Scratch build HMS Resolution Class SSBN

[Davidh]

question about draft angles and undercuts.

Hello all,

This forum is quiet.

I have some questions that will hopefully be answered by somebody soon. I need some advice. The resolution has several array housings along the hull. Two below the waterline that I expect are flank array housings. Then there is what I can only think as being a towed sonar array housing after the missile deck. The flank arrays run for about the length of the missile deck as seen in this launch photo.

Previously I used to make the mould without the long bulge of an array. This made making the mould so much easier and then I would simply get some dowell, split it down the middle and glue it on sand it, seal it etc..

However, this time I am thinking about putting them in on the mould. This will create a challenge for getting F'glass to wrap around that shape. That's not a problem, I have some little tricks. My major question is about undercuts.


I will be making the moulds out of polyester resin and have had many years of experience using it to make moulds, however I have not made undercuts quite like this and wonder how well the mould and part will flex to get the undercut section out. I think I can reduce the draft angles substantially so that especially for the flank arrays the top edge of the array can have an almost vertical surface to it to reduce the draft angle coming out of the mould. How much undercut can you get away with? Or should I not even go there? I'm at a crossroad.. Do people just make a bulge and glue it on?

Any prompt advice on this would be great.


David H

[He Who Shall Not Be Named]

Build the flank arrays scale, but make that portion of your tool from flexible RTV so it can scoot out of the way when you lift the laid up hull out of the tool. A hybrid type tool: mostly rigid GRP, but flexible rubber where the draft is either vertical or undercutting.

M

[Davidh]

Thanks Dave,

I have thought about using some kind of RTV but have never used anything like that before. I am interested in expanding my skill base but would appreciate some more detail from you.

what product names would you recommend ( I have to see what Australian equivalents are available) if the ones you recommend, are not. Also I have read most of your cabal reports and see you use this method a lot, however do you have a tutorial specifically on how to work with this material.

i have also thought about using a split mould.

thanks Dave,

David h

[He Who Shall Not Be Named]

Thanks Dave,

I have thought about using some kind of RTV but have never used anything like that before. I am interested in expanding my skill base but would appreciate some more detail from you.

what product names would you recommend ( I have to see what Australian equivalents are available) if the ones you recommend, are not. Also I have read most of your cabal reports and see you use this method a lot, however do you have a tutorial specifically on how to work with this material.

i have also thought about using a split mold.

thanks Dave,

David h

I use West System laminating resin (epoxy) -- the slow cure formula http://www.westsystem.com/ss/

I use, in this application, brush on RTV. BJB, TC-5040 http://www.bjbenterprises.com/tc-5040-a-b/

Here I'm making a glove-mother mold type tool. Differs in that I'm producing the rubber glove here to capture the masters entire surface features. In your case you will only build up rudder about those portions of the master that would otherwise present an extraction problem (lock-in) were the entire tool to be an inflexible GRP structure.

Brush on the RTV over those portions of the pattern (master) that present negative draft, to an eventual thickness of at least 1/4" (about three applications over the course of three days), texture the final layer of rubber so it will key with the hard-shell portions of the tool. Then lay up your GRP tool over the entire master -- the rubber parts too (one tool for the upper hull, one tool for the lower hull ... duh!). Egg-crate with 1/4" plywood to stiffen the tool. After it all cures hard, yank the masters out of the tools, and you're in business.

The rubber portions of the tool will either distort or pull out of the hard-shell portion during master/laid-up part removal -- just strip off the rubber that sticks to the master/laid-up part and re-insert it into the tools cavity from whence it came and you're good to go for the first/next lay-up.

Have you made a hard-shell GRP tool of this size before? You do know how to prep a master so it won't stick to the laid-up tool, right?

M

[Subculture]

I recommend checking out the instructional videos by Smooth-on, they're pretty good.

I think RTV tooling works best if used with epoxy resin for lay-up and polyurethanes for casting as the shrinkage is much lower than polyester, and it's also less aggressive on the rubber. The extra cost of the resins is not hugely damaging to the wallet when only moulding one or two hulls, and the end result will be stronger and lighter. Plus it doesn't stink out your workshop!

[Davidh]

Thanks Dave and subculture for your comments.
Would still ove some feedback on those hull details that I mentioned.

Subculture, any luck on contacting Ron Perrot?

Yes Dave, I have produced large hard GRP moulds before. I also mould FRG Scale sailplane fuselages so I've done a couple before. I am thinking of doing a split mould down along the bottom of the hull. I don't know if I want to embark on such a big learning curve on such a big model to start with. May start off small. Thankyou for your information, I really appreciate and find that over the years, all the Cabal reports and other documentation that you have generated has been a great source of inspiration and skill development for me.

I emailed the Ministry of Defence in Whitehall under freedom of information to see if they could release some dry dock photo's appealing to the fact that these boats have been out of commission for the last 20 years and I can see no reason why deckplates and weldlines on an old submarine would still be a national security issue. They briefly emailed me to say the issue is under consideration. Oh, well one can only try as all my other requests have only had meagre responses. This is frustrating. I am almost up to detailing the back end of the boat and there are precious few photos of the rear end as mentioned.


The missile deck would generally need less work shaping than the bow. It is basically rectangular and long. The front end would have a subtle curve as it meets a slightly wider front. The blocks glued on the sides of the missile deck and the front would facilitate this. The Back of the missile deck would simply be comprised of several 12 mm pine profile blocks that would be traced from the back of the missile deck and the curve of the top of the hull (pvc pipe) then they would be cut and reduced for the next one and so forth untill they reduced till they would blend in with the rear hull. It would simply be a case of sanding these down.
Whilst working on this section I would eventually have to turn my efforts to the bow array. This has been a little bit of an enigma. The original launch photos show a very concealed bow array with a framework all over it. Looking at the photos of Revenge in dry dock is currently me best bet as to getting this right. The outline of this array is not as prominent as I thought. I dont know however if this was always the case. To make this I would glue a framework of thin strips of pine that would define the boundary. Then I would simply paste it up with autofiller and sand it back. It is mainly a question of how prominent from the rest of the hull the array should be.

The next major step will be working on the sail. This will be a split into two and I will make GRP moulds of either side.

Anyway , enough for now.

[Subculture]

I passed on your details to Ron. If he's not been in contact yet, it's either because he's been busy or forgotten.

[He Who Shall Not Be Named]

Don't let that frame-work you see over the bow sonar window fool you. I'm convinced its a temporary strong-back installed to keep the GRP window (I assume it's plastic, most acoustic windows of the time were) from blowing out as the forward group ballast tank flood-drain holes hit the drink as the beast slides down the ways.

Post launch, Diver's unbolt them and they go back to the yard. Sorry to **** on your parade, but that build-up you're doing over the bow has to be removed.

Another function of that temporary frame-work may be to keep the drag anchors, wires, chain and anchor buoy lines and other ground tackle from scaring the sonar window as it's paid out -- the ground tackle used to keep the boat from backing into the piers the other side of the basin once clear of the blocks and rails.

M

[Davidh]

Thanks dave,

I had thought that the structure around the bow array may have been for protection against debris and chains flying up and damaging it as well as a security issue of protecting some features from prying eyes. I had never thought about backpressure due to flooding tanks at launch. Thanks for that.

I have toned down the profile on the bow array. The bow section has taken up the vast bulk of my work on this. The array at the front only subtly bulges out. I really just followed the dry dock picks that i have.

These photos that I have posted are from work that i did about a month ago. I am gradually working through the write up as I work on the masters. As mentioned I am still trying to get details on the stern of the boat and really not getting far with the contacts I have. It is frustrating as i am still waiting to get word from the MOD about releasing stern dry dock pics, fingers crossed.

I have been looking at several models made of the resolution on various websites and although nice boats , many of them have what look like very boxy, almost wedge shaped front ends that dont have much curve. I am convinced that the front end really makes or breaks this boat.

dave h

[Davidh]

Hi all,

So I have build the wood box frame around the area that would be taken up by the bow array and I've filled it with filler. Then sanded it back. Still for now quite a prominent section sticking out as it wraps around the bow. It kinda looks good but as dave has said, it's not quite right and after looking at the one pic of Revenge in dry dock I can see I'm going to have to tone it down a little. More sanding and a gentle rounding around the edges.

Meanwhile as you can see from the pics the rear of the missile deck is coming along. For most of the deck it is a consistent profile,this makes for a nice change after agonising over the gradual evolution of the front of the boat. I am generally happy with how the front end is evolving and as I mentioned earlier I believe that you really have to get the front of this boat right to do it justice.

I have spent a fair amount of time deliberating about the shape of the boxy foreplane housing. As far as I know this is the only model of Resolution with the box structure rather than the continuous flowing lines and the brief hiccup of the foreplane shaft extending out from the hull. This box design really does break up the flow of the structure as it receeds back. That has thrown my perception a little.

The rear missile deck is simply made of small profile pieces glued end on end and getting smaller. I think i 've already covered this. I intend on making the mould of the missile deck whilst it is fixed down to the hull and the edges of the mould will actually be where the missile deck would theoretically intersect with the hull. I'll use clay around the edges where the long groove occurs. (Is there an official name for this?)


In the words of Raymond Loewy 'never leave well enough, alone'. I just have to go back and filler up the bow just forward of the planes. (still not happy with bow) It doesnt look full enough. I'm not a perfectionist and realise that I could go mental if I want but you have to get to the point where you're happy and I think I'm close.

I have decided that I want to build the sail to be detachable. This will make it easier to transport in a box that one day I intend to make. So to make sure that the sail seats flush on the deck and you don't get any light coming underneath I'm adding a raised step section in the outline of the sail but slightly smaller so the sail outline is on the outside. Tricky thing is that it's smack over the middle of the break where the missile deck separates as a mould from the fore deck.

Anyway, enough for now.

David H

[Davidh]

Hello all,

This thread is quiet.

I have walked across the fourth road bridge a few times. This is me and my son Noah in Janaury of this year. I could see Rosyth in the distance. This was as close as I could get.

O.k Its been a little time and I have managed to do a little more on the boat. Last installent was talking about the rear section of the missile deck and then the raised section that crosses the joint between the fore deck and the missile deck. I simply stuck down the misile deck and then glued this piece crossing the two sections. Once glued down I simpy cut it in half and sanded back.

Then there would be lots of sanding and going over the over all shape of the boat to check for imperfections and divits. I also went over the shape once more and applied filler where necessary. This would all be done before putting a resin coat over the whole boat minus the PVC section in the middle.

The resin coat is polyester. I have done the front and back of the hull and the four smaller pieces. I have also added a grey pigment to colour it like the primer. Once this was done then it was pretty much 200 grade wet and dry and working upwards. Sanding over the resin coat really smoothed down the outer surface and with a coat of primer smaller details, divits and bumps showed up effectively. The overall texture and surface is quiet nice. The hull would soon be ready for scribing the details along the hull. So I move from getting the overall shape right to getting the hull plate detail, cleats, hatches and weld lines right. I have fortunately been able to obtain numerous photos that show the front end of the boat and all the detail from the sail down to the very bow. I am still waiting a response from the MOD in London about releasing dry dock photos of the back end of the boat. The french have a whole SSBN on display ( Le Redoubtable) so I don't see what the impediment could be.

I have found that the back end of a stanley knife works well as an etching tool. Run along the edge of a ruler or a hard curved surface to follow the hull shape, works well. I also have some very small files and I have found that the point of these files also works well.

In some of these pics you can see the scribe work with the smaller masters. These include the two sides of the sail and the top of the sail along with the missile deck. To make the missile doors uniform I have created a small aluminium template to use with a scribe to etch the pattern into the deck. It works quiet well.

I think that will be all for now, however comments and advice once again always welcome.

David H

[He Who Shall Not Be Named]

Too late to be of service to you, with this project. But, some tips for a future project:

Scribing into wood has to be the most difficult, frustrating, and un-rewarding exercises on the planet. Yet, through dogged determination, you did it. Bravo, sir ... may I never encounter you in a foul mood!

First rule of scribing (engraving): cut into a uniform, consistent of texture, substrate. Rule two: never scribe into wood or any other substrate possessing a grain or varying densities.

You, sir, fly in the face of convention.

Now, after delivering that *****-slap, here's some constructive pictures to help guide you along on your next project:

[Von Hilde]

Too late to be of service to you, with this project. But, some tips for a future project:

Scribing into wood has to be the most difficult, frustrating, and un-rewarding exercises on the planet. Yet, through dogged determination, you did it. Bravo, sir ... may I never encounter you in a foul mood!

First rule of scribing (engraving): cut into a uniform, consistent of texture, substrate. Rule two: never scribe into wood or any other substrate possessing a grain or varying densities.

You, sir, fly in the face of convention.

Now, after delivering that *****-slap, here's some constructive pictures to help guide you along on your next project:

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Mighty clever for a torpedoman, Dr M. Im stealing a couple ideas, like the little pen clamp. And a media for poping out a resin pressure hull or two. I have made some 3 dimentional signage with HDU, hi density foam that can be sandblasted with a frisket. Easy to machine, carve, file, sand, and reasonable from sign suppliers. They even have some blocks with various densities imbedded to look like it was a wood sandblasted sign, if desired. Sold in blocks sheets of all sizes. Sold in colors as well. Any particular reason you use NitroStan, instead of something a bit more contemporary? 3M makes a good acrylac glazing putty. Doesnt shrink after drying like nitro. It doesnt "skin over" dry top-still wet, thingie that wants you to sand to early, as well. It has been a big issue topic, over on a couple other forums I follow. (Jalopy Journel} old hotrods and bikes and (The Sludge Trap} custom motorcycle stuff. I do a lot of custom artwork on cars bikes and boats and a few airplanes. Custom signs, paintings, murals are one of my main sources of income since high school. (Of course that was when first grade thru 12 was all in the same 1 room schoolhouse) The consensis is, the old greybeards use it because thats all they ever used since the 60s. The young bucks all swear by acrylac I tried to get the old PPG red oxide filler a year or so ago, but they discontinued it so they gave me the 3m, and Ive been happy with it, so far. 3M comes in other colors too,green,and white.

[Davidh]

Thanks David for the great photo's.

I have been an avid reader of the Cabal reports but havent seen any new ones for a while. With what you know about scratch building, you could write an incredible book on the subject. Yeah i know,you dont have the time/ too small a market. Understood.

Thanks for the advice. I realise now how the uneven surface of wood plays havoc with your scribing tools. Anyway I appreciate the comments and any advice you have. I am happy with how the masters are turning out.


David h

[He Who Shall Not Be Named]

Mighty clever for a torpedoman, Dr M. Im stealing a couple ideas, like the little pen clamp. And a media for poping out a resin pressure hull or two. I have made some 3 dimentional signage with HDU, hi density foam that can be sandblasted with a frisket. Easy to machine, carve, file, sand, and reasonable from sign suppliers. They even have some blocks with various densities imbedded to look like it was a wood sandblasted sign, if desired. Sold in blocks sheets of all sizes. Sold in colors as well. Any particular reason you use NitroStan, instead of something a bit more contemporary? 3M makes a good acrylac glazing putty. Doesnt shrink after drying like nitro. It doesnt "skin over" dry top-still wet, thingie that wants you to sand to early, as well. It has been a big issue topic, over on a couple other forums I follow. (Jalopy Journel} old hotrods and bikes and (The Sludge Trap} custom motorcycle stuff. I do a lot of custom artwork on cars bikes and boats and a few airplanes. Custom signs, paintings, murals are one of my main sources of income since high school. (Of course that was when first grade thru 12 was all in the same 1 room schoolhouse) The consensis is, the old greybeards use it because thats all they ever used since the 60s. The young bucks all swear by acrylac I tried to get the old PPG red oxide filler a year or so ago, but they discontinued it so they gave me the 3m, and Ive been happy with it, so far. 3M comes in other colors too,green,and white.

Official motto of all Torpeomen: "I may not be able to spell it, but I can lift it!"


The pen clamp is part of a waterline marking tool -- a derivative of the machinist's surface-gauge.

Let's have a source for that HDU you speak of. My substrate of choice today for master work is RenShape. http://www.freemansupply.com/MachinableMedia.htm

Nitro Stan? I love the smell!!!! And I don't use it for build-up. Only for scratches and engraved over-strikes. Most idiots at those sites try to use the air-dry touch-up putty as a substrate -- not what its intended use is. And most of those jerks in Internet land spend too much time jacking off in front of a computer monitor, rather than actually doing anything constructive in the shop. **** 'em! The deep fill and re-contouring work is left to the two-part, exothermic curing 'auto body fillers'. I used to hang out at those forums, only to find that most of those guys would rather talk, pontificate, and argue than DO the work! And the Moderator's and Administrator's at those sites are much more concerned about people being politically correct than learning anything. I wish I had a dollar for every forum I've been 'banned for life' from. (Hell, even Mike has banned me from this site on occasion!). Whoosies!!!!

Let's see some pictures of your work, Von!

M