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Deiter
09-05-2007, 04:44 PM
g'day all.

this may be a silly question,BUT, I am thinking about how to improve the handling and stability of my current boat while i am putting coins away for a new toy. Current ride is a 5.5m Profish plate ally halfcab with about a 20deg deadrise at stern. That's right, two guys on one side = bad listing. It rides pretty well considering what it is, but i am always thinking of things that can be improved.

Lately i have been tossing up the merits of adding some weight along the keel to do two things:

a) Drop it deeper at rest, so it aint so tippy,

and b) Provide a bit more momentum for pushing through chop, rather than skidding over it.

Now, b4 you start, i don't need to hear all the reasons why i should just buy a glass boat/ sharkcat/ fisher, whatever, coz right now it aint an option, and ballast is. Maybe there are other ways to achieve this that you can think of. Great - let's hear it!

So far i have thought of welding on some wings like some of the stessyl craft have to combat this lack of stability. Or bouyancy chambers either side of the pod, or even welding a peice of angle under the chines to emulate the Fisher reverse chines that work so well.

Any workable suggestions? Anyone done mods like this b4?

As far as ballast goes, it is possible to access the inner keel to add sandbags or the like, so is it worth doing and what is the best medium to use?

This should be good.

Damo:)

Roughasguts
09-05-2007, 04:51 PM
I would use water for ballast, pump it in and pump it out for trailering.
Just got to work out where you can put the tanks, or what voids you can fill.
Use them for a live bait tank if you wish.

SNAPPERCOFFIN
09-05-2007, 05:45 PM
Wouldn't play around with things like that could affect the handling of the hull. If you want a ballast system buy a boat that has been designed to have one.

Mark

peterbo3
09-05-2007, 06:18 PM
Hi Damo,
The water ballast idea could drown you. The last thing you need is 20 or 30 gallons of water sloshing around unrestrained in the bilge. Even if you have a ballast water tank welded in you cannot be sure how the boat will react.:o
So to the handling on the move. Trim tabs. For around $800 you can fit a set of Bennetts or the like which will give a much better ride in most sea conditions & will level the boat. Plus they will add value to the boat when you sell it.
The addition of pods either side of the motor will probably help the stability at rest but may cause problems on the move as you are changing some basic design fundamentals. Some on this board have had success with pods so I am sure they will chime in.
The Stessels with the "wings" have had some problems too. Plus the $$$$ would big.
If it really is tippy at rest then a few sandbags under the floor around midships may be the go. They will not move but you will probably need at least 100 kg & possibly more. The only way to check this is trial & error.

Chimo
09-05-2007, 07:44 PM
Hi Deiter

Why dont you ask http://www.profishboats.com/ to add some ballast tubes a la some other plate boats that are often on the site?

That way you might get a rig that your happier with that is very much more saleable when the time comes.

Cheers
Chimo

Wayne_Red
09-05-2007, 07:58 PM
I agree with Chimo. Fitting ballast tubes would be the way to go. The ballast looks after its self without the need for pumping etc. No ballast weight when underway.
A mate has a seadevil (fibreglass) with water ballast, very stable at rest.

Depending on how handy you are you could fit them yourself.
Regards Wayne

fishingjew
09-05-2007, 08:42 PM
The free surface of liquids generally causes a reduction in a fishing vessel’s overall stability levels. This reduction occurs when the liquid, and thus its center of gravity "g", shifts to the vessel’s low side when it heels over.
Free surface occurs because the liquids can shift to the low side as the fishing vessel heels over.

Free surface causes a reduction in the righting moments available to counter any capsizing moments acting on the fishing vessel so I would stay away from water ballast also adding weight to the vessell will reduce the freeboard which will cause the deck edge to submerge at smaller heel angles.

snelly1971
09-05-2007, 09:02 PM
I sort of have what you are looking at...i have an underfloor kill tank ...approx 150 liters...I find that it doesnt make a great deal of difference to the handeling of the boat....mine is probably 1/3 from the stern of the boat...

Makes the boat slightly heavier in the arse ...but is hardly noticable....i do find that it does settle the boat down a little bit at rest on the anchor though...

cheers mick

GBC
10-05-2007, 12:05 PM
Get a 200l bow tank and put some wakeboarding stickers on it bro - but then you'd have to add a tower with doof doof speakers too - might cost some in the cred department though.

Noelm
10-05-2007, 02:25 PM
hhhmm not too sure of the idea of adding ballast to an already completed boat, all boats are a compromise, and in ours the trade off for ride was stability, now I am not saying that ballast tubes/sandbags/water tanks etc will not make a difference, but kind of seems to add considerable extra weight (unless it was the draining tube/hollow keel things) I guess you suold just put up with it and look towards compromise the other way when sometime in the future you upgrade, perhaps! my thoughts on this only.

_Dan_
10-05-2007, 02:57 PM
Masterline sell fat sacks, 180 litre inboard ballast for wakeboarding boats, they are sold at any good ski shop.

Pump to fill them and hose empty them, by putting in the hose and dropping the other end of the boat amd when under way they wil empty themselves out.

I think form memory they are about $120, get a pump and fill them in a few mintues.

Yes i wakeboard also, out with injury at the moment,

Cheers
Dan

jimbo59
10-05-2007, 07:16 PM
Twin v8 caterpillers will solve this problem;)

Deiter
11-05-2007, 03:41 AM
aaaahhh, some good suggestions.....and some taking the pi$$. Ha ha, i haven't got much left, so go easy.

Had another thought today, spurred by some of the replies already recieved.

Adding water ballast tubes is a bit too tricky due to the internal 'skeleton of the hull, particularly rigid alloy tubes. SSSOOOOOoo, the 'fat sacks' idea got me thinking, how about some 150mm ag water pipe, one length either side of the centre stringer/frame. That stuff is tough as nails and can easily be secured to prevent excess movement.
With an opening under the pod and ventilation hoses attached at the bow-end, i would think that it would work, raising the centre of bouyancy and dropping the centre of gravity.
by my guestimations, 2 x 4m lengths would hold about 140L. Anyone know approx cross-sectional area and length (or just the volume) of ballast tubes by fisher or barcrusher???

I know, i know, i just can't help myself. Always fiddling with stuff to see if i can make it work better. Last year i bought 2 new tld 25's and took 'em to bits b4 they were even spooled with line. They now both sport beefed up drags and
oversized machined alloy, lengthened double-ended handles. BUT THEY WORK BETTER THAN NEW.
That's part of my justification for all this anyway.

Damo

Chimo
11-05-2007, 11:43 AM
Hi Damo
For your comps.

Getting the fluid in and out quickly wil be an interesting challange for you!

The units of volume depend on the units of length - if the lengths are in metres, the volume will be in cubic metres

A cylinder (http://en.wikipedia.org/wiki/Cylinder_%28geometry%29) (circular prism):


http://upload.wikimedia.org/math/6/9/8/69833501a76a4bf9d7d823316c905b9d.pngr = radius of circular face, h = distance between faces


Cheers
Chimo

Sandman
11-05-2007, 12:02 PM
Just find a couple of nice blondes to take fishing that should do it - Best of luck

Roughasguts
11-05-2007, 03:15 PM
Just find a couple of nice blondes to take fishing that should do it - Best of luck

Forget nice, how about naughty! with very low standards.

Deiter
12-05-2007, 12:51 AM
yes Eddy, I'll lock in option 'C', thanx.

Roughasguts
13-05-2007, 10:20 AM
So what you got planed there Deiter, Anything?
So can you lift the floor, some where forward of your fuel tanks, to get below the deck. Having a tank or bladder of water ain't going to be much differant to having a fuel tank. Can't see anyproblem with it for ballast as long as you can empty it.

Weight equals inertia, and inertia is a good thing that opposes any deflection from waves, wind and sudden change in velocity.

But there was some other thing recently, a gyro scope, that converted the roll movement to a pitch movement. Seemed to work really well, apart from the price that is.

Deiter
13-05-2007, 01:06 PM
G'day RAGS, well, you are spot on with your comments re inertia. So many ppl have stated b4 that weight in a boat is a good thing when the going gets tough, as long as it is still balanced. I am not sure that 2 blondes would be enough though.

Atm, i am leaning towards the placement of a pair of poly agricultural pipes running parrallel and next to the keel. This would be (relatively) easy to make work, just like the barcrusher/ fisher ballast that just empties when you move forward.

My floor is fully welded, but i have an inspection hatch near the stern and another removable plate over the 130l fuel tank about midship. This gives me enough access to do what i need to do. I'm still thinking about the best way to add weight while underway though. Sandbags is easy, and probably a good test to asess what sort of benefits are going to be had b4 diving in head first. Ideally i would like to keep these as low and close to the keel as possible also. Completely open to ideas and suggestions or warnings though.

I still think adding some right angle ally strips under the chines to flatten them out would be a good thing and pretty easy to do, and will be something i will do soon.

Damo