The M1 Disaster

[Kazzer]

Moving along with my experiments.



Here is the mold, make of epoxy and sand poured over the plug.



I drilled through both parts to enable a bolt to go through and tighten the two parts together.
Next, I lined the inside of the mold with duct tape, which was then coated with PVA.
When the PVA had dried, I dropped the support struts over the top of the mold and screwed them into place.



Here, I have a bag of sharp sand -sold as play sand. I placed it on a tray and put it in an over at 200f for an hour, to remove moisture, as this has a tendency to make the resin foam prior to curing.

The resin was mixed together thoroughly, and the sand added slowly until the volume has at east doubled. The slurry was poured into the mold, to cover the Aluminum channel.

Now - we wait - tomorrow!

[Kazzer]

After a summer of gardening and out-door projects, I've at last found a little time to get back to the M1. Fortunately, I procured another model, so I'm going to use it as a master and produce a mold from it.

My plan is to produce an epoxy concrete mold, similar to my work with the conning tower. As I have been doing a lot of drywalling work in my new (old) house, I've been tripping over bits of drywall sheet all summer, and after stubbing my toe on a sheet one more time, the light bulb came on. Why not make the mold box out of drywall sheet?

Here's why I'm giving it a shot!

1. It's easy to cut, just use a utility knife.
2. It's very dimensionally stable, unlike plywood.
3. It's cheap.
4. It's very easy to fit together, drywall screws, compound and tape.
5. It's very easy to take apart, hopefully the master will be easily recovered.
6. Getting the inner box walls smooth is an easy sanding job.
7. Filling edges and gaps is also easy, a wipe with a compound knife, and it's sealed.
8. Sealing the drywall is easy, just brush on a couple of coats of KILZ sealer.

































































The two troughs here are walled about 3/4" higher than the 1/2 section of the model. The dark strip in the trough on the right is 1/8" thick hardboard, to make the keel section. The model has a notch in it so it sits on top of the keel section. You can see the penciled in outline of the model.

At this stage, the joints have been taped and filled with compound and are drying. I'll sand them lightly tomorrow and then fill again to ensure the trough is watertight, as I don't want any resin seeping out.






















Inside the model halves, I've glued in some blocks of wood with Crazy Foam. This is so I can screw them from the underside of the trough. I need them to fit tightly to the drywall sheet.
Once they are secure, I'll run some modelers clay along the edges to ensure I don't get resin underneath the model.




Next job is to cut a strip of drywall to fit over the model along the waterline. This will allow me to make a four section mold.

More to come! I'm enjoying this!

[Kazzer]

Well, today I feel like Thomas Edison! Mind you, a very poor Tom, and on one of his bad days!

He said, when an experiment went wrong, "At least I now know what DOESN'T work!"


To continue this saga -- Here is the entire mold removed from the drywall box.

I poured the epoxy mortar over one section of the plug and let it set up overnight. This morning I tried to remove the mold from the drywall box, and all my troubles began. Even after a couple of heavy coats of wax and several coats of PVA, the darned epoxy stuck to the drywall like crazy. I had to chisel it off, all the while sweating that I would damage my only plug.


I had a great pile of dusty old drywall to get rid of, and a big mess to clean up. So, at least I now know that DOESN'T work!


BUT!!!!!!!! Look below!!!!

Look carefully at the mold. Not a bubble, wrinkle or mark in it! PERFECT!!!!!



AND - it took me less than 5 minutes to pour that mortar into the box! Fiberglass layup would take much longer with much skill required, I'm sure.
I am particularly pleased with the sharp edges on the corners of the mold.

What to do next?

Drywall was a dumb idea, easy to assemble, impossible to take apart. I need to make the boxes from plywood and in such a way that all the box sides are easily taken apart. I'm inclined to think the wood needs to be coated with epoxy to prevent the wax soaking in. A smooth surface will also come away from the epoxy mortar.

I'm also unhappy with the blue clay i used to fill the gap of the dividing board that want along the waterline to split the mold. It's difficult to get this to fit tightly and its easy to get this uneven, so the waterline would not be straight. More ideas required here. Maybe I should try using a car body filler for that gap? Then I could sand off the excess and make it a smooth and tight edge?

[greenman407]

I think that your having way too much fun! I should come over and help you fix it real good.:biggrin:

[Kazzer]

This time I made the box from Melamine coated MDF.

The keel is made from 1/8" hardboard and the model hull has been filled with Great Stuff foam and blocks of wood, to enable me to put screws in from underneath and pull the hull down to the board fairly tightly. Gaps were filled with Alumilite Clay.

I sealed the edges of the MDF with water based Latex caulk.

The inside has been coated with Freeman Wax. Next, two coats of PVA.

[Kazzer]

After mixing up the epoxy and sand, I poured it into the mold and let it cure out for a few hours. It was still warm from the exotherm when I pulled the box edges off and tried to get the hull out without messing it up. It came out easily, as you can see. The blocks of wood inside the model were used to screw into from the underside.

Since doing this first mold, I've worked out a better way of fixing the model to the board.

Mark where you want the model to sit, and if this is the second half, then ensure its going to line up with the first mold. I ensured the waterline marks were the same distance from the mold edge.

Then I pumped Great Stuff foam underneath the model, dropped a 20lb bag of lead shot on top, and let it cure out overnight. It's a bit messy, but easy to clean up with a knife.

Next morning I inspected the work and found I'd pumped too much foam in and the ends of the boat had lifted up.So now I'm stripping that out and re doing it, but with only an occasional dab of the goo!

[greenman407]

I found this picture the other day and thought that it might go well here in this thread.

[Kazzer]

Today I made the mold for the starboard side of the M1.

Some modifications I made to the technique.

1. I gave up the idea of placing wooden blocks inside the model and instead blew Great Stuff foam underneath it and then placed it onto the MDF board. Initially, I pumped in too much foam and this expanded to the extent that the hull had lifted from the MDF by 1/8-1/4". I had to rip it all off and start again. My next effort I pumped foam under each end and in the middle, which allowed the foam to spread sideways. The foam glued the hull to the MDF perfectly! No screws!
2. I treated all the corners, edges, joints etc. with a lick of latex water based caulk, jut to prevent any resin from creeping out.




Before I glued the hull to the MDF I measured the other mold and tried to make the location of this hull in exactly the same position (Note - I DO NOT use the phrase 'exact same')




After pouring the resin/sand mix into the mold and leaving it for 5 hours, I stripped off the MDF board and removed the hull plug.




Here's the second mold, and as I spent a little time poking a paint stirrer stick around the edges as I poured in the mix, I have NO bubbles! And the PVA let the hull fall out of the mold - yet again.
The gods are good- today!

Note the T class in the background!

[He Who Shall Not Be Named]

I'll be damned, Mike! I think you have changed the way we do tooling, my friend. Truly good, innovative stuff there.

David,

[Kazzer]

I'll be damned, Mike! I think you have changed the way we do tooling, my friend. Truly good, innovative stuff there.

David,

Yes, I know! Pure genius! You can all bow and scrape - and send me gifts to express your adoration! Cash is best!

[Kazzer]

My Freeman Wax Sheets turned up today and never having used this stuff before, I was keen to try it.

My idea is to line the M1 molds with a 1/16" layer of removable wax, before I poured in more epoxy mortar. Why? Because I want a plug to put into the mold once I've lined it with a sheet of fiberglass and epoxy resin. I figure that one coat of epoxy and one sheet of woven glass would be quick and easy to do. The plug would apply pressure to the resin, and hopefully it would squish into every corner! We'll see!



The wax boards at 70 f are fairly stiff, so I stole my wife's hair drier and warmed up the sheets to make them sag into the mold.
A quick trim with a knife and the job was done in a matter of minutes. I did poke my finger through in one place where I must have warmed it too much, but this stuff is easy to repair.

I also built up areas where the model needs strength, like the knife edge of the bow. See center picture. Tomorrow, I will rig up some cross bars to hold the plug in the correct position to guarantee I get a 1/16" gap between the mold.

[He Who Shall Not Be Named]

This is an aspect of tool making I've never explored, Mike.

What you are doing with the new tool-making resin, and now the wax to form an annular space between tool cavity surface and displacing plug, is innovative, possibly process changing work. Good stuff, my friend.

David

[Kazzer]

Last job tonight was to add the bars to hold the plug. I used some scrap aluminum extrusion, and dropped two screws into the middle and then screwed the ends down onto the mold block. When I pour the resin tomorrow, the dangling screws will be well embedded into the plug.




Oh! Gawd! I got my toes in the photo!

[trout]

Mike,
I like the idea of using wax as a fill for the mold. Is that a common practice or did you come up with that? What is freeman wax?
Peace,
Tom

[Scott T]

Hi Mike,
Should you also put a layer of wax on the flat surfaces to give room for the excess resin the plug you are making
will push out?

Scott