I'm doin it! I'm doin it! Extinguish my torch?!? NEVER!



Sealant, either RTV (a silicone type) or a 2-part (aviation type), properly applied will
eliminate that risk.


You will still have the two holes from the cheek block and either two or four holes in the curf.
While the holes in the curf aren't a leakage factor, I do think that they weaken the overall
rigidity of the mast. Another method I have seen in these forums is to loop a line around the
mast tip. That eliminates holes into the mast cavity and curf altogether.

Disclaimer: The following is my reasoning for going with the Infusion 18 type of arrangement
over the line type and is my opinion only, which is based on 30+ years in the aviation industry
dealing with aluminium structures and attachments/fittings. Please feel free to pick it apart.

At the risk of explaining something that everyone already knows, lets look at mast construction.
A plain, circular, aluminium tube has a fairly weak bending moment. Especially when your talking
about 30 foot lengths. Adding shape, teardrop or wing, greatly increases the fore and aft rigidity
but weakens the side load rigidity. To offset the loss of side load strength we add diamond wires.
Adding a curf creates a spine that further increases the fore and aft load rigidity. When we start
adding in prebend this curf becomes critically important in preventing tube folding.

There are four types of holes you can have in an aluminium structure. Unsupported; just a
plain hole, Strengthened; where the lip of the hole is partially bent inwards/outwards,
Partial Support; grommet type (like the grommets in a tramp) and Full Support; rivet type,
either pop or solid core. Unsupported being (by far) the weakest and Full Support only
marginally weaker than an unbroken surface.

The line configuration places unsupported holes in the mast curf which, I think, greatly
reduces the curfs ability to act as a spine. I have seen nothing in the forums to support
this (i.e. reports of masts breaking at the curf hole location) but it feels way wrong.

Both the Ball/Steel Bale and the Block/Line Bale configuration provide a positive stop for
consistent Spin Luff length, so that issue is a toss-up.

I think the steel bale offers a couple of advantages over the line bale. One is shape rigidity.
A steel bale maintains a constant, consistant, circular shape for an easier and more predictable
mast rotation during a gybe. The line bale will 'V' under load. I think that this would cause
line skip during a gybe and the luff line 'V' point would not be as consistant. Another advantage
is reduction of friction wear. With both types properly lubricated, I think the steel bale will
cause much less wear on the spin halyard as compared to the line on line setup. Less wear on the
spin halyard means I won't have to replace it as often as the line bale arrangement.

As I've stated, this is my opinion only, YM&OMV. Questions? Anyone? You there, in the back...