Displacement alloy monohull

[bekasi]

A stupid question from a newbie-If a small (40ft)alloy planning monohull design vessel was to travel at displacement speeds,will there be changes made to the planning hull design or is it that simple just to put smaller engines to make it travel at displacement speeds?

 

[AndieMac]

Is the intention to run the vessel inland or offshore?

If you open the thread called 'Spring Cleaning', and have a look at the shallow keel on Omegas' boat, an addition like this would help keep her on track.
Maybe ballast as well, they are pretty light-weight boats, ideal for rugged work or high speed.

 

[Dave_Seager]

Any planing hull will operate in displacement mode if less power is provided, either by smaller engines or less throttle. However, to operate efficiently at displacement speeds the hull shape should be different, designed to part the water and minimise wash. On difference between planing and displacement hulls in the transom design. Planing hulls usually have a sqaure profile whereas displacement hulls have little or none of the transom immersed.

The main difference between aluminium and other hull materials is its lower weight. Weight is significant for planing hulls as they are designed to lift out of the water. For displacement hulls, weight is less important for performance but a lighter hull will tend to be less comfortable as it will pitch and roll at higher frequencies.

 

[bekasi]

Is the intention to run the vessel inland or offshore?

If you open the thread called 'Spring Cleaning', and have a look at the shallow keel on Omegas' boat, an addition like this would help keep her on track.
Maybe ballast as well, they are pretty light-weight boats, ideal for rugged work or high speed.

Inland waters,thanks

 

[oldsaltoz]

Delivered an alloy boat some years ago now, could not get over the amount of condensation that forms on the inside of the hull,

Made life a little difficult as everything below was damp. Also note, the noise made by the hull and lapping waves below deck at night was awful to say the least, we ended up running 24 hrs a day and sleeping when we could on split watches.

 

[Imperial One]

Delivered an alloy boat some years ago now, could not get over the amount of condensation that forms on the inside of the hull,

Made life a little difficult as everything below was damp. Also note, the noise made by the hull and lapping waves below deck at night was awful to say the least, we ended up running 24 hrs a day and sleeping when we could on split watches.

With the Van der Valks and Boarnstreams, we overcome the noise and condensation problem by spraying the hull with expanding foam during build.

It works well, as it stops all noise and vibration traveling through the boat, stops condensation forming and keeps the boat lovely and warm in the winter and cool in the summer.

I do hear that some of the lower cost boat builders don't bother with such things, so I guess while it saves them money it gives someone else a problem. But, now you know the answer to the problem, the solution is as the meerkats say "Simple".

The only problem retro spraying it is that you will inevitably cover up some fittings or electrical parts...................

 

[Keen_Ed]

See here for the Dashew's take on a displacement 64' in Aluminium.

http://dashewoffshore.com/

Slightly different: see here for Nigel Irens' Low Displacement Length - his own 40' is planned to do 11 knots with 40 hp

http://www.nigelirens.com/ldl/yachts-product.php?id=4&idcat=1

 

[AndieMac]

Delivered an alloy boat some years ago now, could not get over the amount of condensation that forms on the inside of the hull,

Made life a little difficult as everything below was damp. Also note, the noise made by the hull and lapping waves below deck at night was awful to say the least, we ended up running 24 hrs a day and sleeping when we could on split watches.

The lapping noise on an un-insulated hard chined alloy boat is pretty harsh, especially for sleeping on a windy night.
The unbacked, conforming 'marine hull liner' usually takes care of condensation. The product is easy to install, very forgiving and hides a multitude of sins, ideal for any 'post' build work.