1974 21' Supersport Rebuild

[bob johnson]

Re: 1974 21' Supersport Rebuild

does anyone know the cubic feet of air that is 'trapped" in a 1 cubic foot of Styrofoam?? I can figure the cubic feet of air inside a tube..then I could compare the weights of each.....bob

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

i had considered some pvc pipe with capped ends for my gunnels. any other ideas for floatation in there, and a way to hold it in. mine dont have anything on the under side of them

 

[barato2]

Re: 1974 21' Supersport Rebuild

Bob-- there;s also the issue that the gunwales curve so you'd have to use some heat to bend em. due to that and all the reasons mentioned by Osby, i think i'd stick with foam under the gunwales. what happens when you decide to add some rod holders, or a bigger bimini? you mgiht be able to fit em laterally under the stern...lots of air space in that big I/O butt

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

Since the weather isnt going to cooperate this week and we wont be able to finish up the paint I've decided to move on to the floor. The PO threw in a good condition aluminum 20 gal fuel tank. Plan is to mount it in between the stringers up towards the bow of the boat. Any suggestions on how to mount it. I dont want to use foam but need a good way of securing it. I was thinking of spar varnishing 2x4's and screwing them to the stringers on top and the two ends of the tank.

I will have 2 deep cycle batteries in front and that 20 gal fuel tank. Plan to get another 20 gal topside tank to put in back along with a starting battery and possibly another deep cycle battery. I'm concerned with having to much weight in the back so thats why I'm thinking of putting the bow tank up front. Any thoughts?

On another note, I got my big piece of aluminum diamond plate mounted on the transom yesterday. Lots of 5200 and a few stainless bolts and I think its going to be pretty tough. The 5200 oozed out and got all over the place so I will have a little more sanding to do but all in all I think it will serve its purpose well.


Plus she is finally resting back on the trailer

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

Should I be concerned with 40 gallons of fuel and maybe 2 batteries in the stern of the boat. Will putting one 20 gal belly tank in between consoles help the boat ride better?

 

[bob johnson]

Re: 1974 21' Supersport Rebuild

Should I be concerned with 40 gallons of fuel and maybe 2 batteries in the stern of the boat. Will putting one 20 gal belly tank in between consoles help the boat ride better?

well 40 gallons cant actually fit in the very back of the boat , unless you have a 3 foot high tank...its only 240 lbs....that's like me standing back there.... the boat wont sink.... the batteries may weigh 70 lbs each....it does add up..... the boat may squat at rest, depending on the weight of your motor.... I don't know if giving up 20 gallons of gas capacity is a good idea....unless you would have another tank besides the belly tank...did you decide on a motor?? personally id like the tank to be in the middle of the boat....I have a 56 galln tank that I am trying to figure out how to shoe horn into the middle of the boat..... how you use your boat and what motor you settle on plays a big role...bob

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

well 40 gallons cant actually fit in the very back of the boat , unless you have a 3 foot high tank...its only 240 lbs....that's like me standing back there.... the boat wont sink.... the batteries may weigh 70 lbs each....it does add up..... the boat may squat at rest, depending on the weight of your motor.... I don't know if giving up 20 gallons of gas capacity is a good idea....unless you would have another tank besides the belly tank...did you decide on a motor?? personally id like the tank to be in the middle of the boat....I have a 56 galln tank that I am trying to figure out how to shoe horn into the middle of the boat..... how you use your boat and what motor you settle on plays a big role...bob

I plan to get another 20 gal tank. This aluminum belly tank came with the boat and its in good condition, so i plan to use it. Just cant decide where to put it and what to hold it in with. For now I think I will stick with the 115 due to budget concerns, although I do have my eye on a 1984 150 Johnson. Looks like its in awesome shape for $1500. But I'm thinking I will wait and see how this 115 performs.

 

[ShowMeGuy]

Re: 1974 21' Supersport Rebuild

View attachment 189454

Geezz.. I think i would've tried to extend that plate as far down as i could on the lower part of the hull below the crack... How much overlap does it have now? an inch? maybe 2?

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

Has 2 inch overlap. Tied into the structural piece on inside of transom. I will be very surprised if anything flexes at all. I guess if it does then i will be on the hunt for a larger piece of aluminum to put back there.

 

[GA_Boater]

Re: 1974 21' Supersport Rebuild

Eck - I think the 20 gallon belly tank and two batteries up front will offset 20 more gallons in the back with two more batteries and will kinda balance out. If you run gas out of the back tank first the stern will lighten as the gas is burned too.

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

Eck - I think the 20 gallon belly tank and two batteries up front will offset 20 more gallons in the back with two more batteries and will kinda balance out. If you run gas out of the back tank first the stern will lighten as the gas is burned too.

Any recommendations on how to anchor down the belly tank. Its aluminum, in good shape. For the rear tank I plan to get a Moeller, with the hold down kit. Just not real sure on how to install this belly tank. Definitely dont want it breaking lose.

 

[GA_Boater]

Re: 1974 21' Supersport Rebuild

Somebody used some epoxied wood strips with a cut up, grooved door mat made from recycled tires to sit the tank on. And epoxied wood spacer strips and top strips to hold it down.

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

Somebody used some epoxied wood strips with a cut up, grooved door mat made from recycled tires to sit the tank on. And epoxied wood spacer strips and top strips to hold it down.

OK that's right along the line of what I was thinking. thanks

 

[jbcurt00]

Re: 1974 21' Supersport Rebuild

The belly tank is aluminum, the new tank is plastic @Moeller, correct?

This is similar to what GA described:

Aluminum belly tank install

 

[GA_Boater]

Re: 1974 21' Supersport Rebuild

Interesting - JB's link says the carbon in rubber is cathodic. Maybe soft plastic strips with an AL tank instead?

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

The belly tank is aluminum, the new tank is plastic @Moeller, correct?

This is similar to what GA described:

Aluminum belly tank install

That's correct, probably the 19 gal. Thanks for the link

 

[eckhoffb]

Re: 1974 21' Supersport Rebuild

Interesting - JB's link says the carbon in rubber is cathodic. Maybe soft plastic strips with an AL tank instead?

In search of some plastic now. Somewhere in one of the restoration threads I seen where someone riveted some split garden hose onto the ribs. I'm thinking I will do the same except use plastic instead of hose.

 

[GA_Boater]

Re: 1974 21' Supersport Rebuild

Hey Eck - Is the belly tank bottom flat or veed?

 

[bob johnson]

Re: 1974 21' Supersport Rebuild

is the consensus , you should not rest the aluminum tank right on the aluminum ribs???......that's what I had planned...mainly because it is almost to high already....bob

 

[jasoutside]

Re: 1974 21' Supersport Rebuild

is the consensus , you should not rest the aluminum tank right on the aluminum ribs???......that's what I had planned...mainly because it is almost to high already....bob

I think most of us backyard boat builders lay down rubber of some sort on the ribs first. Here's my setup, bow side tank in place, riveting down rubber material just before the midships tank goes in...

Only brought it up maybe 1/8" or so.