Scratch-built 1/96 Oscar II

[Guest]

will a 3.5" WTC be

will a 3.5" WTC be man enough, this is a monster by the look of it

[Guest]

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.)

I use GRP sheet for saddles.

Tough as old boots, although I refer to them as 'module mounts'

Andy

[KevinMC]

Thanks Andy, I'll give that

Thanks Andy, I'll give that a serious look.

Albion- I certianly hope that the 3.5 will be sufficient, but if for some reason it isn't I'll manage. One thing I will be doing to help it to work will be to do a very light cloth layup for everything above the waterline.

[wayne frey]

I suspect a 3.5 will

I suspect a 3.5 will not be a problem.
What do you think, props too close together for practical differential steering? (one or two speed controllers?).

[KevinMC]

Hi Wayne,

Although I've been following

Hi Wayne,

Although I've been following the current "One speed controller or two" thread with interest I can't see the value of differential thottles on this boat. The prop shafts are about 3" apart on a hull that's 63" long and over 7" wide- the math supporting diff throttles just doesn't work out in my mind.

Accordingly, I've picked up a singe MCD speed controller for mine.

[KevinMC]

Progress continues...

The last thing I

Progress continues...

The last thing I needed to do for the sail hardback was to add some stabilization feet to the "top" side of the mold. These were made from some bits of scrap paperboard (as used to make the parting board) and glued into place with hot glue.



Now it's time to get back to the hull- this time doing things over again on the top side. This is identical to doing the bottom side, but I've grabbed a few shots anyways...

Clayed up in the parting board. As before, I've set the hull into the parting board so that I'm at least 1/4" above my scribed reference line. Although this means I'll have to trim my hull halves when pulled from the mold, it also means that I can trim the hull halves to mate perfectly when assembled...


"Glazed" with a detail coat of SmoothSil:


...And layered with about 2 coats of Rebound. Notice the unmixed RTV components in the smaller SS dishes. This will be layer 4 of 5. Also notice the lower half hull mold at the rear of the table.


As of last night I completed putting layer 5 of 5 and the alignemnt keys into the mold (no photo yet) so I'll be back to plastering this weekend...

[KevinMC]

The top side of the

The top side of the mold is all done 'but for the drying time...

Here's the final layer of Rebound with the mold keys in. Notice that I've done them a bit differently this time- although those that were done in the first half are sufficient to hold the RTV component in place, re-orienting them in this manner should lock things in a bit better. At least that's the theory- if you don't try you'll never know!



Now onto the plaster. Basically the same as last time, except for the fact that this time I've made sure to get a layer or two of burlap under the areas where the the wooden reinforcement spines will be placed- this seems to be a weak point on the first half of the mold and will be something I'll have to take extra care over.



Last shot- all the plaster and burlap is down, as is the spine. Notice the fan to help get all the water out- this thing will be damp/cool to the touch for a couple of days!



Now I'm off to make mold boxes for the fins...

[pirate]

Kevin,

What's that SmoothSil crap? How

Kevin,

What's that SmoothSil crap? How do you apply it? Does it leave brush marks? Does it dry that glossy? #### that stuff is shiny. Will it work for fiberglass mold resist?

Pete

[pirate]

Hey! Who redacted my message?

Hey! Who redacted my message? All I said was ####.

Well, ##### ### ## who ###### did this ####!

There, that'll learn ya.

[pirate]

I think I'm just #####

I think I'm just ##### going to type these ######(#) now anyway. They ### look much ##### #### better than letters, #### they say much #### more and are #### very educational. And ##### ### #### they make #### the #### message so ###### much easier #### to read.

[KevinMC]

Hi Pete,

Would you believe me

Hi Pete,

Would you believe me if I told you that the RTV in the "shiny" shot is completely cured? No kidding! Once mixed, I poured the SmoothSil where I wanted it and smeared it around with a disposable paint brush, then in less than a minute all the brushstrokes disapear and you're left with nothing but a glassy surface. Of course this gets completely covered up with the orange coloured Rebound...

Once backed up with the Rebound, I'm told that the SmoothSil is a fantastic surface to lay up against. Because it's a silicone, nothing (exept silicone) will stick to it. I can't wait to try laying up parts in this stuff- I always hated the wax-wax-wax-buff-buff-buff cycle. None of that here!

[pirate]

Can it be used on

Can it be used on fiberglass molds?

[KevinMC]

Hi Pete,

How do you mean?

Hi Pete,

How do you mean? I'll be pulling fiberglass parts from these molds, but they were also cast over top of primed fiberglass parts...

[KevinMC]

Delinquent! This is old news,

Delinquent! This is old news, but I forgot I hadn't posted it yet...

After allowing the upper strongback to harden up, I separated the hardback from the RTV component of the mold.



When talking about RTV molds I always thought it was funny when folks talked aobut peeling away the RTV component from the master, but for anyone that's not tried I assure you that's really how it goes down. I snapped this shot "mid peel"...



And here's the resulting 2-part mold (side 2) and pristine master. It, the lower half mold and sail mold are now ready to start pulling hulls from...

[KevinMC]

In my absence from posting

In my absence from posting in the past few days I've been working out how to make the mold boxes for all my appenages. I decided to build simple boxes from 1/4" MDF. Why MDF? It cuts nicely on my bansaw, it's much lighter than the more popular 3/4" shelfboard, I can buy it in small sheets (24" x 24") and it's cheap! The only downside is that the unfinished surface is lousy for casting RTV against, so before use I "seal" the surface with a layer of clear packing tape.

I've started with the simplest molds- those for the fore and aft reactor cooling scoops and the bowplanes. These will be cast into 1-piece molds that will be sliced open to extract the part. I built 5-sided boxes to contain the liquid rubber, suspended the part in the box and poured the rubber in. Here are a couple of shots showing the cast mold with the boxes in their assembled and disassebled states.





A further note on casting with RTV- as noted earlier, I'm using a platinum catalyzed Smooth-On product. Being platinum catalized, the rubber undergoes no noticeable shrinkage during the vulcanization process, so the mold boxes that I build before casting still fit perfectly after the molds are made. (This would not be the case with the less expensive tin-catalized type RTV which does exhibit a measurable shrinkage while vulcanizing.)