Noice Pacey
- got any pics of the boat?
The current foundry is an 'Art Foundry' so it sounds like a similar sort of set up. They are going to pass my work on to another 'similar' set up - I just don't know who yet, and so I am preparing contingencies. Just to clarify, I was advised the hollow
inside the leading edge was the issue. (it's long and relatively fine)
I like the idea of using the AB2 - Apart from it looking uber cool, I will have to look at the density as well. Part of the appeal of aluminium was the weight issue and to take advantage of its lower elastic modulus. It has about the same density as G10 but better hardness and lower elastic modulus. Because the fin is designed for sailing in shallow water, it will invariably touch down. I wanted some 'give' so that it can ride out any impacts without fracturing like G10.
It's also a delicate balance of where do I put the point of failure? Powerbox designs make this easier having been designed from the outset to fail at the bolt insert, but Tuttle is hard. If the alloy I use is too strong, the bolt holes in the fin will be too strong as well - so rather than the fin peeling away as per Powerbox, with Tuttle the back end of the board is likely to be the point of failure. I am still not sure how to tackle this one and still be user friendly.
If I can have a bigger hollow inside the fin because the AB2 is stronger, I can then pack more foam inside and create more buoyancy to offset the weight. But any redesign requires a new 3D design and print - the costs to get this far makes that idea pretty unsavoury at the moment.
The fins I have had cast already were designed by the engineer to be cast in 6k series Aluminium and to withstand fatigue failure. Thus far they show no signs of snapping. I clamped the base to edge of my trailer and stood on the foil (110kgs) with no harm done. I stood toward the end of the foil and managed to get some bend in the tip.
So whilst I am satisfied that structurally it outperforms G10, I need to be very careful about the costs creeping up. At the moment I am aiming to get the cast done for about $110 per unit. (Just as a comparison - ex-factory in China, $8.00 each for minimum order of 100fins!). Add in the postage/courier from the foundry and I think then I will have DIY finishing fins available for about $135 each. 'Finished' fins will be about the same as a Delta G10 in price but will easily outperform them in every aspect of
my design criteria.
I am waiting to hear back from Veem. I suspect you will be right and I will need to do a very large production run to make it worthwhile. I dont think the market for these fins is ever going to be big enough to justify that and although I dont ever expect to be profitable, I would like to keep my losses to a minimum.
Here endeth yet another grand effort from me in procrastinating, instead of doing what I was meant to be doing.
)
That might be worth revisiting though, as shrinkage is not an issue - one of advantages of the fillet is that all the load is taken on the flange portion, so the fit in the box is not so critical.
