Portland Model Power Boat Assoc
Portland Model Power Boat Association
"Showcase" page
This page features works by the members and guests, news, photos of events, things that would be of special interest.
This page will change often, so be sure and check back soon!
so be sure to stop back in then!
I change the "Showcase page" once a month!
The 2007 club float and meeting schedules are posted on the schedule pages. Be sure to check back to the “Showcase Page” for interesting displays! Web Master, Neal
We are asked from time-to-time to show past “Showcase” pages. We will start to archive them for you.
New feature from PMPBA
Now, how the heck am I going to make that?
That is a question we hear around the modeling bench form time to time. If you are scratch building, adding to a kit or changing a “ready to sail”, some times you have to make a part that requires a casting be made. That process is not as hard as you might think. Here are the basics of RTV casting to get you thinking.
A quick instruction on RTV casting!
The subject displayed here is an anchor davit. It needed to made of metal so it could take a small amount of abuse. This model only has one davit but I felt if it were made of wood it would be snapped off during handling. RTV molding is great when you need several castings of the same item. You make one pattern then cast multiple times using the same mold.
RTV is “room temperature vulcanizing rubber. RTV, both silicone and urethane are available here in Portland, Oregon at Stephenson Pattern supply or mail order from Mico-Mark (find their link on the “Links” page) The material is easy to use , a simple 1 to 1 mix and pour.
The pattern is made of basswood and plastic, sanded and sealed with clear DOPE.
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After, mold release is applied to all surfaces; the pattern is suspended by T-pins in a mold box, (made of scrap cardboard) Then RTV is poured in, to fill half way and left to dry.
After the first lift of RTV is dry, mold release is applied to all surfaces and the box filled with RTV and again, left to dry.
After the RTV is dry, the mold is parted and the pattern removed.
A gate and vent are then cut in the RTV to allow the casting material to flow in and through.
You can cast with bismuth metals (from Micro-Mark) a tin lead alloy, melted with a plumber’s torch or casting resin. Each has their advantages and disadvantages. A word of caution, be very careful with the molten bismuth, if spilled can, cause serious burns! Wear gloves (I use the OV Glove) and eye protection! Kids stand back!
Two advantages of metal casting, it only takes a minuet to cool and inspect. If the casting is bad, then back into the melting pot for another try. With resins, you will wait a drying cycle to see your work and if bad, it’s another mix of materials and another wait.
The casting is a perfect rendering of the pattern, make one or fifty. A little file work, some paint and additional parts and you are ready to place component.
The finished piece!
