Fashioning Round Mast -- Tell Me I am Wrong, Please!

[Dennis Marshall]

Hello,since I was unable to find suitable wood for my mast, I took the plunge and ordered some beautiful Doug Fir from Flounder Bay. The mast needs to be rounded to 21/2" dia at its thickest, so I asked for 2 2x4 sticks so that I could laminate 'em and then fashion them to size.

The shipment arrived 2 days ago and I just know uncrated the goods to find that I have some wonderfully clear 1 1/2 x 2 1/2" x 15' sticks. Now, it seems to me that the stock is too thin to get my 2 1/2 " round mast out of it. Indeed, as far as I know, the stock needed to be 8 sided to about the 2 1/2" size. Please tell me I'm wrong and that I didn't go to an unnecessary expense for wood that cannot be used for the purposes intended :mad:

Dennis

[TomRobb]

My math teachers all roll their eyes in unison whenever I put pencil to paper...but glued together I see a stick 3"X2.5"X15' :confused:
What,exactly, is supposed to be the problem?
You can't draw a 2.5" circle inside a 3X2.5" rectangle?

[Dennis Marshall]

Ummmm, no, but I can get a 3x2.5" rectangle in a 2.5in circle. At least that is what my compass keeps telling me. redface.gif

Dennis

[Dennis Marshall]

Ykes, now that I have returned from an alternative universe where the laws of mathematics and physics have no meaning (i.e., my forgetfulness of basic geometry), no, I can see no problem except that I had better go back to school. :eek:

[TomRobb]

No harm - no foul.
Measure twice, cut over and over and it's still too small :D

[NormMessinger]

Only problem I can see is if the edges of the 2x4's are rounded over as is usually the case. You'll have a little groove down each side of your mast. Maybe that's what the scrap you'll rip off the 3" face is for.

--Norm

[Bayboat]

Did something go wrong with your order? If you ordered 2 finished 2x4 you should have received 2
1-1/2 x 3-1/2 pieces. But either way you have enough wood for a 2 1/2" diameter mast.

[ 09-01-2002, 03:46 PM: Message edited by: Bayboat ]

[Bob Cleek]

Well, I don't want to be a party pooper, but.... LOL As far as I know, you don't want to ever laminate a spar out of just two pieces. They may (will) want to take a turn at some point. If you have only two pieces, the stronger one will overcome the other and you'll have a bent spar. If you use three pieces or more, the other two will be stronger than the strongest one and keep it all straight like it ought to be.

[Tomcat]

Piver made a lot of masts out of "two pieces". He used two 2x6 lamed together, he had an odd method of stagering a bunch of intentional scarphs, which is actualy a cool way of dropping knots. Anyhoo, I think it can be done.

Now on the negative, the basic Gougeon rule is no pieces larger than 3/4 or 1", they claim you will loose your encapsulation due to wood movement. Something to think of if you intend to epoxy everything within an inch of it's life.

I imagine you could figure out some way to convert this stock into a hollow octagon with either birdmouths, or the simple biscuit system.

[NormMessinger]

To late to start redesigning. Dennis owns some nice boards and a fair fraction of a trucking company. Glue your 2x4's togeather with the concave end grain pattern of the two pieces facing and glue carefully according to the kind of glue you are using. CPES and varnish would be good.

Next mast, 5, 10, 15,20 years from now when it goes bad use Sitka spruce and build it birds mouth like. Then 5 10 15 20 years after than let us know how it compares.

--Norm

[Seth Wood]

I think the Gougeon rule of 3/4-1" max. lamination thicknesses is to minimize wood shrinking and swelling when it's repeatedly wet (as in: submerged) and dry, such as in a stem or keelson. If your mast is repeatedly submerged you may have more immediate problems than glue line failure from the laminations swelling.

I've not done it and know little about it, but I've read here and there that birdsmouth scarfs, as Norm recommends, are a clean and strong way to build up a mast.

[dale o]

Back to the original problem. Did you set your compass for 1 1/4" Radius? I f you used 2 1/2" for your compass setting, your wood stock would look too small. ( seen it before).