Thread Tools
Dec 09, 2019, 07:52 PM
Registered User
Thread OP
All the Stations are in and will foam the hull tomorrow.

I used some fast glue to hold the 7" x 7" x 1/4" panels together ( left and right sides ).
Then do the layout and cut out. Easy.
Sign up now
to remove ads between posts
Dec 11, 2019, 01:12 AM
Registered User
Thread OP
Walls are built and started foaming the hull. But need to get a little more foam . Pain to work with. Also added a 3/8" / 1/2 " rail doe the chine. May help ? Foam is 4 Lbs. With it being a 'Plug" I want it strong. But lots of carving to do.Need to find the frame of the hull. LOL

Also think the jet's are here from Germany ? Will see Wednesday.
Dec 11, 2019, 05:07 AM
Registered User
Very heavy like that.
Try plastic packaging bubbles to reduce weight.
Seal up zip-lock bags with glue and incorporate between bulkheads...
Dec 11, 2019, 08:18 AM
Latitudes vs Attitudes
Bob Gaito's Avatar
IDK... can you cut poly foam successfully with a hot wire?-just follow the frames?
Latest blog entry: Mark V Navy Seal SOC
Dec 11, 2019, 04:43 PM
Registered User
Thread OP
This is not the boat. It is the plug for building the mold from and then on to making the first hull. So I want the plug to be very strong.
Dec 11, 2019, 04:50 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
That foam is Bondo friendly.... But I'm sure you know that... I found if you use the fiberglass mesh tape for sheetrock. You know the kind with the resin that makes it sticky if you cover the plug with that and then Bondo it it gets very very strong. I did my g a t o sub with that mesh directly on the forms (no need for foam) and skim coated with Bondo to make the plug.
Latest blog entry: Mark V Navy Seal SOC
Dec 11, 2019, 09:19 PM
Registered User
Thread OP
Bob,I will try your way later but working with what I have used before.

Also did a test using the can foam from Locktite. Didn't work so I will cut it out and refill with the other. It will not stand up to acetone.

And yes the sandy color foam will work with Bondo and polyester resin. But I use drywall compound . Sands about the same as the foam with little tear out. Lots of forming during the sanding.
Then I lock it up with resin and then a very fine glass.Then maybe some filler to trim things out. And last will come tooling resin . Then lots of wax and then time for the making of the mold.
Dec 11, 2019, 09:33 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
I did some checking-poly foam should NOT be cut with a hotwire...it requires too much heat and gives off toxic fumes ..they say to cut it with a long thin blade... I see that you've done this before..so chive on..

The Ginsu (Commercial Offer, 1980) (2 min 1 sec)
Latest blog entry: Mark V Navy Seal SOC
Dec 11, 2019, 11:23 PM
Registered User
Thread OP
Nothing that fancy,just a hacksaw blade.
Dec 12, 2019, 01:39 PM
Registered User
Kayaker's Avatar
I made a plug for a fiberglass boat mold and did it almost the same as yours. I used roofing foam because it is so easy to shape and sand. I put tape on as a guide to cut to using a carpenters saw then sanded it and put epoxy on the foam. This gave a firm surface to add Bondo to get the final shape. Then I added a tooling epoxy to a very smooth Bondo surface but didn’t vacuum degas the epoxy. This had too many bubbles to sand the tooling coat so I left this as the final shape.

First photo is the final hull shape (designed for rapids) in two layers of roofing foam before epoxy. Second photo is the deck after epoxy and part of the Bondo step.

I hope this helps to encourage this difficult process.
Dec 14, 2019, 01:13 AM
Registered User
Thread OP
Thanks,Kayaker.

Did some trimming. Then on to the other side.Then the hard part , faring.
Dec 14, 2019, 06:28 AM
Latitudes vs Attitudes
Bob Gaito's Avatar
Looking Great!...I Know that that's just a plug master, but interestingly, that poly foam is the same kind of foam that the Uniflight Corp had sandwiched between the hull layers of Kevlar on the PBR. (Airex construction- same as their cabin cruisers)
Latest blog entry: Mark V Navy Seal SOC
Dec 14, 2019, 12:00 PM
Registered User
Kayaker's Avatar
I’ve been thinking that an easy way to make a prototype hull design that skips the fiberglass mold making process would be to glue foam sheets into the shape of a hull, fair it with Bondo, add fiberglass to both sides and be done. This would NOT be a good way to make a beautiful boat.

A good suppler of fiberglass boat making materials is Jamestown. People use the following foam for making hull sandwiches; https://www.jamestowndistributors.co...80+Grid+Scored

Jamestown has some good “how to” videos. This video uses wood instead of foam to make a surfboard but may be good inspiration:

Building a wood Grain surfboard - Episode 5 (16 min 26 sec)
Last edited by Kayaker; Dec 14, 2019 at 12:34 PM.
Dec 14, 2019, 12:50 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
You can dispense with the fiberglass mold by using a containment box with plaster of Paris... Or if you're rich enough you can cover the master with silicone-based molding compound like alumilite... Also very similar to plaster of Paris is the quick set joint compound very cheap and very strong.. why use a combination of both silicone mold compound and strengthen it with a box of plaster of Paris... The silicone eliminates the need for a parting agent...
Last edited by Bob Gaito; Dec 14, 2019 at 12:57 PM.
Dec 14, 2019, 02:32 PM
Registered User
Thread OP
I didn't go with a one-off because I want to make more than one.

But lots of great info,Thanks.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Help! Help needed on first ever RC build (Nutball scratch build) New Tomi Beginner Training Area (Aircraft-Electric) 8 Mar 05, 2018 09:06 PM
Discussion Building a telemaster 66 (my first build). Need help selecting a few things. helifrek Fuel Plane Talk 68 Sep 28, 2017 06:53 AM
Discussion PBR Help HowBau Scale Boats 7 Sep 01, 2016 09:52 PM
Discussion 1:18 pbr mark 1 build thread CaptDH Scale Boats 70 Nov 18, 2013 08:20 AM
Question Tamiya Intl. mag 1991 PBR build article vintageone Scale Boats 0 Apr 15, 2007 05:01 PM