Forum Replies Created
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I’d propose a different construction, though it’s a bit of a heretic idea to make holes in the hull…
Use longer aluminum crossbars and make them go through the whole hull, using plastic boat thru-fittings:
https://www.amazon.co.uk/through-hull-boat-fittings/s?k=through+hull+boat+fittings
I’d imagine if you cut off the unnecessary length in the hull fitting and choose tight fitting tubing size, it would be pretty airtight. Perhaps with some glue between fitting and hull fabric. I don’t promise it will work, but if it does, that would make quite a solid connection.The 450g nylon from Extremtextil is much stronger than their 275g or even 370g versions. Bigger difference than the numbers indicate.
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“I wonder if aiming a drinking straw at the valve opening and blowing through it would also work.”
It does. I started with various everyday objects. Ballpoint pen barrel was quite ok. The structure above just helps to aim in the middle.
Forgot about the 3D-model: you need to drill the nozzle open to 3-4mm (1/8 – 1/6″). Print has a rough surface that weakens airflow.
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STL-files of the nozzles if someone is interested in printing:
https://drive.google.com/file/d/1JENGRPHTo1_nk3GdEx0I47fs0Hq4R9VT/view?usp=drive_linkThe rods connecting the two nozzle parts are cut from the most common 2mm (14 gauge) bicycle spoke. And superglued into the holes of the 3D model
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15 years ago in Lapland (it’s a catamaran with rigid narrow skeleton):
I think catamaran is a good idea and especially if you can make it work with an inflatable frame. One thing to consider: the two bow waves of the hulls can merge to a higher one between the frames and add drag plus get you wet. It can help to toe in the hulls a bit, so that bows are closer to each other than the sterns. Maybe an adjustable test frame first (two by fours + straps or anything) to find out a good hull placement and then cutting the ‘captain’s bridge’?
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I might have exaggerated the edge shape. you can see the effect in real life in some Thermarest Neoair photos. In your use, the large side pontoons will be more rigid than the mattress and will force the edge to be straight. So I don’t think you need to make changes to the original plan. More baffles and curved edge would just mean more work (and less thickness unless you change the internal baffle walls too).
Project sounds interesting! I live in Finland which means mostly flatwater so better speed and tracking are what I’m after. -
Howdy,
This is a bit late but yes, I think your measures are good, just note that:
– The width will vary a bit due to baffles bulging. It will be quite a narrow mattress but you know if that’s ok for you.
– end ‘chambers’ will be a bit smaller than the rest if you don’t give them 5cm extra fabric due to the missing baffle fabric -
Fittings are screw and nut type and will seal well to the fabric, with perhaps a little glue or a rubber gasket. I’ve used those for attaching inflation tubes. Problem is more likely between fitting and crossbraces as it’s not easy to find exactly matching sizes. And perhaps if your fabric is on the thin and flexible side then the hole in the fabric could stretch and come out of the fitting. For Extremtextil 450g nylon I would trust it while for thinner fabrics some reinforcements could be useful.
But yes, making more holes in airtight hulls is not exactly the safest bet.
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