New at This

[oztruck]

Hi from downunder.

New to RC boating and very new to RC subs.
Due to lack of money but still with a need to have my own sub I had to go with the cheapest sub kit I could get here in Adelaide Australia. I got myself a Dumas Akula, I guess you all know what they look like and how they go together so I wont bore you with that.

Built mine as per instructions and all went together well and after it was done sailed well and did everything to was designed to do, EXCEPT keep water out of the container where the expensive electrical parts are.

After several tries to get it water tight and the loss of 2 servos and a ESC I had had enough of it and decided to build my own WTC.

[oztruck]

My quest to build a new WTC was not going to be as easy as I first thought. I could not find any one here to sell/supply any lengths of clear pipe less than 6 feet in length and without costing an arm and a leg. Still wanting a reliable and water tight sub I had to look at other options.
What I came up with, worked for me and cost in total less than $30

[oztruck]

What I did was get some 3mm plastic for the box and clear perspex 5mm for the lid.

I don't have any build photos but it's not all that hard to build a long box that is square and strong.

Instead of having the battery in a seperate area I designed my WTC to hold everything, but when planing I forgot about future extensions, Never mind! Long story

I cut the plastic sheet by scoring and snaping with the aid of a good straight edge and very sharp hobby knife. I glued the 5 pieces together making shore every thing was square, straight and no gaps. Then I reinforced all of the joins with a strip of plastic covering where both parts were glued together.

Around the top of the box I then glued some "Evergreen" square 1/4" rod. After the glue had set I then placed the clear lid I had cut out to fit on top of the whole lot and carefully marked where the retaining bolts were to go. Off the the drill press and drilled 2 holes, one each end. I then marked both the lid and one end so I knew which way it was to go together and then ran a couple of screws through the lid and into the holes I had just drilled. Next step was to drill the rest of the 18 holes through both the lid and 1/4" square rod. I then ran the bolts UP through the holes and locked them into place with some super glue, the holes in the lid were then enlarged so they would slide over the bolts without too much trouble. After a good clean I applied a bead of silicone around the top of the box being careful to keep it even. After a good spray with teflon spray on the inside of the lid it was then placed very carefully over the bolts and down onto the new silicon , gently pushing it down evenly till it was showing that there was a good surface coverage on both the top of the box and the lid.
The next part was the hard part. Don't go near it for 2 days to let it set up.

[Slats]

There is a big problem with this type of box and lid /gasket approach (I hope you avoid it). Problem is you tend through cycles of opening and closing the lid, to impact on the integrity of the gasket seal (in your case silicon) and after a time the seal you initially had ain't the seal you now have. Also you can never be sure that you have applied exactly the same torque to each of the restraining bolts nuts, the resulting differential pressure between each of these mechanical fasteners can compromise the water tight seal between lid and seal and leaks can eventuate. The points of the mechanical fasteners offer depressions in the seal and this too contributes to potential for leaking. The only way around this is have the gasket seal away from the influence of multiple mechanical fasteners. Better still use a cylinder with end caps.

I have a good friend that has had a Dumas Akula for many years with no leaks from the supplied "box type" WT space that comes with the kit.
Is there any way you could perhaps repair it where the leak was?

Just wondering what size motor that is? - seems massive for both the submarine and tiny nylon propeller that its pushing.

J

[oztruck]

Thanks John for the tips and what to avoid. I guess anything that is water tight that is opened and closed often enough will eventually start to leak. To date I have put a total of at least 12.5 hours on this WTC without the slightest bit of moisture getting in. It is so reliable I tend to leave the sub in the water all day on a club day (3hours.). Mechanics have used this type of seal on things that are under a lot more stress and pressure than my Acula will ever see. Time will tell.

The problem with the kit I got was that when the clear plastic lid was vacformed the plastic was streched too thin on the return bend and as a result developed small but very painfull and expensive leaks. the motor is of course the Dumas 6 volt 5 pole that is recomended for the kit and it seems to do a good job although I don't have anything to compare it with. YET.

[oztruck]

After the silicon had set up I removed the lid, cleaned it again and applied a small bead of grease around the contact area. Placed the lid on, put the 18 washers and 18 nuts on and ran them down watching as the pressure pushed the grease to the outside areas.

Almost forgot. Before I put the lid on I filled the box with all the drill bits and heavy things I could get my hands on to give it some ballast.

After the lid was secured I raped a length of rope around it, took it out to the back yard and gently placed it in my 6 foot beep rain water tank. Looked to see if there were any bubbles, yes there was, but they were from the rope. I left it sitting there all weekend 6 foot down in the dark and cold water. Took it back out after work on the Monday and it was as dry as a bone. I was very happy.

Now confident with my new WTC I then installed the running gear and electronics. I used all the same stuff that was in the origional Dumas not quite WTC. At the same time I installed an other servo for the front dive planes. I used rubber boots partly filled with grease over all the control linkages.

With it all set up with the running gear and a charged battery it was bath time. Time to get it set up all nice and level. That went well and only took about 35 min. But I left it sitting in there all night and day. All good no leaks. The next afternoon it was rope and rain water time but this time with the complete sub. I left it in there for 14 hours without a drop getting in.

Because this is a dynamic diver at the moment most of its running time will be at or above periscope depth. So should give lots of good service.

PS sorry about the spelling but every time I try to use the spell checked I loose all of the text.

[oztruck]

This is my first sub and as such is my test bed to try out new ideas, most of which have worked out ok. BUT we all make mistakes and one of mine was not to plan for the future. The next step is try "Snorting". To do this I would need at least a pump but there was no room in my new WTC (lack of planing) What you can see in the photo below is the front end of my WTC with a large ugly lump of foam stuck to it. That is there as a guide as to how the boat will handle when some room is made for the snort pump etc.
It is about the same volume as the area I need for the pump.
There are 2 way I can do this, first is to make a small wtc for the snort or make a new and larger WTC, both have there +'s -'s




Also here is a video of sub doing its thing.

http://www.youtube.com/watch?v=NxZvMctYZRg

Thanks Chris

[Slats]

Thanks John for the tips and what to avoid. I guess anything that is water tight that is opened and closed often enough will eventually start to leak. To date I have put a total of at least 12.5 hours on this WTC without the slightest bit of moisture getting in. It is so reliable I tend to leave the sub in the water all day on a club day (3hours.). Mechanics have used this type of seal on things that are under a lot more stress and pressure than my Acula will ever see. Time will tell.

Sounds good, - but be prepared for leaking near or around the nuts. I'd add some vaseline around the threads as you do them up. Also if you can get hold of it (or you might have it - Norbert Bruggen's "Model Submarine Technology" -chapter 4 discusses this sealing method. He cautions primarily not to use due to water pressure, but i guess your not going to go too deep.
J

[Slats]

The lump of foam is problematic - looks like ordinary packing foam? If so it will absorb water over time - screwing with what you thought was dialed in trim.

I use a Dow product called Blue Insulation Extruded Poly Styrofoam. This does not absorb water. You can also use surfboard foam. To affix this to the hull I use an RTV silicon. In Australia Selley's Marine sealant I find has great adhesion.

J

[oztruck]

Thanks John for the heads up on the packing foam, that is what I thought. I picked up a second hand surf board at a garage sale and cut it up into usable size pieces a few week ago. That's what the white foam is. Looked all over the place down here for the blue building foam but couldn't find anyone who knew anything about it. Thanks for the name of the product, the next time I go looking for it I should have better luck. I use the black silicon that I make the gaskets out of for holding down the lead that you can see. I used the lead to act as the weight of the snort pump to help with triming and to work out how much air I need to take on to get the sub up to the correct surface level. It seems to work quite well. In the mail today in a package from Ebay I found some very nice closed cell foam that is light as a feather and water floats off it like water on a ducks back. When I get a chance it too will find its way to the botom of the rain water tank for a day or two. Again thanks for the hints and tips.

[Slats]

Happy to help.
Hope you enjoy this site and that the sub behaves the way you intend.
J