Like you Rod I had a go at doing the large curved fillet, but quickly realised that it was going to take a lot of material and that it was quite a difficult job working upside down. So I decided on a smaller angled fillet instead. I firstly went along the bottom outside edge of the stringer with a small plane to take the corner off, and then I used about a 100mm wide flat spatula to form a flat angled fillet of about 45 degrees. The first run left a lot of hollows so I went back over it a couple of times with more filler to get a better finish. This angled fillet then transitions to the curved fillet where it is more visible where the front of the fwd beam meets the hull, but probably only about a 120mm radius. It did not seem to use too much resin and filler powder doing it this way, and the final appearance is good. I have attached a photo which if you zoom in on you can see some of the underwing fillet.

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David

Hi Rod,

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I bought a block of PU foam ( ), and cut this to shape. I think there are photo’s in the album of the build of my ECO 85 Electric: /g/K-designs-Multihull-Sailboats/photosearch?p=updated%2C%2Ceco+85%2C20%2C1%2C300%2C0&jump=1

I hope this clear to you.

If not, please let me know, and I will make some extra photo’s.

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Regards,

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Jack

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I have to admit to being quite surprised at the apparent need for a layer of fiberglass, for strength, over the outside of the hull to bridge deck fillet. This sent me scrambling back to look at both my plans, and the building instructions, to see if I had missed some important part of the Eco 6 construction. But nowhere in either the plans or the building instructions is the need for the fiberglass mentioned, the plans only show a fillet in this area . But as they say; ‘the proof is in the pudding’, and after almost two years of use including some hard sailing in rough sea conditions, and the whole process of jacking up the boat and moving it to the launching site, there is no evidence of failure in that join, or any cracking in any area of the fillet.

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It seems to me that the strength of the hull to bridge deck join, and the rigidity of the whole structure is more dependent on the successful fitting of the main cabin bulkheads and the aft beam. If those joins are strong there should be no noticeable flexing of the structure, and the bridge deck to hull join should be locked into place. At least this would apply to the small catamarans we are talking about here. Certainly on a larger vessel greater strength will be required, and that hull to bridge deck connection needs a ‘chamfer panel’ to reduce pounding of waves hitting that inside corner. But given that my boat has already seen hard use, and there is no sign of any problems in that bridge deck to hull join, I am confident that what I have done is fit for purpose.

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David