mortise for boom:

http://www.picturetrail.com/gallery/vie ... 2&offset=0

UCanoe_2
Finn US 547
Landlocked in Mount Solon, VA
UCanoe_2
Finn US 547
Landlocked in Mount Solon, VA

Garry R

Re: Finn Wooden Boom Repair

Post by Garry R » Wed Feb 27, 2008 10:18 am

Definitely scrape away the old glue (it will likely just "ping" off when you scrape it as it will be very brittle) and then any repair that you do - use epoxy. It was once put to me that if epoxy had been available when the boats were being built they would have used it. In an area like this where there is wear and abrasion the epoxy with microfibres should do the trick. When you are glueing up the boom remember to make sure that the groove for the sail foot is well cleaned out to allow the sail to slide in. If you get hard lumps of epoxy in there it will be a devil to get out. Acetone on a paper towel is a great solvent to run along the slot once you have clamped up to make sure it stays smooth inside. Don't over-saturate - just enough to get it wiped down.

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PeterV
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Re: Finn Wooden Boom Repair

Post by PeterV » Wed Feb 27, 2008 8:00 pm

I agree with everything Gary's said about the repair. It looks from your photos as if your boom hasn't got any cheek pieces on it. These are hardwwod pieces that bear against the hardwwod patch around the boom slot at the rear side of the mast. I'll try and take soem pictures of my wooden boom and mast to post. The scrarfed piece looks to me as if it's been added to repair the bolt rope groove where it's been worn or split.
PeterV
Finn K197 & GBR564
Warsash

UCanoe_2
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Re: Finn Wooden Boom Repair

Post by UCanoe_2 » Thu Feb 28, 2008 4:21 am

Garry R,

"if epoxy had been available when the boats were being built they would have used it."

Of course you are correct.

"In an area like this where there is wear and abrasion the epoxy with microfibres should do the trick."

Are you saying I can just rebuild the worn areas with epoxy and microfibers? Would that resist abrasion as well as hardwood? I was thinking of using black locust. Don't know if you have this species across the pond, but it has been described as "hard as a prostitute's heart and durable as sin."

Peter,

Your boat is awesome.

The hardwood part of the boom is probably original. The softwood is on the outside of the scarf. That is backwards from the way someone would usually construct a repair.

Cheek pieces sound like a good idea. Here is a photo showing them on restored H 112:

http://www.finn-dinghy.de/finns/finn-h- ... e-0003.htm

Thanks for your advice,
UCanoe_2
Finn US 547
Landlocked in Mount Solon, VA

Garry R

Re: Finn Wooden Boom Repair

Post by Garry R » Thu Feb 28, 2008 9:15 am

I think that epoxy with the microfibres in general gives the strongest joint. I had not really thought about filling an area with epoxy and using that as a bearing area. Of course there is nothing wrong with that - the centreboard piveot hole on my Merlin Rocket was very badly worn so I filled the old hole with epoxy/fibres mix and redrilled and it was perfect all last year so yes I suppose it would be strong enough but the wooden cheeks would look much nicer!!

LASERTOURIST
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Re: Finn Wooden Boom Repair

Post by LASERTOURIST » Thu Feb 28, 2008 3:45 pm

Hello!
On old OK's or Finns some people used Tuphnol strips or dometimes brass or stainless steel to protect the boom in the mortise/ gooseneck zone, along with a primitive vang made with a solid Tuphnol wedge un a thick stainless steel band that was forced in place by a block / purchase arrangement , with a fixed point on the foremost mainheet block boom fitting...very crude compared to modern vangs

Even funnier on some early OK's the boom was protruding going a good 2 or 3 Ft on the bow side, with a block /purchase system coming from somewhere mid mast to force upwards the front end of the boom.... :idea: :roll: :idea: :roll:

UCanoe_2
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Re: Finn Wooden Boom Repair

Post by UCanoe_2 » Sat Mar 01, 2008 1:51 am

LASERTOURIST wrote: On old OK's or Finns some people used Tuphnol strips or dometimes brass or stainless steel to protect the boom in the mortise/ gooseneck zone, along with a primitive vang made with a solid Tuphnol wedge un a thick stainless steel band that was forced in place by a block / purchase arrangement , with a fixed point on the foremost mainheet block boom fitting...
What is Tuphnol? Is that the same material as the old sheaves on my sheet tackle? It looks like brown plastic with cloth reinforcement.

My boat has the wedge vang. The wedge that came with the boat was wood, but was splitting, so I made a replacement. Originally I used ipe, but then discovered that ipe does not float. Not a good material for important boat parts that may get dropped overboard. My new replacement wedge is oak.

You can see the wedge tension line on the photo of H 112 (see link above).

Thanks to all for your help.
UCanoe_2
Finn US 547
Landlocked in Mount Solon, VA

LASERTOURIST
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Re: Finn Wooden Boom Repair

Post by LASERTOURIST » Sat Mar 01, 2008 9:05 am

Yes, Tuphnol was the hi tech material in the 50's for blocks, sheaves, cleats (gets quick wear on the teeth though)...
It is basically (sometimes even cotton) hard presed and saturated with phenolic resin, and some qualities are harder than most qualities of wood (and denser than water...)
It is still available, and though there are better materials today it sometimes adds a touch of authenticity to a restored 5O's boat.

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Ed
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Re: Finn Wooden Boom Repair

Post by Ed » Sat Mar 01, 2008 11:26 am

Tuphnol is getting harder to source.

I have heard that making it is rather a 'dirty' process and most of the factories have had to close due to the expense of updating their machinery to new factory standards.

As you say, it is still made and you do still see it used even on modern equipment such as International Canoe seat runners.

cheers

eib
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neil
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Re: Finn Wooden Boom Repair

Post by neil » Sat Mar 01, 2008 1:20 pm

I had to by some tufnol sheet for increasing the thickness of a rudder stock......plenty available on eBay
http://search.ebay.co.uk/search/search. ... tle=tufnol

I bought some from this seller - http://stores.ebay.co.uk/Fantastic-Plastic
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PeterV
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Re: Finn Wooden Boom Repair

Post by PeterV » Sun Mar 02, 2008 10:30 pm

My wooden boom has cheek pieces at the front end as below:
Image

The mast does have small pieces of Tufnol let into the bearing areas (Bruder mast from about 1963 or 64. The Tufnol may be a later repair). I found it difficult to get a clear photo because of the reflections, but hopefully you can make them out:
Image

As Neil says, Tufnol is still available, I use it for various engineering uses in Submarine propulsors!

Not a submarine but the mast and boom in action (although it nearly behaved like a submarine down the runs yesterday when it was extremely windy!):
Image
PeterV
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UCanoe_2
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Re: Finn Wooden Boom Repair

Post by UCanoe_2 » Mon Mar 03, 2008 1:13 am

Thanks, everyone. This is very helpful advice.

Does epoxy stick to Tufnol? It won't adhere to most slippery plastics (HDPE, polypropylene).
UCanoe_2
Finn US 547
Landlocked in Mount Solon, VA

Rupert
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Re: Finn Wooden Boom Repair

Post by Rupert » Mon Mar 03, 2008 9:43 am

Yes, provided you roughen it first. Unless anyone else has had a bad experience and I've been lucky?
Rupert

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Ed
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Re: Finn Wooden Boom Repair

Post by Ed » Mon Mar 03, 2008 10:51 am

No it sticks to Tuphnol.

The tufnol cheeks on the side of slot on bruder mast are not original....I put those on myself when I had that Finn. There was quite a bit of damage underneath. I considered cutting out a slot and inserting a bit of oak or something.....but considered this a better fix and the beauty of Tuphnol is that it looks so in place on classic boats.

cheers

eib
Ed Bremner
CVRDA


Jollyboat J3
Firefly F2942
IC GBR314 ex S51 - 1970 Slurp
MR 638 - Please come and take it away
Phelps Scull
Bathurst Whiff - looking for someone to love it

LASERTOURIST
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Re: Finn Wooden Boom Repair

Post by LASERTOURIST » Mon Mar 03, 2008 8:36 pm

In France Tuphnol (suppose the name comes from phenol as it is phenolic resin - a rather poisonous chemical- on cloth) is called Celoron...don't know why....there was a marine hardware company that was called CELINOX...all the products (very similar to Gibb) clleats , blocks...etc were made of Celoron (tuphnol) and Inox (stainless steel)....to glue it properly , you have to take out the glossy finish with coarse sandpaper, and it is better to add a few brass screws as a backup.

Some adjustable OK mastgates were made of thick tuphnol before thick solid nylon came in trend....There even were camshaft timing gears made of tuphnol on some Renault engines
(Frégate or the Goelette /SG2 light lorry.)...but though it helped reduce engine noise, it was not lasting very long and was later replaced by metal gears...

It is common whith designers and engineers...when some new material becomes available they try to use it everywhere , even in completely unsuitable uses :lol:

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