Re: A54 Main Sail furling foil weak point


Arno Luijten
 

Hi Scott,

Thanks for the compliment.
It depends on your particular situation if a reinforcement would make sense. The main point would be if you have a connection in the foil at a low point, say in the first meter of the foil. This is where the torsion forces are the worst. If the connection is purely depending on the rod inside the foil you will have a problem at some point.
I image the worst being a Chinese gibe (that should never happen, but....) with a partially furled sail. The rod inside has not enough intersection space to be stiff enough. A circle shape has a much better resistance against torsion then a flattish bar.
This is why the collar makes such a difference and why the total of 12 fixation points really prevent the twist in the tube. 
I have no drawing at the moment but I will try to come up with something shortly. The collar is actually made from a piece of anodized tube that had the exact right inner diameter. I will look if I can find the exact specs of the tube but I choose it here at FKG on basis of what was available. I was lucky to find this I suppose. FKG used a router to cut the slot. The holes are all done by myself with the connecting rod in place using a small drill-press.
The important bit is that the screws are sideways in the rod from two sides and not just from the back. You want to have al the materials act as a system making it much stronger then the individual parts.
I did have to use some persuasion to get the slight deformation at the top end of the small piece of foil back into shape. The rod twist caused the top end to skew a bit.  Using a big plier and a lot of protection-cloth to prevent markings by the pliers worked for me.

In all cases do check if the reinforcement inside the base of the foil is seated properly to support the bolt going through the foil.

Regards,

Arno Luijten
SV Luna,
A54-121

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