pvc marathon tanks

[GuyWithTheCoolBoat]

was suggested to me to try 4" or larger pvc of some sorts to make marathon fuel tanks. any comments on this. bad idea? things tried and failed? things that work? was looking for something other than aluminum. does the pvc soften or break down under fuel? was looking for about 5 gallons total but wouldnt mind going up to 6 but would try to stray away from less. im a heavier marathon runabout (csr) that eats a tad more fuel than the little guys. the suggestion came from tom johnston who does inspections at the top o's.... just a thought as id like to do this soon. thanks

[jeff55v]

I used the same PVC tanks for Top O' the past two years. They worked fine for me. The advantage they have over aluminum is that you can easily make 'em yourself with stuff from the hardware store. The disadvantage is they probably cost the same as custom aluminum tanks. Those big PVC parts are expensive! Also, I think my aluminum tanks weigh less.

[GuyWithTheCoolBoat]

thanks eh. up here where im at welder fabricators worth 2 cents are hard to come buy. at least ones that can work with aluminum... i priced out spun aluminum small buggy ones but those are EXPENSIVE... 150 a pop... i need two.. ouch right? is there any pvc i should get in particular? anything not to get? how about glues? i was thinkin a big round piece of pvc a few end caps and tap my fittings into the end.. but was wondering on what fuel will do to pipe tape or should i epoxy or cement them together and skip the tape (was plannin on glue of some sort as well)? id just assume make them myself. about how much less are your aluminum ones? im in a sorensen marathon c so im already bigger and heavier from the get go but im a smaller guy so im not sure the extra couple pounds would make that big of a difference?

[Graham 18ce]

I made my own PVC - just standard 6" i think it was - about 4.5 gals for an A...used the PVC cement and caps from Home Depot - i had no problems at Top O...
venting was the only problem i had...Vent has to be the hightest point and be able to withstand the sloshing of fuel! opps...

[Tomtall]

PVC tanks

We have these two that are already made. 1.5 gallons each. Your more than welcome to use them.We no longer use them in this boat. We will be coming up Friday a.m. to Indian River. Let me know.

Tom

[Tomtall]

Something different

Just a FYI. We switched over this cottage racers fuel system to the OMC oil injection 3 gallon tank. If you have the room they work very well and mount easiely with their quick release hardware kit. You can find new and used ones on e-bay.

[GuyWithTheCoolBoat]

for a while i had a 6 gallon plastic tank up front forward of my wheel but the way things are made up front, after a few bumps i would start to crack at the seam have to re epoxy everything.. big pain.. so im going back to side tanks but want nothing to do with wood. so i guess the bow idea is out just because of the outward rather than inward force. i think ill pass on using the tanks, but thanks tom. im probably looking for a bit more fuel capacity as i have an incurable rookie fear on running out of fuel 100 yards from the finish line. i was thinking of something along the lines of 4 gallons in the sides and the .6 gravity tank that would fill from them, and if it was a rough day i could fill the grav tank as well and run the extra fuel. weigh isnt a huge huge concern with me.. ill just be happy if i finish something other than dead last or dnf. any ideas on sizes i should shoot for to hold about 2 gallons per side? and just a thought tom.. i used to race buggies off road and my fuel cell breather had a long hose that went to a high spot with a filter... perhaps a bit of fuel line run right to your cockpit ( or up through or to your deck) to a high spot might help with the breathing issue and sloshing... its a thought turning in my head for mine anyways.

[GuyWithTheCoolBoat]

tom. how do you fill your tanks? are they screw off caps on the end??? i was thinking something on a top "side " but wasnt sure how to attach

[Tomtall]

Filling

Well after much thought about the fill caps/deck plates and all the hassle we opted to just hook a 3 gallon outboard fuel tank with primer bulb to the engine feed line of the tube (lower bottom/stern of tube) and fill the tube till gas came out the vent hose at the Top/front of the tube. It worked great. In fact it actually gravity feed by placing the 3 gallon tank on top of the engine cowl. We opted not to install sight tubes to monitor fuel level as they sometimes break or come loose then you have gas all over the inside of the boat and empty fuel tanks. The two tanks were connected using a "Y" hose to keep the fuel level the same in both tanks while running. Just make sure the feed lines are as low as possible in the hull when doing this.

Good Luck!

[Tomtall]

Measuring size vs. gallons

OK if you love math you can calculate it out. If your lazy like me just buy one long piece of PVC in the diameter you can fit into the space your dealing with. Put an end cap on one end. Stand it up on end and fill the open end with water using an old one gallon milk jug as your measuring device. Heres the important part, keep track of how many gallons you pour in. After you have the amount of liquid in the tube you want mark were your fill line is on the outside of the tube. Measure the lenghth to the line and cut your second tube to that lenghth also. TA DA two matching fuel tanks. Make sure you drill and tap your two end caps for the fuel feed fitting BEFORE installing the cap. Do the same to the top/front of the tube for the vent. This way you can clean all the plastic shavings out before putting everything together.

Good Luck

[GuyWithTheCoolBoat]

thanks tom. headed to the hardware store right now to go snag some pvc. was thinking 3 gallons per side. i had the fill idea in my head but didnt know if there was a better way to do it or not. i might try to add a filler valve up top that i can fill through that will have a stubbed off fuel line. or perhaps fill through the breather i plan on installing? not sure but its an easy thing to figure out. was thinking of using black pvc (i think its schedule 40) just for cosmetics over white. any reason not to?

[Graham 18ce]

what i did for filling was to get one of the PVC "trap" i think it was called...like a y joint which has a cap that you would unscrew to run a snake through...was only a couple of bucks and had a gas cap included.

[Tomtall]

Black vs White PVC

was thinking of using black pvc (i think its schedule 40) just for cosmetics over white. any reason not to?

I cannot answer that question. I do not know if the black in compatible with fuel. I know the white is. Some of the black tubes are actually made of ABS plastic and require a different cement to bond them. Maybe the hardware personel could help you out on that one.

Graham - I like your idea.

[36run69n]

calculate capacity

A 6 inch dia. pvc with id of 6 in. volume would be calculated by 3.14 x 9 (radius squared) x length in inches. so 3.14 x 9= 28.25 x 24 in. long = 678.24 cubic ins. There are 231 ci to a gallon. Divide 678.24 by 231 = 2.935 gal. per tank x 2 tanks would be the approx. 6 gallon capacity desired. Hope this helps, math majors please verify.

[Graham 18ce]

I used the black...only for the two days of the Top O and had no problems. i saw no signs of the fuel eating it in any way, good for another use...

Although i did run out both days just as i was hitting indian river. hahaha - i had my closed course tank on still just in case...lol...switch lines and finished the race both days! Hahha