Scratch-built 1/96 Oscar II

[bcliffe]

(to keep Ben C at

(to keep Ben C at bay!)

#### that thing is a monster ... my boats are running for cover!

Just as a heads up, it looks like the cottage get together may be late August if that works for you.

Cheers
Ben

[KevinMC]

Woo hoo! Late August should

Woo hoo! Late August should be just fine.

<An evil grin breaks across Kevin's face> ...And I should have my 6-barrel fish-launcher ready to go by then too.

[KevinMC]

One of the more prominent

One of the more prominent "detail bits" to be added will be just inside the flood/drain holes on the easy case. In almost any of the closeup photos of OSCAR a "grill" can be seen in the upper vent holes, so I've set out to find a way to replicate this with a minimum of effort...

Here's an oblique shot of what the vent grills looks like, seen in the lower left-hand corner of this photo of the crew of the ill-fated Kursk. (My prototype.)



Having opened up all the vent holes, I build a frame from styrene plastic onto which I'll glue 30AWG wire to make the "grill". Okay, reality check time- There are 52 exact copies of this type of grill on the upper surface of the hull, and there's no way I'm going to build them all. Of course the easy solution is to build one master and pull the required number of copies from Alumilite resin, which is what I've started to do in the photo below.



And here's what the grill looks like in place on the hull... (This is only temporarily held in place, I'll fix them in permanently after I shoot the hull with one more round of primer.)

[pants]

Nice , very nice http://www.subcommittee.com/forum/icon_smile.gif

Not

Nice , very nice

Not alot more to say, keep up the good work.

Regards,

Kor

[KevinMC]

Allright, I've got about a

Allright, I've got about a week-and-a-half's worth of updates, so here we go...

I made up a set of indexing strips for the lower hull half. First the semi-circular ones were installed fore and aft, then for the side walls. In the photo below, the fore and aft strips are glued in and one of the side strips can be seen next to the hull in preparation to glue it in. All areas to take glue were roughed up with 80 grit paper to ensure that the epoxy had plenty of surface to grab on to.



I mixed up some general purpose epoxy (System Three) with a healthy dose of Cabosil to thicken it up, then aligned the index strip using many clamps to ensure that it didn't budge.



Once all the strips were in place, I found a couple of areas on the upper hull that wanted to pop away from the strips, so the next thing to do was to make up some capture tabs that I glued to the upper half of the hull. These keys act to hold the upper hull tightly to the index strip.



The keys were installed along the length of the upper hull at roughly 4" intervals. Maybe this is overkill, but since I want to be able to hold this 5' split hull together with only a single screw, bowing at the sides is a legitimate concern...



I've used what may be referred to as the Sharpe method (?) for attaching the upper and lower hulls, using the indexing tabs to key the upper and lower halves together and affixing them with a single screw in the rear. Here is the "receiver" for the hold-down screw, secured to the rear-most hull former.



Not wanting to disturb the scale outlines of the hull with an unsightly screw, I elected to counterbore the screw head into one of the circular scribed features already present in the hull. The photo below shows my crude (but effective) coutersinking bit, and the scribed hull feature that will be used to mask the location of the hold-down screw. To make the counterboring bit, a pair of wheel collars were affixed to an ordinary drill bit to act as a stop when the correct depth was reached...



And here is the resulting hold down screw, nicely hidden...



...More to come...

[KevinMC]

The next thing to do

The next thing to do was to back-fill the stern cone with epoxy to create the bushing housing for the main shafts. This is a well documented procedure that David Merriman uses on all his builds, and I've followed it to the letter.

First, a pair of 5/16" aluminum shafts were waxed up and affixed to a brace made of MDF. The brace was used to ensure that both shafts would run perfectly parallel and true with respect to one another. Next the shaft assembly was inserted into the aft end of the hull and secured with clay. Left-to-right alignment was made visually, top-to-bottom alignment was made with the aid of a torpedo level.



Once everything was triple checked and weep holes drilled (sorry, I didn't get a good shot of these) the whole assembly was tipped up on its end and backfilled with epoxy up to the level of the weep holes.



The following day, I took the brace to the bandsaw to ease the process of removing the shafts.



Then, with a twist on each shaft, the aluminum tubes were withdrawn leaving a perfectly cylindrical recepticle to hold the shaft bushings.



At this point I wanted to test fit the cast screws seen much earlier in the thread. I cut a pair of stainless steel shafts to length and test fit the oilite bushings. Perfect fit!



The OD of the hull where it mates to the bushings still requires a bit of finessing however, so using the bushings as a guide I marked where I'd need to remove material.





Any areas showing pencil marks will be sanded down. Later on I'll go back and use some filler to blend the aft end of the hull into the bushing.

...Still more to come...

[colin-stevens]

my, followed this thread with

my, followed this thread with keen interesst, learnt alot. but i seemed to have missed something. how did you make the hull from the mouls, ie lay in the cloth ect.
carry on the good work
colin

[KevinMC]

I've also been prepping the

I've also been prepping the aft end for the appendages. Here's the appendage set, cleaned of mold release by scrubbung with steel wool and acetone. Note the carbon reinforcement at the tips of the surfaces- I hope I won't need it, but it's good to know it's there.



Although I scribed the appendage outlines in the hull, I failed to mark where to drill the holes for the control rods. Here, the scribed outline has been enhanced with pencil, and I've also marked where I'll drill the (oversize) hole for the control rod of one of the ventral fins.



Last shot, the hole's been drilled with a ball-ended dremel bit. I could'a used a big drill bit for this one, but since the hole location is inexact I wanted to be able to test fit and grind away as I went. (Elongated holes don't really matter here as I want to have oversized holes for the control rods anyways- they're designed to be supported by the lower-friction brass bushings cast into the control surfaces.)

[KevinMC]

i seemed to have missed

i seemed to have missed something. how did you make the hull from the mouls, ie lay in the cloth ect.

Hi Colin,

You're right- I did skip that part. I figured I'd get the process better refined before I presented it. So far all the molds I've worked with seem to have a "personality" of their own, and you have to learn how they want to have the cloth laid into them before a really good product results.

Not to worry, I'm hoping I'll be pulling more hulls shortly and I'll be happy to detail the layup process on the next one I pull... (If anyone's interested in taking a look at a highly detailed 1/96 OSCAR II kit, come hunt me down at Carmel...)



Edited By KevinMc on 1152661127

[colin-stevens]

ta, thought i was cracking

ta, thought i was cracking up.

[the black knight]

thats a nice looking sub

thats a nice looking sub so far! keep up the good work kevin
the black knight

[KevinMC]

Thanks Jon!

Well, I don't have

Thanks Jon!

Well, I don't have much in the way of photos to show this morning but what's here should speak for itself. Perhaps it's not the wisest of goals, but I decided a while back that retractable bowplanes were to be included on my "minimum equipment list" for Carmel, so I've been busy "figuring" and here's what I came up with.

This design borrows from the best of both the Engel and Lecma RC bowplane retract mechanisms. Engel's design, while relatively easy to manufacture, uses up a fair bit of volume that I don't want to give up. Lecma's system, while elegant, is based on an injection molded knuckle that I have no desire to try to replicate. As such I spent about a week-and-a-half of "background thinking" trying to figure out how to easily make the components I needed in a way that would not consume a large portion of the bow section of my boat. Here's an exploded veiw of what I settled on...



These were manufactured last Friday using nothing more than a Dremel and a drill press. (Mostly the Dremel.) I then spent the better part of Saturday getting it all installed. (This is where Engel's influence can be seen... Also note that the control rods that come forward will ultimately be hooked up facing aft- they're just there so I can actuate the mechanism without getting my hands in the way!)







I have a .MOV video clip of the mechanism in action- if anyone can recommend a good way to make this available to the masses it does a much better job of showing how everything works...

Also, I'd like to thank Licka Libor for taking the time to grab some shots of the bowplane mechanism on his Akula (under construction). Amongst other things is significantly cut down on the amount of wheel I needed to re-invent!

Tonight I'll be working on installing the hatch mechanism for the sonar dome, and once installed and filled I'll finally be ready to put some primer down. I'm expecting to be in the water late this coming weekend, early next week at the latest. I've got a busy week-and-a-half ahead of me!

[the black knight]

kevin
i might have missed this

kevin
i might have missed this somewhere, but what did you use for a relise agent on the silicone?

[aeroengineer1]

Kevin,

Your mechanism looks

Kevin,

Your mechanism looks great, but there is one concern that might arise, and that is there seems to be some components that are made of regular music wire. And the balls look to be of regular steel. I would sure hate to see that whole thing rust up on you.

Adam

[KevinMC]

Jon- Although the silicone molds

Jon- Although the silicone molds will release without a release agent, I've been using vaseline thinned with laquer thinner to help get things out easier.

Adam- Okay, you got me. There are a few bits for which I broke down and used materials that will be prone to rusting. Unfortunately I couldn't come up with anything else that would do what I needed it to, so I'll just have to keep an eye on it. (And seal it up as best I can before hand.)