high volume bows

[John Harding]

I am curious to gain opinions from experienced users on the merit of high volume bows like Delta or Humber boats provide. I am thinking of buying a RIB in the size range 5.8 -6.5 with about 120/130 HP 4-stroke outboard and have been steered by friends to look at Delta or Humber boats. Can anyone offer any advice especially on the question of high & high volume bows? I think it is clear (at least to me) that deep v hulls with the V running right aft are best but I might be wrong. I want to know that when it gets unexpectedly rough or a return passge has to be made in bad conditions the boat will not let me down!
John

[timw]

Do you mean high volume in that bow is upturned like a Banana?

I was researching the same thing, but eventually ended up buying a RibEye which has quite a flat bow, and I'm really pleased with it in rough weather as nothing comes over the bow.

Maybe it does make a difference in the severely rough stuff but I'm not going to find out.

[Richard B]

I've always thought that a high bow, like a Humber or Delta was different from a high volume bow, like a Ribtec or Osprey, which is the result of a constant deadrise hull?

I've taken a Ribtec 5.8m RIB out in a mixture of rough conditions (big rollers and short sharp chop) and was really impressed with the way it handled. The bow didn't pitch much at all, and in comparison other similarly sized RIBs, I thought it was a very good ride. It seemed like the volume of the bow helped to stop the nose dropping into the water when coming off a wave.

But, this weekend I confirmed another suspicion that I have had - that loading the bow seems to work well. I added a new anchor, chain and warp in bow locker well up front - I guess about 20kg in total, and this seemed to help keep the bow movement under more control.

[Alan]

Interesting Richard. As you know Blue Ice was originally fitted with a bow ballast tank. Overkill IMHO and the reason the previous owner removed it. However I often thought she could do with a little more weight in the bow and it sounds as though you've got it licked with the extra anchor and chain!

Alan

[Mosser]

I always thought you used the engine trim to raise or lower the bow to suit the conditions.

Is it that on bigger boats this doesn't work quite so well and that ballast tanks are needed?

While I'm here...anyone got a simple explanation for what a constant deadrise hull is?

[Richard B]

trim, throttle or weight distribution.

See Pete7's posting in "Hull design - which is better" as it's better than any explanation from me!

Constand Deadrise hull - is exactly that, as I understand it... the deadrise angle doesn't change from transom to near the bow.

Look at Janis Petrov's Osprey bow in the "stolen RIBs" section.