Scratch-built 1/96 Oscar II

[pirate]

Kevin,

Also, don't forget to

Kevin,

Also, don't forget to put that Guiness in the materials list you develop, maybe the most important element.

Pete

[KevinMC]

Hi Pete,

Although I'll probably wind

Hi Pete,

Although I'll probably wind up doing that in the next day or two anyways, I did flip the whole thing over this morning and carefully extract the hull/RTV from the shell without incident. (I didn't get those photos yet, I'll post them this weekend.) I agree that it's worth taking all the necessary precautions to ensure that my hardback doesn't crumble, but I'm pleased to report that the burlap seems to have worked very well to provide intergrated support to whole thing.

Yes, the Guiness is definitely an essential component of a successful build!

[KevinMC]

We interrupt the regularly scheduled

We interrupt the regularly scheduled thread for an update on the OSCAR prop mold making process!

David Merriman has completed the RTV tools off the propellor masters I made and pulled some initial shots out of those molds. Equally important, he's also sent me these great photos of the whole process. Thanks again David!!!


The first photo shows the "masking" process of the masters. Due to the complex shape of the props, the mold must be done in two pieces. Non-sulphur based clay is used to "mask" the areas where the high-temp casting RTV should not go.


Care must be taken when claying up the masters since the blades are cast from polyurethan resin, and only about 0.050" thick, and could be bent quite easily.


Using a Lexan tube to define the outer wall of the mold, mixed RTV is poured into the formed cavity...


...and place in a hot box to speed up the vulcanizing process. (These are a great thing to have 'round. I've made one for myself using 1" white styrofoam board glued together with white glue. A 15W bulb is all that's required to generate plenty of heat!)


One more step remains on the first half of the mold- pouring the sprue channel. This "extension" will ensure that there's plenty of head pressure to force the molten metal out to the tips of the blades when it's poured into the mold, but by makig it from a smaller diameter tube valuable RTV is not wasted.


Now on to side two, the clay masking is carefully removed from the props and vulcanized RTV.


Wide pieces of masking tape is used to contain the RTV this time.


...And in goes the RTV. BTW, David uses BJB TC-5050 RTV for all his props. I've pulled the data sheet on this stuff, and it has an extremely high working temperature. (If memory serves, it'll take up to 850F!)

[KevinMC]

And for the casting process...

http://www.subcommittee.com/forum/ACF265E.jpg
The

And for the casting process...


The prop molds are first brushed with talcum powder to completely dry the inside surface of the mold. Any moisture (from the air) inside the mold when the molten metal is introduced will instantly boil off and leave a bad finish on the part. David casts his props from white metal, which he tells me is 95% Tin - 5% Antimony. The molds are weighted down with strong-backs, and the metal is heated in preparation for pouring.


And here is a whole bunch of props as they come out of the mold. Once the sprue is trimmed off, these will be chucked up on the lathe and trimmed down to the correct length.


Last shot- 5 sets of props, resin cast vortex attenuators, molds to make more, and my masters all ready to be shipped back.

I'd like to take this opportunity to sincerely thank David (again!) for lending his expertise to my project, and for doccumenting his work so that we all may learn from it. He really is a wonderful guy, but don't tell him I told you so!

[pirate]

Those look great!

I think we

Those look great!

I think we should call David "Master Yoda"

[liftmys10]

Woahhh really nice work!!!!!!!!

Woahhh really nice work!!!!!!!!

[novagator]

I wish I had the

I wish I had the time to scratch build like that. Beautiful Work Kevin and David!


now where is the waiting list to get one of these Oscars?

[KevinMC]

Thanks much guys.

John- I've been

Thanks much guys.

John- I've been trying to keep tabs on who's expressed an interest. Consider yourself added to the list.

[novagator]

Thanks much guys.

John- I've been

Thanks much guys.

John- I've been trying to keep tabs on who's expressed an interest. Consider yourself added to the list.

thanks!

[tmsmalley]

I wish I had the

I wish I had the time to scratch build like that. Beautiful Work Kevin and David!

Hah! I've got the time - I wish I had the SKILL to scratchbuild like that!

[wayne frey]

I would expect you to

I would expect you to be at the regatta this summer with a hull.
hint,hint



Edited By Wayne Frey on 1145307580

[KevinMC]

Da, Comrade Frey! http://www.subcommittee.com/forum/icon_wink.gif

Da, Comrade Frey!

[novagator]

I would expect you to

I would expect you to be at the regatta this summer with a hull.
hint,hint

heck I hope to be at the regatta with a working sub.

[wayne frey]

Novigator,
It is fun to

Novigator,
It is fun to bring a boat, but we enjoyed the last one together without one, right? I am looking forward to seeing everyone.

Mr soon-to-be-Oscar driver, You have plans to do index lips,wtc saddles, and epoxy hull???
No pressure
We have talked of the expoy/poly resin before. Just wondering what you are thinking.
I have this D and E 3.5 endcap rigged for two motors. What are you planning to do?

[KevinMC]

Hey Wayne,

The plan for now

Hey Wayne,

The plan for now is Epoxy hull and sail, resin cast appendages and detail bits and white metal props. Hull indexing will be done with strips glued in after the fact. I will have to figure out something for WTC saddles, I'm just not sure yet what material I'll use. (I have a D&E 3.5 Mod 2 for mine.)

I've almost completed the top side of the mold. (Photos to come shortly.)