Where would you place my gastank?

[bigboy]

Hey,<br /><br />Here two pictures. Where would you put the tank? No other solutions are possible. It's for a 17F fletcher arrowbeau wit a 140 suzuki. I've heard that they have a lot off bow lift...<br /><br />This is wath others would do:<br />

<br />This is wat I wanted to do...<br />

 

[QC]

Re: Where would you place my gastank?

I would not put it in the bow. Can't really fix that if she is bow heavy when done. If she ends up stern heavy, you can store more stuff toward the bow and add trim tabs. My .02

 

[bigboy]

Re: Where would you place my gastank?

Originally posted by Quietcat:<br /> I would not put it in the bow. Can't really fix that if she is bow heavy when done. If she ends up stern heavy, you can store more stuff toward the bow and add trim tabs. My .02

You've got a point there. But normally the bow gets very high when yoy accellerate. With a 200 horses on it you can't give full throttle or it would flip over. I know somebody and with less throttle his boat also the bow goes very high... What do the others think?

 

[QC]

Re: Where would you place my gastank?

Will it porpoise at WOT and full trim as it was before? Where was the tank then?

 

[bigboy]

Re: Where would you place my gastank?

I cant say that... The tank was in the front with a 200mercury... No idea. The one i know with his gt200 has his tank in the back. When it floats you can see that the back is deep(5-10cm more than normal) in the wather.

 

[Dhadley]

Re: Where would you place my gastank?

I'd never put it in the bow, personally. Its a lot easier to add stern lift than bow lift. Just like Quietcat says.<br /><br />A lot depends on the hull design. We always go for balance. You show those as your only two options. Dont know why thats the only options but another consideration might be to put the front of the tank at the lift point (usually about 1/2 way forward, maybe slightly back).

 

[G DANE]

Re: Where would you place my gastank?

bigboy, I am building a much lighter hull, and I decided to keep all weight back, anyway. I hope to keep the balance by trim, but I've only got 115 HP, but on a much lighter boat. My brotherinlaw had a arrowbeau, but it was converted with a 170 volvo I/O. Ran fine, well balanced, but a little stern heavy. It it true, that weight in bow will make porpoising potential. Wont you have enough negative trim angle to awoid too high bowlift at takeoff. You added the knee braces, didnt you, I dont recognize them as original design.

 

[QC]

Re: Where would you place my gastank?

Originally posted by G DANE:<br /> weight in bow will make porpoising potential

Sorry to contradict, but that is the opposite of actual. Too much weight in the stern causes porpoising. This can be countered with trim and/or trim tabs.

 

[Richard Petersen]

Re: Where would you place my gastank?

I was always told that porpoising was the lifting of the bow off of the water and then it quickly touches down again. The result is accelerate decellerate every second or 2.----------------------------------- All the tail heavy boats with excess power just BLOWOVER when they hit a fast gust of wind head on, because there is no weight in the front. Ever watch racing OB Hydros. They do it a lot on windy days.

 

[fishingdan]

Re: Where would you place my gastank?

The bow is typically not a good idea. Too much variable weight (full tank vs. empty tank) that will affect the trim. <br /><br />I think you need to consider all of the weights in the boat and then find a good location. You should look to balance the weight as much as possible. I would target an area between the stringers somewhere just behind the operators position. However, I not sure what the layout of the interior will be and what you expect for a typical load.

 

[QC]

Re: Where would you place my gastank?

Originally posted by cyclops2:<br /> I was always told that porpoising was the lifting of the bow off of the water and then it quickly touches down again.

You are kinda right, but I would describe it as the uncontrolled oscillation of the bow up and down, and it is caused by balance that is stern heavy and/or excessive trim. Like your wander issues it can be corrected with trim tabs. Boats are fastest right on the edge of porpoising, that is why I am recommending not to put the tank in the bow.<br /><br />Blow-over is a whole different thing.

 

[bigboy]

Re: Where would you place my gastank?

Originally posted by G DANE:<br /> bigboy, I am building a much lighter hull, and I decided to keep all weight back, anyway. I hope to keep the balance by trim, but I've only got 115 HP, but on a much lighter boat. My brotherinlaw had a arrowbeau, but it was converted with a 170 volvo I/O. Ran fine, well balanced, but a little stern heavy. It it true, that weight in bow will make porpoising potential. Wont you have enough negative trim angle to awoid too high bowlift at takeoff. You added the knee braces, didnt you, I dont recognize them as original design.

Yes i've added them!

 

[Richard Petersen]

Re: Where would you place my gastank?

I have a light, 16' X 7' wide, aluminum Lowe, shallow 15" stern and 15" motor, a 9.9 hp. I can get Porpoiseing into the wind very easily if it is about + 40 mph gusts. AND the 45# battery is at the very point of the bow with anchor, chain lines, and everything movable. Light over powered boats should ony be opened up on CALM days. Even if you do not blow over, You can make a turn from straight into the wind, to a turn and the exposed planeing bottom of the boat will increase and you lift on the wind side that lifts it and the suddenly drops the bow. The front of the boat drops hard on a chine if you have them. You may or may not flip from a chine roll. You are way beyond what the boat was designed for. You are now more operating the boat in a unknown area. You are racing by your self.

 

[SiggiJo]

Re: Where would you place my gastank?

I was going to put my fuel tank in the bow, but decided I would need that space for storing my back-up engine & some other stuff, so I ended up putting both fuel tanks and battery in the back. As I still don´t have it in the water, I don´t know how it´s going to ride, but I recon I can always add smart tabs if it turns out too stern heavy. I remember seeing that Mark42 installed a permanent fuel tank in the bow and was happy with it and you have a fair size lump of engine sitting on the back....

 

[Mark42]

Re: Where would you place my gastank?

SiggiJo is right. I put my tank in the bow mostly because I had a porpoising issue at top speed. The extra bow weight made the boat ride much better. But I only made the choice of putting the tank in the bow after testing the affects of weight in front and rear on the porpoising. Also made adjustments to trim settings (no trim tabs). So I was sure that the weight up front would help my specific condition and it did. <br /><br />Your boat is bigger and much more hp. So make the decision that works for you based on the info you have and research you can do.

 

[Richard Petersen]

Re: Where would you place my gastank?

Lets try the easy and safe way. Put a small tank you can carry in and out, 2 ,6 gallon tanks at most. 1st is for testing, 2nd is to get you home. Shock or stretch cord them in place. Now take the overpowered rocket out with bags of stone, 40 or 60 # from HD or Lowe. Move them and add them till the boat does what you want. WARNING! the plastic MAY MELT with some old gas touching it. Since you know the weights everywhere. You can start putting real stuff slowly back in.---------------------- MEEE. I always put the full fuel tank in front of the balance point so the bow gets higher as the tank emptys.

 

[deeep water]

Re: Where would you place my gastank?

if you have more than one place to put it ,,i would put in two tanks each with a guage ,,the one at the stern should be at least 1/2 larger than the front ,,and put in fuel transfer front to rear and rear to front ,,keeping them, as close to center balance and just forward helps with bow control,,put the center console at balance and use duel batteries to balance out ,,trim tabs are for extra ppl and gear,, i wish i had a bildge in my whaler big enough to hold my uh1 helo tank,,its big and black and ugly in front ,,but it holds 45gal and gets me to the deeeep water,,my 24gal rear tank gets me home

 

[CalicoKid]

Re: Where would you place my gastank?

Having a similar style setup (16' baja 110 johnson) I would lean heavily towards the tank in the rear. My boat runs faster and handles/ responds better with as much weight removed from the front as possible. It takes a lot to lift the bow of a boat but it is easy to drop it with trim in. Bow lift = speed and efficiency. If it gets dicey trim in and put the bow down into the water. With a hundred or so pounds of fuel in the bow you lose a lot of your trim control over the hull itself.<br /><br /> You're not going to blow over unless you are flying into a major headwind trimmed all the way out. And if you do it won't be due to too much weight bias to the rear, it would be due to operator error. Power trim and throttle used properly will keep you well under control. Put too much weight in the bow and you give up the ability to really air out the hull no matter how much you trim out.