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1/25 Type VIIC/41 Scratch Build.

This is the place to post your submarine build- ups.

Postby tsenecal » Sat May 19, 2007 11:18 am

Mylo,

I have not yet purchased any of this product (I plan to for my next large mold project), but it appears to be considerably cheaper at $99 ($89 bulk) for a TWO gallon kit.

http://www.dickblick.com/zz335/08/
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Postby Mylo » Sat May 19, 2007 12:11 pm

I would be very interested in seeing how you make out with that product.

Thanks for the link.

Mylo
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Postby Sub culture » Sun May 20, 2007 3:15 pm

'Why are you staring at an empty pond?'

Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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Postby Pirate » Mon May 21, 2007 10:21 am

I've used the Por-a-mold product from DickBlick. It's worked very well for me. If you don't have a lot of undercuts in your piece, get the hard. It will give a much more rigid mold which will be more accurate each time. Soft is almost too soft, and does tear easily. Medium is good for undercuts.

This is good for large molds, but it definetly needs a backing of some sort.

For small parts, the one-to-one RTV from Micro-Mark is great. It only has a 4 hour settup time, compared to at least 12 hours for the Por-a-mold. And it's very easy to mix by volume—doesn't need weighing.

Pete
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Postby Mylo » Mon May 21, 2007 3:01 pm

Pete,

Thanks for that info. Good to know.

Mylo
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Postby Mylo » Tue May 22, 2007 11:55 pm

Step 61 : Casting Parts

Time to complete : 30 hours.

Total time to date : 408 hours.



I decided to spare no expense and purchase a very high end injection system in order to cast my parts with. This "system", otherwise known as a turkey baster, cost me JUST ABOUT $2.00 !! I modified the baster with a brass end piece that would fit the holes in my rubber molds nicer.

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The product that I used to cast my parts is called Smooth Cast 305, a Smooth-On product from the same Sculpture Supply Store that I got my RTV material from. It is a resin that mixes 1:1 and is very easy to work with. It has a "working time" of 7 minutes according to the label, but it's closer to 5. After that, it starts to gell up pretty quick. I found that mixing a cup of each, for a total of 2 cups was the most I would mix up at one time. Any more than that and I found it was starting to gell before I could inject it into my molds. ....depends how quick you are I guess. A 2 gal kit of Smooth Cast 305 cost me $120. Castings could be demolded in about 1.5 hours, but they are still a bit soft. Total cure of the castings took about 3 hours. The cured resin is white....very white, easily visible through the semi transparent rubber molds.

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Casting of the parts is where you find out how good your molds are. I found I had to modify my molds after a few trial attempts to cast the parts in order for the parts to be produced bubble free. It was just a matter of adding some venting channels where needed. Knowing what I know now about making molds and casting parts, my next go at making molds will be a little different and produce a better mold. The last mold I made, which was for my fore dive plane armatures, was the best mold and produced the best parts. I figure that's no coincidence.

The actual casting of the parts is simple. Put a hard back on your rubber mold, clamp secure, and then get the liquid resin in the mold. In my case, it was a matter of using my high end injector to force the resin into the molds through the small channels. My injector technique worked very well. You want to make sure that you don't clamp the hard back to hard as to distort the mold. You just want to clamp to hold the two mold halves securely against each other. Once the mold was full, I would keep forcing the resin in, allowing some resin to seep out the vents to ensure I was getting a full casting and eliminating any trapped bubbles. Once the curing time has elapsed, the two mold halves are separated (no release agent required), and the casting removed. After removal, the excess resin sprue was trimmed off. Without question, this is a very effective way of reproducing parts.

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I attempted an experiment which I did not have a lot of confidence that it would work. I tried to cast my deck railings using the same exact rubber mold techniques as the other parts. I felt that the small diameter brass rod that I used to make the master railings would be too small to produce an effective mold. I was very pleased to discover that in fact I was able to cast these railing parts. The savings in time is huge. It took me about 2 hours to solder the railing out of brass rod, ....and about 2 min to cast the railing out of resin. The math is simple. The final casted railing will require some fine tuning on behalf of the modeller, but in all, I was pleased with the results.

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Once the parts were casted, I cleaned off the flash, trimmed, filled any minor flaws with plastic putty, sanded them, and prepped them with a first coat of primer. This process was time consuming but produced a more refined part.

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A modeller assembling the kit should have very little work to do on the parts to bring them up to a finished standard. This kit was intended to be a toy to play with in the lake/pool, and not a museum static display model. In total, I casted 142 parts, which is enough for 6 kits, plus 6 extra pieces that I will be using as templates.

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The "Time to Complete" includes all 142 parts for 6 kits with all the work I did to the parts after casting. Take this into account when looking at the 30 hours.

I am now going to be making molds and castings of the tower, putting my knowledge to good use.

More to come.

Mylo
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Postby Warpatroller » Wed May 23, 2007 3:54 am

Mylo,

Nice set of photos on your resin casting technique! I see you didn't use a pressure pot....your turkey baster is far more economical for eliminating air bubbles.

You plan to make this into a kit then, very cool. I found your reference to it as a toy for use in a lake or pool a bit humourous :lol: At an approximate length of 8.8 feet, I wouldn't exactly call it a toy submarine...and you'd have to have one big fricken pool to be able to turn that model around in it!! :wink: I've seen pools that are too small for a Revell VII, let alone yours. Also might need a jet ski trailer to haul it to and from a lake.

Awesome work though! I look forward to seeing it when your finished and hearing about your plans for providing kits. I can just picture a wolf pack of 10 of these models patrolling together on a big lake.... :twisted:

Steve
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Postby Mylo » Wed May 23, 2007 7:25 am

Steve,

No, I did not use a pressure pot in casting the parts, only to make the rubber molds. I wanted to try the turkey baster injection system first. I found it to work very well. Had it not, casting in the pot was my next choice.

Yes, I will be offering this sub as a kit. A finished date / price is yet to be determined. I will be completing my prototype completely before putting together any kits. Every kit will include my personal written guarantee of 100% satisfaction or money back. I'm not in this for the money, I just thought it would be kind of cool to make a few sub kits that modellers might enjoy building and operating. To say it is a toy is a bit of an understatement. The point being, I've designed this "thing" to be played with, ....or...I mean....to be used as a scale representation of a German U-Boat in order to recreate and simulate naval battles, .... yeah, that's better, .... and not just looked at, with attempts made to make the parts as robust as possible while still maintaining some detail. .....you don't want to worry about breaking something everytime you pick it up.

For sure, it would take AT LEAST an olympic size pool to turn this baby around in. It will not be known for it's nimble handling characteristics. If a person is looking for a sub to "scoot around with", this is NOT it. Ohh.....and I have plans on it's own custom trailer too. ....but that's a different thread for the future.

....could you imagine....you and 1/2 dozen of your buddies on patrol getting into position to launch an attack on some unsuspecting water fowl with some scale torps

TORPEDOS LOS !!!

:twisted:

Yep, potential for some good fun.


Mylo
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Postby Mylo » Fri Jun 01, 2007 5:21 pm

Step 62 : Tower Enclosure

Time to complete : 14 hours

Total time to date : 422 hours.



I decided to cast the tower enclosure in the exact same manner as I casted the other parts. This mold was going to take quite a bit of RTV due to the shape of the enclosure. I decided that I was going to cast the enclosure as one solid piece and then machine out the openings for the antanae later. I was thinking that this would increase the liklihood that the mold was going to make good castings by keeping the complication of the mold to a minimum. I'm not sure if there is any validity to this theory, ....it just seemed right to me.

LESSON LEARNED :

** DO NOT USE FOAM MASTERS IN THE PRESSURE POT **


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Earlier in the build thread, I showed how I made the large antanae enclosure out of extruded foam glued to the wood tower enclosure railing. It turns out, the 75 psi inside the pot during the curing of the rubber mold literally crushed this foam. In other words, foam masters will not work if the pressure pot is being used. I had to clean off the crushed foam, shape another enclosure out of MDF, glue it onto the railing, fill with putty, sand, and prime. Basically, I had to rebuild the enclosure.

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Once the enclosure was rebuilt, I had to cut out a section of the rubber mold that had been distorted from the crushing of the foam. With this chunk of the rubber mold cut out, I re inserted my rebuilt enclosure and poured a new batch of RTV into the gaps in the mold that were cut out. I just let this cure at ambient pressure instead of putting in the pot. This fix resulted in a reasonable mold, not great. I was running short (again) on RTV so I decided to live with this "patched up" mold instead of repouring another one. I will very likely re pour this mold in the future but for now, I used it to cast the part. Again, this mold uses a lot of RTV so repouring it is going to be costly.

Once casted, the antanae openings were machined out by drilling out the material followed by using various drum sanders in my rotary tool. This process went well, but it was messy. A by product of this process is stuff that will work real good as snow in a diarama or model railroad scene. .....not sure exactly when I'll use it, but I've got some snow when the time comes.

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After machining, the flaws in the casting were filled with plastic putty and sanded. Because of the flaws on the large antanae enclosure part due to the mold being patched up, I had to sand off the molded in rivets. The rivets were re applied to each enclosure separately. With the prep work done, the enclosure was primed. The damage to the mold created a LOT of extra work and I'm not terribly thrilled with the castings. They're passable....but barely in my opinion. The enclosures are still going to require some fine tuning by the modeller during assembly.

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Postby Mylo » Fri Jun 01, 2007 5:47 pm

Step 63 : Tower Antanae

Time to complete : 14 hours

Total time to date : 436 hours.



For the round antana, masters were made using brass rod in the proper scale. The brass rod was shaped around a piece of wood dowel, taking into account the amount that the brass was going to spring back. It turns out, a 1" dowel produced a nice 1 1/2" loop, which was the size needed. Once the brass rod was coiled around the dowel, individual loops were cut out with side cutters. The ends of the loops were sanded flat. The loops were placed in the antanae jig that was made which held the loop in place just right against the brass post. The two pieces were soldered together. Once soldered, the area was then ground with a sanding drum in my rotary tool. Three masters were made in the same way for the mold. The mold of the three round antanae were made in the same fashion as all the other molds. Experience was showing as the molds turned out really well, producing a nicely casted part that required very little cleaning up.

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I couldn't see any way to cast the large rectangular antanae because of the complicated shape (maybe someone can set me straight on what each antanae does), so I decided that each rectangular antanae would be scratch built. Initially, I used brass strip/rod soldered together to build the antanae with screen door mesh used for the "mesh" part. After getting 3 built, I ran out of the brass strip that I was using. I COULD NOT find the right dimension of brass strip to complete the other antanae and I was having no luck cutting my own strip out of brass sheet. I did find the proper dimension strip in styrene and so decided to build the antanae out of this instead. It turns out, I like the styrene better not only because it's easier to work with and cheaper, but it produced a nicer looking light weight model. I built a little jig to hold the parts in place for gluing. ....I pretty much build jigs for anything. Each antanae took about 45 min to scratch build.

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All the antanae were primed once built. I had noticed that it was very difficult to tell the brass ones from the styrene ones apart once primed...except that the styrene ones looked just a little nicer because of the lack of the soldered joints.

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More to come.


Mylo
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Postby Mylo » Fri Jun 15, 2007 9:38 pm

Step 64 : Schnorkel

Time to complete : 12 hours

Total time to date : 448



The construction of the schnorkel required different sizes of brass and aluminum, both rod and pipe, as well as MDF to build the mold masters from. Nothing different here. Dimensions obtained from plans, masters made from a variety of materials, rubber RTV molds made from the masters, resin parts cast from the molds, flaws filled with plastic putty, sanded, primed. The Kohl plan set had a real nice diagram of the schnorkel mast head that I was able to get very accurate dimensions off of to replicate the 1:25 scale head. As can be seen, I molded the float valve shut off right into the mast head. I tried to mold the mast head bolts into the castings, but they just didn't turn out well so I ended up sanding them all off in doing some prep sanding on the heads. The modeller will have to re apply these bolts if desired.....not hard to do. The schnorkel tube was made from 3/4" aluminum "stream lined" tubing. This stuff is basically tear drop shaped. In both ends of this stream line tubing, brass tube was inserted. The tear drop shape wave deflector was glued to the top of the aluminum tubing, with the brass tube glued into that with the help of machinging out an opening for the tube to fit into. Since the stream lined schnorkel tube is free flooding, small air vent holes were drilled in the top near the wave deflector so that the tube itself does not trap air on diving while the schnorkel is in in the upright position, which would screw with the bouyancy calculations. On top of the brass tubing, the mast head was mounted with the same technique. The small air vent was then mounted. A hole was drilled directly throught the lower pivot casting to allow the insertion of a stainless steel rod. This rod is going to be the pivot point and allow the schnorkel to be raised and lowered manually. It is made out of stainless to reduce the corrosion. The pictures tell the story, I'll let them talk.

** NOTE The wave deflector casting is not in the photo but is part of the castings to assemble the schnorkel. **


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All the castings and parts to build the schnorkel will come with the kit, but it will be up to the modeller to assemble it. Machining to the lower pivot casting, mast head, wave deflector has been done to ease the build process.


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Postby Mylo » Fri Jun 15, 2007 10:05 pm

Step 65 : Hatches

Time to complete : 20 hours.

Total time to date : 468 hours.



Building the hatch masters was no problem....easy in fact. Building the RTV mold was a completely different story. To keep it short, I had to repour the rubber mold for the hatches FOUR TIMES !! before figuring out that the primer that I was using on the masters was causing the RTV not to cure. Why this primer was doing this while none of the other primers I have been did, I have no clue. HOT TIP ** Don't use Tremclad metal primer on any RTV masters **. This lesson cost a LOT of time (making, remaking, remaking masters, molds, ...etc., etc.) and a lot of money, ...like most lessons do. Each time the mold didn't turn out, I would change something that I thought was effecting the cure. As mentioned, it took 4 goes at it before I changed primers, which fixed the problem.

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In addition to the actual hatches, I made the latches as well. 1/8" brass rod was used for the shaft and 1/16" brass rod for the handle. The 1/8" rod was ground flat every 3/8" so that the drill bit would not slip off when drilling the hole for the handle. A 1/16" hold was drilled out. The shafts were then sheared off to created each individual shaft. Then the proper length of handle was cut with a slight taper sanded on the ends. The four upper deck life boat hatches as well as two of the smaller ammo containers have 1/2" handles while three of the other larger ammo containers have a 5/8" handle. Once the handles were made, they were inserted into the drilled out holes of the shafts with the shaft then ground down to size. 1/8" holes were drilled out of the hatches to allow for the insertion of the handles. The handles were glued/pressed into the hatches.

All the materials required to make the latches will come with the kit for the modeller to assemble. These little latches make for real good first time scratch build projects.

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Next came the construction of the hatch hinges. 7 hinges in total would have to be made, 4 for the upper deck life boat hatches, 1 for the main tower hatch, and 2 for the larger ammo storage containers. The 2 small ammo storage containers do not have hinges.

I will let the picture speak for how the hinges were built. Drill some holes in brass flat strip, bend. Put length 3/32" brass rod through as the hinge pin. Cut some flat brass strip as the hinge arms. Simple....a little time consuming, maybe, but simple none the less. This little project as well makes for a real good first crack at scratch building something.

All the materials needed to build the hatch hinges will come with the kit for the modeller to build.

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Postby Mylo » Fri Jun 15, 2007 10:14 pm

Step 66 : Upper Wintergarten step ups.

Time to complete : 2 hours.

Total time to date : 470 hours
.


Very easy little project. Masters made from the plans. Masters made to trace out on .040 styrene sheet. Step ups cut out of styrene sheet using scissors. Sanded. "Wood grain" etched into the styrene by dragging a fine tooth saw across the surface multiple times for effect. Styrene was used instead of actual wood to avoid any warping problems from the water. These steps are quite thin and if made out of actual wood, would warp easily. Once painted and weathered, the simulated wood grain on the styrene will look very much like wood without the warping concerns.

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More to come


Mylo
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Postby Mylo » Sun Jun 17, 2007 12:13 pm

Step 67 : Conning tower parts Cont'

Time to complete : 6 hours.

Total time to date : 476 hours.



These three conning tower parts include:

Attack scope mount
UZO mount
Ammo cannister.

The masters were shaped / sanded out of wood dowel of the proper size.

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More to come.
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Postby Mylo » Mon Jun 18, 2007 1:51 pm

Step 68 : U-Boot ZielOptik (UZO).

Time to complete : 2 hours.

Total time to date : 478 hours.



For those unfamiliar with what an UZO it, it is basically an optical device, not unlike a set of binoculars, used to target vessels while the U-boat is on the surface. They have the appearance of a very large set of binoculars with some additional "gadgets" on it.

I felt that the conning tower would be incomplete without this very important little device, so I decided to model it. My Kohl plans had a real good drawing of the UZO which provided for some accurate measurements. While the UZO would be modelled, I wanted to keep it simple as each UZO would be scratch built out of brass. I did not want to spend the next year making UZOs. This simple build would consist of modelling to scale the two main binocular housings with an emphasis on the taper from the eye piece. The two individual housings would then be CA glued together, using the CA sparingly. When mounted on the pedestal, the glued side would face down so as to expose the more detailed side that does not have glue on it.

Machining the two individual components was easy. I simply chucked them into my drill press and used a file to shape. Once shaped, a slight taper was ground to the eye piece to give it a more realistic and finished look. A drop of CA and the two pieces were connected. Once together, I ground the lens side down very slightly so that both were flush.

I'd like to point out something about scratch building. Trying to figure out HOW to do the build can take just as much time as actually building the part. I must have tried 1/2 dozen different techniques to make these UZOs until I came up with one that produced not only a decent looking part, but was relatively quick to do. Once I settled on the technique, it only took a few minutes to make each UZO. Discovering and inventing scratch building techniques is one of the things I enjoy about the process, but it does eat up the clock. You have to be willing to throw a lot of attempts in the garbage.

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Thought I'd throw a simple little job in here.


More to come.


Mylo
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