Keeping aluminium boats cool enough to touch in high temperatures?

Looking at getting an aluminium dive boat built here in Egypt, the intense sunlight is magnificent for coral growth in the Red Sea, but it does cause a problem as well - anything metal in the sun quickly gets incredibly hot! Any tips on what to do about this as obviously being on a dive boat involves touching things like handrails, ladders, etc etc. Coatings? Wrappings? Any ideas would be appreciated as the heat issue could be a show stopper!

 

Can you have an aluminum hull with a plywood or composite deck? Railings can be all wood.

 

The ally cat in my avatar photo has painted decks and treads on ladders, but otherwise the rest of it (including hand rails) are unpainted, and I have never heard of any reports where passengers were complaining that the aluminium is too hot (and the boat is now 22 years old, and has been all this time carrying pax on snorkelling tours).
Although I think that your temperatures in the Red Sea are probably much higher than ours here in the Caribbean - our day time temps are typically around 30 - 32C.

 

Cheers Bajan! Day temps here are 40-42C in summer - and for about 9 months of the year there is not a cloud to be seen. Water temps are 32C in summer.

 

On my fiberglass boat, I have stainless steel hand railing which can become very hot to touch on an average summer day. On the other hand, I have ladders made of aluminum to climb up from the water. Even when the ladders are out of water they are completely safe to touch on the same day when the hand rails are hot.

The reason is simple - Aluminum is one of the materials with the highest temperature conductivity (between 88 and 251 W/m*K), the main reason why it is often the material of choice for heatsinks. So, you could consider the whole aluminum boat as one huge heatsink.

Stainless steel on the other hand has much lower thermal conductivity - around 15 W/m*K, which is pretty low for metal material.

(W/ m*K = Watt per (meter*Kelvin), just to avoid confusion of units)

 

OK that sounds great - one more potential problem now has a line through it!

 

Not really.

Aluminum deck will get super hot.

The point he is making is the aluminum ladders that enter the water are dropping to the water temp. That won't occur on the deck.

There are strategies to reduce metal from heating, but a simple idea would be to flood the deck with water or to specifically design a deck that is not metal, or to shade the aluminum deck from the sun with a hardtop which would also shade divers in black wetsuits.

 

???

 

I did miss that point, but the deck is not the same as a piece of aluminum in space. It does get hot as spaces beneath it heat inside. The advise for a top for shade also helps divers in hot weather.

 

I can relate to great feeling of doing that , even when no action required.

Well, see the above answer from bajansailor. We could say the following as additional explanation - due to the mentioned high thermal conductivity, the heat is "almost instantly" spread on the whole aluminum hull and the hull has huge surface area in contact with other "materials" to which it transfers the heat - air, water, hull elements, etc. Mind just the surface area in contact with the sea water (I would really disregard even the potential paint due to the amount of surface area and the high thermal conductivity of aluminum). Compared to that, my ladders, attached to fiberglass with two small hinges, could be considered as just a small dot in the sun and the only place where they could transfer the heat is to the surrounding air (around the dot) and they are still "cold". But, in such a harsh environment, I agree with you regarding creature comforts requirement i.e. shade for divers, just not considering the same root cause of the inconvenince.

 

I fished aluminum boats from as far north as togiak to as far south as san Diego. There is a a reason aluminum rules puget sound up through Canada, it never gets to terrible hot or to terrible cold and the water always stays cool. Aluminum never really caught on in the gulf or Florida... for the opposite reason.


Remember the first time it hit 26.6 c on my aluminum boat one rare day in Bristol Bay. We ran the deck hose every 15 minutes to cool the deck. But we had 12.7 c water to cool it with.

The squid seiner had light colored superstructure roofs. But it didnt do much to make the tophouse stateroom liveable anywhere south of half moon. We fished at night so wasn't bad but sleeping during the days was usually a pad on the floor with windows on. I cannot imagine the Temps your doing...