Vance, While I agree with you that they do have some effect, one of the issues that came up in reviewing the Seehund design was how effective the control surfaces were. Through the short life of this sub, the surfaces kept growing in size. The Perry boats are probably an order of magnitude in size as compared to the typical PSUB and there is an exponential factor (either squared or cubed…probably can squared , this is later in my classes) associated with increasing the size of a vessel and associated control surfaces. Would have to go back and look at it but if I remember correctly the Perry surfaces were quite large. This is not a detriment just an observation. And while Harbor Branch (i.e. Link) may have found control surfaces unnecessary, I am speaking more from the naval architect’s perspective (even though I am an HB intern product J). R/Jay Resepectfully, Jay K. Jeffries Andros Is., Bahamas Save the whales, collect the whole set. From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of vbra676539@aol.com Spoken like a true Harbor Branch alumni. Dive planes and rudders are, in fact, astonishingly effective when designed correctly and incorporated into the vehicle overall. Hyco never used them, but we surely put a million miles underwater using them on the Perry's. Even the apparently small surface area of the dive planes were good at 1 knot and better, and could be used at any rate to help trim the boat or otherwise adjust attitude when operating on the bottom. The old flat planes and rudder are notably less effective than even the simplest chord design. We've been through this before and there might be some good info in the archives somewhere. Vance |