Building a Wooden Mast

[lohwaikin]

This is a spin-off from the "Terminally Cheap" thread where I briefly described my intent on building a wooden mast.

I did some internet search for self-built wooden mast examples and basically am presented with 3 possible approaches. The first was the almost ubiquitous Birdsmouth construction. The second being Paul Goodwin's 1990 article on the DN mast of airfoil cross-section, and lastly a triangular mast by John Atkins 1946.

In order to get a rough idea the difficulties involved in building a laminated 26-foot wooden mast, I constructed a 2 ft 4" long trial piece using Paul Goodwin's 1990 design, but enlarged all dimensions by 25%. Why 2 ft 4" long only is because I have some leftover Kapur (Dryobalanops Aromatica) planks at 4 ft 10" lengths. I reckon that if the cross section lamination process is manageable at 4 ft 10" length, full scale construction should be feasible with about 5.4x the insanity...

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[lohwaikin]

Once the epoxy cured, a little planing on the leading edge, and then orbital sand all around.

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Haven't produced the luff groove. According to Paul Goodwin's article, I'll have to route a round groove on the trailing edge, glue on an aluminum tube (maybe dia. 12mm X 1.5mm thick), and then slot it through to the throat thickness of the sail slugs.

[lohwaikin]

Weight wise : This trial piece is currently 1260g at 710 mm length, converts to 2.28 kg/m (1.52 lb/ft)! That's before adding the luff tube and final glass cloth. Sounds like a Dwyer DM-450 category....
I'll probably redesign the cross section arrangement, use thinner planks.
In drawing B2: "Rigging" the given approximate mast section of 2.44" X 3.68" kind of describes the Dwyer DM-368.

[Chad]

Very cool. Based on Gentry's stuff, I'd probably stay away from the classic teardrop shape. Here's a quick layout of a birdsmouth mast modified to his GoLD shape, scaled so its thickness is 3":

BirdsmouthStarMast.pdf

[micah202]

Very cool. Based on Gentry's stuff, I'd probably stay away from the classic teardrop shape. Here's a quick layout of a birdsmouth mast modified to his GoLD shape, scaled so its thickness is 3":

BirdsmouthStarMast.pdf

...umm Chad,,isn't the boltrope channel on your layout going right through the laminate?

...great progress Loh Wai Kin!

[Chad]

I assumed an external track.

[lohwaikin]

Thanks for the Birdsmouth "G-LD" Star Mast construction, Chad.
I have yet to overcome the gyroscopic effect of my Maktec router.
My compression post was made this way, or should I say it is still "Birdsmouth",since I practically filled up all the mostly void-joints with thick epoxy?

There is not much scientific reason behind my choice of the tear-drop mast section, just plain simple construction.
Currently I am revisiting Paul Goodwin's 1990 design to see if it is still possible to simplify the construction and to reduce weight.
I do not have much good wookworking tools here (nor skills in the woodworker himself...).
This trial piece was made with planks shaped on a circular table saw with a "not-so-square" fence.
For the actual 26-foot mast I will order the planks finished to final dimensions from the timber yard.
Maybe need to pay extra, not just for the original timber size but also for labour.

I am also currently trying to figure out the cheapest and easiest way to construct a 24-foot long right-angle "straight-jig" for the final mast construction, out of plywood strips stapled together. I will need this for maintaining straightness during scarf joining, L-section forming, and when the 2 halves glue together.

And I'll surely run out of clamps...

[Chad]

A table saw is perfectly capable of cutting the birdsmouth V's. If your fence is suspect, clamp a board down instead, add some feather boards and give it a try.
Goodwin's DN mast has very different requirements than a keel or sport boat:

Not to say you can't make it work, just recognize what he's trying to achieve versus what you're looking for!

[ryderp]

Do you guys have TrusJoists (http://www.woodbywy.com/floors/f_TJI_joists.aspx) or equivalent there? These are basically plywood I-beams that are very straight. They would make a nice jig for the mast.

Phil

[lohwaikin]

Strip-plank mast? I didn't know it can be made this way...
From Fust Art Clapers.

fust-art-clapers_mastils_2.jpg

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[Tim Ford]

Wow...that is interesting! Any idea what the glue and liner are? The shot in the upper right looks like the liner is Kev/CF hybrid cloth...I have no idea what the black stuff is holding it together. Wood looks like pine, too...wide growth rings and not particularly clear, either. Isn't pine too pitchy for this kind of laminate?

Lots of questions, but it looks pretty cool....looked at the website but my Catalan (Castellano) is a bit rusty


[edit] found the site that speaks 'merican! That Marwood 34 is perty dern sexy!! http://www.fustartclapers.com/marwood34_en.html

[lohwaikin]

Since last October I've been muting over an easy design for constructing an wooden foil-section mast.
Here's the drawing of my design, and a rough concept of the wooden fixture (to be built from 16mm thick blockboard).
The mast design is a fusion of Paul Goodwin's DN iceboat mast design and the easy-build principle of John Atkin's triangle mast.
Stock materials are Kapur (Dryobalanops A.) milled to exact dimensions, prices below:
1) PLANK,KAPUR 0.5IN X 3.5IN X 10FT FINAL MILLED, SGD 11.00/PC
2) PLANK,KAPUR 0.875IN X 1.25IN X 10FT FINAL MILLED, SGD 9.75/PC
3) BLOCKBOARD,0.625IN THK 4FT X 8FT ONE-SIDED PVC WHITE LAMINATE, SGD 27.00/PC

My design objective is centered on ease of construction, in an environment of minimal tooling, temporary floor space (fixture must be shelved up during the day!), and 20-minute pot-life epoxies...
The ideal design should be one that is easily reworked at any stage of build, and with minimum "critical phase" (the short glue pot-life is a problem, and I still have plenty left...).
Scarfing slender strips of timber is still my weakest competency...
And I realised also that appyling a 26 feet long bead of glue is no simple feat...

That was before I came across the strip-planked wooden mast from Fust-Art-Clapers.

[Chad]

Fun stuff!
There's lots of strip scarfing methods out there: using ramp fixtures for a router, an angled fence and a table saw, or an angled fence and a disc sander (or stationary/clamped belt sander). That won't/shouldn't be the hard part of this project. Order a couple extra lengths of the "planks" so that you can cull out any non-straight grained portions.

Using a plastic ziploc bag as a pastry bag works well to dispense long beads, or you can even use a well cleaned caulking tube (but go fast, the tube will hold in the heat and speed the exotherm). This might even be a good use for West's 610 product- a self mixing pre-thickened epoxy in a caulking tube with disposable mixing nozzles. It goes for about US$25 per tube, and one tube would probably do the whole mast.

I have a smaller 14' mast I'm about to start making, and my goal is to beat the standard aluminum section weight used. I'm using a smaller version of the Gentry section posted further up the thread:

ElToroMast.pdf

The figures look good so far, but I'm using carbon for the primary load bearing so the wood is minimized so that it becomes just a way of holding the shape while the outer fiber is applied- sort of a leave in place mold or mandrel. That gets pricier with bigger masts of course.

Keep the updates coming, it's great to see these alternate ideas coming together.

[admin]

question: is there an efficient way to fair 26' of mast laid up as shown, to the shape seen in the diagram? Seems like that would be a bit of a chore.

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[M&S]

A power plane, a #8 jointer plane, templates and a good eye. A torture (fairing) board. Tylenol for after.

[Chad]

A skilsaw, power plane, a #8 jointer plane, templates and a good eye. A torture (fairing) board. Tylenol for after.

Fixed; gotta knock the corners off first, or you're in to the smoking power plane zone. My little Makita makes a special burning plastic smell when I whale on something too long...

[Tim Ford]

Oh man, that sounds like 26 feet of agony. Think I'll stick to the old fashioned tools: a ballpoint pen and a checkbook.

[lohwaikin]

Chad,
You're pretty fast into action while I'm still doing mental R&D and DFM....

Tim,
I can't bear to part with my money to the shipper.
A Z-Spar Z170 is GBP 267, but the shipping cost to Singapore is GBP 395.
A Dwyer DM368 around USD 585 but Jay has yet to quote shipping.
An Australian S100 was quoted AUD 1335 and Michael of YachtMasts Aust. wouldn't want to handle shipping (I suspect Jay of Dwyer has the same reluctance too).

A wooden mast can be built for as little as SGD 350 (USD 280) [planks/fixture/nails/glasscloth/resin/peel-ply/UVR], excluding sweat equity....
Let's see how it goes. If it turns out I cannot saw straight, I'll resort to the cheque book...

Did I told you about my Maktec MT360 router which has a mind of its own?
I'm trying to work on a cross section design to avoid its use as much as possible (ironically that's the first tool I bought after receiving the boat plans...)

Cheers,

[Tim Ford]

WHoa! I see your point.
I was joking, please forgive my stupid comment. Not only do you save money, you also have the pride of ownership, looking at your rig and saying "I made that."
My comment was more about the fact that if I fabricated that rig, it would be a lot less straight and a lot less dainty. Plus, I was lucky enough to glom on to the deal that others (Kevin and Jeff and Ron and jray) did the heavy lifting on, with the C-Tech deal.

so I have no room to talk! Cheers and thanks for contributing some great info to the forum.

[ryderp]

Loh,

Of the two methods you've shown above, I would probably go with the strip-plank approach, except instead of cutting different widths and chamfers for each and every piece, I would probably cut strips 3/8" thick with the same widths and then round one edge and cut a cove into the other so that they fit together nicely with a curved surface. The nice thing about the strip-plank approach is that you could use shorter length strips and then stagger them. Either way, good luck with this, and we'll all be following your progress.

Phil

[M&S]

Here's an idea. I am nuts to begin with so that's a constant. but could this work;

strip plank laid in a female half mold,
use narrower strips and fix them in place with a hotmelt glue gun, glue applied to the mold supports to hold the strips in place at a gentlmanly controlled pace.
Thin strips will yield a more uniform wall thickness.
When half of the mast strips are in place, epoxy and fiber on the inside surfaces of the half.
Do the second half.
obtain some surgical tube the length of the mast that can expand to the interior diameter of the mast-to-be. About 10 lbs. /sq. inch pressure should work ( someone help with metric; Kg/cu.m x 1.33 newton fortnights / 2 furlongs???)
lay the surgical tube inside the Carbon knitted tube sleeves that are available from Soller Composites both in 45+/- and uni with stretchy knitted binding.
Wet out the two mast halves with slow epoxy.
Tape around the mast or use zip ties. Make sure it is as straight as you want (prebend?)
Inflate the rubber tube gently. Epoxy will be forced into the spaces between strips. the knitted fabric carbon tubes will stretch and be the interior reinforcement.
Then all you have to do is finish the mast as you would a purchased tube.
I think I am nuts.
Do I hear a second?????

[Chad]

Surgical tube that size is also very thick walled, and pricy. It takes about 40 psi to get 1.5" tubing to grow to mast size. (I did this for my mast base and the sleeve for my rotator cup).

The carbon braided sleeving almost definitely won't work like this. It trades length for width, finger trap style. So like a spliced rope, it's not going to grow radially without shrinking lengthwise, and it's not going to shrink lengthwise because of the finger trap grip on the tubing. Even with a single wrap of biax and a very modest overlap (so not continuos like a braided sleeve, so should have expanded easier), the short sleeve I did had trouble expanding to the inner circumference of the mast because it tries to grip the tubing too aggressively.

Sorry, withholding my second on this one!

[ryderp]

How about:

> Create mast halves using thin strips in a female mold of sorts and then lay CF cloth onto the inside of the mast haves. You could even put a taper on the top of the mast this way if you were so inclined
> Glue the two mast halves together.
> Use the braided cloth on the outside of the mast with vacuum bagging for light weight and to get rid of voids
> Add an external sail track

Phil

[lohwaikin]

Ran out of primer for the hull bottom, so time to get the mast build started while waiting for replenishment...

A month ago I ordered the bunch of exactly-milled Kapur (Dryoblanops A.) planks, and also a 4x8 ft 5/8" thick block-board for constructing the fixture.
Took about 6 hours to get this fixture constructed.

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This fixture will assist me up till the point of gluing up the triangular section.
I will have to figure out something to secure the wooden section while power-planing the exterior to the final tear-drop shape.

The primer would probably arrive before I'm done with scarfing the planks...

Cheers,

[lohwaikin]

The first plank went in as early as 26 APR '13.

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