Laminating a mast

[44xt]

I am about to laminate the mainmast for my Bill Garden Eel, but I have hit a couple of snags. My wood supplier was able to get me clear Douglas fir in 2x4 format, one piece is 20' long and the other is 18'. I have two problems. The first is, the mast is to be 19'-8" finished length, so by glueing these two pieces together I am short by 2' on one side. Should I scarf a two foot piece on? I am thinking this will be OK as the mast is stepped on the keel and supported at the deck, and if I locate the 2' chunk at the bottom, it is away from high stress.
The other isssue is the mast is to end up 3.5" diameter for most of it's length with tapers at each end. In my exuberance to start this mast I forgot that while I have 3.5" in the 2x4 width I do not have it in the other direction (2 x 1.5") I am thinking I will add a 3/4" layer of Doug Fir between the two 2 x 4's giving me 3.75" to work with. Is the 3/4" piece best in the middle? or offset to one side?

Recommendations for proper epoxy and clamping suggestions would be greatly appreciated.

[paladin]

I would say in the middle paying attention to the grain....and minor clamping using T-88 epoxy...do not squeeze out the epoxy, as a matter of fact some cinder blocks to hold it in place may be better than clamps.....

[rbgarr]

IIRC Eel's rig is gunter and the deck partners to mast step distance is about 18" (?) If so, your scarf joint at the bottom of the mast would be at one of the higher stress points, i.e., just above deck level.

Isn't there more taper at the masthead than the mast's heel? If so, put the scarfed piece at the top... but altogether i don't think it will make much difference.

My two cents anyway.

Good luck.

[andrewe]

Use a 12:1 scarf and it won't matter where the join is. But, I agree with nearer the top/head.
Gunters put a load at the jaws, so best further up or down.
A

[JimConlin]

The size of many masthead sheave boxes makes the mastheads fatter than they need to be to carry bending stress, so that argues for putting the scarph at the top. Aesthetics argues the same way.

[Philip Maynard]

depending on how much taper there is at the top, are the long tapered cutoffs wide enough to scab/scarf the missing piece, especially if the whole mast is laid out with a straight side?

[SBrookman]

I ran into the same thing with the masts for the Sharpie. I planed some spruce and laminated it in the middle to get it to 3 3/8. Makes it easy to find the center of the spar!
http://otterwater.com/Sharpie/masts.jpg

[Mrleft8]

I'd look elsewhere for your lumber.

[BBSebens]

The size of many masthead sheave boxes makes the mastheads fatter than they need to be to carry bending stress, so that argues for putting the scarph at the top. Aesthetics argues the same way.

i see a lot of people who paint the top section white.

i think thats only 1 cent...

for the other cent, i agree with everyone else on the shim in the middle.

[SBrookman]

Another thought on the lumber, DF is relatively cheap. My local lumber yard let me wander through their yard and pick and choose. I couldn't find any clear enough 2x4's so I selected some 2x8's, and a 2X10 with some 1" spruce thrown in it came to $72, delivered. I now have enough wood to build more masts than I have boats for. (at least for now)

[obscured by clouds]

Another thought on the lumber, DF is relatively cheap. My local lumber yard let me wander through their yard and pick and choose. I couldn't find any clear enough 2x4's so I selected some 2x8's, and a 2X10 with some 1" spruce thrown in it came to $72, delivered. I now have enough wood to build more masts than I have boats for. (at least for now)

Jeez you are sooo lucky over there. In the UK enough DF to build a 20' mast from my local timber yard, who is by no means expensive, would set me back close to $300 and for that, chances are that I would'nt get a decent clear length.

Oh, I'd have to fetch it too.

[andrewe]

Yes, clouds, I feel that way too. Around here, I bought "sapin rouge"(?) That might be DF. but not too expensive in 18ft planks IIRR about $30/ plank, enough for the mast with a some scarfs to avoid knots.
They are building a copy/replica of Lafayette's Hermione near here, and had to scoure the country for enough oak. The original took 6 months to build, this one is 10 yrs on and might be launched next year. Nice job though.
A

[Charles Burgess]

I am about to laminate the mainmast for my Bill Garden Eel, but I have hit a couple of snags. My wood supplier was able to get me clear Douglas fir in 2x4 format, one piece is 20' long and the other is 18'. I have two problems. The first is, the mast is to be 19'-8" finished length, so by glueing these two pieces together I am short by 2' on one side. Should I scarf a two foot piece on? I am thinking this will be OK as the mast is stepped on the keel and supported at the deck, and if I locate the 2' chunk at the bottom, it is away from high stress.
The other isssue is the mast is to end up 3.5" diameter for most of it's length with tapers at each end. In my exuberance to start this mast I forgot that while I have 3.5" in the 2x4 width I do not have it in the other direction (2 x 1.5") I am thinking I will add a 3/4" layer of Doug Fir between the two 2 x 4's giving me 3.75" to work with. Is the 3/4" piece best in the middle? or offset to one side?

Recommendations for proper epoxy and clamping suggestions would be greatly appreciated.

You need 3 of the 2x4's. Scarf the shorter pieces 12:1. You will end up with a 3.5"x4.5" - so take 0.75" equally from each side of the 4.5" face to get your 3.5"x3.5".

A good scarf will hold if you bond with West Systems 105 epoxy using a slow hardener. If the location is chosen carefully, you can use iron or rope mast bands to support and hide the scarf joints: If you use hemp rope, dyed black, wound around the mast (covering the scarf) and served, and then saturated with West's epoxy....very strong and looks really good too.

[JimConlin]

...If the location is chosen carefully, you can use iron or rope mast bands to support and hide the scarf joints: If you use hemp rope, dyed black, wound around the mast (covering the scarf) and served, and then saturated with West's epoxy....very strong and looks really good too.

If properly done, the scarphs won't need to be hidden.

[Charles Burgess]

If properly done, the scarphs won't need to be hidden.

Very true.

Many people are not comfortable with seeing the scarf joint - thus the cosmetic treatment.

[UCanoe_2]

Charles, shouldn't he take only 1/2" off each side of the 4-1/2" face to yield a spar 3-1/2" square?

[Charles Burgess]

Charles, shouldn't he take only 1/2" off each side of the 4-1/2" face to yield a spar 3-1/2" square?

You are correct....my bad :eek: I was working on another taper when I took a break and posted the above....ooops.

[py]

"Should I scarf a two foot piece in?"

No, you need to get a longer piece to allow for the scarf.

[RFNK]

I can't help thinking that I'd rather put a scarf in an area of the mast where there is less bending so that there's less likelihood of the join opening up i.e., I wouldn't put it in the top section which bends the most. Am I missing something? Rick

[Mrleft8]

I'd look at "Lumberyard Spuce"....Around here it's usually Black Spruce. I got two 18' 2x8s mostly clear (one had a couple of pin knots on one edge) for around $20.

[rbgarr]

Isn't the spar at the top about as big around as your wrist? I can't see that there's going to be a huge problem with a scarf there.

[RFNK]

Well, if it's that big, I agree - that's not going to bend much! Rick