Question on mast materials for small sailing boat.

[PsiPhi]

I'm building a 12ft flat bottom (boat that is) for calm waters and it requires a 10ft mast to carry the sprit sail.

• Can't find aluminimum poles in this area.
• Only hardwood in the DIY stores seems to be Tasmanian Oak - is that OK for a mast of this size? (or any size?) What diameter would it need to be?
• I Have heard of people using UPVc poly-pipe with a bit of hardwood stuffed down the middle for masts/booms?

  • Strong and flexible?
  • Pure myth?
  • Dumb Idea?
    

I would welcome anyones thoughts or experiences in this area - even the lurid inter-racial slurrs of the more regular contributors to this forum


a spacious workroom very important in boat building (I now find )

[raw]

Contact the Queensland 125 association. They use a cheap alloy section for all their masts. You would get mast and boom from one length or someone might have second hand stuff lying around if you are lucky. A previously broken one might be ok too.

Somebody in SE Qld will have a stockpile under there house for their members.

A heavier option is a laser bottom section, though this is probably more like 8 feet long not 10.

[DanishBagger]

Why use hardwood at all? Why not use something like pine?

[alan white]

I have no idea what Tasmanian oak is, but I'd guess oak would make a heavy mast indeed. Fir, spruce, larch, do those names ring a bell?
Of course, a ten footer with but a ten foot mast could have a heavy mast. After all, your own live ballast is proportionately great enough relative to the sail area that the mast could probably be made out of cast iron and you wouldn't notice.
Look for straight narrow grain, no knots, no pitch pockets, shakes, or warp.
Nothing like a varnished wood mast. The pvc idea will make a bendy mast because the outermost part (the plastic) has little stiffness, The inner wood stick--- why not just get a bigger piece and dispense with the ugly plastic?
The mast could be tapered, but it could be square instead of round, which is easy to plane to a taper (especially if you have access to a jointer).

Alan

[PsiPhi]

Tasmanian Oak is apparently a eucalyptus! http://www.gunns.com.au/timber/tasoak.html
I had thought to make it hollow, square for ease of constuction, depending on how big the cross section needs to be.

As to my 'live ballast' - it is proportionately great enough regardless of vessel size.

[PsiPhi]

OK - so stick with wood, does look better.

Originally Posted by DanishBagger

Why use hardwood at all? Why not use something like pine?

I always assumed something like pine would not be strong enough?

Can anyone suggest how big a cross section a mast this size would need
a) if solid wood
b) if hollow

[DanishBagger]

Originally Posted by PsiPhi

OK - so stick with wood, does look better.


I always assumed something like pine would not be strong enough?

Can anyone suggest how big a cross section a mast this size would need
a) if solid wood
b) if hollow

No idea on how to calculate that thing, but then again, I doubt it would have much an impact, if it were a bit too thick. And it if it were a bit too thin, it would flex instead. Take a look at similar size dinghies with a wooden stick - and then guesstimate from there.

Spruce for instance is used for most (wooden) mast here in scandinavia. Both solid ones and hollows, although fir is also used, and for a dinghy that size, you could use fir too.

Frankly, I wouldn't bother hollowing a mast that short, but I'd taper it. If for nothing else, then for looks – unless, of course, I was choosing a rig like this:



It's from here:

http://www.megin.dk/

P.S. Many of those boats are made with spruce-coamings, spruce mast etc..


Many pictures here (scroll down):

http://www.megin.dk/Meginnyt.htm

Edit: I meant spruce in this post, not pine - it's corrected now. I'd make a lousy translator of botanical books.

[alan white]

Originally Posted by PsiPhi

OK - so stick with wood, does look better.


I always assumed something like pine would not be strong enough?

Can anyone suggest how big a cross section a mast this size would need
a) if solid wood
b) if hollow

My local pine, Eastern white pine, isn't quite as stiff and resistent to splitting as fir or spruce, but then again, the pine family is huge, including all sorts of weights and qualities. Ask locally about your indiginous pines, how they hold up to bending.
Spruce in particular has amazing tensile strength, making it the most dreaded wood in my firewood pile. Harder to split than oak or maple.

A ten foot unstayed mast of spruce, which is the most common mast material, I would make 2 1/2" at the thwart and 1 1/2" at the top, and maybe 2" at the step. It would be tapered with a slight convexity to the taper so that at the 5 ft point, it would be 2 1/4" or so.
It makes no sense to make it hollow, it's so light already. If it was hollow, it might be a bit bigger diameter, maybe 2 5/8" or so at most.
Ten feet can be done on a lathe (if you've access to one) if you set up the tailstock on a bench to extend the capacity. Otherwise, it's real easy to sixteen-side and then just sand by wrapping a 36 grit inside-out 3"-4" belt around it. Best to cut the belt and spiral-sand it to fair it better.

Alan

[PsiPhi]

Thanks guys.

DanishBagger - Great site, wonderful photo's, something to aspire to.

Alan - Thanks that's the sort of into I was after.
My local DIY has limited options for timber, and what timber yards I have found seem to work the same hours I do - never open when I'm off.
I was going to build hollow because most of the (good) timber I could see was either 19mm or 30something mm thick - nothing at 3 inches (except very soft pine).

I know just enough about lathes to know I wouldn't let some one like me near one - but I'm quite handy with the power plane.

Simon.

[Landlubber]

Danish Bagger, Thanks for those great pics, what is that rig in English?

[alan white]

Originally Posted by PsiPhi

Thanks guys.

DanishBagger - Great site, wonderful photo's, something to aspire to.

Alan - Thanks that's the sort of into I was after.
My local DIY has limited options for timber, and what timber yards I have found seem to work the same hours I do - never open when I'm off.
I was going to build hollow because most of the (good) timber I could see was either 19mm or 30something mm thick - nothing at 3 inches (except very soft pine).

I know just enough about lathes to know I wouldn't let some one like me near one - but I'm quite handy with the power plane.

Simon.

I'd still go solid. Just glue several pieces together. This is totally acceptable and done all the time. To make such a small mast hollow will be four times the effort, to save 2-3 lbs from a six to nine pound mast.
If, on the other hand, you would do it for the experience, by all means go for it.

A.

[alan white]

DanishBagger,

I noticed the bottom construction of those boats you posted. What is the reason for the double bottom and the shape produced by the construction?

A.

[DanishBagger]

Alan and Landlubber,


An amateur's ( me) translation of part of the site - http://www.megin.dk/Priser.htm says something like this:

The Megin Yole (dinghy) is a modern danish smack dinghy related to traditional fishing boats and the ships of the vikings. "Meginhufir" was the name the old shipsbuilders gave to the "bottom planks-on-edge", which gave their ships extraordinary strength. Our dinghy has the same form, and it turns out that the channels in the bottom results in more speed and calmer movements.

The Megin Yole has a ( and here my dictionaries aren't any help) "sprit stay rig" (is there something called that in english? At least that would be the direct translation), as the old fishing boats.

[…] The long keel is made of wood. 3-4" tall, and in connection with the meginhufir-edges delivers a good balance and stability (course-wise).

PsiPhi,

I'm with Alan on this one. I'd also go solid. One usually only goes hollow in order to save weight, but since that isn't really a problem here, why bother?
P.S. the mast of the Megin I have linked to are solid too.

[alan white]

DB,

Shown off of Roskilde, must be close to where I lived--- Helsingborg. You must be near Helsingor.
I'm still wondering about the construction details of the keel. Do you have a close-up?

[DanishBagger]

Well, I live just outside of Copenhagen – in Valby.

I have found a couple of pictures from a few sites:





This might be interesting:



There's a 15ft'er for sale here:

http://www.dba.dk/asp/soegning/detai...nceid=51728682

Take a look at these threads – it's "Grand Megins" ("Stormeginer"):

http://www.yacht-treff.de/showthread.php?t=1284

http://www.viborgsiden.dk/fdf/sejlad...nglishtxt.html


I don't really know where else to look.

Btw, the Peer Bruun who designed the Megin, is also the bloke who designed the Spækhugger, the Kaskelot etc:

This is a spækhugger:




I hope that it helps a wee bit, although I can't seem to find the close-up you're looking for :-(

Now, the thing is, the Megin dinghy isn't all that special. It's nice, and so forth, but in reality it's not very different from any other smack dinghy ("Smakkejolle") around these parts.

Another one is the "lynæs-jolle":

Oops, here's the Lynæs-link: http://www.robertpeel.dk/sejlads.htm