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Author Topic: Darnell U-570  (Read 13985 times)

Flying Sparks

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Darnell U-570
« on: September 12, 2010, 08:05:44 PM »

Today myself and my son Michael went to Old Warden for the last model fly-in of the year and we came home with U-570! We were planning on building a Robbe Seawolf later in the year, then today browsing the second hand stands at OW we stumbled upon U-570 with a sticker stating "Submarine - 130 - TLC required"  O0
We had a good look at the boat and found that the hull looks in good condition but the ancient radio was fitted by a person with 10 thumbs, the metalwork was rusty (push rods etc), most of the deck fittings are broken or loose and the perspex radio box lid must have been cut with a chisel. The single motor and gearbox looks OK. After a bit of haggling we agreed on 100. The TLC bit looks a bit of understatement but as I mentioned the hull and drive train look good.
Now the model is on the bench and we had another look and noticed the sticker on the motor stating that it came from Darnell models in Leavsden. A little bit of Googleing we found that this hull is still available from Models by Design.
The model is quite big at 1700mm long and by the time batteries and things are fitted it will be quite heavy, funny, it didn't look that big lying on the ground with the deck off. I will post some photo's soon.
Now, a few questions for people in the know if you don't mind; Did we pay a fair price? Is the single motor and gearbox powerfull enough for this substantial beast? Should we build it as a static diver? Was it a wise move to buy this?
Any advice/comments good or bad are welcome and no doubt we will have many more questions as we dive deeper into this model.
Thanks

Phil.
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Mankster

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Re: Darnell U-570
« Reply #1 on: September 12, 2010, 08:30:38 PM »

100 is a fair price for you got. No reason why a single motor and a gear box wont work as long as it has enough go. I would use it as you already have it. Most people would fit 2 motors in a hull this size. Yes static diver, you already have experience building dynamic subs and the hull is big enough for an easy install.

Subculture

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Re: Darnell U-570
« Reply #2 on: September 12, 2010, 09:17:50 PM »

Darnell kits used to come with a USE pump (converted steam engine) which was used with air bags. Does the model have this (perhaps you could post a few pics?). Also what workshop equipement do you have? This makes it simpler to advise on the best course of action.

To get these boats to statically dive from a scale waterline usually requires about 1 litre of displacement.

Flying Sparks

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Re: Darnell U-570
« Reply #3 on: September 13, 2010, 03:17:51 PM »

Thanks for the replies, all comments are welcome.

Mankster, We will test the motor before deciding if to stay with this setup or not. I don't think Michael will be very pleased if the sub was not a static diver, it's his dream  :-))

Subculture, There is not a pump with the model so we have to buy one. I have a reasonably well equipped workshop, I can weld, drill, braze, forge, cut and drill but as yet no lathe or milling machine.

I need to catch up on submarine technology and I have seen a book by Chris Jackson called Simply Submarines, do you know this book? Or would reccomend a different one?

Photo's to follow..


Phil.
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Subculture

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Re: Darnell U-570
« Reply #4 on: September 13, 2010, 06:10:20 PM »

Ahh that's good- you don't need a lathe or milling machine (a small lathe is ever so handy though).

I would recommend Model Submarine technology by Norbert Bruggen (also by Traplet). A tough read, but a good one.

Don't bother with the USE pump, there are much better alternatives these days.

Flying Sparks

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Re: Darnell U-570
« Reply #5 on: September 13, 2010, 09:56:44 PM »

Norbert Bruggen's book is ordered  :-))

Here are a few photo's of what we've let ourselves in for  :o

As you can see one of the forplanes is missing. Also on the shot of the keel it looks like something else is missing, you can see a pencil mark for the centre line but looks like somthing has come off, any idea what that might be?

Thanks

Phil.
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Mankster

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Re: Darnell U-570
« Reply #6 on: September 14, 2010, 04:21:08 PM »

I don't think there would have been anything of use attached to the keel, and there is no need to attach anything there either when you rebuild here. Are you going to keep the watertight box or go for a cylider?

Sub driver

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Re: Darnell U-570
« Reply #7 on: September 14, 2010, 05:44:33 PM »

Hi.

Looks ok for 100, the holes in the keel are drain holes under the box and for nothing else, this can build into quite a nice model, I would try the motor first prior to removing it and if its ok go with it, as Mankster says are you keeping the box or going with a water tight module ? if you stay with the box you can make a ballast tank in the centre by adding two bulkheads and a separate lid and then use a car tyre compressor to " suck " the air out and store it in the for compartment this is quite a cheep way of getting a static dive sub as the components for this are about 20 quid all in and with your workshop facilities and engineering expertise will be a doddle to do.

I have a scratch built type 1X that uses this system built in 1988 and still a good performer, can send some pics of the interior if you decide to check this route out.

Regards sub. :-))
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Flying Sparks

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Re: Darnell U-570
« Reply #8 on: September 14, 2010, 06:12:02 PM »

Mankster, My first thought is to keep the radio box rather than a WTC to keep the cost down, but if there is a huge benefit in having a WTC then would could go down that route.

Sub, I like the sound of your idea if there is enough room left for batteries, pictures of your setup will be nice to see.

We will take U570 to the Brockwell dive next month for people to laugh have a look at and give any hints and tips. It's unlikley that any work will have started by then.

Phil.
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Mankster

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Re: Darnell U-570
« Reply #9 on: September 14, 2010, 07:29:15 PM »

Both systems have their advantages and disadvantages. A WTC generally handles water pressure better, easier and quicker to seal, can me moved from boat to boat to keep cost down if you have more than 1 sub and usually results in a lighter boat as its easier to be efficient with the space within a cylinder.
A box gives much better access to component and is easier to install working periscopes and masts. You can make use of the sides of the hull to form the sides of the box (dry hull) to maximise available space in a hull) No need unhook all the plane linkages and prop joint everytime you want to gain access.
My current project is going to have a hybrid design with 2WTC connected to a central box for the best of both worlds ;)

See you at Brockwell
http://www.facebook.com/group.php?gid=133360626703083

Subculture

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Re: Darnell U-570
« Reply #10 on: September 14, 2010, 07:35:49 PM »

Lots of drilling and filing of slots on the deck required to get it looking like a Type VII- I don't envy you that little job! One of the nice things about many of the later (not Darnell) Type VII kits is that they came with photo-etched or milled decks, which saves a lot of work.

A cylinder will not significantly increase the cost, unless you opt for a ready made version. Materials are quite inexpensive, if you're happy to use opaque PVC pipe instead of acrylic, then I find 110mm waste pipe is usually found in skips (unused I hasten to add) and can be recycled into something more fun. A pair of endcaps is not a big deal to rustle up, what is a little more challenging is deciding on a ballast system and how to lay it all out inside the cylinder.

The radio system in that boat looks rather ancient, probably 27mhz (did it come with a TX?). If the servos are a 3-wire type, then they may be compatible with a modern RX if fitted with newer connectors- just observe you have the wires correctly configured. With perfectly decent servos available from Hobbyking for a pound or two it may be easier to just order some new ones.

The ballast system described by Sub Driver works okay. There are a couple of disadvantages to this system, and I speak from experience as I have used it, the air sucked out of the ballast tank is high in humidity, and as you are compressing it in the forward compartment, the cold WTC walls act as a condenser and you end up with a forward compartment with very damp air- any electronics in there can suffer. The second issue with this system is that it maintains an air bubble in the ballast tank, which is vented at the bottom. As the boat dives deeper the air bubble compresses and your boat steadily gets heavier. If you are running with only a few grams of positive buoyancy, this can result in a boat which heads straight to the bottom.

If you only dive at shallow depths it doesn't have much effect, but it does become a problem below about three feet or so. If you fitted a valve at the bottom of the tank (known as a Kingston valve) this would prevent this problem.

One more thing, the ballast tank will require baffling as you have an exposed water surface. This is all covered in Norberts book.

One system you could consider is a water pump in an aspirated main tank, based on 85% of the boats overall ballast volume, and a smaller tank mounted within this large tank using a secondary ballast system, based perhaps on a water pump or a small piston tank (large syringe?) to trim the last 15% of the boats buoyancy.

Flying Sparks

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Re: Darnell U-570
« Reply #11 on: September 14, 2010, 08:13:27 PM »

Wow, lots to think about and decisions to be made. We are not rushing into this one as we have a couple of projects already on the go.

I will ditch to radio gear as I have plenty of useable stuff spare. We just need to get another receiver and as I've now acquired a 40MHz module for my 8 channel JR radio, we should not have any worries in that department.

The main consideration is in deciding wether to stick to a radio box or change to a WTC. Hmm.....decisions.

Thanks guys keep them coming

See you at Brockwell.

Phil.
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Subculture

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Re: Darnell U-570
« Reply #12 on: September 14, 2010, 08:31:41 PM »

Have a look at this link-

http://www.youtube.com/watch?v=N3a7-CSuoIw

From 1:26 to 1:44 is a Darnell Type VII, which was re-engineered internally by Nick Burge for Bernie Woods. The boat started life as a surface runner, and was built by Jim Ward. Bernie purchased the boat, and Nick built a cylinder for it using a compressed air ballast system. I don't know what became of this boat after Bernie died, but it demonstrates what nice models they can be made into.

Flying Sparks

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Re: Darnell U-570
« Reply #13 on: September 14, 2010, 09:01:06 PM »

I had a look at your youtube video, nice looking boat with a huge amount of detail.
Thanks

Phil.
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hmsantrim

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Re: Darnell U-570
« Reply #14 on: September 16, 2010, 01:57:44 AM »

Hi Phil.
            May be just a bit a head of the programme but the weapons fit replacement from here on P 5 & 6.

          http://www.alwayshobbies.com/Boats/Fittings.ice

                                                 cheers Frank
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Flying Sparks

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Re: Darnell U-570
« Reply #15 on: September 16, 2010, 08:12:10 AM »

Hi Frank, Not to early to gather resources and getting bits for the final fit out  :-))

Cheers Frank

Phil.
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Flying Sparks

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Re: Darnell U-570
« Reply #16 on: September 17, 2010, 09:55:17 PM »

Norbet's book arrived today, I'm off read and try and digest it now, might take a while  :o

Phil.
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Martin [Admin]

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Re: Darnell U-570
« Reply #17 on: September 17, 2010, 10:18:41 PM »


Don't want to hijack your thread Phil but who else has built a Darnell sub?

I 90% finished Ulholder ( HMS Uncertain )
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Flying Sparks

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Re: Darnell U-570
« Reply #18 on: September 17, 2010, 10:55:55 PM »

No problem Martin, nice to see pictures of other Darnell boats as I assume the gubins (technical term) are similar. Is that a can of gas sitting in the middle of your boat  :o

Nice looking boat by the way.


Phil.
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hmsantrim

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Re: Darnell U-570
« Reply #19 on: September 17, 2010, 11:01:35 PM »

 Hi Phil.
           I had the idea of chopping a mountain bike inner tube and using it as a gasket seal for the perspex hatch.

                 wonder wot the experts think of that.

                                       cheers Frank

              
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Subculture

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Re: Darnell U-570
« Reply #20 on: September 17, 2010, 11:19:01 PM »

o-ring cord works best.

Flying Sparks

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Re: Darnell U-570
« Reply #21 on: September 18, 2010, 09:06:03 AM »

Martin, that looks like an OS carby sitting on top of the cylinder, is this part of a secret form of propulsion??

Frank, we may ditch the radio box and fit a cylinder, nothing is decided yet, thanks anyway.

Subculture, what is O ring cord and where can you get it from?

Thanks

Phil.
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hmsantrim

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Re: Darnell U-570
« Reply #22 on: September 18, 2010, 09:09:34 AM »

Hi Phil.

              pix here..http://www.jameswalker.biz/group/products/o_ring_cord.html

                           frank
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redboat219

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Re: Darnell U-570
« Reply #23 on: September 18, 2010, 05:31:59 PM »

Love your vent valve :-))
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Subculture

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Re: Darnell U-570
« Reply #24 on: September 18, 2010, 06:25:14 PM »

http://www.polymax.co.uk are excellent for 0-rings, rubber sheet, o-ring cord etc.

They do have a 10 minimum order, so it's best to order up all the stuff you need in one go. As the hatch seal will be one of the final thing you need to do, it should allow you plenty of time to fathom out what you need.

Andy
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