10 meter tunnel hull with a mono bow.

[firth_andrew007]

hey everyone i am on the ass end of building a 33ft tunnel hull flybridge structure. as soon as i cut and shut and mount the new hardtop on the bridge i am either going one of two ways.

option one: shut the tunnell off and turn this boat into a simple mono. which will give me more space for tanks etc. but the beam of this boat is only 6ft. and the LOA is 33ft. so i think the sponsons add stability to the boat. but if i employ a Moderate Deadrise it should account for the stability. the bow will still have a deep v. so cutting through chop should still be comfortable.

option two: extend the hull as a tunnel hull and make space for 2 outboards. the extension will simply be a duck board with two pans for the outboards.

but more importantly has anyone seen a boat like this before? or the hull shape?

[Mr Efficiency]

Are you sure it is only 6 feet wide ? I did build a boat with some similarities years ago was 6m x 2.4m though. It did have some handling peculiarities inasmuch as it tended to jink around a bit in beam seas, but ride and stability were good. I'd say try it as it is before attempting radical surgery.

[firth_andrew007]

hahah yeah i might just build the extension for the outboards for the moment. its just such a strange thing. if it turns out to be a dog in the water i can always pull it out and turn it into a mono later on. but yeah the beam is 6.5 feet. its so skinny for how long it is. im just not sure about the hull. i have been been working at australia's largest marina for awhile now and i have never seen anything close to it. i have had a guy say that he has seen it before. he said it looks like a water taxi? for motors i was thinking 150hp outboard a side. maybe a little bigger. i definitely cant go inboard the cockpit would disappear if went that way.

[firth_andrew007]

but a mono hull at the bow and a tunnel hull come stern?? what properties would this have? good for choppy water at the bow. stability and speed at the stern maybe?

[Mr Efficiency]

The boat I built looked eerily similar, looking from behind the stern, as yours, it had one outboard centrally mounted behind a nacelle in the tunnel, the cav plate about half way between the roof of the tunnel and the bottom of it. That worked OK, don't worry that the forward part of the hull will interfere with water flow, the level just rises to meet the prop. My boat was considerably deeper forward than yours, but a differently proportioned thing altogether, not long and skinny.

[Mr Efficiency]

I can't speak to the motives of the designer of your curiosity-piece, but my intent was to create a vessel with the kind of ride quality and resting stability of a cat, without the need for twin engines. I'd say it met those criteria, but I was never happy with the tracking in an arc between beam and stern quartering. No alterations i made cured it completely.

[Village_Idiot]

This is the way to build a displacement tunnel:

http://www.bateau.com/studyplans/ST2....htm?prod=ST21