[PSUBS-MAILIST] fiberglass shell

Wed Aug 12 21:55:58 EDT 2020

Brian,
what about sand! There are people that make some pretty sophisticated
sand sculptures. As an artist I developed a technique for taking sand patterns off
the beach. I would have a very diluted pva glue in a bottle with just a manual
spray mechanism. ( the type you might find in your kitchen) I would wet the sand with
a fine mist so as not to disturb the surface, give it several hours to dry, & 
repeat the process several times. I would then remove the pattern from the surrounding
sand & back it with fibreglass ( in situ on the beach) then take it home.
If you googled on sand sculpture you could make the form & then use my technique
to solidify it.
Alan

> On 13/08/2020, at 1:39 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Sounds like a lot of work.   With my hole method I could actually spray gel coat and get that gel coat exterior finish .  
> 
> Brian
> 
> 
> 
> --- personal_submersibles at psubs.org wrote:
> 
> From: David Colombo via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] fiberglass shell
> Date: Wed, 12 Aug 2020 14:48:45 -0700
> 
> Brian, four ft dia is a big cone. My suggestion would be to cut a plug out of styrofoam with a hot wire. Once rough sanded, skim coat with drywall mud and finish sand. Seal with Famwood Glaze Coat epoxy. Coat with a mold release agent and then layup a few layers of fiberglass to create the mold, then pull your part from the mold as usual. Should require minimal  finish work when complete. I will be doing this method in the next couple of weeks on a number of parts on the SeaQuestor.
> 
> 
> Best Regards,
> David Colombo
> 
> 804 College Ave
> Santa Rosa, CA. 95404
> (707) 536-1424
> www.SeaQuestor.com
> 
> 
> 
> On Wed, Aug 12, 2020 at 7:08 AM Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> Ian, Alan,  Thanks for your observations !    the cone I have to make will have to be pretty large , like around 4' in diameter .  It be easier to do a straight hemisphere but I was thinking more of a elongated cone shape . I'll have to play around with some parabolic shapes.   Yes I guess I've been looking at too many of Hank's videos, but I would like to keep the expense down .  Seems like a hole in the ground would be pretty cheap, I could get a couple of hombre's to dig the hole for me , and maybe get a plastering person to do the form as well.  I spent so much time on my previous mold it was just insane, so many steps !   
> 
> Brian
> 
> 
> 
> 
> 
> --- personal_submersibles at psubs.org wrote:
> 
> From: Ian Juby via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] fiberglass shell
> Date: Wed, 12 Aug 2020 09:45:29 -0400
> 
> Hi Brian,
> I've done a lot of working with (and sculpting with) plaster of paris - I love the stuff, but think you'll find it just makes a mess in this case because the surface will be near impossible to finish properly. Partly because of the size of area you need to work really, really fast just as it's setting up. How big does the cone need to be? And can it be spherical or does it have to be cone shaped?
> If I may suggest, a good old dollar store beachball or sports ball makes an excellent mold. You can inflate it to the right size, and then plaster that and put plastered burlap on the outside of the plaster to hold its shape. Simply deflate the ball to remove it, and now you have a nice, even, smooth finish plaster mold which will be much more easy to release your fiberglass from. And your fiberglass winds up with a super nice, smooth finish.
> Further to that, but along the same idea, you can get tons of cheap, inflatable pool toys that may have a cone shape you can use as well if you need a cone shape. 
> Just be aware that pressure changes will occur in the inflatable because of temperature variations. Namely, plaster will both heat up the ball and the air in the ball, and so the ball will expand. This was a fatal problem for me because I was trying to make a huge globe, so I either had to make it in two halves (and the halves would invariably wind up different sizes because of the variable expansion of the ball as a mold) or make one sealed sphere, which both trapped in the heat and the outward pressure of the air expanding inside the ball would stress the plaster mold and crack it. I had to have tolerances that were too tight so the two halves would match to make a sphere. But in your case, I suspect you have some tolerance and room for error on the size of the cone/sphere? So that shouldn't be a problem for you then.
> Do you have access to a wood lathe? Can you turn a stryrofoam blank and produce a mold from that? Or apply the fiberglass straight to the styrofoam? Sculpting fiberglas and getting a decent finish is a pain. You've got the right idea to make a mold in which to cast the cone - that's the best way. 
> For what it's worth, here's one short article on sculpting a fiberglass nose cone: https://www.apogeerockets.com/education/downloads/Newsletter413.pdf
> But by far and away, the best thing is to start with something cone-shaped and the right size already.
> Oh - if you can get away with a sphere, you can blow-mold a sphere as well. 
> 
> Ian
> 
> On Wed, Aug 12, 2020 at 12:32 AM Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> Alan,   I could coat the plaster of paris with resin and then polish that really well , then apply mold release to that , then shoot gel coat over the mold release , then fiberglass and resin over the gel coat.  I would bury some sort of lever underneath the cone so I could pry it out of the ground.
> 
> Brian
> 
>  
> 
> --- personal_submersibles at psubs.org wrote:
> 
> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] fiberglass shell
> Date: Wed, 12 Aug 2020 16:24:28 +1200
> 
> Hi Brian,
> I am hearing alarm bells. The plaster of Paris will have to be pretty dry & any
> resin from your fibreglassing would suck in to it unless you gave it several coats
> of shellac first then put on a mould release wax. This is from memory from a long
> time ago. Also I have vague memories of coating polystyrene with pva glue which
> doesn't dissolve the polystyrene, & fibreglassing on to that. 
> Will take a big block of polystyrene.
> Alan
> 
> On 12/08/2020, at 3:14 PM, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hi All,
>                I"m thinking of doing a fiberglass nose cone for the front of my sub which will have flotation foam in the top part of it.  This time rather than make a whole mold assembly I was thinking I would dig a large hole in the shape of the nose cone, use plaster to get it smooth and then just put fiberglass against the inside of the plaster.  Then lift the thing out and break off the plaster.  
> 
> Brian
> 
> 
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