Hi Emile, With temperature and pressure there is definitely sliding required on the surface. One reported distance of sliding was over 10mm but that was over 750 meters deep. This is why rubber / neoprene is not used. I tried to see how much mine moved but it was not easily obvious. You should calculate the thermal expansion from 0 to 38 degrees (design limits may vary) for the diameter you are using and then if it is a 90 degree by 1.414 for the amount sliding by temperature. If you have the FEA then you can see what pressure will reduce the diameter by and can estimate the minimum seat diameter for the cone. I have a separate cone seat which is then bolted to the steel hull so later when machining the hull seat it can be just face and bore rather than angle seat which is much harder for portable boring / facing machines. The seat is also greased with vacuum grease. Any comments Vance?? I used a similar seat arrangement to the Perry subs but mine is 90degree whereas Perry is 113 degrees I believe. Hope that helps. Regards, Hugh From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Emile van Essen Hi, For the new bigger bowdome of eurosub we use a conical seat In my opinion is it a good idea to have a flat rubber gasket between the acrylic and the metal .This for sealing and avoid stresses in case of an imperfect surface . In the “handbook of acrylics” this is never mentioned. Why is this not done; too high surface pressure, sliding?? Hope you can help. Regards, Emile
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