strength question

[ford351c594]

so I am installing a new platform for a new tank to sit on today. it is 3/4 coosa 26. I laminated it with 2 layers of combo and then used 2 more layers of combo to glass it in? Think that is enough to support a new fuel tank? If my temp let fits later today or tomorrow it should hold about 225 gallons so approx 1300lbs? If it fits and works I'll post a pic and the dimensions for anyone with a 28 that wants more than the 160 gallon tanks that are offered.

[Yannis]

225 gl is 1300 lbs? Its more like 1900 lbs. Plus the weight of the tank.

Are you sure you can fit that monster in there?
Sure I would like to see pics !!!

[ford351c594]

225 gl is 1300 lbs? Its more like 1900 lbs. Plus the weight of the tank.

Are you sure you can fit that monster in there?
Sure I would like to see pics !!!

I made a template out of old campaign signs and cardboard. By adding " wings" in-between the shafts and the strut mounts can really increase capacity. Also by getting rid of the v shape and doing "stacked rectangles" 6 in tall by 25 inch width and 60 inches long between the stringers and then opening up to final dimensions with an angled top. I was in the process of bringing the coosa board over to the boat just now when the skys opened up. So will have to wait till either this evening or tomorrow I guess...........

Here is a pic of the template.

[ford351c594]

kinda of hard to see the design, but if it fits I'll post dimensions and pic of the real tank.

[ford351c594]

wife is not happy about that being in the living room for the last 6 days........ I just keep blaming it on the rain..

[Yannis]

Just in case you wouldn't know, there is a more comprehensive solution to the problem of a nagging wife !
Then, you can keep the template in the living room for as long as you want, lol !

It would be interesting to see how this tank will hold 225 gls...post pics along the way, thanks.

[Carl]

Just tell your wife to be happy its only the cardboard mock up and not the real tank sitting in the living room...

[White Bear]

The "stepped" design creates a great number of 90* angles. Will you be able to have the side pieces bent to include these or will they have to be addressed by lengthy welding of individual metal strips? I'm not convinced that the added capacity is worth the complexity and failure points of the "stepped" shape as compared with a "vee" shape.
By the way, 225 gallons of gasoline would weigh approximately 1,425 pounds depending upon its blend.

[Raybo Marine NY]

Deck supports are usually outside the stringers, tank looks like its going to interfere with that, unless you already have something else planned?

[Yannis]

Raybo,
There are no deck supports in the 28. The deck rests on its surrounding frame.
There are two beams ON the tank so that it doesn't curve inwards when you walk.
The original, pre-28 II configuration, leaves about 8cm between tank and deck, so the beams are more or less 8cm high on the tank.

[Raybo Marine NY]

i wasnt paying attention thought it was a 31

maybe i missed it also but whats the need for so much fuel in a 28?
i also dont think that tank design with those 90s is a good idea looks too tight to bend and thats a lot of welding

[ford351c594]

The plan is to definitely to bend as much as possible. The Baffles will be in the wings to add strength there as well. First test fit didn't go so well, forgot to account of the rudder boxes at the back, and then it started raining again.

as for floor supports I have tabs on the top to bolt 2 pieces of mahogany on top to support floor.

it is being tig welded where needed.

Also as far as why, because it is not a short run from New Orleans to the gulf. The boat barely has enough fuel to get out and back. Forget running about out there. Hit some 2 or 3 rigs and hope for the best. Can end up in a lot of wasted time. This should help that.

[mike ohlstein]

Also as far as why, because it is not a short run from New Orleans to the gulf. The boat barely has enough fuel to get out and back. Forget running about out there.

Take the South Pass, and get fuel in Port Eades......

[Yannis]

Ryan, how many miles do you count doing and at what speed ?

[ford351c594]

[quote="

Take the South Pass, and get fuel in Port Eades......[/quote]


have done that. can't afford it. LOL

not a terrible place to stay over nigh however.

[ford351c594]

Ryan, how many miles do you count doing and at what speed ?

speed and fuel consumption is unknown at this point with new motors. Haven't made that run yet with them

[Yannis]

Fine, you'll test and find the best combination...

Just to give you an idea, my tank holds 550lt max and my consumption is anywhere between 2.3 and 2.5 lt per n. mile (at 2800-3000rpm and 21-24 knots cruising).
Therefore, I can run 200-250 n. miles with a fuel tank, assuming a 10% safety.

[ford351c594]

This is it in the boat. Had to make a few more modifications to fit the rudder boxes again.

Final dimensions. base is 64 long, by 24 wide, by 6 tall. opens up 16 inches wider and tappers from 22 inches total height to 18 in the back. The back 11 inches are narrowed to 31 inches total width to fit between the rudder boxes.

The white wings on the template or 27 long and 8 wide and average 20 inchs tall through the tapper.

Grand total is 252 gallons of fuel. With that quantity and the fact the white wings only hold 18.5 gallons, I will eliminate those. giving a final capacity of 233 gallons.

It will also make for a much less complicated tank.

[Raybo Marine NY]

Just be sure to leave height/clearance for the fill, vent, feed and sender

[Yannis]

Ryan ,

The rear of the tank is perhaps too much aft. Are you sure that when you're going to put the deck back you will still be able to reach, clean AND remove, if need be, the rear bilge pump (through the rear middle hatch)?
Are these any kind of wings near the stuffing boxes? Will you be able to work around them with the tank so close?
It doesn't show on the pics, but do you have access to all four nuts of each of your struts?

[Tony Meola]

Ryan

Sorry but I don't remember what engines you have, but if they are gas, you need to consider the weight factor. It is going to take more push to get her up on a plane, then the engines have to work harder to keep her there so you use more fuel. You might find you don't gain that much range.

My father had a friend that had saddle tanks in his 31( I know you have a 28) he carried 300 gallons full. Exhausts were under water, when he went offshore. 5 guys, ice, bait and fuel.

He found that until he burned off at least 50 gallons the boat at cruise rooms ran slower than she normally would with the original fuel of 220 gallons.

Just giving you some food for thought.

With diesels you would have less of an issue.

[ford351c594]

I used for clearance checking a 2x4 clamped with the 4in side up and down under the floor rail from front to back. So I should have room for everything. approx 3.5 inches under the floor.

the new motors dyno-ed at approx 400hp and 500ftlb torque. all forged 383's.

[ford351c594]

also, my calculations were way off. I multiplied by 3 instead of 31 for one section. This tank would be closer to 275 gallons. So I have eliminated the wings and shortened the tank by 4 inches. Giving 230 gallons.

also damit yannis... now you got me second guessing myself. LOL

yes the struts are no issue nor are the shaft seals. easily get a 1/2 ratchet and socket on them....

I didn't remeasure the height with the template in the boat!!!

[ford351c594]

good thing you did. I put it back in and need to drop the height. I just wanted to 200 gallons so dropping a bit is fine with me as well.

my original measurement were with the 2x4 turned with wide side up and down for clearance.

[Tooeez]

Having nothing to do with the tank, I see in one picture a through hull fitting the starboard bilge inboard of the muffler. That's about where my cockpit washdown intake is located, and on a snappy (and even not so snappy) day the boat rolls enough for the pickup to suck air, which travels to the pressure switch, resulting in the pump running and pumping nothing until someone notices the noise or uses the washdown. If that fitting is a pick-up for something you might want to move it now while everything is open.
On my next haulout I am moving my pickup to the center of the starboard bilge between the aft end of the fuel tank and the transom. If I roll that out of the water I think I will take up golf.

[ford351c594]

Having nothing to do with the tank, I see in one picture a through hull fitting the starboard bilge inboard of the muffler. That's about where my cockpit washdown intake is located, and on a snappy (and even not so snappy) day the boat rolls enough for the pickup to suck air, which travels to the pressure switch, resulting in the pump running and pumping nothing until someone notices the noise or uses the washdown. If that fitting is a pick-up for something you might want to move it now while everything is open.
On my next haulout I am moving my pickup to the center of the starboard bilge between the aft end of the fuel tank and the transom. If I roll that out of the water I think I will take up golf.

it is for the ac and the wash down pump. I have the pump on a switch so it makes no difference. Funny you mention that. This is the first time I have opened the floor since I had the boat and the first thing I noticed is the white hose from the Tee to the wash down has no clamps on it..... kinda scary. I plan on leaving that pick up there but before the floor goes back all of that mess is getting cleaned up and re ran. A lot of work to do before the 4th......