Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: 1 2 3 4 5 6 [7] 8 9 10 11   Go Down

Author Topic: Salt Water Darnell U37  (Read 54912 times)

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,010
  • Location: North London
    • Dive-in to Model submarines
Re: Salt Water Darnell U37
« Reply #150 on: November 01, 2013, 10:11:04 am »

That's an easy one to answer- for every halving of volume you must double the pressure.

If you have say a 1 litre ballast tank/bag and you have a 1 litre reservoir, then your pump will need to compress the air to one atmosphere (14.7psi) above ambient pressure. If you wanted to squeeze the same volume into a 500ml pot, then you would need two atmospheres (29.6 psi), and so on.

In the case of the diaphragm pumps, they make about 1 atmosphere, beyond that you're pushing your luck, and they're inefficient at pumping higher pressures anyway unless you series pumps up.

One of the problems with older submarines, and indeed some newer ones is high freeboard, and the need for large volume tanks. If you're using a recirculating system then you need fairly high volume reservoirs or you have to run at higher pressures, which comes with its own set of issues.

If it's difficult to find the space for a reservoir, then I wouldn't rule out a partially vented tank system, perhaps to get the boat to decks awash, then take the tower under with a recirculating system based on any system of your choice. The diaphragm pumps work well with this system unlike piston based pumps, which can't afford to ingest any water.

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #151 on: November 01, 2013, 01:31:13 pm »

You know, I waded through three model submarine books and a fairly useless submarine special and couldn't find that sort of info, much appreciated :-)) .
That gives me all I need to know. The vacuum pumps are good up to 32psi at 12v, I am running at 9.6v so will assume a little less output, I will now look at either air or water based pumping, with or without an auxiliary reservoir, at no greater a ratio than 2:1 volume. If I cannot use my newly silver soldered pressure tanks for reservoirs, I can always use it to fire torpedoes!!
Logged
Listen politely, nod approvingly, then do what you want, works for me!

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,010
  • Location: North London
    • Dive-in to Model submarines
Re: Salt Water Darnell U37
« Reply #152 on: November 01, 2013, 02:07:50 pm »

It's Boyle's law. http://en.wikipedia.org/wiki/Boyle%27s_law

There are online calculators for this sort of thing, but it's pretty easy to work out in your head.

32psi sounds high. Is that through testing, or are you going by the pumps datasheet (which is a bit optimistic IMO).

Silver soldered pressure tanks sound complete overkill. I've hydraulically tested plastic coca-cola bottles to over 100psi (don't be doing this unless you know what you are doing please), so they happily can take the pressures likely in your submarine, without the weight penalty.

Davy1

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 313
  • Association of Model Submariners
  • Location: Cumbria
Re: Salt Water Darnell U37
« Reply #153 on: November 01, 2013, 02:31:44 pm »

I hope that you already have "Model Submarine Technology" by Norbert Bruggen on you bookshelf.

If not it is well worth getting (second hand only now, I think.) since it really is the "bible" of model submarines. Very good if "in depth" theory  (sorry!) which is still very sound. The electronics is rather dated. But all the dive and construction systems are there, many of which you have already looked at in your build log.

The theory is extensive but it is also very practical since he has actually  done it, unlike some experts.

David
Logged

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #154 on: November 01, 2013, 04:34:17 pm »



32psi sounds high. Is that through testing, or are you going by the pumps datasheet (which is a bit optimistic IMO).

Silver soldered pressure tanks sound complete overkill.


I am a slave to the data sheet, but will test thoroughly first. Silver soldering is kind of second nature to me, mostly working cannons in sailing ships etc, rather than subs. I am aware of the remarkable capabilities of the humble fizzy drink bottle, but they do look like fizzy drink bottles from the outside!!


I hope that you already have "Model Submarine Technology" by Norbert Bruggen on you bookshelf.

If not it is well worth getting (second hand only now, I think.) since it really is the "bible" of model submarines.

David

Yes, I have Model Submarine Technology in my collection, It may be too in depth in places though, and I did not find the last valuable nugget of info in the book, regarding relative tank volumes.
Logged
Listen politely, nod approvingly, then do what you want, works for me!

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,010
  • Location: North London
    • Dive-in to Model submarines
Re: Salt Water Darnell U37
« Reply #155 on: November 01, 2013, 05:41:39 pm »

There is a formula on page 57 of that book that allows you to calculate the volume of the reservoir. Norbert doesn't spend much time discussing systems outside of the ones common in Germany (not surprising), so systems very common in the UK like recirculating compressed air and sealed tank water ballast systems get little mention.

It is a book quite heavy on math and formulas, and a lot of modelmakers get somewhat bamboozled I think.

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #156 on: November 02, 2013, 09:27:46 am »

I do bamboozled better than anybody I know!
Norberts book makes for an interesting read, I particularily like his distinction between torpedos ( being warlike and 'beligerent' ) and submarines ( underwater buses, no harm to anyone ), different cultures I guess..
Logged
Listen politely, nod approvingly, then do what you want, works for me!

merriman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 36
  • I wanna go back ....
  • Location: Virginia Beach, Virginia
Re: Salt Water Darnell U37
« Reply #157 on: November 02, 2013, 03:32:58 pm »

I guess, in Norbert's book, I'm a bit of a savage then. Oh, well. Another sleepless night.
 

 
Here, my little 1/72 ALFA is busy making the local pool safe for Communism.
 
David
 
Logged
"Anything the human mind can conceive is possible -- you know that, Blake!"

TheLongBuild

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,447
  • Build em, and play hard..
  • Location: Everywhere, But Nowhere !! But mainly in England....
    • Runcorn & District Scale Model Boats
Re: Salt Water Darnell U37
« Reply #158 on: November 02, 2013, 04:55:37 pm »

I guess, in Norbert's book, I'm a bit of a savage then. Oh, well. Another sleepless night.
 

 
Here, my little 1/72 ALFA is busy making the local pool safe for Communism.
 
David

Is that just compressed air ?..

Are you the same D. Merriman, " Stop using my air Merriman "(or similar)  ?..  Love to have your SeaView build on here ..

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #159 on: November 02, 2013, 05:07:47 pm »

I guess, in Norbert's book, I'm a bit of a savage then. Oh, well. Another sleepless night.
 
 
David

I am fairly sure you are big enough and ugly enough not to be too bothered...
Logged
Listen politely, nod approvingly, then do what you want, works for me!

merriman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 36
  • I wanna go back ....
  • Location: Virginia Beach, Virginia
Re: Salt Water Darnell U37
« Reply #160 on: November 02, 2013, 05:10:53 pm »

LOL! Right you are, sir.
 
David
Logged
"Anything the human mind can conceive is possible -- you know that, Blake!"

merriman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 36
  • I wanna go back ....
  • Location: Virginia Beach, Virginia
Re: Salt Water Darnell U37
« Reply #161 on: November 02, 2013, 05:25:57 pm »

OK, enough. We're high-jacking this thread. Bad form.
 
David
Logged
"Anything the human mind can conceive is possible -- you know that, Blake!"

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #162 on: November 06, 2013, 11:28:05 am »

I have been in a secure panic room over the weekend, Hijackers you know!
Anyway, this is the system going in U37, its a water pumping system, isolated from the main RC compartments, avoiding damp sea water air entering where it shouldn't. The tank will fill to the probes with the auxiliary tanks fitted. Only my higher pressure water pump has the guts to fill this, so heres hoping it doesn't fail me as I dont have a spare. When left with the pinch valve open, the pressure in the system is enough to two thirds empty the tank without the pump engaged. The tank took on 730 grams of water from empty, hopefully enough for the job.
And it looks really cool too ok2 .
Logged
Listen politely, nod approvingly, then do what you want, works for me!

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 4,010
  • Location: North London
    • Dive-in to Model submarines
Re: Salt Water Darnell U37
« Reply #163 on: November 06, 2013, 12:01:41 pm »

That's a bit like a mix between the systems used on the sheerline and OTW units.

I have no idea what the displacement of a Darnell Type VII is, I would hazard a guess it's more than 750ml though, so you may have to live with a lower than scale waterline.

Will your pump cope well with the salt water.

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #164 on: November 06, 2013, 02:03:43 pm »

The pump has nylon gears and is not directly driven from the motor shaft, so shouldn't suffer from the creep of water that the MFA pump suffers from below waterline. Much though I would have loved to use the vacuum pump(s) on this model, the air reservoir available, unless I was willing to use the main RC compartments, was just too low. No problem, I have two Craycraft tubes which would love a new vacuum pump each.
I would scale down the submerged and surfaced displacement of the Type VII, however the Darnell moldings are six months pregnant, so the figures probably wouldn't help me greatly :}
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #165 on: November 15, 2013, 05:20:30 pm »

Have been busy over the last couple of weeks, re-setting a Set Top Box, Throwing a Set Top Box out the window, avoiding being re-elected Secretary ( failed, nuts! )and sorting out a re-design of the pump compartment etc..
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #166 on: November 15, 2013, 05:27:30 pm »

The old upper acrylic tray was replaced with a shorter, wider one, onto which went the servo for the pinch valve, one only Action Switcher now, a snazzy voltage indicator from Component Shop ( 3.95 from Warwick, bought two :-)) ) and nothing else yet. The Bruggen/Engel Ballast Tank Controller is going under the top tray, in a splash proof box not yet built.
Salt water being an ever present risk to the electrics, I purchased an Acrylic Circuit Board Protective Spray from Maplins...fairly sure its just acrylic varnish, but three coats later the various lumps of electronics were a little less vulnerable.
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #167 on: November 15, 2013, 05:32:19 pm »

Pinch Valve..having built a plunging rod in a bit of acrylic for a fellow Mayhemmer, no names, no pack drill :} , I decided I dont like them...so tried this option. I am sure its as old as the hills but it seems to work. Two ballraces on the servo arm, a right angle of aluminium, and a shim of plasticard to get the 'pinch' just right. Works so far.
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #168 on: November 15, 2013, 05:43:23 pm »

Yes, I line up my screw heads, not mad at all, just a little %% or maybe a little :(( . Dont care, criticise if you will...you will all be doing it by the weekend....
Ballast tank, a reworked, shortened unit from my CHANT Tanker, baffled, like me, and epoxied shut. Along with the two 22mm copper 'overflow' reservoirs for the pressurised air. The ballast tank is currently designed to clip onto another 22mm pipe running between the fore and aft compartments. It does end up a little high, which will affect the waterline when on the surface, but it works. If I can find a neat solution to fix it in place a bit lower, while allowing easy removal, I will incorporate it, but for now..
Not sure how the copper pipes are going to be secured yet, but thats half the fun, surely.
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #169 on: November 15, 2013, 05:48:40 pm »

And finally, I have re-worked the through bulkhead tank feed, last time it was pumping air, now its water, under a fair bit of pressure. So, I replaced the old tube, 5/32" Dia brass, with a longer bit of the same. At the same time, epoxying a right angle bend to the 'free flood' side of the tube, to provide feed to the pump from the central free flood compartment. I may fit some sort of Klunk Tank Filter to the end of it, maybe..
Logged
Listen politely, nod approvingly, then do what you want, works for me!

triumphjon

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 790
  • Location: portsmouth , hampshire
Re: Salt Water Darnell U37
« Reply #170 on: November 15, 2013, 06:24:10 pm »

the screw heads havnt  had the locking wire fitted yet !

Logged

U-33

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 5,337
  • K-157 Vepr. Akula-11
  • Location: Eastbourne, Sussex, UK
Re: Salt Water Darnell U37
« Reply #171 on: November 15, 2013, 06:40:58 pm »

That's a clever bit of work, skip..have you thought about using Velcro to secure your tank? I'm using it to secure the cylinder in the X craft, the Dragonfish and the Skipjack...it's cheap, holds like concrete, but it removes easily.
Logged
Rich

K-157 Vepr. Akula-II (project 971U)
---------------------------------------------------------------

~~~~~~~  "Motorflotes need love too...."  ~~~~~~~

MotorFlote build log : http://www.modelboatmayhem.co.uk/forum/index.php/topic,15222.0.html

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #172 on: October 21, 2014, 06:17:02 pm »

almost a year....good grief..when the call came to help the Display Team finish off our Fort and Harbour complex, who would have known what a pain in the arts it was going to be..and how it would delay ( more! ) my projects. Anyway, it floats, it explodes when asked, and it looks great, so lets get on with something else..
I have started to work on U37 again. The Engel/Bruggen Dive Controller is now neatly fitted..no photos, and the ballast tank is bonded in, silicone for the ply to copper and ply to acrylic joints, then secured into the model via nylon spring clips, as long as I dont swing it round my head it should all be secure.

So thats how it stands at the moment..back on the Red October, got to finish that, I have sold it!
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #173 on: August 11, 2015, 06:49:20 pm »

Another season nearly over and I can get on with some of my stuff again :-) . Just replaced the locator pins for upper to lower hull locating. Not sure why they were too skinny at 2.5mm dia, but replaced them with 1/8" dia instead...much more imperial! Lid fits with little wobble now. However, the joins are ugly again. So last night was out with the green filler again and make the joint good again and ruin the paint job again!
So I have just been re-reading the thread, trying to figure out why Humbrol 31 Slate Gray has a satin finish on the model, while the paint patch applied yesterday is flat matt? Simple answer..dumb luck. Its the same pot of paint, only now over a year and a half older, and half full only. Following a stir all is matt. Only problem, the sub is satin.

Tonight I shall be buffing my U-Boat..they can't lock you up for it, surely?
 :-))
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,080
  • Location: Portsmouth, England, third rock from the Sun....
Re: Salt Water Darnell U37
« Reply #174 on: August 11, 2015, 06:51:51 pm »

Some say I am a slow builder...to them I say "Tune in next year for my stinging rebuke of your accusation!"
Logged
Listen politely, nod approvingly, then do what you want, works for me!
Pages: 1 2 3 4 5 6 [7] 8 9 10 11   Go Up