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[bbdave]

I'm considering dive methods for a small sub and wandered if a snort would fit the bill as a simple system to build.

Dave

[coolbumble]

Hi Dave

Enter  Caswell snort sytem on googlle

Caswell does one lots of info about his snort system on his site this may help you decide the way you want to go .

Hope this helps

Ian 

[bobk]

I agree with that Dave. I have a Caswell snort system on the sub I am building.  It is extremely compact, a very small pump with control PCB soldered across the pump terminals and a lead that connects straight to your receiver. As long as you are at periscope depth you can either pump air in or water out at low amps.  You may however have to consider an alternative system for when you go below this depth.
I have a 2.5 inch diameter Caswell WTC, which also has a small gas bottle system rechargeable via a Schraeder valve.  Probably the best of both worlds for a very slim or small submarine.

[bbdave]

Thanks chaps bob does the pump pump the water in aswell? i'm having problems finding drawings/pictures of the system so i know how to make one as i don't have the luxury of being able to buy a complete WTC and looking at making my own. i need to know how the water is expelled and air in.

E.g if you pump air into the top of a tank it can push water out of hole in the bottom air pressure stops water comming in then reverse the pump air comes out water goes in. does that sound right?

Dave

[Subculture]

To fill the tank you open a flap valve at the top of the tank using a servo. As the tank is already vented at the bottom, the air escapes, and the chamber floods.

To blow ballast, the air pump sucks in air from the surface (via a snorkel pipe). With the flap valve closed, the water is pushed out back through the vents on the bottom of the cylinder, whence it came. The pumps are diaphragm based, so aren't adversely affected by ingesting a bit of water, you shouldn't use a piston based pump for this system.

Do bear in mind that you need to ballast your boat so that it is just positively buoyant, or you will need to drive your boat to the surface to clear your tank. If you have a gas system fitted too, then that isn't necessary (belt and braces).

[bbdave]

Seems that this will fit my requirements sounds simple enough as i'm only planning boating lake type voyages

i see Caswell do pumps so looks like the gear will be cheap

Dave

[Subculture]

There are various sizes of pump available on the market. Mike Caswell does a couple of different size pumps, which will suit small to medium size boats; you can also parallel them up to increase flow rate.

If you're building a larger boat, with a ballast tank in excess of 500ml volume, then the vacuum pump available from Sparkfun is a good candidate.

[bbdave]

It'll be a small sub as i don't have much space trying to find some good plans so i can decide what to build

Dave

[Subculture]

I like midget subs for smaller models- chunky details, large control surfaces for the size of boat, and usually quite broad across the beam for easy access.

How about a Welman? John Lambert does a nice set of plans for this boat (no model construction details though...)

I've only seen a picture of one model of that boat, and it was built by a German modeller I believe.

[Patrick Henry]

Just a thought...how about a British X craft? Nice sized boat if you don't have much room to play with (like me). Models By Design do a set of mouldings, although if you want a scale boat there's a fair bit of work to do on the hull to make it look more representative of the full size. Plenty of room for a cylinder inside as well.




Rich

[bbdave]

The welman is one i've been looking at and i can go slightly bigger than the plan as long as the lines are shown i'd be fine building. would prove an interesting one to do.

 I have looked at the X craft but do find the cost of a set of mouldings quite high (being a cheapskate) specialy if i need to alter them. I have seen the UC minelayer mouldings Desi on here is making and am tempted but the cost again is a factor this side of Christmas, he has offered to make one up and hold for me into the new year which is very kind but i don't like to keep someone hanging around if my circumstances alter. 

I fancy the idea of building everything specialy for a sub, i enjoyed making the tech rack for my U47 conversion and was very happy when it all worked.


Dave

[Subculture]

The drawings give three elevations, but no lines. However with a few pictures it's easy to interpret the general shape which is very simple. A few still exist, but the only one that was in the UK was broken up for scrap some years ago. Like many midget boats, there is quite a bit of variation in details between the surviving boats. The one depicted in the drawings looks like an earlier version.

As the Welman is cylindrical you could scale it to a piece of PVC/ABS/Lexan pipe, leaving fabrication of the bow stern and conning tower. These could be constructed in any number of ways- GRP, vacuum forming over wooden masters or even bread and butter techniques, but perhaps using plastic in place of timber.

[bbdave]

Sorely tempted to give it a bash may just get the plans to peruse.

Dave

[Subculture]

Well even if you don't build the boat, you can always frame them and hang them on the wall- John Lambert's drawings are a real work of art!

[Patrick Henry]

Isn't there a Welman at the Gosport Museum?

[Subculture]

Well I've never seen it if they have, and I've visited quite a few times in the past. Apparently the wreck of W10 was donated to them, but was scrapped- presumably beyond salvage. More here, about a third of the way down the page.

http://www.mcdoa.org.uk/News_Archive_25.htm

There is a Biber at Gosport (which is AFAIK the only operational u-boat from WWII)- the Germans reverse engineered a captured Welman, and stirred in a few of their own ideas which resulted in the Biber.

According to the linked article, there are surviving Welmans on display in Oslo and Norfolk, USA. As you can see in the pictures, there are some marked differences in hull shape and conning tower features.

[Patrick Henry]

It used to be stored under wraps around the rear of the museum building, somewhere I have pics of it, including one of Bernie Wood standing right by it.


Rich

[bbdave]

Shame it would be good to have a look at one best get looking on google for pics and info.

Dave