Scarfing New Ends on Old Spars

[Chris Waite]

I have a chum

No, really!  He has just bought a second hand boat and found the end of one of the spars has rotted a tad, here is the text of his e-mail to me:

"The spars are all fairly new and look near perfect but the peak of the gaff is very rotten where it had been trimmed down but not re varnished before it's end fitting was screwed in place. I have grave doubts as to whether any of the screw holes in any of the spars would have been anointed with varnish/ paint/ glue before the screws were fitted and rot bugs may have got in.
 
A few questions;
 
Would you think a couple of good doses of wood preserver in the screw holes followed by some epoxy a few days later be a reasonable course of action?
 
The spars are spruce. Is it necessary to use spruce for a scarf repair? How about sepele or mahogany or douglas fir?
 
Do you know where to find suitable timber?
 
Would an 8 to 1 scarf glued with epoxy be OK?
 
Hope you can advise....   "

He hopes I can advise, but unfortunately scarf joints are way to technical for an old bodger like me, as is which wood to use.

So can any of you folk advise?

Fire away chaps

CW

[momist]

Chris,

I believe that the "chippy" on the old sailing ships would have used a "birds mouth" joint on such a spar.  This takes the form of a Z, with the middle bar of the Z on a similar plane to a conventional scarph, i.e. at about 8:1 slope, and the ends sloping towards the joint.  The end cuts could be at any suitable angle to the centre bar, to suit the timber being used, but can very easily be at 90 degrees to the centre bar slope.

The joint is cut by sawing one Z end cut at a suitable distance from the end of the spar, and then the slope of the scarph from the end,  to meet the first cut.  Both timbers are treated in the same manner.  Then the sharp point is cut off each of them to produce matching sections which interlock at exactly the same centre length.  The depth of the end cuts is chosen to suit the size and strength of the timber in use, to avoid splitting.  The additional timber should be over-size to allow for errors, and then taken down to finished size after the joint is complete.

The advantage of the birds mouth scarph is that there is a mechanical advantage to resist compression in the spar along the grain, and prevent the scarph from slipping.  It's a lot of work, but in the sailing ship days they didn't have any epoxy (or any strong glue at all really) and the joint would have been served and parcelled.

A quick and dirty fix would be a simple scarph with one or maybe two included dowels or biscuits, or even screws, to increase slippage resistance, sealed up with epoxy.  I would bet that epoxy on it's own would suffice anyway.

If your chum is going to put epoxy in the screw holes, tell him to put petroleum jelly on the screw threads, so the screws can be taken out again if necessary later.

For choice of timber, I would expect that anything would do the job, but weight should be taken into consideration.  If the spar is to be varnished, then colour will also count.  However, I've always admired those spars with smart white ends - which could be concealing anything!

HTH

Ian





On 08/08/11 09:35, Chris Waite [via UK HBBR Forum] wrote:

I have a chum

No, really!  He has just bought a second hand boat and found the end of one of the spars has rotted a tad, here is the text of his e-mail to me:

"The spars are all fairly new and look near perfect but the peak of the gaff is very rotten where it had been trimmed down but not re varnished before it's end fitting was screwed in place. I have grave doubts as to whether any of the screw holes in any of the spars would have been anointed with varnish/ paint/ glue before the screws were fitted and rot bugs may have got in.
 
A few questions;
 
Would you think a couple of good doses of wood preserver in the screw holes followed by some epoxy a few days later be a reasonable course of action?
 
The spars are spruce. Is it necessary to use spruce for a scarf repair? How about sepele or mahogany or douglas fir?
 
Do you know where to find suitable timber?
 
Would an 8 to 1 scarf glued with epoxy be OK?
 
Hope you can advise....   "

He hopes I can advise, but unfortunately scarf joints are way to technical for an old bodger like me, as is which wood to use.

So can any of you folk advise?

Fire away chaps

CW

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[Jeremy]

I repaired the top of an old spruce mast by scarfing on about two feet of new wood.  I used some straight grained pine that I had available and it didn't look too bad in terms of a colour match.

I used a straight V splice that was around 6:1 I think, liberally glued with epoxy.  This was around 20 years ago and when I last saw the boat (maybe 5 years ago now) the mast was still fine.  I didn't use any other fixings at all, just the epoxy.  Whilst it was setting I wrapped the join in cling film quite tightly to help hold it together, then added four small splints to ensure that it remained straight, also held in place by cling film.

Jeremy

[LASER41420]

Hi,

I had to scarf in a new bit on the bottom end of the Mermaid's gaff, i.e. the end that has the sliding brass fitting that goes up and down the mast. I used about an 8:1 scarf glued with epoxy, the wood was left oversize and planed down once the glue had dried. Despite taking all the weight of the gaff the repair survived some sailing on the Thames raid plus being bumped on a bridge!

Steve

From: Chris Waite [via UK HBBR Forum] <[hidden email]>
To: LASER41420 <[hidden email]>
Sent: Monday, 8 August 2011, 9:35
Subject: Scarfing New Ends on Old Spars

I have a chum

No, really!  He has just bought a second hand boat and found the end of one of the spars has rotted a tad, here is the text of his e-mail to me:

"The spars are all fairly new and look near perfect but the peak of the gaff is very rotten where it had been trimmed down but not re varnished before it's end fitting was screwed in place. I have grave doubts as to whether any of the screw holes in any of the spars would have been anointed with varnish/ paint/ glue before the screws were fitted and rot bugs may have got in.
 
A few questions;
 
Would you think a couple of good doses of wood preserver in the screw holes followed by some epoxy a few days later be a reasonable course of action?
 
The spars are spruce. Is it necessary to use spruce for a scarf repair? How about sepele or mahogany or douglas fir?
 
Do you know where to find suitable timber?
 
Would an 8 to 1 scarf glued with epoxy be OK?
 
Hope you can advise....   "

He hopes I can advise, but unfortunately scarf joints are way to technical for an old bodger like me, as is which wood to use.

So can any of you folk advise?

Fire away chaps

CW

If you reply to this email, your message will be added to the discussion below:

http://uk-hbbr-forum.967333.n3.nabble.com/Scarfing-New-Ends-on-Old-Spars-tp3234923p3234923.html

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[Timmo]

Isn't epoxy wonderful!

Scarphing will work. I think it would be best to scarph so the spar is left long on the side the sail lies and the patch scarphed on has it's long face is away from the sail. I would also epoxy one or two angled dowels in at the bottom of the scarph (where it's being pulled open by the sail) though that's probably overkill. I wouldn't put any screws or bolts in. I prefer wood on wood.

The V scarph sounds better, cleverer and prettier but more difficult and probably not absolutely necessary. Depends on whether your friend wants an interesting workshop challenge, or just wants to get the boat afloat and sailing.

I have also added hardwood tips (up to 6 inches long) to spars by drilling a wide hole 3 to 4 inches down into the end of the spar (not easy to do straight) and turning the hardwood tip to create a long dowel like section to epoxy into that hole. The tip then being planed and sanded to size once fixed. I think they look pretty, wear less where cordage goes through holes and protect the end of the spar when I treat them carelessly. They're almost vital if you make the spar hollow using the birdsmouth approach.

One place to get interesting short bits of hardwood can be old furniture. I'm still working through hardwood I got from a garden table and chairs an acquaintance was going to burn. They saw the ends of the feet etc were rotten and discarded them. I saw the amount of wood that wasn't and wanted them! A good swap for a few logs from the back garden that they could burn instead.