Molding a Hull Using the “German Rubber” Method. by Geovanni Rompato, Greg Vasileff
I learned this procedure from Jim Linville and the friendly people from the Minuteman MYC. It’s fairly simple and fast once you get the hang of it.
The materials you will need are:
* Hull plug, mine is the Zipper III, a USOM designed by Steve Andre, made out of MDF that I I built during the winter (the plug is fixed on a 2x8 or 1x10 wood board). * Staple gun, and staples (a lot) Two latex sheets big enough to cover the hull completely and allow for 10” overhang on each side (minimum). * Fiberglass, 1 - .7 oz. (I personally prefer the 1 oz.) enough to cover the hull twice. * CF, I used plain weave 5.7 oz fabric. * Epoxy (west system 105 and 206 slow hardener) – The pumps are a must!! * Acid brushes, mixing sticks, disposable containers, and plastic bags to cover the floor… * GLOVES (the epoxy is toxic) * A hard rubber roller sold at most artist shops.
Once you have all the necessary materials, your mold is ready and fixed on the wood board and the floor protected from epoxy spills, the fiberglass and CF cut to size you are all set and ready to go. The first step is to cover the plug with the first layer of latex. Just lay the latex over the plug and eliminate all the wrinkles. Starting from the center of the hull using the staple gun fix the latex on the wood board (use pieces of cardboard so that the staples don’t rip the latex) on one side of the plug, once your done move on to the opposite site of the plug ad stretch the latex, tightly but not to much, and staple it to the wood board as you did before (Be careful to staple the latex as close as possible to the inverted deck of the plug, in this way you will generate a flange on your hull that you can trim or keep for more hull strength). Work your way towards the bow and stern of the plug, always alternating sides to cover the plug nice and tightly. Once this is done, lay your first inner fiberglass layer, followed by the CF and the outside glass layer, smooth out the fabrics by hand so that no bubbles/creases are visible and the layers are covering the plug nicely. Once your satisfied with the look its time to wet the fabrics with epoxy. I use the West System 105 with 206 slow hardener, four pumps of each are enough for this particular hull, start from the center line and work your way forward and aft, don’t worry about making sure all the layers are wet just apply a nice and even amount. Once this part is done cover the wet plus with the second latex layer and repeat the stretching/stapling, don’t worry too much about bubbles. Once the second latex layer is nicely stretched over the plug using the roller rolls the bubbles out, along with the excess epoxy starting form the centerline of the boat and working along the sides so to move the excess epoxy on the deck. This step has to be done carefully to ensure a nice and smooth end product without to many dry spots or excess epoxy. Once your satisfy with your work let the epoxy cure at least 24 hrs. at 60-70˚F to ensure an even and complete polymerization before peeling off the first latex layer. At this time you can carefully take the plug hull from the plug and peel of the inner latex layer as well or you can wait for another 12 hrs. before doing it. In any case the hull should cure on the plug for another 4-5 days to ensure a complete curing and hardening of the epoxy.
Geo
NOTE: I will post photos of the finished hull soon. It was still in the mold when I did this page I will aslo get the type and sorce of latex used.
 The Plug. Shaped from MDF.
|
 Geo lays the first sheet of latex over the plug.
|
 It's a two man job. Geo stretches the latex while Ron staples it using cardboard strips.
|
 Stapling the cardboard so the staple don't tear the latex.
|
 Geo makes sure the latex is stretched smooth while Ron staples away.
|
 The bow section is the toughest part, especially on this very narrow bow of the Z-III
|
 Ron clamps up the bow.
|
 The latex makes a real smooth surface on the plug. Not it's time to do the easy work.
|
 First a sheet of .75oz. fiberglass cloth is laid over the plug.
|
 Next, a sheet of 5.7oz Carbon Fiber is laid over the glass.
|
 ...then another sheet of .75oz. fiberglass cloth.
|
 Ron and Geo start wetting down the layers with West Systems epoxy with slow hardener #206. They start from the center line and work their way forward and aft ...
|
 ...and then down the sides. About four pumps of hardener and resin were used on the entire hull.
|
 Laying on the epoxy is complete. Geo is very careful to go light. Ron and Geo are now ready to lay the second sheet of latex over the hull.
|
 Laying the latex.
|
 Geo gingerly smoothes out the latex.
|
 ...and now back to the work of stretching out the latex.
|
 All done. Note the air pockets under the latex. ....
|
 ... Geo rolls them out, along with the excess epoxy.
|
 All done. Ron will pull the hull in a day or so.
|
|