Italcraft 35 fast, get on plain problem

[tonipu]

Can you send me e link where you find this picture, i cant find?

Yes the flaps can fully retract, and the stracture and the mehanizam are very strong, but i dont understand fully mr. Efficency What you sugest

 

[Mr Efficiency]

Like this:

 

[tonipu]

Ok, and you dont sugest to make it wider, or jo sugest that i do both, hinge and widening the flaps?

 

[tonipu]

I mean wedge, not hinge

 

[Ad Hoc]

Can you send me e link where you find this picture, i cant find?

It is not difficult to type - Italcraft 35 - into Google and get:
Italcraft Fast 35, preowned motorboat for sale in Lazio (Italy) https://www.yachtvillage.net/en/detail/3a573091-69ef-480a-8f83-c2c70870eccf

 

[Mr Efficiency]

It would be dead easy to fit a wedge to both flaps, as an experiment, widening the flaps a bigger job. Wider is certainly better than narrow, but you could get a big increase in lift from wedges, it becomes a matter of how aggressive (angle of attack) What is ideal might vary according to the characteristics of the boat, obviously a wedge does have an increase in drag, but the nett effect of drag from the boat+tabs is likely to be a reduction of the planing hump. It probably depends on the amount of drama involved in removing the boat to and from the water, balanced against the complexity of the modification carried out, but my initial impulse was a wedge was worth a try.

 

[gonzo]

12 people plus seats is about 1 ton on the stern. The boat is overloaded and the CG shifted aft by quite a lot.

 

[Mr Efficiency]

He appears to be happy with the boat at speed, but looks to get easier planing, and presumably better ability to stay on plane, backed-off. The tabs appear to be area to concentrate on.

 

[TANSL]

The mission of the tabs is not to increase the planing surface but to create a force that helps correct the trim. Therefore, longer tabs produce a force farther from the hull's axis of rotation, increase the lever arm of the force generated by them and increase, without varying the total force, the trim correction moment.

 

[Mr Efficiency]

They produce more lift by being wide rather than longer, the leading edge being longer.

 

[Mr Efficiency]

I assume the semi-cylindrical ducts/shrouds are used to turn the boat ? Perhaps a downturned lip at the top of them, might create lift when taking off, but not be in play at speed, but maybe loading them up at the end may be putting too much strain on them.

 

[BMcF]

We built a small surface effect ship that had two of the early "Levi Drives" installed. Late 1980s. The take-off performance of that setup was terrible, and despite several changes to the propellers (Levis was directly involved in the project), the craft never behaved well. This picture is, in fact, one of the only ones ever taken of the craft "on plane", moving along at over 40 knots. It was quite light but with a number of 55-gallon barrels full of water placed on the deck in forward part of passenger cabin. Only moments after this picture was taken, the craft executed a hard-over uncontrolled turn directly in front of the 35-meter surface effect ship that I was taking the pictures from. The barrels full of water went nearly through the side of the passenger cabin...

And those steering shrouds..ugh...not very effective as it turned out.

 

[Mr Efficiency]

Not having those drums tied down sounds like negligence.

 

[tonipu]

Yes, once it get on plain with 12 people, it got without problem 30kts at 2450rpm.
Other issue of this drive is that you can go 10, or 25kts and cant crouse in betwen, for exemple you cant cruise 20kts, with Will help in heavy sea, but actauly it is good and seaworthy boat

Other issue is the turning issue, if you dont align it with flaps very well the boat go in one direction, oposite of your steering direction, i was thinking to add litle bit of surface to this semitunel

 

[BMcF]

Not having those drums tied down sounds like negligence.

In hindsight...it probably was. Nobody was anticipating any violent maneuvers or motions in the flat calm conditions. Fortunately, the only injury was to cabin bulkhead.