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jacks

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Doc Holliday

Doc Holliday

Well-known member
My boat has what I guess is a jack in it too......if someone could explain the how and what about it, it may help us both out.

BTW, my hull's a 13-foot Rivermaster, fiberglass (maybe all Rivermasters are fiberglass?).
 
you should put 1/2" to 5/8" in front jack to part the water if you have a mid ship one put 1/4 to 3/8" if you have an aft (stern) jack leave it flat (they dont use them any more) they will not help hill running at all they are for parting the water like a v hull if not it will push the water up then come down then push up then come down its to help stop porposing but there are other factors that will still make your boat porpose this only deals with one of them hope this helps
 
I agree with croc, jacks are simply for parting water,therefore running deep water better(no porpoise)
 
I agree with what croc and bobby said about jacks. But would like to add another consideration. I may be wrong, but I have been told the following.

A good dry running boat should have a slight bow downward (very slight) in the middle of the hull. Should be located near where the point of balance is. Easiest way to see if it does is set it on a good level concrete slab. I have seen at least 2 - 15 footers that one man could pivot by hand on the concrete. They also ran fairly well. Lots of the Palm Beach style hulls have this shape as well. A boat with this in the hull will have much better ability to manuever on the ground and will tend to slide better.

I was told this by 2 builders of Palm Beach hulls and by one builder of welded hulls. Have seen 2 supposedly indentical boats by a small builder in Louisiana as well, one ran like a scalded cat and the other did ok. The first was much easier to turn on the flat ground.

But I believe that shape is built into the hull and I don't know whether you could fix it with a jack.
 
Pat,

I have heard you say that before, and I would really like to know how the Palm Beach builders are putting compound curves in the bottom of a boat made from heat treated material. Try it with a piece of paper, it will wrinkle. The material has to be stretched to do that.

I know how they do it with the soft welded boats. They force it with jacks and the metal does stretch.

Jim
 
I was told the jacks are for keepin the bottom flatter so it didnt form a suction effect. I can turn my boat around by myself sittin on dry ground. I cant do it in the mud but dry ground she spins easy enough I did it on the run saturday so no one got prop blast from me at least I hope they didnt.
 
my 12ft laser (glass) is a s.o.b. to turn on the ground. it gose ok dry but in water
it's like ridein a wild bull a trim tab is the only thing that has helped . i've
moved the gas tank up and the batterys that helped some to. a guy told me to move the riggin up 3inches not done that but the other stuff has helped would a jack make a differance on my boat.
 
i was told that the jacks are used to keep from having the entire bottom of the boat on the ground. it pushes down the hull and allows the boat to rock on dry ground, acting like a pivot point.
 
If your boat porpoises in water put in a jack about a foot from the rear of the boat and pull the stringers up this cup will make the bow come down. If your boat rids on the nose push down on the stringers. Jacks are mostly intended to improve how a boat handles in the water. I know on the hill flatter has always ran better for me less PSI per square inch of surface area. Picture it like pulling a heavy weight across grass would you rather drag it on a 2x4 or a sheet of plywood?
 
Cracker - All I know is two of the Palm Beach hull builders told me the same thing. And I understand the piece of paper idea, but there is a slight curve from side to side and back to front.

If I had a clue how they do it, I would be building one myself.

And yea to what Thunder said.
 
I repeated what bobby and vinnie at diamondback told me after they did this my boat ran like glass .but recently it started porposing again. what thunder says makes alot of sense so I am going to give it a try this weekend. and see what it takes to get it back to riding like glass again
 
the jacks will help run dry better but to much it will be like a roller coaster in the water, put to much jack it one, 1 time and it was all over in the water you just want to get the hook out. If you look at the river master hulls they have a slight v in the bottom to have less surface on the dry ground.
 
Hey Thunder,

The bottom of your boat does not look flat to me:

THUNDER.JPG


Jim
 
My hull has a wide running bottom before it curves up. The radius doesn't start till about 14'' from the side. You would be surprised how few hulls even have 38'' of true flat bottom. The older hull builders really liked the narrow running bottom with a rounded side. Their theory was the whole hull floats but when on a plane less hull was in the water they worked great in the water but didn’t run dry that well. I have owned narrow and wide hulls and found the heavier the boat the better it run’s dry with more running bottom. I don’t know if this applies to aircraft motor boats it does seam like the only concern to aircraft guy’s is weight.
 
If you look closely at the picture of the Hamant hull it appears to be one sheet that is flat on the running bottom Then the sides are welded on. See I have owned a Hamant hull also so I know exactly the width of my boat and a Hamant and a Thurman and a Gore and a Gilleo and a Hawk hull. However my running bottom numbers is something I wish not to divulge.
 
You should not have said that. Now someone is going to feel compelled to sneak up on it and measure it, but I wouldn't do that. :D :shock: :D

Jim
 
Measuring is the easy part it’s getting the compound angles and radius’s that will take some ciphering. Just remember every combination is different, what works best for a car motor will not be the best for an aircraft. I can say to buy a Hammant because they seem to be the best all around ride boat hull car motor or aircraft.
 
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