Building A sub Mold

[Guest]

I have just finished a plug of a Balao class sub, 63 inches long. I need info for the next step in making a fiber glass ? mold so that I can make more than one boat. thanks. Dude

[JWLaRue]

.....moved to the General forum

.....moved to the General forum and out of the tips & tricks forum.....

[cougar]

dude .
i am in the

dude .
i am in the same spot. i have a plug for a 1/48 scale gato and a 1/72 scale 571 nautilus. just need to know how to make the 2 or 3 part mold. any help out there for us?
cougar

[carcharadon]

Fiberglass molds are difficult to

Fiberglass molds are difficult to make. You want a mold that won't warp so there has to be a substantial amount of fiberglass or resin actually around the plug. Make a box out of cheap pinewood and be sure it doesn't leak. Whenever large amounts of resin are used you have to be careful not to add too much catalyst otherwise the resin generates a lot of heat and cracks. You can use fill material such as small blocks of wood to reduce the amount of resin needed. More than likely even with the proper amount of catalyst the resin will probably crack. Large blocks or volumes of resin require less catalyst than what is recommended. Thin layers of resin require more. To work around this complete your mold with the first pour to about half inch below the halfway mark of the plug. After the resin solidifies top off the remaining half inch. This should fill in any cracks and since the volume is much less then the first pour it should not generate much heat. Be sure to thoroughly mix the catalyst with the resin you cannot mix enough otherwise you could end up with a soft spot in your mold.

On the plug itself first prepare with a layer of parting wax, and then spray with the liquid part all or part off something like that. It's an alcohol based release agent that’s soluble in water. Support the plug in the wooden box on chunks of fiberglass resin before pouring. So after the mold resin hardens and you want to release your plug add water, which should dissolve the alcohol based release agent. The wax is hard to get off but if you want to save your plug it’s a good idea.

Also here's a suggestion that I have not used myself but have thought about. Since you risk your plug when making a mold you might want to try using a piece of PVC pipe larger than your plug. If you've made a successful mold for the PVC pipe, then it's just a simple matter of putting your plug in the PVC pipe mold. This way you get some experience and if it turns out right you haven't wasted any resin and you can finish with the correct plug.



Edited By Carcharadon on 1103121604

[boatbuilder1]

see this site guys

http://www.fibreglast.com/

see this site guys

http://www.fibreglast.com/ they are great people tp deal with and have a ton of referance books and vhs available
I highly recommend getting one if not a few vhs to see what is entailed in grp mold making
the next site is quite good for pictorial referance

http://www.cstsales.com/HTFiberglassMold.htm

hope this helps

[Rick Teskey]

First off decide if it

First off decide if it will be a 2 or 3 piece mold , this is determined by the amount of under cuts or shape of the plug..
Think of an egg , then visualise a horizontal split a long the circumference length wise.
If you are too high or low your plug will be key locked in the mold so you would need a seam 90 degrees too that point.
Wax the heck out of the plug about 10 seperate thin coats buffed between the coats till it is smooth as glass. then having decided where too part the mold lay a strip of tape along the seam and then hot glue a piece of plastic card ( I prefer the plasticore stuff) along the edge of the tape , not the plug , this will be the basis for your first flange in making a hard glass mold. along the flange you can put a blob of plastercine too create an indexing key for regestry of the halfs.
When this is done pva ( poly vynal alchol) the exposed plug and flange. When dry apply 2 seperate coats of gel coat letting each harden between each coat. then start laying up several layers of 2 , 4 ,6 ,10 oz cloth letting each on cure a day till the whole lot is aprox 1/8th -3/16 thick depending on how many pulls you want from the mold.
When this step is done remove the tape and plastic backing and indexing keys , now you have a surface too lay up the other half of the mold,but do not remove the plug from the mold, just wax the flange and pva it and repeat the lay up.
This will give you a 2 piece mold.
Now befor you split the mold halfs drill the flange for 1/4 inch bolts too secure the 2 halves together when you do your lay up this makes removing the finished part possible with out being key locked in a negitive.
I hope this helps.
I belivev Dave Merriman covered this topic in previous reports.
Take your time , plan and try too visualise the process this will help avoid problems.
This is the basic steps mixing and measuring the materials is critical or you will have a guey mess and destroy months of work.
When indoubt seek out a glass shop, pick their brains or ask them what they would charge you too make the mold.
Making a mold can be done but it will only reflect the effort you have put into the plug , if it is bent or warpped so will the parts be .
Depending on what the plug is made of it may or maynot survive the molding process.
Styrofoam alone will not last if that is you building material , it must be encapsulated in bondo or glass too retain its shape .
Also try a noncritical smaller part too experement on too get you feet wet.
Rick

[eckloss]

...what about a brushable rubber

...what about a brushable rubber material to use for the innermost layer of a mold, then supprted by plaster or resins? can someone suggest a specific brushable rubber?

[boatbuilder1]

any rtv rubber can be

any rtv rubber can be brushed on but there are specific types that are formulated for this they are a bit thicker and have a peculiar way of preventing runs and drips anti gravity wow
I was refered here by big Dave Merriman]http://www.bjbenterprises.com/products/product3.html[/url]
and this one I found a few years back

http://www.shopmaninc.com/moldmaking.html

I am still working on my halibut masters and plan to use a 1/2 rtv jacket then back it with fiberglass
chuck

[Guest]

I've found that you can

I've found that you can purchase thixotropic additives, which you can add to RTV rubber to thicken it for brushing onto a mould.

Therefore, you only need to select the shore hardness you require- dependant upon on the undercut of your mould- and purchase a tin of rubber with the correct additive.

I've used rubber from Smooth-on, including their urethane range, which is worth a go as it's very, very tough.

Also used RTV slicone rubber from Alec Tiranti.

Andy

[carcharadon]

Dude, I've uploaded a picture

Dude, I've uploaded a picture of a simple mold for the Nautilus wheelhouse and a cast using the mold in clear resin with a tint of blue to my SC webpage.


http://www.subcommittee.com/SubComm....rID=184

[bob the builder]

I've used Smooth-On's Brush on

I've used Smooth-On's Brush on 50 rubber for my Nautilus. It's cheaper than the higher quality rubbers, but more than adequate for most jobs that aren't professional, museum quality pieces, or pieces requiring a huge number of pulls. I think I've pulled about a dozen or so from mine, and they still look new.

A full write up on my mold-making process can be found by clicking here]Nautilus Mold Making Writeup[/url]