One of the saddest sights you can see in this hobby is someones radio controlled pride and joy sinking, no matter how gracefully, beneath the waves. Well, assuming it's not a submarine model in which case the saddest sight is the operator wondering why it hasn't resurfaced!
I still find it surprising that so many models do not have the rudimentary safety precaution of the simple transverse bulkhead to divide the hull of the model into watertight compartments. Take a hollow hull, often found in kits as a GRP or plastic moulding, Fig 1. Now if such a hull springs a leak, gets a hole punched in the side (often accompanied with a cry of "where the hell did that come from!") or whatever, then water will flow into the hull and the whole hull can fill with water. Don't blame water, if it finds an opening it will flow through it, that's its nature, Fig 2.
If our unfortunate modeller is lucky, the inrush of water is modest and there may be time to sail the model back to shore before the internal workings decide they have had enough and cease responding the increasingly desperate assault on transmitters controls. Or, they could be lucky and another person might be able to make a recovery with their model. However, I have seen the occasional enthusiastic "helper" cause more damage and even make the model they are trying to save sink even faster..!
Now even a single bulkhead placed somewhere roughly amidships can save the day. The water will be confined to one half of the hull, Fig 3, and there's a good chance that the model will still float. Many models with a decent amount of freeboard will have a more than adequate reserve of buoyancy even with half the hull open to the water. Even if this is not so, a single bulkhead can make the model "sink slower" and give you more time for recovery.
I must admit that the way most of my models are built means that they have multiple bulkheads. This is even safer as any flooding will be limited to one, or if unlucky, two adjacent compartments in the hull, Fig 4.
The value of these bulkheads was brought home to me many years ago. A model based on a destroyer was being sailed in a club steering event. It was quite rough but my model seemed to be coping with the course that had been laid out on the lake, although at times it could be momentarily lost in the waves. It was only when it was coming in for the final docking maneuver did I see that the rear half of the deck was underwater! The rear three compartments had been flooded by water coming over the decks and leaking inside the hull. Luckily the first two compartments were dry and able to keep it afloat. They also contained the receiver and allowed me to retain control.
One final point about bulkheads is that they will offer no protection from sinking if holes are cut through them. If wires have to be routed between compartments I try to run them over bulkheads. If this is not possible small slots can be made in the top of the bulkhead to accommodate the wires. If forced to make a hole in a bulkhead, I make it as small as possible and well above the bottom of the bulkhead.
Glynn Guest