US1M Mistral Construction Project

Tom - Don’t stop posting photos - as this was one big sticking point early in the year … Too many ideas and theories, and few (if any) results to see! Tired of “hearing” about stuff - photos save a ton of words.

Keep posting them as I was intrigued by the process (ummm - until the 80 lbs. of mold mix registered with the brain [:-graduate]) and will like to see the basic steps toward completion. While I can’t speak for everyone, the “process” is important to a lot of people, especially those who may have purchased a boat, but now would like to try their hand at building one.

Photos of a “process” are as important as photos of a completed boat, so keep them coming - just at a smaller size ! I already see some possible use (but at less pounds) for other items as well.

Wow, Looks awesome! What is this UltraCal? is that like Plaster of paris? How long did you let it dry before you started waxing?

The Ultracal 60 (or 30) is more like cement than plaster. The 60 is 60 minutes till it hardens or 30 for 30 minutes.
It is used extensivly in the tool and die business and pattern making business. Unlike plaster which is farely soft when cured, Ultracal hardens rock hard like a stone.
The one thing is it has an extremly small shink rate of only 0.065. (No shrinkage)
I can see this stuff being great for keels and rudders and small things like that. Being this stuff is small production run quality, you should be able to pull 100 or so hulls with no problem. I also let it sit for 2 days before I began laying down the thin epoxy coats in the mold to seal it.

it can also be a great medium for casting lead bulbs

Well, I have finally completed the mold.
I must say it came out way better than I expected it to. As you can tell, almost a month later I finally found the key to a smooth mold. I used the West epoxy with the graphite filler to coat the inside of the mold with a thin coating. I would then use 180 grit and the then 400 grit followed up with a 800 grit wet sanding. With all the foam brush marks being sanded down (the low spots will remain shiney black) you sand until the entire surface is matt black. I went a little deep in some spots and exposed the Ultracal in a few areas so I just added another coat of the graphite mixed epoxy. Once the entire mold was matt black with no read through, I gave it a 2000 grit wet sand. Glass smooth [:D] The white band you are seeing in the mold is the floresent lighting reflecting in it. I then gave the mold 6 coats of the mold release wax. Nice and slippery now. Now I need to add the part all liquid and finally begin to make the carbon fiber hull. The main reason for choosing black for the mold is it will be very easy to see where the epoxy is layed down on the cloth. It will gloss right up where the epoxy is placed. I will go into detail as to what epoxy I will be using for the hull once I get going on it.


This is brilliant Tom. Can’t wait to see the next step…


Hey tom!

Lookin good. I am intreagued to see how this turns out for you. I would however encourage one thing from my experience. Take that mixture of west system and graphite, and apply some to the top surface of your mold. When you are laying up a hull you will cut the cloth larger than the actual hull and it will drape over onto those flat surfaces. it will be easier to remove the part, and clean the tool if it is nice and slippery just like your molding surface.

Quick question if you dont mind me asking. . . how much did the 85 lbs of ultracel cost?

This looks like a good quick way to build molds and am considering it, or a slight variation using a slightly different substance.


The top of the mold has 3 coats of just clear epoxy on it. It also has the 6 coats of mold release wax and will also be PVA coated.
As for the Ultracal 60 or 30, it is produced by US Gypsum and it runs about $30 for a 100lb. bag. It also comes in 10 and 20lb. boxes.


Have you ever actually used this for a lead mold? I know that plaster baked at 250 degrees for 48 hours still had moisture and failed when the lead was poured in. If this can be used for lead casting it would be a real treat.

I too would be really interested in using this to cast a bulb. And a keel fin.


Hey guys,
Lead melts at 621 deg F and this might be to high of a temp to not have it crack. US Gypsum does make a similar product that is made specifically to cast metal with. I am sure this would work much better for casting lead.


The temp is usually not the problem with lead, but the moisture. If you have any moisture in the mold at all… the lead will find it and change it to steam instantly and then you have lead flying around… not fun. I have emailed these guys and if I get anything from them I will forward it along.


The drier the mold the better the pour.
Less air entrapment and a smoother finish and a sight increase in density.

I can remember in the good old days (30 years ago)when I hepled in pouring keels for a production 25 footer in concrete molds. The last pour of lead was far better out of the mold than the first one of the production run. The mold was drier and warmer.

I believe these days steel moulds are used, these wpould need to be preheated to get good flow of the lead.

this could help

My father is a dentist and I saw him using a vibrating machine to avoid air aso… when he is mixing stuff


_/ if it isn’t broken, don’t fix it! _

As a kid, I remember my grandfather making lead fishing sinkers by pushing a hole into the clay ground in the back yard, and pouring the lead straight in. The clay was always damp, and there was certainly a fair amount of steam and spitting. I don’t recall any major burns - probably through good luck only. Are yes - we were reckless in the good ol’ days eh?


Not to mention that if any of the lead got away… particularly the slag on top, that it is a Hazardous Material that the EPA will fine the living $#!t out of you for contaminating the Earth. I have to recover the nasty stuff and store it in a concrete container and then return it to the local foundry for disposal. Granted we live over an Aquifer, so they are more than anal about it… but… this is something that you really don’t goof around with. Dog licks it… death, you breath it… death, you touch it… it is in you forever… I guess like anything else these days… if it is fun… it will probably kill you sooner or later. I wear a clean suit and respirator everytime, and it is still getting to me somewhere I am sure. Oh well… Superman won’t be able to see what I have in my back pocket.

Safety whats that.

We use to wear shorts and t shirt and probably jandels.
The fire was lite under the melting pot, every now and then disel was thrown on.
Once melted the lead was piped to the mould.
The sag was scooped off and dumpped on the ground.
The whole process was lubricated with the sponsers fine products “Lion Red” in quart bottles and crates.

Ar the good old days when you could do anything you wanted without a person in a suit telling how to done it, and forms to full in.

Don’t want to go off topic - or get too political here - but see post in PUB !

Easy guys…back to the subject at hand.
Well,I layed down the epoxy clear coat last night. When it was tacky but not coming off on my finger tip, I layed in two layers of uni-directional carbon cloth. It layed down very nicely into the corners and up the sides. I also added an extra piece in the nose area and two extra larger pieces in the area of the keel. Once the epoxy was still slightly tacky but still soft, I trimmed the excess cloth from the top of the mold off with a new xacto blade. Once it hardened overnight, I then sanded down the deck edge while it was still in the mold. I figured it would never be as flat as it was in the mold.

Well, today…the moment of truth.[:-shake][:-shake] I loosend the edge and began to use some compressed air to break it free from the mold and while I was working it…POP…it broke free. I crossed my fingers and flipped it over to see what I had. [:D][:D] It came out perfect!! I then washed off the PVA with some water.

Mmmmmm…carbon fiber…[:-drool][:-drool]
You know most people think that the way you get that mile thick depth clear gel coat is to cake it on really thick. But the truth is (as I was told from a guy who does this for a living) is that you put the clear gel coat on super thin. I am talking .003 thick. Really thin. You are then using the optics of the carbon fiber to give it the really deep depth. You know what, he was right. Just take a look at the picture below. I kid you not, it looks like the weave is 1/4" thick.

Now it is time to start thinking about the deck and all the guts that will go inside. Back to the AMYA US1M manual.


VERY nice…great


_/ if it isn’t broken, don’t fix it! _