# Scarf Joint in a Wooden Mast



## CatfishSoup (Nov 23, 2008)

Anybody know what sort of scarf joint i would use on a wooden mast? i just need to replace the bottom three feet or so. Also, what sort of strength am i losing in a scarf joint? should i just get a whole new spar?


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## davidpm (Oct 22, 2007)

How big is the mast?
how is it constructed. Solid, stave's, box etc.
What kind of wood.
What is wrong with the bottom 3 feet?

Pictures?


The answer will be different depending on your situation.


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## CatfishSoup (Nov 23, 2008)

davidpm said:


> How big is the mast?
> how is it constructed. Solid, stave's, box etc.
> What kind of wood.
> What is wrong with the bottom 3 feet?


 No pictures. I don't actually own the boat, it's an impending purchase. The boat is on the other side of the state from me so its hard to get info that I forgot to check out last time I was there. The spar is solid and rectangular shaped. I'm no expert, but it will probably be doug fir. The boat is a 31 foot gaff ketch, so you can guess the length; I never measured. The bottom three feet is a little rotten.


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## CatfishSoup (Nov 23, 2008)

I just spoke with a schooner captain who told me a half-lap with through-bolts or screws would be fine.


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## davidpm (Oct 22, 2007)

CatfishSoup said:


> I'm no expert, but it will probably be doug fir. The boat is a 31 foot gaff ketch, so you can guess the length; I never measured. The bottom three feet is a little rotten.


The kind of glue is very important.
Epoxy has been said to not be the best in this application.
resorcinol is the old standby but it does leave a glue line and needs a good fitting joint.
If you are putting bolts in I doubt if a glue line is a problem.
Sitka Spruce is considered very good.

Depending on the nature of the rot some properly scarfed in Dutchman may be stronger than chopping off the bottom. And can look cool too.

A half lap is going to loose some strength but may be OK since most of the force will be compressive near the bottom of the mast.

A fancy scarf joint will be stronger but harder to do right.
Traditional Tools » Forums » Tools & Woodworking » Woodworking » SCARF JOINT


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## sailingdog (Mar 19, 2006)

I think a 8-to-1 scarf would be a better solution IMHO... but as davidpm said, harder to do right.


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## CatfishSoup (Nov 23, 2008)

Im no expert woodworker, but it seems to me a half-lap would be very effective because most of the force would be, as DavidPM said, compressive because of the shrouds, and for the same reason, just a plain diagonal 8:1 scarf (I don't know what that is called) would be not as strong. It seems like the half lap would be pressing wood butt to butt, whereas the latter would not. Hope that makes sense.


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## badsanta (Oct 16, 2006)

If the bottom is rotted, I would e very concerned about the rest of the boat. I love wooden boats, I also know they are a lot of work. If you have the time and skill, go for it. If is your first one, this may be more than you can handle if this is going to be done by your self, I hope you have lots of time of money either way. Even a free boat can cost you a fortune. Not trying to talk you out of this, you need to do what you want. But having tried to rebuild one, it was more than I imagined. Don't forget to add the price of repairing sails, rigging, plumbing and electronics. The list will go on for ever. best of luck.


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## okawbow (Feb 15, 2007)

A well fit half lap joint would be strong enough for a mast base. If it were higher up; a finger joint would be better. Half lap joints are used in post construction in buildings for compressive loads.


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## davidpm (Oct 22, 2007)

badsanta said:


> If the bottom is rotted, I would e very concerned about the rest of the boat. I love wooden boats, I also know they are a lot of work. If you have the time and skill, go for it.


I second what badsanta said. You may be on your third wooden boat restoration and anything I say is obvious. If not I'll make a couple of comments.

The rules for wooden boat survey are radically different than for glass boats and not everyone knows them anymore ever all surveyors.
Removing a few fasteners is a pretty common request. A plank, fastener and rib can look perfect and be completely gone inside. Removing a fastener or 6 is the minimum that is considered prudent.
Removing a plank is even better.
Pulling a keel bolt is not considered excessive.
So that means just doing a proper survey is not for the cost conscious buyer. Take if from someone who is still traumatized from the experience and is wiser for it.
If maintenance is let slip for even a few months a wooden boat can be seriously damaged. If it is let go for a couple of years it can be fatal.
If it is stored out of the water it can be even worse.


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## davidpm (Oct 22, 2007)

okawbow said:


> A well fit half lap joint would be strong enough for a mast base. If it were higher up; a finger joint would be better. Half lap joints are used in post construction in buildings for compressive loads.


If you did the modified scarf joint with a key from the link I posted you would have excellent compressive strength and excellent tensile strength.
I would not cut off a solid spar lightly. 
What is the cross section of the spar?
I'm trying to image a spar of say 8" square with rot damage more than a couple inches deep. Rot has zero strength so digging it out to see what you really have would be a first step.
The current owner may be willing to dig and take pictures. He has little to loose. It may be a simpler repair than imagined.
If it is surface a Dutchman or three with 8 to 1 bevel will look cool and retain up to 100% of the original strength.


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## CatfishSoup (Nov 23, 2008)

davidpm said:


> I second what badsanta said. You may be on your third wooden boat restoration and anything I say is obvious. If not I'll make a couple of comments.
> 
> The rules for wooden boat survey are radically different than for glass boats and not everyone knows them anymore ever all surveyors.
> Removing a few fasteners is a pretty common request. A plank, fastener and rib can look perfect and be completely gone inside. Removing a fastener or 6 is the minimum that is considered prudent.
> ...


 Well, I've never even touched a fiberglass boat, so I don't suppose I will be set in old ways too much in terms of survey. I haven't made a full checklist for the thing, but I intend to peek and poke at every frame I can reach, tap and poke all the planking, deadwood, stem and keel. I don't know if I will go so far as to pull planks off. Pull fasteners at the points most susceptible to corrosion and rot, look over every inch of rigging including shrouds/stays, blocks, and hardware. I probably should pull the keelbolts, but that is fuzzy territory for me, I'll have to do some research on that. The steering needs inspection...it feels sloppy. I need to figure out what has been done with the seams, ie are they caulked properly or not caulked and meant to be that way? Overall, i want to be as thorough as possible, and although she was built in 47' she seems pretty sound so far. I'm only 18 so I can only have so much knowledge packed into my head at this point, but I'm trying.


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## CatfishSoup (Nov 23, 2008)

davidpm said:


> If you did the modified scarf joint with a key from the link I posted you would have excellent compressive strength and excellent tensile strength.


 That makes even more sense. Like I said, the boat is on the other side of the state. I'm going to head over there for a full weekend and do a complete and serious survey of the thing...I will keep that in mind. Hopefully you are right about it just needing a Dutchman, that would save me the trouble of finding lumber large enough to replace or trying to do a complicated multi-pieced scarf.


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## davidpm (Oct 22, 2007)

Someone that has a boat like this for sale almost certainly has a strong desire to have it go to a good home. You could probably negotiate some try before you buy deal. 
IOW agree to fix a couple things for the guy for free maybe with his help to get a taste of what you are into.
You will learn more in doing some real work on this boat in a weekend than in hours of surveying time.


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## CatfishSoup (Nov 23, 2008)

davidpm said:


> Someone that has a boat like this for sale almost certainly has a strong desire to have it go to a good home. You could probably negotiate some try before you buy deal.
> IOW agree to fix a couple things for the guy for free maybe with his help to get a taste of what you are into.
> You will learn more in doing some real work on this boat in a weekend than in hours of surveying time.


 I imagine if the owner hasn't launched the thing in two years, he likely isn't going to do so for an 18 year old kid to take 'er out for a spin. And paying for the launching and the mast step myself would be out of the question...limited budget.


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## davidpm (Oct 22, 2007)

CatfishSoup said:


> And paying for the launching and the mast step myself would be out of the question...limited budget.


That's not what I had in mind. I'm thinking more along the lines of you saying:
_What if I was to come out next sat and sun and you let me do the following chores on your boat:_

_Remove a replace a plank and take pictures?_
_Pull and replace a keel boat and take pictures?_
_Dig out the rot in the mast and repair?_
_You want to sell the boat. I want to buy it, I think. _
_Any prudent person will want to do those three things before buying the boat anyway. If I do the labor for free and like the results you have a sale._
_If not you didn't have to pay for some work that needed doing anyway and you have a better idea of the condition of the boat._

By the way are you willing to tell us how much the boat is going for?
What is the condition of the inside? 
What are the planks made of, cedar, pine etc. It makes a big difference
Does it have full ceiling from bilge to gunnel?
I ask because I have an idea about getting the hull to take up.
What kind of standing rig? Iron?
Sails?
Engine?
What is your wood working experience?
What tools do you have available to you?


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## Jeff_H (Feb 26, 2000)

A couple quick thoughts here,

Having restrored several wooden boats including reglued wooden spars when I owned a 1939 Stadel Cutter and lost a glued up wooden spar over the side that was completely rotted out for nearly 3 feet either side of the partners, the first thing that I would say is if you see rot in the bottom three feet of the mast, the rot is probably far more extensive than that since spars often rot out from the inside out and the rot can travel for yards from a point of entry.

By back to the repair, a lap joint is totally unsuitable since this concentrates the loads at a single point. A proper scarf joint makes a much stronger connection. The scarfs should be staggered so that they are several feet a part. The butt of the mast is the worst place (except for the gooseneck) for a butt joint since this piece of the spar can have the highest bending loads. (Think of the whole first panel as the lever and the partners as the folcrum.)

Davidpm hits the nail on the head when it comes to surveying a wooden boat, as it can cost many times the value of the boat to repair or even maintain one that is in rough shape. One of the problems with wooden boat construction is that wooden boat components rot out from the hidden to the visible part of the wood. For example, frames can look perfect on the surface and be 'troughed' meaning that the interior of the frame where it touches the planking or deck can be completely rotted out.

Wooden boats were typically designed for a 20-30 year lifespan and that was it. While the neat thing about wooden boats is that they can be rebuilt almost forever, the reality was that they were designed to be refastened, replanked and reframed at comparatively short intervals. Back when wooden boats were the norm, nearly every small sailing town had a yard that could do that kind of work pretty cheaply. Today the materials are hard to come by, the quality of the materials do not come close what existed back then and the prices for these materials are wildly expensive. Similarly everything from proper fasteners to boat building tools are more difficult to find and more expensive to buy.

Going cheap on a wooden boat does not make sense. It becomes a losing battle as the parts your replace do not last long enough for you to get the next crisis averted.

Frankly owning a wooden boat today, requires you to be a skilled wood worker. Your concern about doing a scarf vs a half lap suggests that your skills may be evolving but not fully there yet. I might suggest that you look into a course at the something like the International Boat Restoration School. http://iyrs.org/Portals/0/PublicDocs/IYRSCatalog1doc.pdf before undertaking the restoration of a 60 year old wooden boat.

Lastly, wooden boats do not do well sitting out of the water for years at a time. Two years out of the water, without proper maintenance, could spell the end of a boat that was reasonably healthy when hauled out.

Respectfully,

Jeff


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## CatfishSoup (Nov 23, 2008)

davidpm said:


> By the way are you willing to tell us how much the boat is going for?
> What is the condition of the inside?
> What are the planks made of, cedar, pine etc. It makes a big difference
> Does it have full ceiling from bilge to gunnel?
> ...


 I've mentioned in other threads...she is going for 2k. The interior needs a lot of work; everything is filthy with dust and there are no cushions. There is no head. As for water systems, I'm not sure whats going on there. I don't really require running water. I find it just as easy to buy three gallon jugs of water and re-use them. Easy enough for drinking water and washing a few dishes here and there on short cruises. A head with attached tank isnt too expensive (although not necessarily ideal.) Standing rigging is galvanised, if i remember correctly. Sails are old but serviceable. I know the engine isnt an atomi4, but i dont remember the name. apparantly it still runs. My woodworking abilities are higher than average and i know basics when it comes to how wood likes to behave and what types of woods work well in what situation. I have a shop oufitted to maintain a 154 foot 84 year old wooden schooner at my disposal.


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## davidpm (Oct 22, 2007)

CatfishSoup said:


> I have a shop oufitted to maintain a 154 foot 84 year old wooden schooner at my disposal.


Cool can I come and visit?

It's really simple.
Add up all the parts you need. Source them on the INTERNET. 
glue, paint, wood, rudder, screws, nails, varnish, pfd's insurance, docking etc.
Multiply times maybe 4 or 5. 
If you got the money and time it may be fun.
You may be 18 but if you hang out with folks working on a 154' boat you probably either know more or know people who know more than I do.
As you have already found out the experts almost never agree about anything. Whereof your schooner captain.

I think that almost everyone will agree that it will take at least 5 times the money and 5 times the maximum time you could ever imagine. So what do you want to do for the next 24 to 60 months. Boat carpentry etc or sailing. You get to choose.


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## davidpm (Oct 22, 2007)

Jeff_H said:


> the first thing that I would say is if you see rot in the bottom three feet of the mast, the rot is probably far more extensive than that since spars often rot out from the inside out and the rot can travel for yards from a point of entry.


That I didn't know, my rot experience was on ribs, floors, planks and deadwood. Makes perfect sense for a hollow spar though.


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## CatfishSoup (Nov 23, 2008)

davidpm said:


> Cool can I come and visit?
> 
> It's really simple.
> Add up all the parts you need. Source them on the INTERNET.
> ...


Ah, that shop really is a beauty too... Big open tables, table saw, miter saw, giant band saw, jointer, power plane, three drill presses, a full hardware selection to match a small hardware store, and every weird little hand tool imaginable.

In terms of how much I know? I've built two small plywood boats since i was thirteen, which really isn't that difficult. At the time I didn't know squat about sailing characteristics or how the hull interacts with the rig. Most of my skill is to be found on deck and underway (im a deckhand, you know). I know most maintenance, proper painting and varnishing. I know how to set up and tension a rig, I understand that keeping water out of places it shouldn't be is top priority. I am proficient with marlinespike seamanship. I've sewn sails from scratch and patched many others. The only things i am really introductory on are things in the engineering department. I would be almost useless with an engine problem..."spark, fuel, air...i dunno man, we're screwed." Wiring is still a bit of a mystery, and plumbing is another gray area.

Generally, when sailing i think that experience is the most important thing one can have...If you are going to be able to respond to "oh crap" moments, it helps if you've seen it before, or had something similar happen that gives you insight. For example, i've never gone through truly heavy weather, but i have sailed through 35 kt plus wind and driving rain and lightening. The boat i was on was a 65 foot steel schooner, only slightly reefed and we put the rail under...then the pin rail...and then we put the leeward deck under. Had i not experienced this, i don't think i would be nearly as capable a sailor as i am now. I have an idea of where the edge is, and although boats behave differently, i wont be losing my head if i happen to get caught in heavy weather in a passage.

I get the idea that this concept of experience exponentially increasing and building upon itself expands to all aspects of the boat, and probably life, but i wont go there. Hopefully i can build some sort of resume with all the aspects of a sailboat.


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