The Metcalf P Class Re-Build

[Subculture]

I don't think Dave Metcalf has any interest in model submarines, it was just an extension to his moulding business. He is a member of a club I used to belong to NLSME, and is heavily involved with O-gauge/Garden railways.

I few years ago I organised a sub day at the NLSME pond at Colney Heath, and although he was a member, I never saw him bring anything along.

Simply put, there is no rule of thumb for this kind of thing, you have to use empirical methods to figure it out.

[jeep4grog]

I shall do so...

[Kazzer]

Metcalfe got out of the business a while ago and doesn't seem to answer emails. Now the Darnell molds belong to Andy Grigg, and his workmanship is far superior. These are the models we sell.

Unfortunately, there are no instructions for these boats other than one set I have of the S Class, originally drawn up by Darnell. The drawings don't have any mention of the amount of lead, so it's suck it and see. However, threads like this will be a great asset in the future, so please post your findings.

[jeep4grog]

I have an older Metcalf glass hull that I had to reglass a bit.... so who knows the actual weight. I know the procedure but I was hoping that there might be a starting weight to add to the model in the instructions. Since I dont have the instructions for this one (even after several emails and two letters to Metcalf), I hoped that this info might exist here since Caswell sells a very similar hull.
I see ads here for lead weight sold for several other models and was hoping that a build had been completed and that info was avaiable.
I don't mind trial and error a bit, but maybe a rough starting point would keep the wife from getting too excited if I could reduce the ammount of bath tub testing time! It is about 14 deg (F) here today and everybody has thier pools emptied for the season...
Turns out the wife and some friends are going shopping Sunday so I guess that is the day to test.

[Subculture]

Yep you got it. In reality neutral buoyancy is very tricky to achieve, and your boat is always a bit positive or a bit negative, but the hydrovanes can usually take care of a few grams either way.

[Kazzer]

Ballast your boat down with lead until it is as close as you can get to neutrally buoyant.

Can you just clarify exactly what this means please. I imagine it is that the boat is floating, but all parts of it are underwater, just below the surface?

[Subculture]

Now I don't know if your 3.5" SD has a variable ballast tank or not (some of the eariler ones had a screw jack didn't they?). The standard way of going about this sort of thing as outlined by Skip Asay is thus-

Build your boat, then place it in a test tank.

Hopefully it's significantly buoyant.

Ballast your boat down with lead until it is as close as you can get to neutrally buoyant.

Now add foam blocks (make sure these are fairly accurate and uniform) below the waterline until your boat reaches the required waterline. You may need to make a cradle to hold the foam, or use some sort of lash-up of string and zip ties etc.

Once that's achieved remove the foam, measure it, and calculate the volume of the blocks. That's the size of ballast tank you need.

Having got that, any additional weight needed to get the boat down to the require waterline is placed in the keel of the boat, as low as you can get it.

If you don't have much reserve buoyancy, you can add foam either side of the SD. This should be placed as high as you can get it, but below the waterline.

Note that although the boats may come from the same moulds, there can be significant differences in displacement from boat to boat. Some are laid up thicker or thinner, so it's difficult to say use 'x' amount of lead. Injection moulded models have a higher tolerence in this respect, so it's a lot easier to predict the weight needed.

[Kazzer]

This might be a question for Kazzer?

I see you sell the same size P Class hull that I am resurrecting (and as we all know, necromancy is a sin and I am sure I will pay for this).

I did pick this up used and in need of a complete rebuild. I have no instructions and I was wondering if you could give me a "quesstimate" of how much lead weight I should start with in the hull.

I have the 3.5” Sub driver that Mr. Merriman made me last year.

No idea, sorry. I haven't even thought of doing that boat. Don't we have some documentation on doing this - somewhere?

[jeep4grog]

This might be a question for Kazzer?

I see you sell the same size P Class hull that I am resurrecting (and as we all know, necromancy is a sin and I am sure I will pay for this).

I did pick this up used and in need of a complete rebuild. I have no instructions and I was wondering if you could give me a "quesstimate" of how much lead weight I should start with in the hull.

I have the 3.5” Sub driver that Mr. Merriman made me last year.

[He Who Shall Not Be Named]

The kit supplied direct-drive motors were awful. Go with two geared 380-400's. Use about 3000mAh of Lithium-polymer battery and you'll have plenty of room for an inside hard tank so you can make it a static diver.

David,

[jeep4grog]

Bummer,

Guess it's an Engle tank or I will see if I can figure out a modified snort/gas/balast tank type of system. If all else fails, it stays a dynamic diver

[He Who Shall Not Be Named]

Unfortunately, if I remember right, the cylinder of that kit is a vital structural element, the armature in fact, off of which all the hull frames and other foundation pieces are glued. Sorry, pal, you're stuck with that tube as your water tight space.

David,

[jeep4grog]

Here are a shot of the Robbe U-47 that is coming.

A Red lead bottom? What was he thinking???!!

[jeep4grog]

Wow time flies...

Getting cold in Ohio again so it's back to finishing the sub!!

We spent the summer working on the new house and building a second garage on the property to have a place for the '40 Packard re-build my wife and I want to start.

In late Feb the sub hull had an major accident and was knocked off the workbench in the garage. It split the hull and damaged all the planes on the port side as well as destroying the rudder. I had to re-glass the hull and make all new planes and a rudder. It all came out pretty well.

The Sub Driver is almost complete and the shaft struts, planes and rudder are installed. Now it's time to fit the SubDriver in the hull and hook everything up. It will have functioning forward planes too!!

I also finished off a section of the basement and added a project room for the wife and a place for me to build.

My next project is on the way from LA. I found a Robbe U47 with "blown" electronics for $250. It’s built but needs some work and TLC. Does The Magician Dave have a recommended Sub Driver for this one? I would like to make it a static diver too...

[jeep4grog]

Well heck yes I did use enough heat. I started with a soldering gun, went to a MAPP torch and ended up with an Oxy Acetylene torch to braze the parts… It way too thin and wouldn’t stay in shape. I think it was the flat stock. The solder would stick to the tube, but just ran off the flat stock. The bearings are not soldered in. I cut a small groove into them and pressed the tube into the grove. They lined up well and the shaft rotates freely.

Another way to “recharge” the oillight bearing is to put a cup of light oil into a tall can and heat it by placing it into a pot of boiling water. Put the bearings into the hot oil for about 15 min and it will soak in. Not as good a David’s method, but if you don’t have a vacuum pump it will do in a pinch.