brunnhilde's cassette toilet - part 4

This weekend I got around to conduct the bonding test on what I presumed a shower pan made of ABS.


my 7d died so I took the new photos with the iphone; this camera and zoom lens has been with me through thick and thin; I can't see carrying a better but heaver combo when travelling

I found a small area on the raised platform for the old toilet to test. Should anything goes wrong I can always abort the project. I wanted first to verify the pan is made of ABS or other plastic of similar properties. I took a small cotton cloth remnant and dabbed it with some lacquer thinner to test on the surface. This serves two purposes. To determine the characteristic of the pan material, and to prepare it for the bond strength with epoxy resin that I set out to use. I could use either lacquer thinner or acetone but the latter is way too aggressive to be used unless extreme care is exercised.

p.s. acetone is what some professionals used to clean optical lens used in aviation and space applications. It cannot be used with lens mounted with anything acetone can attack.

Sure enough rubbing the small spot on the shower pan remove the surface dirt as well as dissolved the plastic. This confirmed it is ABS or ABS-like plastic.

Next I mixed up a tiny bit of West System's epoxy resin. It is odd. The 205 hardener is a deep reddish brown. I cannot remember it was this color when I last used it 15 years ago. Pulling up the data sheet yields some clue. It says the hardener will darken in color with age but should not affect the other properties. I bet who wrote the data sheet did not expect anyone would attempt to use such old compounds. Actually seeing that the lacquer thinner can dissolve the pan material, I thought to myself it should rough up the surface enough to from a strong bond with epoxy. I almost decide not to conduct the bond strength test thinking with little doubt the bond would be strong. It would be a bad idea.

the red spot is epoxy with a layer of s-glass cloth

i learnt always keep a coupon for checking cure-ness so you don't have to disturb the work

6 hours later the resin has harden enough for handling. While it would take much longer to achieve the full strength it is good enough for gauging the bond strength. I tried to peel off the fiberglass cloth. There was no adhesion at all and it peel off as if a mold release compound has been applied to the pan surface.

the side where it mates with the shower pan surface is glossy as if a mold release agent was applied

The experiment show epoxy resin would be a poor choice for the project. To use it will require a primer that etches a rough surface to allow the epoxy to form a chemical (with the primer) or mechanical bond.

In my brainstorming of ways to use the existing shower pan one idea I didn't mention was to use the existing pan as a mold for the smaller new pan. I decided against the idea because I perceive it as too impractical, high risks, and technically challenging (as I have not work with mold release compounds before). Also to do this the work would have to be all done in the bathroom with the old shower pan in situ. Now it seems that idea is not all that crazy after all.

OK. What I learnt from the experiment are:

1. To modify the existing pan I need to use polyester resin. Using polyester resin will require care so not to deform the interface area as well as not to let the resin or concentrated vapor near the plastic surface of the bathroom (walls and the upper molded shelf assembly). Searching the web I found a CNC tech forum talks about using polyester resin on ABS instead of epoxy for better bond.
2. Using the existing pan as a mold to build the new pan. Obvious the outer dimensions of the new pan will take on that of the inside dimensions of the mold but the fit would not be affected if I just make the lips on three sides wider.

I haven't written much about how I would address the finishing so the modified shower pan will have a finished look. You can see in this video I took of the Berlin to Paris sleeper train there are two ideas. Cover the fiberglass floor with a clean looking flooring as under the toilet. Cover the fiberglass floor with a teak wood panel as in the shower floor.

beautiful bathroom in berlin to paris sleeper train

Planning on also how to make neat cuts to create the access opening for the waste water cassette, I decided to buy the Fein Multimaster kit.

Fein offers a lot of specialty cutting blades so it would be wise to do some test cuts with similar material least to be caught short when I need them. While the kit comes with an assortment of blads, only 2 may be 3 are suitable for this project.
comes in a storage case designed to stack - like the Festool who came up with this innovation first

I just realize with 4 posts I neglected to make it clear how the new cassette will sit in the bathroom, especially for those not familiar with the Westfalia James Cook. While there are someone else photos showing the configuration I want to respect their intellectual rights and not post them in my blog.

The cassette will be placed against the wall in the top of the photo below. The width of the toilet is an exact fit between the walls to the left and to the right. The whole portion of the shower pan above the ruler has to be cut out because the new toilet sits directly on the subfloor. For the shower pan the raise platform south of the ruler in the photo needs to be trimmed off. This will leave a void exposing the subfloor.

Hence it is where the fiberglass work comes in. Fiberglass cloth will be use to cover the void left by the raised platform. I will need to use a few layers to line the horizontal surface of the existing pan but cut around the round drain opening. A dam will also be formed with the fiberglass along the ruler in front of the base of the new toilet.

What remains then is the finish work to make the shower pan floor with a factory look.