Gwen's all metal scratch built 1/32 Type VIIc

[gwen]

Re: Gwen's all metal scratch built 1/32 Type VIIc

A quick update on my progress... I haven't had a lot of time the last week to do much on it but here are a couple photos of the aft dive plane control linkage and the aft torpedo tube installations.

After giving a lot of thought to the metals issue I think I may use foam, sealed on the outside with epoxy and then covered with thin sheet aluminum glued to the surface. I'll do some tests and see how this works.

[gwen]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Having a Engel kit, I can say that most of the metals that are in contact with the water seem to be stainless steel and brass. The rest stays inside the water tight 'deck,' surrounded by the fiberglass/epoxy hull and deck. Even the w/t deck cover is stainless, though every one I've seen on the web has had theirs replaced with a sheet of clear Acrylic.

Gwen, have you done the math yet to determine what will be needed for positive and negative buoyancy? I'm also interested in what water you'll be sailing in (fresh, salt, chlorine). I didn't see anyone bring this up, but salt (some pools are salt now) and chlorine water are fantastic conductors which speed up the anodization process. Fresh water isn't as good, but is a better oxidizer. I've never heard of it being used in scale, but in real life sacrificial metals like zinc are used to slow anodization and oxidation. Most ships and some subs have zinc bars along the hull that gets oxidized and anodized away to preserve the hull. If you want to go down another path there is always Anti-fouling paint, but thats a bit extreme and expensive.

Some good thoughts there. I have not yet done the math on buoyancy. I could actually use some help finding how to calculate it properly.

Gwen

[southern or]

Re: Gwen's all metal scratch built 1/32 Type VIIc

http://formulas.tutorvista.com/physi...y-formula.html Keep in mind that fresh water is the least dense while salt is the most with chlorine somewhere in the middle. For those of us who use static diving systems (ballast tanks) going from one water type to another can cause problems since the amount of water needed for floating and submerging ballast is different. For example-if my typhoon was setup for high salinity and I used it in a low density fresh water pond the water line would be off and with the ballast tanks full it'd sink like a rock-but that can be over come with diving planes similar to dynamic diving-where the force of the dive planes and the momentum of the boat force it under rather then taking on water in tanks.

[JWLaRue]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Gwen,

First thing we'd need to know is whether you are going to go with a dry hull or wet hull boat. Once we can get an idea of the displacement, we can start figuring how large the ballast tank needs to be.

-Jeff

p.s. I probably should not assume that the term "dry hull" and "wet hull" are obvious in their meaning, please holler if they don't!

[gwen]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Gwen,

First thing we'd need to know is whether you are going to go with a dry hull or wet hull boat. Once we can get an idea of the displacement, we can start figuring how large the ballast tank needs to be.

-Jeff

p.s. I probably should not assume that the term "dry hull" and "wet hull" are obvious in their meaning, please holler if they don't!

No, I understand the terms. I plan to go with a wet hull, with all flooding ports open to the water and a watertight pressure hull for the electronics and ballast tanks. I am pretty sure I want to use piston type ballast tanks.

[JWLaRue]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Okay...so in really *rough* numbers (and assuming my calculations are correct!), the workable ballast volume looks like it'll need to be around 1700-1800 ml. Ultimately it will depend on the actual displacement of that part of the U-boat that is at and above the surfaced waterline. I based my estimate on what's required to lift/float an OTW Type VIIC in 1/32nd scale.

Caveat: Since you have transverse frames that will be above the waterline, it's possible that a bit more may be required.

-Jeff

[salmon]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Jeff'
Would you step me through how you came up with that? It would help me.
Peace,
Tom

[Guest]

Re: Gwen's all metal scratch built 1/32 Type VIIc

A clue in Jeff's posting, Tom!

I based my estimate on what's required to lift/float an OTW Type VIIC in 1/32nd scale.

[tsenecal]

Re: Gwen's all metal scratch built 1/32 Type VIIc

A clue in Jeff's posting, Tom!

I based my estimate on what's required to lift/float an OTW Type VIIC in 1/32nd scale.

Which Jeff built one of.

[salmon]

Re: Gwen's all metal scratch built 1/32 Type VIIc

I did not mean to sound dumb, but I did not know if there was additional calculations involved. if Jeff may have taken the otw one and made adjustments for material.

[steveneill]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Got my eye one this one. Always wanted to make a metal boat. Great job so far!

Steve

[JWLaRue]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Yea, sorry...no concrete mathematical magic in this case. However I did notice that in my build, the ballast tank did not need to be full in order for the U-boat to submerge to periscope depth. So I "eyeballed" the delta between that and a full tank. But then to be conservative, I added some ballast volume back in because the construction of Gwen's sub has more upper casing structure.

My goal is/was not to provide a number that can be taken as an absolute, but rather to provide guidance so that sufficient space can be made available for the eventual ballast system.

If anyone is curious, I could have, but did not, do an actual calculation based on the 1:1 scale Type VIIC since this will be a wet hull boat and the displacement would likely not scale out correctly.

-Jeff

[southern or]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Scale is a huge problem. If we were to use scale rudders our boats won't turn and scaling down ballast math won't work. For my surface boats I have 2 setups. One is on my much prized SS United States that has a scale rudder but is operated with 2 throttles to the 2 operational props. That's how she turns, slow or reverse one prop. My 2 destroyers (arleigh burke and a Sovremenny) have oversized rudders. The problem is we can scale down the ships and boats themselves, but you can't scale the physics behind how water reacts. About the only thing that remains a constant is If the density of an object in the fluid is greater than the density of the fluid, the object will sink. If the density is less than that of the fluid, the object will float due to the buoyancy from the fluid. An object of lower density will float to the top and only be submerged by an amount according to the ratio of the densities.

[JWLaRue]

Re: Gwen's all metal scratch built 1/32 Type VIIc

While the scale effects of water are as you noted, scaling the displacement works. The surface boat folks seem to make the work well.

-Jeff

[gwen]

Re: Gwen's all metal scratch built 1/32 Type VIIc

Got my eye one this one. Always wanted to make a metal boat. Great job so far!

Steve

Thanks Steve! I have a lot of work ahead of me on this project but I'm having a lot of fun with it.

Gwen