[PSUBS-MAILIST] GRP hatch

Tue Apr 28 13:57:03 EDT 2020

Hank,

How would a flat acrylic hatch work out?  You are already familiar with the required thickness requirement for design depth.  Would such a thick piece of acrylic be just as heavy as your current steel hatch?  Alternatively, a shallow acrylic dome hatch may be lighter. At least acrylic would provide you with good upward visibility while surfacing.

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Alec Smyth via Personal_Submersibles
Sent: Tuesday, April 28, 2020 8:28 AM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] GRP hatch

Hank,

I'm only aware of a couple of subs with composite hulls, and the thing is I understand them to be not hand laid but constructed by the computer-controlled spinning of a single strand on a big megabucks machine. And even then, I'heard they discovered voids when cutting the hull open. 

The trick might be just to concentrate on emptying those MBT really fast by using bigger valves or more of them. That, or an MBT design that reduces the free surface area during diving, or which divides the surface areas into smaller ones via internal MBT bulkheads. I'm guessing you have something like that in mind? 

Thanks,
Alec

On Tue, Apr 28, 2020 at 10:13 AM hank pronk via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Alec, yes it is a bit out there.  I was thinking I would clamp one to the K350 hatch and sink it to test depth for testing.  I figures if there are GRP hulls then why not a hatch.  I do have a design for MBT's that could  solve the problem.  The sub is fine when submerged.  Maybe that is the safest solution

Hank

On Tuesday, April 28, 2020, 8:05:13 AM MDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote: 

Hi Hank,

Personally I'd have to research stress calculations in GRP before going that route. But even once that were figured out, the build variations in hand-laid GRP would make me sceptical of my own calculations. I suppose the alternative would be to make a number of them and test to destruction. It would have to be a number of them, not just a single sample, because evaluating standard deviation would be just as important as confirming the depth rating. That's rather painful, so for my part I'd look at other solutions.

Thanks,

Alec

On Tue, Apr 28, 2020 at 9:50 AM hank pronk via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Alec, I think Mike has a submarine parts warehouse lol.  I would like to use what I have, just so I don't have to make too many major modifications.  Have you ever heard od a GRP hatch?

Hank

On Tuesday, April 28, 2020, 7:44:51 AM MDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote: 

Hi Hank,

May I suggest speaking to Mike Caudle? He has two acrylic cylinder CTs, complete with hatches and all, that are beauties but I believe much lower displacement than the one on your project sub, and very lightweight because they are aluminum. If you can arrange a swap or something, one of those might be just what you need.

Best,

Alec

On Tue, Apr 28, 2020 at 9:17 AM hank pronk via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Hi All, I am have some real trouble with my DW style sub mods. If you recall it has an acrylic cylinder CT and a K350 hatch.  My problem is, the sub lacks volume to support the heavy hatch\land assembly.  I do plan to increase the volume by installing a larger diameter leg tube.  This volume increase is still not enough to give me enough buoyancy for stability during transition from surface to being submerged.  Options are to loose the cylinder and go with dome.   Make a lightweight hatch with GRP, or come up with a creative MBT that maintains buoyancy longer during submerging.  

Hank

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