Efficient and ocean-going?

Yes, it is not some radical experimental design. I think for long distance and reliability, tried and tested systems are best. Keeping everything as simple as possible is also a plus.

 

Curious what kind of aluminum alloy is used to build a go anywhere boat?

Aluminum Yield Strength & Tensile Strength Chart https://amesweb.info/Materials/Aluminum-Yield-Tensile-Strength.aspx

 

@portacruise 5083 is usually the standard used for marine aluminium plate, while 6061 is often used for sections (ie framing, like angle bars and tees).

@Ad_Hoc mentions them in the post in the link below - he is an authority on the subject of aluminium boatbuilding, and he has given me a lot of good advice whenever I have approached him with a problem or a question.
would you use 5086 or 6061t6 https://www.boatdesign.net/threads/would-you-use-5086-or-6061t6.48268/#post-650808

 

Thanks!

 

Something about this post seems off to me.

Unless I am mistaken, you cited planing craft above as your models you covet. But then you are suggesting a vessel operating at hull speed as your goal.

Can you clear this up for me?

Vessels designed to plane are not optimal for operating at hull speeds, so I am confused and perhaps it is just me, but the citations do not match the stated SOR.

At the same time, 440hp is not going to win many races at 63 feet or 18m, so the power also seems a bit odd to me. What was the original power plant for these hulls? And how do you arrive at the 440hp requirement? Was that the calculation to just attain hull speed at stated loading?

The reason I ask is I’ve seen planing vessels operating just under their hump and they are woefully inefficient and push massive bow wakes. A planing hull in rough seas operating at hull speeds is not going to be very pleasant and unless I am mistaken, is this not a planing hull? A planing hull will pitch at low speeds as the aft section rolls over the wave because the hull is made to lift off, if you will.

Anyhow, you have to clear a few things up here, imo.

 

Also, for 440hp intended power, what rpm will you be running at for hull speed?

 

Hello everyone,

@Portacruise: Unfortunately, I don't know what type of aluminum the ship is made of.

@fallguy: Perhaps there has been a misunderstanding. I am looking for a displacement boat. My references are Steve Dashew's FPBs or an LRC65 from Artnautica. As I understand it, these boats belong to the LDL design category. They are "fast" and efficient displacement hulls. They have very round bilges, which means they roll very easily. Therefore, stabilization (gyroscopes, fins, DMS Magnum, flopper stoppers, etc.) is very useful. The FPBs in particular have excellent ocean-going characteristics.

The hull I have visualized is significantly wider in the rear and the bilge is flatter. The wetted area in the rear is significantly larger. The initial stability should be higher than that of the FPB reference. But I wonder how the design will cope with following seas? How will it perform in serious but normal offshore conditions? I dont mean 10m waves, but lets say 2-4m...

2x220HP

 

to be honest, I don't know

 

The RPMs would depend on the engine.

 

Yes, I also think that the rpm at hull speed depends on the motor. But as far as I understand it, the resistance of the hull is also a decisive factor. And it is probably also necessary to consider how much of the motor power generated is actually transferred to the water by the transmission, the shaft, and the propeller (losses in the drive train). This is how I imagine it:

Hull resistance in KN + powertrain losses = required power

I can then read the rpm at the required power from the engine manufacturer's power curve.

The whole thing could be an approximate value that does not take sea conditions and growth (waves, wind, current etc.) into account.

I used Delftship to create a extra Delfship model to find out the resistance. Unfortunately, Delftship calculates absurd values:



I have no idea whether you can look at it that way.

 

That is correct. However, unless it is only used in nice weather there should be a power reserve calculated. For example, you may find that the resistance increases by 12% when against a 40 knot wind.

 

OK
What losses can be expected in the drive train?

 

There are no increased losses on the drive train, but increases on the resistance.