darnell porpoise class submarine

hi
this submarine lark is starting to get a little serious i have just bought second hand a darnell p class submarine of modelboatmayhem for £60 a bit of TLC and repainting and fixing and of we go hopefully ha ha (i do get a lot of enjoyment rebuilding old thing so this is right up my street)

i thought i would start a post as im going to need all the help i can find as this is my first venture into static diving ie
size of ballast tanks size and layout of the WTC
as you can see in the photos the motors are housed in there own little box i know the motors have got to be replaced as they have seen better days they are only speed 400 and i have 4 new ones under the bench or would i be better of taking the lot out and putting the motors in the main WTC?
one thing i dont like is the a angle on the UJ
also in the photo you can see the red cradle that the original WTC used to sit in these are well spaced apart and may be of no use as i would like to put the main drive battery in the free flood area saves taking the WTC out all the time when im at the lake.
i had never thought about the p class sub as a project but after getting one its a nice looking sub
it will be a slow start so bear with me as i want to get the bits and pieces together while im finishing of my revell u-boat

many thanks and take care geof

Hi Geof,

She looks nice externally. Internally - you can probably scrap a lot. The motors for a start - direct drive is probably not best - some gear reduction (1: 3 say) is usually advisable. (Have a look at some MFA geared motors to see how they would fit in side by side.)

You are going to have to think hard about your WTC arrangements, I would suggest.

I hope someone on here can give you some guidance on ballast tank volume and location. (I don't have any experience of Darnell subs but that has to be a good starting point.)

Don't rule out using Lipos within the WTC. A lot of people (myself included)do this now and it gives a lot of flexibility fitting things in. (I have to sound a "health" warning though. I spoke with Norbert Bruggen himself at Dortmund last year and he said that he would never use Lipos because of the fire risk!)

Have fun!

David

Thanks david as you say the motors are better of scraped
The motor box is very small the speed 400 just fit but the angle of the prop shafts are server so I would be drawing more current so it may be worth taking the lot out including the box.
I was looking through the AMS website today and I think richard posted a picture of his one so when he is back on his feet he may have some ideas (hope your ok richard)
Another thing I'm going to have a look through all the old up scope articals I have from the 1990s that may have an idea.
I think a lot of people worry about lipos but as long as you look after them and charge them correctly and use a lipo bag there should be no problem ive been using them for years in my model aircraft I have fitted a lipo the the uboat.

Thanks again geof

Without any better information, I would work on a ballast tank volume of 1.5 to 2 litres. Positioned centrally (i.e under the periscope) or a little bit forward.

To make the most of the ballast tank volume, keep the displacement of everything above the surfaced waterline as low as possible (i.e thin and strong).

To minimise roll problems, keep the superstructure weight down.

So the superstructure needs to be thin, strong and light weight!

David

looking forward to this build geof as my avatar is of a p class HMS sealion which my dad served on and which i was christened on so keep the pics coming

thanks for the advice might try and lighten the top from the underneath with a large sanding drum taking it easy not to build to any heat on the glass fiber.
i had a look through the old upscope articals and came across a building artical of Paul Cooks Darnell S class submarine and he went into depth about the ballast tank.
The ballast tank had a capacity of 1900 milliliters which was way to big but inside the ballast tank he had 2 200 milliliter air cans for the compressed air and a small can of airbrush propellant for emergency surfacing this i cant find out the size of plus there was a 25mm air gap at the top of the ballast tank to stop the compressor sucking in water.
so may be a ballast tank of 1.2 to 1.5 liters may do the trick i feel i have read this some were on the internet about ballast tanks for darnell subs may be something ron perrot mentioned.
one thing i have decided is im going to use a seal ballast tank so i will have to take into account the air gap for the air to commpress into.
last question for today is it better to have a long thin or wide and short WTC the one that was in it was about 90mm wide.

Tattooed you have now put the pressure on with your dad serving on HMS Sealion which this model has Sealion on the side of the cooning tower which im going to keep (i was told renaming a boat is bad luck and i need all the luck i can get) and yourself being christened on board how many people can say that brilliant.

The colour scheme on my model i would like to keep as its a little different from just plain black does any one know if this was used on the full size submarine or were i could find out been hunting all over the internet and found nothing.

thanks for the interest and help geof

That is very good information about the ballast tank (And now I remember the same article!) Paul is always available to ask but he is more active on our Facebook page.

The pressure ballast tank is a very good and simple system. One of the few downsides is that you will only be able to get it 2/3 full, with the gear type pumps we use. So the tank is bigger and more difficult to fit in.

The required ballast volume you mention sounds about right. 2 litres is a heck of a lot and if you can trim back the superstructure that will all help.

I would go for fat and short WTC if you see what I mean! You will be able to get in much more volume into your tank for the same distance (Diameter squared) Long and thin tanks can give "sloshing" type instability also. For the same reason I would recommend a ballast tank with baffles in it.

Don't forget the smaller the WTC volume the lighter the sub.

Sorry no idea about colour schemes!

David

Thanks david thats very helpfull I cant wait to get started but I must finish the uboat
Should have some pictures to post up in a day or 2 of the u boat WTC

Thanks again geof

Hi To Everyone
Now my little U-boat is finished and having sea trials it’s time to look into my Darnel P class sub so here’s the questions on ballast tanks and WTC
I’m looking to get a acrylic pipe from ebay 90mm outside dimension and 80mm inside dimension this has a 5mm outside wall is the 5mm outside wall over the top or would 3mm wall be thick enough?
The end caps to the ballast tank and WTC i am going to ask Mark Model Boats to make them i am very pleased with the ones on my U-boat not a drip inside after 3 hours in the bath.
Would there be any problems if the WTC and Ballast Tank being Separate ie the ballast tank held in by a strap under the conning tower and the WTC sitting behind it with a pipe running to the ballast tank to fill it with water.
Richard was going to use this idea in his MMB LA sub



Hope he does not mind me using his picture to explain what im trying to say.

Here comes another Question the pressures involved seem very high and im not sure if my building skills are up to it.
In the old days they used a water prob in the ballast tank that cut of the compressor when the water touched them my thinking is when the water is pumped into the tank could the air be pushed into a separate air tank so when the water touches the probs the pump would cut this would lower the pressure in the system quite a lot depending what size air tank used when you want to surface reverse the pump and up she comes there is plenty of room up front for a air tank.
I found on microgyros a box of tricks called the ballast servo controller that may do the job

to monitor ballast tank start/stop by microswitch or water sensing and failsafe
simple setup of two servo positions
Isolated (non-plating) water level detection
Selectable servo position on dive + failsafe/surface
• 2 second radio failsafe
• Four status lights to aid alignment
• small dimension 1.3 x 1 x 0.4 inch (33 x 25.4 x 10mm)
• operates glitch-free with a poor radio signal



im sorry for all the questions this is a big step for me
many thanks geof

Hi Geof,

No problem having the ballast tank separate. Personally I prefer a single end cap at the stern - makes things simpler, to me.

3mm or 5mm depends on the pressure but it looks as if you are backing away from higher pressure systems anyway.

I was hoping someone with hands-on experience of a level probe would answer, but here goes.

They are certainly used but maybe a little bit old-fashioned now. (I'm waiting to be shot down on this!) They were used in the Craycraft modules of many years ago. The important thing is that the probes are fed with alternating current (to avoid electrolysis) and the Microgyros  ones are. I've met Mike S of Microgyros on many occasions (last time at Haydock Park this August) and I've used his speed controllers at least twice. So I can't see you having any problems with the product etc.

Hopefully someone will answer who has used the actual  Microgyros unit. It has been available for a number of years.

Richard doesn't post on here now but you can find him over on the "Dive_In" Facebook pages.

David

thanks David that cleared a lot up so i know im going in the right direction if im going with a module its going to be 3mm side wall for main WTC and 5mm side wall for balast tank.
i can only get in a 300mm long WTC may not be big enough in the back between the ballast tank and back of sub so may need to have a front module as well.
i have also been pointed in the direction of the Kavan fuel pump by paul cook this pumps 1.8 litres a min on 12 volt it is a bit bigger than the red/orange pumps.
At the moment i am reading the book simply model submarines there is a lot of good information in it in particular paul cooks HMS satyr which uses boxes this i use on my fun sub with no problems a lot cheeper to make modules work very well but find it a fiddle getting the WTC out having to undo everything.
on the subject of good information is the RC Submariner DVD from Traplets it goes into great detail on how subs work with out getting to technical .

all the best geof

Yes "Simply Submarines" is a nice book and the Traplet DVD also - Paul C knows his stuff!

For a slightly different approach you may also not be too far off appreciating "Model Submarine Technology" by Norbert Bruggen.  I say "not far off" because it is a harder read with more theory in it. Someone said there is "nothing so practical as a good theory" and because it is largely based on theoretical principles it does not date too quickly. (The mechanical details are still fine but the electronics are now out of date.)

thanks for that dave forgot i had that book as you say a good read.

geof