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QUESTION: Running R/C subs in salt water environment ?

R/C Submarine modelers

QUESTION: Running R/C subs in salt water environment ?

Postby menatarms » Sat Jan 17, 2009 3:07 am

Sorry for the rookie question ..

Reason I ask is because I have very limited access to private pools large enough to run R/C subs, and easy access to a number of salt water lagoons in my area (Hong Kong). I had heard the radio signals don't travel well in salt water. Does this mean I should not consider running R/C subs in anything but fresh water (there might be public access to fresh water man-made lakes) ? Thanks in advance~!
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Postby Andreas_dk » Sat Jan 17, 2009 8:57 am

It is correct, that salt water does limit the transmission range, but unless you want to operate your sub at the dead sea, your sub should still be able to get the signal at a depht of 1 meter. You must remember, that the frequenzy on your transmitter have to be as low as possible. In europe we use 40 or sometimes even 27 mHz. Also having a good nice reduction on all your electronics including motors will dramatically improve the depth at which you can get a signal.
And one thing too, transmitters with a frequenzy above 1,2 GHz (not sure of the precise number but 1,2 GHz is rather close) will not penetrate water. The signals will simply be absorbed in less than a centimeter water.
As closer you get to 1,2 GHz the water absorbs more and more, so keep your frequenzy as low as possible.

When talking about salt water, remember a normal swimmingpool has a far higher concentration of salts (Chlor and natrium based) than sea water. The biggest problem in natural ponds or open sea is normally that you can't see you sub when below water. So unless the waters around you are very clear, transmission should not be a problem if you use a proper transmitter and reciever and you do as much electrical noise reduction as possible

Theoreticly the best waters to sail in is demineralised water (water with no minerals or salts). The worst would be highly poluted water.

Hope it helps

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Salt Water Operations

Postby Mike Dory » Sat Jan 24, 2009 1:28 pm

Howdy - I can only speak from my own expirence in running model Subs in Salt Water. That dates back to 1958. For much of my life I lived in San Diego Calif. San Diego has a model boat pond which is salt water. I have wonderful memories of running subs at that pond. There are a few things you will need to keep in mind but nothing that will prevent you from not having a great time with your boat. Some of these, like choosing a low frequency on your radio has already been covered. I found that I needed the radio antenna to be 2 inches out of the water in order to receive a signal. I did this by adding on 6 inches of brass rod to the antenna, cover it in heat shrink, put a drop of ca glue on the end and run it up next to your periscope. This I found limited your diving depth to that of your antenna but it also increased my skill in running at periscope depth. I discovered it was also a good Idea to increase the delay in the failsafe (SubSafe) unit so as to prevent it from going off every time some other boat's wake would cover your antenna. (The Subsafe units from Sub-tec. are easy to adjust and Mike Shubar will be happy to help you. The other issue is your going to need to add more weight to your keel. My boat was 8Ft. long (a 1/32 scale Type IX U-boat) and it needed 7 Lbs. more weight On the down side, when you run in salt water, your going to need to hose off your boat and clean it up real well after each run. Salt water is not as forgiving as running in fresh water. Best Wishes on your project....Mike Dory
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