Mylo's 1:25 type VIIc/41 part III

**mylo** · 10-16-2007, 12:45 PM

Step 77 ]

I've been

[b]Step 77 ]

I've been very busy in the ship yard for the past 2 weeks.

I finished assembling the other 5 tower halves which included fitting them together and filling/sanding/priming. It took some effort to get a perfect fit of the two halves due to some slight shrinkage in the resin causing distortion on the flat top and bottom surfaces. In hindsight, getting this perfect fit on the top and bottom was not crucial because I found myself removing a very large portion of both these areas on my prototype to lighten up the tower anyway. I expect to eliminate this in the future by making these castings from epoxy. The end result will be the same, just less work to get them there. ....and so goes the learning curve.

My order of 3/32" brass rod FINALLY arrived and so I got busy building wintergarten railings for the remaining 5 towers. Each railing had to be scratch built using my jig. As much as I tried to find a quicker way by making molds and castings out of plastic, all my experimenting failed to produce a nice railing, and so....I went with the decision to make them all out of brass. I feel that wintergarten hand rails are a detail on U-Boats that just can't be compromised in their appearance. It's probably one of the first details I look at when I'm looking at a U-Boat model of any kind. As labour intensive as it was, I'm happy with the results. Even the soldered joints have the appearance of welds which, in a boat of this scale, are the kind of details that I like to pay attention to.

I intend on building two complete models, one weathered, and one that is not weathered to represent the actual boat on display in Laboe Germany. The remaining four will be part of the kits that I intend on offering for sale. In the above photo, the tower on the far right is my completed/weathered prototype. The tower on the far left is the start of the non weathered U-995. My prototype represents what can be done with the parts included in the kit. There are no additional "detail" parts added to this prototype. I've included the following 3 pics to give an idea of the tower detail "right out of the box".

After a lengthy delay in progress, I'm back at 'er. All ahead, flank speed.

More to come.

Mylo

**mylo** · 10-20-2007, 01:24 PM

Step 78 ]

The decision

[b]Step 78 ]

The decision on exactly how to go about creating the main deck piece did not come easy. I toyed with the idea of designing it with CAD and having it hydrocut out of styrene, but this was going to run me several thousand dollars to tool and program the hydrocutter. If I was making thousands of them, this would be the way to go, but 6.....uhhhh....no. In the end, I decided to make a rubber mold in the exact same manner as I made the deck pieces for the wintergarten. I was pleased with the results of these wintergarten pieces and this was the reason I chose to go this way. However, those small wintergarten deck masters took me a long time to make, I knew what was facing me in making the master for the main deck.

I started by building the mold box. I'll let the picture speak. It can be noted the modification made to the box to reduce as much as possible the amount of rubber mold material needed. At $220/gal....you don't want to be filling up needless voids with this stuff. If you are thinking about building a lot of mold boxes, buy yourself an air nailer. Mine has saved me a lot of time and frustration. I was able to build this fairly complicated little box in 1 hour thanks to it.

This main deck piece is 80" long. I needed to glue together two pieces of 1/8" hardboard to get this length. Once the glue had cured, I had 1 piece, but it was very delictate to handle because this joint was weak. It didn't need to be strong though, I just needed it to hold the pieces together until I had them nailed into the mold box. I put the main hull plug inverted (flat upper deck facing down) over the hardboard. The perimeter was then traced onto the hardboard using a marker with a LOT of care. With the outline of the upper deck traced onto the hardboard, I cut out the entire piece on my band saw. This was a circus act to say the least, trying to balance this long, flimsy, piece of hardboard while I made the cut, which had to be accurate as to the mark. In my case, I set up all kinds of tables and stands to support the board, but having two people for this job would be best. I found myself cursing quite a bit. Once cut out, I placed the hardboard template onto the hull plug for a test fit. I found I had to do a little fine tuning with my sanding block, but in all, the cut was a success.

I then placed this cut out template into my mold box and nailed it down with small finishing nails. The idea is that once I get the deck master completed with all the planking, plank bolts, hatch details, and whatever else, it will be secured to the bottom of the mold box. THEN...then rubber RTV will be poured in, which will totally cover the master because the walls of the mold box are higher than the top of the master. When cured, the rubber mold will be lifted out. Voila, main deck mold. Further photos to follow will help clarify.

The main deck template was now secure in the mold box, time to detail it. I used strip balsa (exact same stuff I used for the wintergarten decking) for the decking. Not rocket science, but it IS very precise work to get the decking in place properly. I drew a reference line down the exact centre of the template and starting laying the decking from the inside, working out. I used some HO scale railroad tie spikes to secure the decking down to the template. These spikes make very nice scale looking deck bolt heads and are the perfect size to nail down the decking with. I did have to drill pilot holes for each nail with a pin vise so that the nail would not split the balsa.

Once all the decking was laid, I added further deck bolt detail, then I cut out the hatch markings. Further deck bolt detail was added in these areas. After the hatches, I added the metal plate detail using styrene. I had to fill the cracks between the balsa strip wood that lies underneath these spots so that when I pour the rubber, it does seep in under them, making removal of the mold likely to trap these styrene pieces inside. Wood filler was applied and sanded to do this. The final thing I added to this master was a reference point as to where the tower is mounted.

The main deck master was finished. I would have been ready to pour the rubber, but I decided that I wanted to thin the rubber out so that it would capture all the fine detail of the master a little better. I had to order a thinning agent for the rubber molding material and am currently awaiting it's arrival. Once I get it, I will pour this mold and then be ready to start casting plastic resin deck pieces from it.

Today, October 20 2007, marks the 1 year anniversary of my start date on this project. It's been a year of continual learning and a boat load of dedication. My enthusiasm towards this project continues to be high. Good sign.

More to come.

Mylo

**mylo** · 10-29-2007, 01:34 PM

Step 79 ]

Upon receiving

[b]Step 79 ]

Upon receiving my rubber thinning agent, I went to work pouring this massive mold. I took a lot of care to make sure the master was sitting perfectly level to ensure that the rubber would flow evenly, and not pool at one end, or one side. (pour a mold like this sometime, and you'll know exactly what I mean). It took 16 cups of rubber material to make this mold. The thinning agent worked very well allowing the rubber to flow better into the fine details of the mold master. It took very little of this thinning agent, just a few mls per cup. I let the mold cure overnight, giving it twice as much cure time as I had given my previous molds. I should point out that the thinned out rubber was able to release the air bubbled in the mold better. In extracting the rubber from the master, the master had become quite badly damaged from little pieces of balsa breaking off and becoming stuck in the rubber. Thankfully, this did not deter from the quality of the mold as it just meant I had to pick the tiny pieces out of the rubber, but it did mean that the master was good for one pour only without having to spend a lot of time repairing it.

I put the cured rubber mold back into the master box to cast the part, with of course, the mold face up. This is done to provide a rigid support for this long, relatively thin, and flexible mold. Without doing this, the risk of positioning the rubber mold in a "bent" position, resulting in a "bent" casting.....even if ever so slightly, is possible. Placing the mold back in it's master box prevents this problem. The box also allows for the rubber mold to be leveled because just as it was important to avoid pooling of the rubber material, the same holds true for the casting resin. The casting was poured which took 1500 mls. of Smooth Cast 305, which is the same stuff I've casted all my parts with.

The casting was extracted from the mold after letting it cure over night. I continue to be impressed by the rubber mold and resin casting products from Smooth-On. All the detail of the master was replicated into the mold, and subsequently into the casting. I'm happy with my decision to cast this main deck part as one piece, it will make for easier assembly of the model. I left about an 1" of deck at either end of this main deck casting so that in assembly, a perfect fit can be obtained between the main deck and both bow and stern deck plates with the excess material of the main deck casting simply trimmed off. ....easier to remove material than add it.

The full 80" length of the main deck casting.

Details such as the individual planks, plank bolts, hatch openings and wood grain were captured in the casting. The "half moon" area on the deck in a reference point for locating the front of the tower.

More to come.

Mylo

**mylo** · 10-31-2007, 02:43 PM

Lessons of the day:

Lesson 1:

Lessons of the day:

Lesson 1: Always test your product before pouring it into a mold.

I used a totally new batch of resin to cast my second main deck casting. The resin didn't cure.....for some reason. It ended up sticking to my mold. When I *tried* to remove it, the mold was ruined. 19 hours of labour and $150 worth of rubber down the shitter. I will have to build a new main deck mold from scratch. Not happy.

Lesson 2: Always test your fillers/primers before applying rubber RTV to it.

I had to repair some minor damage done to my hull plug from all the handling I had to do on it to swap it around in my parting box to mold the other half.....I ended up putting a little ding in the keel. No biggie. I fixed it with wood filler. After letting the wood filler cure, I applied grey primer to the area, sanded, and had the repair totally invisible. After letting the primer cure over night, I applied the Smooth Sil 920 rubber RTV to the plug, just as I had the other half, let set overnight to cure. Next day, the rubber was not cured in the area of my fix. I had a hell of a mess on my hands. Not happy. The next several days was spent experimenting with different primers to see which ones inhibited the cure. As well, it turns out that wood filler is a NO NO, do NOT use wood filler on your masters, it inhibits the cure in a big way.

From left to right, primers and their effect on RTV curing:

Tremclad Inhibits cure
Painter's Touch No problems
Painter's Touch primer No problems
Armour Coat Inhibits cure
Krylon No problems
Krylon plastic paint Inhibits cure
Krylon H2O No problems
Professional Primer Inhibits cure.

To sum it all up, TEST YOUR PRODUCTS on sample pieces. It could save you hours and hundreds of dollars in materials.

Major set backs this week. .....Not happy. I continue to have such lessons beat into my head with a sledge hammer.

More to come, once I get through cleaning up my little disasters, ordering MORE product, and re doing stuff again.

Mylo

**mylo** · 11-02-2007, 05:16 PM

Step 80 ]

Time to

[b]Step 80 ]

Time to finally put to use that hull plug that has been sitting around so long by making the hull molds from it. The technique is the exact same as when the molds were made for the tower, only of course on a larger (and therefor more difficult to handle) scale. To recap:

1) 1/2 of the plug is to be exposed for the making of the rubber mold. I chose port and starboard halves, but I see no reason why an upper and lower configuration couldn't be used. This is done with the use of a parting board. A hole is cut in the board the shape of the plug, with the plug positioned inside it, exposing one half of it. The remaining gaps are filled in with Clay to make a seal. For this hull plug, I built a box to contain those foam packing peanuts that I put inside. This foam supported the plug from underneath. You do not want the parting board to be supporting the plug, it acts as a shield only. Before putting the plug in the parting board, I used 1/4" masking tape down the exact centre, all the way around the plug. This tape is going to leave an indentation in the mold, which will be cast onto the part, looking like a line. This line will be a reference to where the part needs to be sanded down to. Without this reference line, getting the part sanded down to the proper size after removing from the mold would be a HUGE hassle, if not almost nearly impossible to do. This will become evident when I show the casted hull parts and the removal of the excess material.

2) With the plug now in position, time to get out the gooey stuff. I used Smooth Sil 920 from Smooth-On as my initial RTV glove. I just brushed it on with a paintbrush after mixing it 1:1. I did not use any release agent of any kind. This glove is going to capture all the fine details of the plug. Let cure overnight.

3) With the initial RTV glove cured, I applied two coats of Rebound 25 from Smooth-On. This stuff is mixed and applied the same way. It acts as a rubber reinforcement to the somewhat delicate initial glove, giving the whole rubber mold some thickness and strength. This stuff is orange coloured. Each coat is left to cure over night. Rebound 25 WILL stick to the Smooth Sil 920, forming one unified piece of rubber.

4) The rubber mold is now basically done. I trim the excess away around the plug leaving a nice clean edge. Now a hard back is needed to provide the rigid support for the rubber mold. Without the hardback, all you have is a floppy rubber "thing" that is useless, if you can imagine a person without a skeleton............anyway..... Now I apply two layers of polyester fiberglass resin / fiberglass cloth, letting each layer cure, which takes about 4-5 hours. When the whole thing cures, it's hard and is perfectly conformed to the rubber mold, providing what is essentially an exo-skeleton for the rubber mold. I prefer the fiberglass hardback over other materials such as plaster due to it's light weight. With the sizes I'm dealing with on this 1:25 scale U-boat, I have to consider such things. One of those molds complete with the hardback and stand weigh about 25lbs. I could probably add a zero to that if it was a plaster hardback.

5) Before removing this whole thing from the plug, I will put a base on it, making sure it's level. I use Gorilla Glue for this and let it set overnight.

Those are the steps to make a mold for 1/2 the plug. Now comes the difficult part, extracting the plug from this stuff you've piled on top of it. Granted, the Smooth Sil 920 does not stick to the plug, but there is a bit of a vacuum created that keeps everything stuck down. It's a matter of fiddling and prying, and pulling to get them separated. The tough part is not to do any damage to your plug or the hardback in the process. It can be done, I did it twice, once for each side. To make the other half, repeat the process by inverting your parting board, and positioning the other side of your plug. I used a particle board parting board, which was crap. It broke when I was removing my plug so I had to fix it too. If I was doing it again, I would use 5/8" plywood, maybe even 3/4". I cheaped out on the particle board and it cost me time and effort.

This pic shows the parting box, parting board (which is basically the lid for the box), and all the layers of rubber as well as fiberglass hardback complete with stands applied. Under all that stuff is the plug. This is now ready for removal.

This pic shows the two port and starboard molds. The upper one has cross supports already in place. These supports ensure the correct shape of the hardback, given that the hardback does have a little bit of flex in it. I thought about simply making the hardback thick enough that it wouldn't flex, but I decided that this would not only make it much more difficult to remove from the plug/rubber but as well be considerably more costly / time consuming to make. I concluded that I would probably add the supports ANYWAY to a thicker hardback to make sure things were bang on. I figure that even a thick hardback would flex a little. Making and installing the braces was not difficult, and took about an hour and once in place, the hardback is very rigid, as in....it does not move at all. The same supports will be put on the bottom one. The bottom mold has the rubber pulled away from the hardback to show how flexible that rubber mold actually is as well as exposing the hardback underneath and how it conforms. The rubber mold has captured all the details of the plug very nicely.

These molds are ready to start producing some hull castings. Ooooo Goody

More to come.

Mylo.

**anonymous** · 11-02-2007, 11:11 PM

Excellent Mylo. Soon you'll have

Excellent Mylo. Soon you'll have a boat to build. Congrats! That worry is out of the way. It only gets better from here.

Steve

**mylo** · 11-03-2007, 01:27 AM

Steve,

You hit the nail

Steve,

You hit the nail on the head with that comment. Getting these molds made (successfully) is a BIG hurdle and quite a relief actually. She's all good stuff from here on in. (only took a year to get to the "good stuff). Should start seeing my prototype model coming together fairly soon, I'm pretty pumped about that. Pumped = motivated = putting lots of time in to see results.

Mylo

**mylo** · 11-06-2007, 11:26 PM

Step 81 ]

It is

[b]Step 81 ]

It is important to make sure that your rubber mold is seated PERFECTLY in the hardback otherwise, your casting will be distorted in some way, even if just a liiiitle bit, and it will be junk. (Care to ask how I know this ?) Do not be careless with this step as I was. What I did discover on making the first casting from West System Epoxy, is that the Epoxy was chemically repelled by the rubber mold. It just would not stick to it, it would bead up, like trying to make oil stick to water. While there are other solutions to this problem, I chose to experiment with applying my first thin coating to the mold using fiberglass resin. I found that when I used the resin for the towers, that it captured the details of the mold very nicely and stuck excellently to the rubber mold, so, I would use it for the hull castings. This first layer simply captured the detail of the mold and is a fraction of a mm thick. Given this, there were no problems associated to resin shrinkage. It turns out that this experiment/fix worked very well because the Epoxy stuck very well to the resin. Chemicals....go figure. I applied the initial coat of resin and let cure overnight.

With the resin fully cured, I applied two coats of West Systems Epoxy. It was time to try out my new toy that I bought from Aircraft Spruce. I have their catalogue and MANY of the things, materials and tools they have in their composite airplane construction section apply to building subs. I decided to buy the Epoxy dispenser.

I can not speak highly enough for this thing. It makes handling Epoxy a breeze, quick, easy, and most importantly, without a big mess on your hands. In the case of West Sytems Epoxy, it is mixed 5]http://i119.photobucket.com/albums/o153/Mylo42/81c.jpg[/img]

After trimming the excess cloth from the casting, I primed it. Another nice thing that I like about the resin is that when it is extracted from a mold, it's still a little tacky, this is just the way this stuff is and has nothing to do with it being partially cured. When primer is applied to this, it is bonded completely to the casting. The tackiness lets the primer really bite into the casting. I've tried to chip and flake the primer off on test pieces, and it will not, it is part of the casting, which is really nice. Once the primer is dried, there no longer is any tackiness to the casting. I prime it at this point so that no sanding dust from the sanding of the casting sticks to it as well, it makes the sanding reference lines easier to see.

With the primer on the casting dried (takes about an hour), I sand the casting down with a belt sander to the reference line that is cast into the part (if you recall me mentioning this is a previous step). It can be seen how difficult it would be to sand the casting down the right amount if there was no reference line casted right into the part.

18 hours later, I have two Epoxy hull halves.

I was very happy with the castings. As suspected, the resin captured all the details of the mold not the least important being the reference markings for the flood holes. It can be seen in the following photo that the flood holes have been drilled/ground/filed which would be a hell of a job without those reference markings. The casting was made deliberately thinner in the areas of the flood holes to give the thickness in the area a more realistic/scale appearance. I did grind some Epoxy out of these areas from behind (obviously) to thin it up a little more.

More to come.

Mylo

**anonymous** · 11-07-2007, 06:38 PM

Mylo,
Not one question was

Mylo,
Not one question was asked other than some limited instruction awhile ago and you make this impressive first time casting and you have the limber holes too! I am so impressed. Give yourself a huge pat on the back!!

Excellent work! Bravo!

Steve

P.S. Send me an email to: sneill@socal.rr.com some one very special would like to talk to you.

**mylo** · 11-07-2007, 07:26 PM

Steve,

I ask questions when

Steve,

I ask questions when I'm COMPLETELY clueless, otherwise, if I *think* I know how to do it, I give'er a go. Mind you, my first attempts have about a 22% chance of hitting the garbage can. As much as they are frustrating, the lessons I learn the hard way teach me the most. I'm getting better at this whole sub building thing and working with these types of materials/techniques.

As far as the limber holes are concerned, those were machined out the "old school" way.....see step 82.

Mylo

**mylo** · 11-07-2007, 07:40 PM

Step 82]

First, I drilled

[b]Step 82]

First, I drilled out the ends of the holes with my rotary tool on max rpm and a high speed drill bit of the right size. Then I machined the middle out using the same bit. The high speed drilling/machining avoids chipping of the Epoxy. It takes a very steady hand to do this without making a mess of your hole. After the holes were roughed out, I got out the old flat and round files of the right size (which were in a mini file set that I have), and went at it. Once the holes were done, I turned the casting over and ground out some Epoxy around the holes to thin it out in these areas for a more scale appearance. BIG TIME caution has to be taken not to grind through the hole. After that step, I Epoxyied all the small supports in place on the "long flood hole". In all, getting the holes done is quite a delicate operation. Afterall, limber/flood holes MAKE a U-Boat.

More to come.

Mylo

**mylo** · 11-10-2007, 03:01 PM

Step 83 ]

I was

[b]Step 83 ]

I was not expecting these two halves to fit together like a Swiss watch, and so it came as no surprise for it to take a great deal of time to get them fitted just right. I knew I was in for a bit of a challenge since I had made these two casting very different from each other, being that I'm still in experimental/learning mode. On the outide, they are identical as to the mold. Their thickness of Epoxy is another matter. The first casting I made was overkill, WAY too thick and rigid. Could use the thing as a diving board. The second casting is much closer to how I plan on making my others. Now I was faced with sticking these two pieces together and in the process, I had to form an invisible seam.

I started out by double checking that I had sanded the castings down to the reference line. I needed to do some touching up by hand with a sanding block to do this since the belt sander tends to take a lot of material off very quickly, even with fine grit paper. Once this was done, I placed the two castings in the stand. I was pleasantly surprised to discover that the two pieces married up better than I was expecting with some minor grinding needed at the bow and stern only. Since I figured the bow was the most important feature to get as good as I could, I started there. I secured this area with duct tape and then did the same with the stern. Once the two ends were done, I fiddled around with the keel, using clamps, until I had it as good as I could get it. Things were progressing nicely.

In two hours, I had the both halves ready to be epoxied together, fitting quite nicely.....except for the 8" area at the limber holes on the underside near the bow. In this area, the difference in construction of the two halves was really showing it's ugly head, they just were not aligning nicely here at all.

If you're going to be a scratch builder, you might as well consider yourself an amateur tool builder as well. I had to build a special tool that would hold the two hull halves apart just a little bit for them to fit right. I call this tool a.......hull separator....yeah....a hull separator. I had to build two of them of different sizes in order to tackle my particular situation. This tool is very simple and is essentially wedged in between the two castings to force them apart. I had to build them very close to the size I needed, but the extended nut in the middle does allow for some minor adjustment. The sharpened ends dig in to the epoxy castings to keep them in place. These tools worked great. *PATENT PENDING*.

With the tools in place, I zip tied the underside. This allowed for the fit I was looking for.

With the both halves secured and matched up, I began brushing the epoxy all along the seam from the inside. I then put in some fiberglass cloth along this seam and applied more epoxy. This will make for a strong joint, or closer to what I'm after is to eliminate the joint all together since the epoxy will bond to itself and form bascially one piece. This is why I chose a starboard/port configuration for my hull halves. This configuration lends itself very nicely to applying this epoxy/fiberglass cloth since the majority of the seam is in the keel, which is easy to get at and do. With the two hull halves sitting upright in the stand, the rest of the seam is also not difficult to get at, with the epoxy flowing into the seam with the help of gravity. Additionally, the seam is going to be located in a far less noticable place being along the very bottom of the sub. ...AND....there is no need to worry about the seam along the top since that area is cut out to allow access into the hull. Once this initial application of epoxy had cured, I applied another coat and let this cure. The result was a very strong bond between the two hull halves. This whole process took about 6 hours. The remaining 10 hours was spent doing the finishing to the seam on the outside, making it invisible.

I've said this before, but, if you have a fear of sandpaper, do NOT take on a scratch build. To make it short, I worked the seam with fillers and sanding until I got it as good as I could. 10 hours was spent doing this.

I finally pushed myself away from it and said, "That's good enough". This hull is not without flaws, but I believe in order to make it PERFECT, would likely mean that I would never get the thing done. This first hull I'm making is not much more than a practice/display only model. I felt I practiced enough on this part.

Now for my Lesson of the day portion.

When you apply epoxy from the inside of your hull, pay attention that you aren't applying it over top, or even near for that matter, of the limber holes that you have already drilled/ground/filed. You see...what happens is, ...the epoxy leaks out of the limber hole and drips down the outer side of the hull. When this epoxy cures, you have to redo (yep, get those files out again) all those limber holes that have filled up with epoxy as well as spend a stupid amount of time sanding the epoxy off that dripped down the outside of the hull. This will mean that you will have to replace HUNDREDS of those tiny rivets that were casted so nicely into the part because you had to sand them off to get the epoxy off. This little lesson cost me 5 hours, save yourself the grief and be careful with your epoxy brush.

More to come.

Mylo "Master of doing things twice" Hall

**raalst** · 11-10-2007, 04:07 PM

Hi mylo,

thanks for

Hi mylo,

thanks for the continuing education.

If you are planning on sailing this first boat,
please consider that the difference in thickness
of the halves probably mean it is going to have a
weight asymmetry and will require
some lead to have it floating upright.

**mylo** · 11-10-2007, 05:48 PM

Ronald,

.....and THAT....is exactly why this

Ronald,

.....and THAT....is exactly why this first boat will be display only. I feel that the hull castings are just too different in weight/displacement due to the thickness. This would very likely cause stability issues or at the very least, some wacky weight/balance problems. I could just see it with a 30 degree list to port no matter what I did. This is something I plan on rectifying in my next hull castings by ensuring the exact same weight/volume of material is used for each. I'm hoping that this first one will turn into a reasonable U-995 display model, even though it IS basically a practice session. I've got a number of things that I plan on doing differently.

Mylo

Mylo's 1:25 type VIIc/41 part III

Mylo's 1:25 type VIIc/41 part III

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