german rubber method

Current image - Zipper III plug on top of Zipper III kevlar hull.

The hull fabrication method has got to be far superior to tan packing tape. You don’t have to sand out the ridges for one thing.


hey scott that is a good looking site. got some good info there.
keep up the good work

Ok the zipper III looks nice but I have to ask the logical question

What is the German Rubber Method???
And where can I find more info about it???


Yep, that?s basically it.
The carbon fiber (5.6 oz.) is sandwiched between two layers of fiberglass (1 oz.) and I would nor recommend the use of the CF/Kevlar hybrid tissue that I?ve used in mine, the end product was quite ?bendy? and definitely not rigid enough (plus the Kevlar is a real b?. to cut), next time I will go with CF alone. If you want a really stiff boat you can try to lay a light Kevlar cloth under CF (3.6 oz.) and fiberglass on top, but stay away from the inter-weaved stuff.
One last point, I didn?t invent this method, it was originally showed to the Minutemen MYC by the German girlfriend of one of their members, hence the name ?German rubber? <font color=“red”>(there is some discussion going on about the mane, it is felt that it could be considered a racial slur and it?s being changed to ?latex mold??? FYI), </font id=“red”>and I learned it from Jim Linville, and other members of the MMYC ?a real great bunch of guys ? this winter.
As Greg mentioned we will mold another hull this weekend and with his help, now that we have officially enrolled him in the ?Boat building club? we?ll see if he can get some nice pictures (I did start last time but forgot to keep going after the third ??. It sound easy but this method is definitely a ?two man job?) to post with a write up.

If you have any other questions, just ask.


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this sounds
very intresting
i cant wait for photos. it should be a very lite and strong hull.
i would like to hear more about this
kudos for you people

and greg
why do yu consider us germans( my dad was a kraut) kinky?

I really need to know, while this “Latex Mold” Hull is being made, where does Miss Whippy stand???

do i see? hmmmmmmmmmmmmmmmmmmmmmmmmmmm
canting keel? and bendable keel? strage chech?

At the risk of being serious. If you are building a boat with a destroyer type bow, how do you deal with the excess rubber(latex) on the first layer. You could never pull it tight enough to get rid of all the slack. Maybe packing tape for the first layer?

Vancouver Island

Going back on the technique (the lady with the whip will be on your lower left side if your on the port side of the mold wich is inverted, but it works well on the right side too), the main advantage of this method is the first latex layer smoothes out the mold without sticking to it to tightly so all the dings and dents are eliminated quickly and you don?t need an flawless plug.
I thought about using vacuum instead of the second latex layer, but it looked quite complicated and not real easy to bag the plug. This method is quite simple and quick once you know how to do it.
As for using the heat shrink wrap I think it would eliminate the advantages of the first latex layer, plus I?m not really convinced that the heating will do any good to the resin, yes it will make it runnier, but it will start polymerization too, and not uniformly, by working with west-system I found out that the temp needs to be in the 65-70 range but uniformly, like in a warm room or an oven (in that case I have a temp of 85 F).
Don, the bow is the though part, it needs some fantasy and trial and error, In my case I/we used camps and two pieces of wood to stretch and tight the latex, I think that the best solution for this part is not to have a bow, I mean have a bumper ready bow like an IOM.


What kind of latex do you use? I can see rubber glove type being about the right thickness but where does a person buy sheets of that stuff?

Vancouver Island

I have bought some carbon/ kevlar combo 5.4 oz. You are saying this stuff is no good or are you talking something lighter. You are calling yours tissue.

We got the latex from a medical supply company in CT, I don?t know witch or the address, I didn?t get the stuff, but if you do a careful Internet search (your still get a lot of ?alternative lifestyle? hits) you may find something in your area.

Hoj, my tissue is 6 oz. When I got it couple of years ago it just came out, or was relatively new (it was sold as a ?new? item where I got it) I only used to laminate balsa and worked good, When I had the plug done, had not enough CF -some in order- ad din?t wanna wait, so I thought I may use this stuff.
The results were OK, but I had to lay some CF inside the hull to provide some strength, the hull was strong but not stiff at all just by holding it you could dent it (something like squeezing a empty soda can to much). Probably the water pressure would have been enough to squeeze the hull in, especially in the bow section (because of the Zipper design). Somebody told me that if you want to have both strength (kevlar) and stiffness (CF) you should keep the two materials separated; two different layers and not interweaved like they are here (to strengthen their point they showed me a hull with 3.5 oz. CF sandwiched between Kevlar (inside), I think 3.2 oz, and 1 oz. Fiberglas, talk about a bullet proof hull, you could drive a nail with it?? OK I?m exaggerating, but to get the point)
I have now some 5.6 oz. CF in the hull and it?s much better, today I would go with cF alone or the two sepatate layers.

BTW this is a picture of what I?ve used :
OK I’ve problems getting the picture…[:-banghead]I will try later.


The rubber can be purchased in sheets from Greene Rubber in woburn Ma.

Give them a call, they can sell you any amount you need.


This was a great post. Many thanks for your efforts. It will encourage me to try this technique.

It doesn’t look like there is a lot of pressure applied by the latex. Do you think that a balsa plank hull could be used as the plug?

A balsa-planked plug, covered with 6 oz. Glass was actually my first (well second) plug. It didn?t work out to well, I was not really sure if the plug would be strong enough, there is actually quite some pressure on the plug especially with the second latex layer and when you roll out the bubbles, but what really made it hard to use was the way it was build. The plug was build with the classic method, shadows fixed on building board, and it would be very hard to stretch latex over it, almost impossible, the board and the shadows extensions form the deck line to the datum live were in the way. The plug would have required quite some modifications. I just took the easy and proven way and rebuild a solid plug??. It took me only two weeks of sporadic work and most of it was sanding.

If you want to try this method go with the solid plug.


After seeking a source for latex here in Sydney I’d appreciate knowing the common uses of the latex sheet used. We have silicon rubber from 0.3mm (not cheap) and rubber at 0.8 mm and 1.5mm. Are the properties of these comparable with Latex rubber?
If it is desired that a boat float a little higher then layers of latex could be added to effect the extra displacement sought.


I have two questions about the latex hull molding. From the pictures it looks like the fiberglass is several inches longer than the plug and therefore it must wrap around the plug. When do you trim this? Your follow-up post indicates that the latex can be reused. I can see myself cutting the first layer when trying to trim the cured fiberglass.

In light of the first question and the fact that the stern appears like is formed. How do you take the hull off the plug?


Yep, the FG and CF had about couple of inches overhang on each side, this was done on purpose, I wanted to generate a deck flange to stiffen the hull, and make the deck assembly easier. For this purpose the first latex layer was stapled tight at the deck/holding board junction, as the second layer. I timed the flanges after I pulled the hull from the plug and peeled off both latex layers, after 24 hrs of curing.
Pulling the hull from the plug is easy, it?s not bond to the plug, and once you unstapled both latex layers it just need a little wiggling and it slides off.
Well, I forgot to mention that the bow was still open, the first latex layer extend several inches from the bow and the FG/CF less than one, in this way the two bow haves are not joint together and you can gently pull them apart to lift and slide the hull (still attached to the inner latex layer) from the plug.

For more information you can check (if you haven?t done it already) the write up and picture on the GHMYC site ( Hope this is helping and if you have more questions, just ask.


I see where the last post to this thread was in 2003, so I may be too late to be helpful. Having just “pulled” my first hull, I thought some of my misadventures might be useful to others considering this method.

I designed the hull I wanted using Hullform, which I had downloaded maybe six months ago. It might have been longer ago than that, as we haven’t been back in our home in Slidell that long, following our three months evacuation for Katrina.

My intention was to build a planked hull first. While I liked the method for constructing a male plug sketched out on the Minute Man Model Yacht Club site,, the Hullform hadn’t produced any longitudinal forms. Maybe it can do so, but I had already printed out shadow shapes, so went with the planked construction instead. If the rubber method didn’t work, well, I could always use the plug to make a female mold.

I intended to use thin pine for planking, but after cutting out enough pine strips on the table saw to do the job, I discovered that it was difficult to get the pine planks to stick to the 1/4 inch plywood shadows with CA glue. I didn’t have enough pins, clamps, or whatever to use any other type of glue, so I switched to using 1/4 inch balsa. I had made no allowance for the thickness of the planking when I cut out the shadows because I had intended that the planking be thin enough that, for my first hull based only on what I thought looked good, the resulting additional “size” of the hull was as likely to be good as to be bad. Switching to 1/4 inch balsa therefore caused me some concern, but I have to say that the result looks about as I intended. Another mistake was not cutting away the shadows at the sheer, with the result that I could not tell with any accuracy after the hull was made just where I had intended the sheer to be. Finally, I messed up in figuring the spacing on the shadows and wound up three inches too short overall. I had already figured on making the bow from polystyrene foam insulation, so also made a stern from the stuff to make up the length. The foam is easy to work with, but flexes a little too readily to be good for use on a male plug. Next time I’ll try something a little stiffer. Balsa would be fine, I’m sure.

I did a terrible job of planking. In part this was because I was relying on being able to sand and fill to correct any problems, and in part it was just due to the difficulty in bending 1/4 inch thick balsa around the curves. The two advantages of the thick balsa were that I had little worry about sanding through the planking, and it was stiff enough to not flex away from the sanding block too much. Still, I had considerable difficulty getting the smoothness I had hoped for. I filled with wall jointing compound, sanded, put on a couple of coats of shellac to bind everything together and to provide better visual clues about how smooth I was getting the hull, sanded some more, filled with more joint compound, sanded, shellaced, etc., for several days. My sanding block was a 2x4 about 15 inches long, and most of the time I was using it lined up along the hull but moving it in diagonal patterns. When I was attempting only to smooth the surface, as opposed to shaping, I used a sanding sponge to back up 400 grit wet or dry paper used wet. The shaping was done with 80 and 100 grit dry paper.

While the hull still seemed to have imperfections I decided to go ahead with the rubber, fiberglass, and carbon fiber, anyway. For several of the hull smoothing sequences it had looked like just one more would make it perfect, so I had begun to suspect it wasn’t going to get much better unless I switched to some other type of filler.

The website above has links to suppliers of the latex sheets, and carbon fiber and fiberglass. I used 10 mil latex, as described on that website.

My hull has a “destroyer bow,” and it was difficult to pull the latex smooth over it. Then the latex split, right at the knuckle. Rather than make another attempt from scratch, I just waxed the plug in that location and went ahead. I found it fairly easy to staple the latex down to my construction board, and was able to get this part of the job done by myself. I waited until my wife was available to help in applying the epoxy to the fiberglass and carbon fiber. I think this was not actually necessary, as I was using West Marine’s system with 207 hardener, which is very slow. It may not even have been necessary to have help stapling the second layer of latex on top, with this slow system, but it is at least useful to have another pair of hands. If some care isn’t taken in stretching the top layer of latex, the whole mess might be slid around on the hull. Once the second layer of latex was stapled down, I got on with rolling the epoxy around to make sure everything was saturated, rolling out the air bubbles and excess epoxy.

The next day I pulled the top layer of latex off, then worked the hull off the mold. The bow resisted coming free, but this might not have been related to the split in the latex. The epoxy does not bond to the latex well, but it does bond well enough that the latex has to be “stretched free” somewhat. The hull at this point in the curing process was still pretty flexible, and that probably helped in working it free.

After allowing the hull another couple of days of curing on top of the plug, I glued in balsa strips at the sheer, then trimmed the hull down using a cutoff wheel in my Dremel, using a cylindrical sanding wheel for smoothing the edge left by the cutoff wheel.

I’d been a little careless with the latex top sheet, allowing a few wrinkles around the bow, and a couple at the stern that got up high enough on the form to remain after the hull was trimmed. Otherwise I’d say the result was nearly perfect. The hull came out light, thin, and smooth. I’m sure I’ll do better next time, but overall I have to say that the technique works well, and just about anyone can handle it, as I think I just proved.

Mike Biggs