Altering Flooding Hull SR5.4

[Sun-dry]

I'm thinking of altering the Flooding Hull on my Searider 5.4 / 75merc. Have had this great boat for 3 years now and have found it very stable at rest, and in a large swell. My main issues with it are launching/recovery, when it grounds too soon, and won't clear sandbanks like my mates Sparrowhawk will! Sucking up most of the floor of the Menai Straits cant be good!!!
The other is in a big head-to-sea situation. Because the boat speed might only be 5-10knts, your dragging many gallons of water over every wave, which increases fuel consumption (may be critical if trying to get home)!
I like the concept of the flooding hull on the sr5.4, but it would be nice if I could have some control of it when needed.
I thought about fitting a hinged Scupper over the rear 100mm hole, and leaving the front holes open. I only want to keep water out just befor recovery / shallow ground, and keep most of it out going head-to-sea. Othertimes, I could open the scupper with a cord etc, and have it as normal as you might say.
A lift up semi-flex trunk, may catch the motor and would not let any accumalated water out automaticaly, however as the front holes would sit higher with a dry hull, this may not matter too much, apart from long head-to-sea situations.
Maybe a hinged circular scupper with a full 100mm opening (to dump water), would be the best, but I can't find one that big anywhere, other than the hinged 7"x 5" rectangular alloy type, which wouldn't look very neat and may not even fit the V profile.
The nearest idea so far seems to be one I heard of on a previous thread here, of making a hinged flap out of a piece of rubber/neoprene, and tying a cord to it to keep it open, its very simple and could work. It only has to keep 95% of water out for about 10 mins, anymore would be a bonus!
The flooding hull has created so much debate in the past, there must be somthing that can address different peoples requirements in one shot, without losing any of the qualities of this boat???
I would appreciate it if anyone has done something along similar lines and their thoughts.

Many thanks

[chewy]

To use the hull as a ballast system a start will be blocking the holes in the bow and having a breather exit within the boat.
Are you relying on it filling up at rest? If so some imagnitive pipework/fabrication to clear a trunk of the engine and its sorted.

[Sun-dry]

Hi Chewy.
Inboard front vent holes would certainly prevent unwanted water entering the hull, unless water was getting in somewhere else. Good idea though. The rear exit is the tricky one, I want the hull to flood under normal conditions at rest and mobile, but not when in shallow water or in big head-to-seas. I would need a large hole to let water out when in normal flooding mode, but be able to close it up at othertimes (ideally with a one-way scupper valve in it, incase water did get in, if closed for a long time).
A rigid pipe may get damaged or snagged on the motor, a flexi one would have to be lowered up and down each time you thought water had got in. In heavy seas, this could be a problem. Am trying to make it fairly automatic and neat if poss. I'll give the rear pipe some more thought though.

Thanks

[PeterM]

So - a thought about your plan....

How about a circular 'plate' hinged at one side - spring loaded to be clear of the 'big hole' .... unless you have pulled it over the hole by use of a cleat etc as per elephants trunk ? Or vice versa - sprung closed unless held open....

So you can leave the bow as is & control if you leave the stern open to drain/fill as normal , or close it when empty/on the plane and while it may leak abot slowly when stopped or going very slowly - nothing like it does if it was fully open ....... and no need for a pipe

Thinking along the lines of the threads about runaway diesels and the air intake cut offs that 'I think' operate in a similar way ?

I can see it in my mind if nothing else

[Nos4r2]

I think the only way realistically you're going to keep the flooding hull empty for longer periods like launch/ recovery or sand bars etc is to seal it completely.Any partial solution is going to leak enough that you'll find the draught slowly increasing when you don't need it to.


For head seas though, it's a bit easier. I had a home made partial drain flap on my sr4 which worked as long as you didn't come completely off the plane for more than 4 or 5 seconds-see here. http://rib.net/forum/showthread.php?...r4+flap&page=3

[chewy]

You need a scoop at the back like the Atlantics have, it goes down to fill and when up is angle so when on the planing it create a venturi sucking the water out.
I wouldn't want to try and use any boat with water in the hull though, theys a reason it drains when your under way, if it was partially full then it would slosh about and become unstable.

[Sun-dry]

Thanks for your thoughts so far, I like the idea of the hinged flap. I had thought about a similar idea a bit ago, where you would have an ali flap, top hinged, with a circular piece of neoprene a bit bigger than the hole, bolted on the inside face of it. The edges of the neoprene would be left floppy so as to suck themselves on to the face of the fibreglass around the hole, when water tried to get in. The flap would hinge open automaticaly to let any water out.
A small lead weight on a protruding arm could be fitted to the top edge of the flap, to help it to close, if turbulance was keeping it open.
A light piece of shock-cord could also be fitted to this arm, so when pulled verticaly, the flap would be kept in the open position, for normal use.
I dont realy want to seal it permenatly, as it makes it a bit corky when at rest etc.
A small amount of water ingress would still be an improvment over a completly flooded hull.

Trev