The M1 Disaster

[Kazzer]

Won't silicone inhibit the cure of the resin?

Not that I've ever noticed.

[He Who Shall Not Be Named]

Er! Moving on ......

[ATTACH=CONFIG]8839[/ATTACH]
Firstly, I filled the hulls with Crazy Foam, and placed some blocks of wood into it, to enable me to screw into the hull and pull it onto the melamine board.

[ATTACH=CONFIG]8840[/ATTACH]
I cut the profile out of the pine board and screwed it on top of the 1/2 hull. There was a gap between the board and the model, so I filled that with modelers clay and smoothed it out.


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Here is the completed article, duly coated with Carnuba wax and silicone.
The next job is to lay up epoxy and fiberglass tape in stages, to ensure the edge detail of the mold is captured correctly.

No! Like Andy alluded too: wipe off that silicon. Don't smear on the fillet and gel-coat till you put down a good layer of PVA, damit!

You're do'n good; don't screw it up now, Mike!

David,

[Kazzer]

Well, I'm not happy with the first result of making a mold. The tight edges on this model are very difficult to get glass fiber into, and my mold had several blow holes in it. I messed and fiddled with chopped strand etc. and after a while though to myself :"Why are you doing this?" Answer, because this is what everyone else does to make a mold.

I've never been a fan of following the flock, so I decided to give MY method a go, but on a small scale first. I've made numerous molds in the past using epoxy mortar. What is that? I hear you say.
It's simply a slow cure 100% solids (no solvent mixed in) epoxy, with a sharp, clean, dry sand added, to the point that the mix is a sloppy slurry, a little like a cow pat at spring flush (for you country folks).



In the picture above, we have the conning tower of the M1.

I have filled the inside of it with Crazy Foam, to keep the sides etc. stable, cut off excess that spewed through the top, then skimmed it over with Sandit Evercoat filler. That's the pink stuff you can see. I've also used this to fill in minor blemishes.

I made a box out of plywood and cut out one panel slightly oversize over the centerline of the tower. The gap has been filled with modelers clay - that's the blue stuff.

All the wood, the conning tower, and the Melamine base were coated with Freeman Release wax. The tower was screwed down with drywall screws coming up from the underside.

Finally, the last panel was screwed into place in the front. It was removed here to show you what was going on.




In the picture above, the slurry epoxy was poured into the mold, on the side where the edge was on the center line.
After pouring, the mold was lightly tapped numerous times to shake any bubbles out.

A piece of steel rod was dropped into the resin to act as a reinforcing bar.




Success! The resin has set and the now the mold needs to be cleaned of the modelers clay, then the other half of the mold can be poured.

Tomorrow!

[He Who Shall Not Be Named]

Looking forward to the next move, Mike. You might be onto something.

David

[Albion]

I'm in process of joining the two halves of mine, little bit of a disconnect but not too bad. I cut away the excess over the weekend.

Being that i live in a hot environment, do you think that "ageing" my hull, IE letting it settle after joining the two halves, will mean that it wont go "ping" into a funny shape when i cut it open at the join.

Also do you think W/L is a good place for the cut, that's going to give me about 3 1/2 - 3 3/4" gap to get a 2 1/2" WTC into

[Kazzer]

Being that i live in a hot environment, do you think that "ageing" my hull, IE letting it settle after joining the two halves, will mean that it wont go "ping" into a funny shape when i cut it open at the join.

Also do you think W/L is a good place for the cut, that's going to give me about 3 1/2 - 3 3/4" gap to get a 2 1/2" WTC into

I'm not sure about that, I've never tried it. When I have hopefully finished these molds, we'll have the 'cut' positioned at the waterline, so the hull halves will be the correct way for an r/c boat.

This will also allow for the stern to be easily accessed, an area I always have problems with getting into to put in things like yokes.

[Kazzer]

I have a little submarine tale to tell regarding epoxy mortar.

Millions of years ago, I was a distributor for Belzona Molecular, (out of Harrogate, Yorks). I sold a range of epoxy mortars in kit form, and I was asked by the Department of The Environment (DOE) to repair the edges of a lift gate which lead down a mine shaft in the village of Corsham, Wilts. The shaft was dug at a 45 degree angle and had a platform which descended some 75 feet below ground.


Underground was a myriad of huge tunnels, dug in the days when large quantities of stone was quarried for the construction of the cities of London and Bath. These tunnels were 30+ feet wide and the ceilings, in places were 20 feet high. It was a hive of industry, an underground city, vehicles, traffic lights, and people everywhere. Why? Not for stone, but it was the Royal Navy Submarine Spares storage facility!

My job was to repair the edge of the concrete where the platform met the joined the floor. A huge steel gate descended when the platform descended to the mine.
I was originally going to make a wooden former, then trowel up the mortar to that, but when I arrived there on a Saturday morning, I had a change of heart. It was so much work, and there was the steel gate edge, butting up nicely. I could get a really good fit if I just waxed up the edge of the gate?

I raised the gate, it was about 20' wide, and coated it with wax (correctly called Release Agent) and set to work knocking out all the loose bits of concrete. After priming the concrete with resin, I lowered the gate, mixed up the mortar and troweled it in, skimming it perfectly using the gate as the edge. It looked perfect!

I went home with a smug look on my face, I think I stopped and had a pint on the way to celebrate a job well done!

Sunday morning, I returned, to check on the cure and tidy up.

I pressed the button to raise the gate, and the motor whined and struggled. The damned gate was well and truly stuck. It would not budge. Oh! Dear! Was I in for it now. Thoughts of WWIII starting that morning, and no spares for our lad's submarines because we couldn't get the damned gate open, ran through my mind.

I said to myself, "Don't Panic, don't panic!" just like Mr. Jones The Butcher, in Dad's Army. But I did, and ran around for several minutes like a chicken with its head cut off.

Fortunately, I found a sledge hammer somewhere nearby, and a proceeded to whack the bottom of the gate, from one end to another for about 15 minutes. It was a terrible din, but thankfully, being Sunday, not many folks were around. Eventually, the motor stopped whining the release agent worked, and the gate sprang up and sedately raised to its full open position.

On Monday, I reported to the DOE Clerk of Works, and we strolled over to look at the job. Boy, were they impressed! "How did you get it troweled up so smoothly and tightly fitting?" they asked. I just smiled and said nothing, as I accepted all their praises for a job very well done.

[Subculture]

When dealing with sharp corners in laminates I always mix glass chippings in with the resin to form a radius. Then lay the CSM/cloth over that.

Works everytime.

I should say that I use polyester resin, as opposed to epoxy, but the principles appear to be the same.

[Kazzer]

When dealing with sharp corners in laminates I always mix glass chippings in with the resin to form a radius. Then lay the CSM/cloth over that.

I think we call that material crushed glass, and it comes in different grit sizes.

We also have a material called Cabosil, which is made up of micro sized particles of hollow glass balls. It's a very good resin thickener. It doesn't slump very well, whereas the crushed glass probably would, making it preferable for my application.

I don't think it matters whether it is epoxy or polyester, I only use epoxy because I have it in 50 gal drums.

[Kazzer]

Here's an update on the process I've employed to make master molds for the M1. The experiment has been carried out on the conning tower.


I used a 1/2" drill to drill 3/16" deep holes in the face of the first half of the mold to produce registration marks, male and female, in the finished product.

After pouring the second half of the mold, using the face of the first half as the part line, I placed the two sections in an oven at 120f for 4 hours, just to speed up the process.

The main mold split apart extremely well, and I used no PVA, just the Freeman Release Agent.

I'm going to say that this is a rip-roaring success!
I love the stability of the mold. The aggregate bulking it out gives it great dimensional stability, there will be no flexing here. I see a couple of very small dings in the surface, but these will leave minor bumps in the finished product, and are easily sanded.
As for longevity of the mold, I'd say it was pretty indestructible.

I guess the real test now is to bolt the two halves together and cast something.

[Rpmtech1]

Damn look at Mike go! I love it.

Polyester sucks for tooling, brittle, lots of shrinkage etc. You got it right using epoxy from the start!

Sometimes its to your advantage to have the tooling a little flexable, depending on the part. Lets you pop the part out easier.

I would ALWAYS use PVA for composite parts. One time of the objects bonding themselves together and having to throw it all in the trash cures you really fast of skipping PVA LOL

Keep at it!

[Subculture]

I agree that epoxy does have superior properties to polyester, although I've found it can behave oddly in some respects especially in the way it softens when worked. However if you use polyester resin properly, and consolidate the laminate well I find it does the job. It's also important to peg mouldings and tools to prevent movement, although even epoxy will creep over time if it isn't indexed in some way, although not quite to the degree polyester will.

Epoxy is much expensive in the UK than polyester resin, at least four times the price, and if you're laying up a larger boat the price soon creeps up. No surprises then that just about any model sub hull made the UK will be made from polyester resin.

[Subculture]

BTW, a tip I picked up on the net- hairspray works quite well in place of PVA. Or use it over the wax first then apply a coat of PVA- guaranteed release everytime, and it sweetens the smell of your tooling!

[Kazzer]

Epoxy is much expensive in the UK than polyester resin, at least four times the price, and if you're laying up a larger boat the price soon creeps up. No surprises then that just about any model sub hull made the UK will be made from polyester resin.

Agreed that as a rule epoxy will be more expensive purchased in similar quantities, and most model makers buy a few gallons at a time - at most. I buy 2-4 x 50 gal drums of epoxy at a time, which probably makes my epoxy actually cheaper per gal. than buying a couple of gallons of polyester.

[Rpmtech1]

Its not bad to make parts from, just tools that have a lot of detail wont last. i dont know what your talking about when you say it has "odd softening" never heard of that.

Polyester has its place for sure though ;) i use it for cheap one time use tools. cures very fast