Building a Carbon Fibre boom for a BR or BRe

[Sea Simon]

Llafurio, OK?

I await next winter's (possible) project with anticipation!

[Llafurio]

Llafurio, OK? I await next winter's (possible) project with anticipation!

Yes Simon, super, and thanks for understanding.

A good thing you have time enough to prepare for the job. That makes it simpler, and probably even cheaper., as you do not have to buy in a hurry.

1. Windsurf mast
As Mark Darley has already recommended, buy windsurf masts where you find them cheap, always good to have some spare mast in reserve. SDM, i.e. standard diametre, used, new, any length (you can always shorten them). Preferably with carbon content of around 60%, which makes them lightweight and tolerant to work on. Masts with a higher carbon content are a little lighter in weight still, but the material gets increasingly powdery with increasing carbon %s.
I buy them often in a particular way: I visit boating and windsurfing shows on the final afternoon, when the exhibitors get ready to pack in. By that time, many dealers are offering very, very good deals. If you take yourself some time, you will find a good offer sooner or later.

ICMS: Fot the mainsail boom you do NOT need a high ICMS -stiffness- value. But if you come across a cheap long mast with a high IMCS (30+), you could use that to replace a too whippy topmast yard, and recycle the old whippy topmast to become your new main boom.

There is actually a good chance you can pick up extra long and extra stiff windsurf masts at an exceptional bargain price, because these masts are not very popular among mainstream windsurfers.

BTW, the IMCS value is related to the length of the mast, it's a relative stiffness. You get the best abolute stiffness, if you buy a long high-ICMS mast, and cut that back to your required length.

2.
Then you'll need a length of proper hardwood for both end-plugs, 52 x 52 mm square section minimum. To have minimum moisture swelling of the plugs, Teak is best, but Mahog will also do.
The plugs will have to be turned to the required diametre on a lathe. Many guys have that, ask around, or buy a cheap lathe yourself. Very useful to have.

3.
Outdoor adhesive /sealant.
To glue the plugs in. Many think, only Sikaflex will do the job. But there are many cheaper products on the market today that will do just as well.

4.
A few small to medium Nylon mooring cleats, for the reefing system, and stainless screws to match.

5.
A suitable Allen pin gooseneck, you will probably already have that on you mast, A4114-1 (for a track) or A 4009C (screw-on for round mast).

So much for today. And as a shopping list for the upcoming summer.

I am presently 1,000 miles away from my boats, so cannot send photos at this time. I will be back in Ireland from May, and can send more details and photos then.

Kind regards,

Claus

[Llafurio]

For the meantime, a photo from a few years ago.
The mainsail boom bends, but does not break. By a kind of ropehorse under the boom the mainsail sheeting force is distributed. Again, the main point of the carbon boom is to have a boom with smallest possible mass (weight) and consequently inertia when gybing the boat in high winds. Therefore it is single-wall only. The small weight of the boom and its round section also helps when boom meets head.
IMO, costwise, such a maintenance-free carbon boom is not more expensive to make than a varnished heavy wooden boom from knot-free pine.
(Photo credit: Steve Morton)

[Sea Simon]

Many thanks L. Some food for thought here.
I'm hoping for some photos in due course.

[Llafurio]

Simon,
here an old photo of my patent mainsail boom end setup complete with automatic sail foot outhaul. You can let the mainsheet snapshackle ride on the ropehorse under the boom, or hook it in the bowline hook at the boom end. If you want to control the outhaul forces, you do that through lengthening or shortening the ropehorse. If you do not wish the automatic outhaul you can block it with a simple knot.
Note that the main sheeting and outhaul forces are led through the teakwood boom-end plug.
C.

[Llafurio]

Many thanks L. Some food for thought here.
I'm hoping for some photos in due course.

What do you want photographs of?
C.

[Sea Simon]

Many thanks L. Some food for thought here.
I'm hoping for some photos in due course.

What do you want photographs of?
C.

Some details of the gooseneck and kicker attachments please.

[Llafurio]

Some details of the gooseneck and kicker attachments please.

Here a photo of the gooseneck connection.
There is no kicker, it's a spritboom.
C.