Underfloor Fuel tanks

Sonar · 09 March 2010, 07:12

Looking through the forum threads and I have seen a lot of built underfloor tanks.

For a 6 mtr rib what do the members suggest as a suitable capacity for 2 tanks.?

150 ltrs plus.? or more...

what does your 6 mtr tanks hold.?

bedajim · 09 March 2010, 07:21

Quote:

Originally Posted by Sonar

Looking through the forum threads and I have seen a lot of built underfloor tanks.

For a 6 mtr rib what do the members suggest as a suitable capacity for 2 tanks.?

150 ltrs plus.? or more...

what does your 6 mtr tanks hold.?

My single is 220L and I'll go a little bigger next time

Sonar · 09 March 2010, 14:48

Quote:

Originally Posted by bedajim

My single is 220L and I'll go a little bigger next time

is this for a single 200 hp engine.?
what sort of mileage do you get for that.? approx.

I was thinking for a 150hp 182ltrs in two tanks would have been enough for me I will have to rethink .

Downhilldai · 09 March 2010, 15:27

Obvious, but it depends on how far you want to go.

Sonar · 12 March 2010, 14:48

Quote:

Originally Posted by bedajim

My single is 220L and I'll go a little bigger next time

some bigger ones here.
http://shop.ebay.co.uk/jaymetalworke...&_trksid=p4340

Bargain.

HUMBER P4VWL · 12 March 2010, 15:00

As suggested, depends how far you want to go and how easy is it to fill up, do you launch each time you use or is on the water. Our 6.3 with a 175 does very roughly 1L per mile. We have two 75L tanks in the console. Gives us plenty of range for our usage and easy to see how full they are. Horses for courses.

PeterM · 12 March 2010, 15:58

I only have 120L ( i found to my cost

) despite being told it was 180, to run my 200. I reckon it about 4 hours at 25knts , 3 hours at 35knts, and about an hour and half at 50knts !

I managed , but then I dont go long distance and keep it topped up whenever i can ( on the water).

Sonar · 12 March 2010, 18:22

Quote:

Originally Posted by bedajim

My single is 220L and I'll go a little bigger next time

Do you do a lot of distance with your rib .?

I have just been looking at a 220 ltr tank myself.

bedajim · 12 March 2010, 18:37

Quote:

Originally Posted by Sonar

Do you do a lot of distance with your rib .?

I have just been looking at a 220 ltr tank myself.

Sometimes but it's also useful if your away camping etc with no waterside fuel

We've done a few trips to the Isles of Scilly where getting fuel can be a pain

We camped for a week at Ardmair Point just north of Ullapool last year and topped up every day with 3x 20 litre cans, but by the end of the week the tank was getting a little dry as we explored the coast

Great for recovery and the 550 mile drive home when the boat is 200 kg lighter

My next rig will have a larger tank 30-50% more

Jim

Sonar · 28 March 2010, 07:54

Well I now have a 210 ltr tank ready for conversion .

However it looks very large and will be half in and out of the deck.

So i am now thinking maybe making a grp tank that will go under all the deck.

This is the type of resin

http://www.ecfibreglasssupplies.co.u...t/default.aspx

Seen a few posts on grp fuel tanks
anyone got any comments on a grp tank ?

BogMonster · 28 March 2010, 11:37

I am probably going to stick with the std 150L if I get a Vipermax, because a partly empty fuel tank "breathing" all the time (the volume of air in the tank expanding and contracting with temp changes) is likely to mean condensation inside the tank, and keeping a big one full all the time is just carting extra weight around.

Speaking of which, if I may make a minor thread hijack, what do we do about cleaning out a tank sealed under the deck when you get poo and water in it? My old Humber was easy, as the tank was in the console, so stick a jiggle syphon in it and "hoover" around the bottom with the end into a can at deck level, but I have no idea what to do if you can't get at it?

willk · 28 March 2010, 12:13

Quote:

Originally Posted by BogMonster

what do we do about cleaning out a tank sealed under the deck when you get poo and water in it? My old Humber was easy, as the tank was in the console, so stick a jiggle syphon in it and "hoover" around the bottom with the end into a can at deck level, but I have no idea what to do if you can't get at it?

Exactly the same technique. The underfloor tank is/should be accessible via the fuel sender. Lift/unscrew the deck fitting over the sender, unscrew the sender and hoover away with the removal line exiting a trunk and into a can below the hull

In addition, and I'm not judging, but you might consider not pooing in your new tank

Hightower · 28 March 2010, 14:24

Quote:

Originally Posted by Sonar

Well I now have a 210 ltr tank ready for conversion .

However it looks very large and will be half in and out of the deck.

So i am now thinking maybe making a grp tank that will go under all the deck.

This is the type of resin

http://www.ecfibreglasssupplies.co.u...t/default.aspx

Seen a few posts on grp fuel tanks
anyone got any comments on a grp tank ?

GRP tank is fine for me! Just don't start sticking screws into the deck around the area of the tank

A call to Ospreys might well sort you out with a GRP tank if you want an "off the Shelf" ready made unit.

Sonar · 28 March 2010, 14:45

Quote:

Originally Posted by Hightower

GRP tank is fine for me! Just don't start sticking screws into the deck around the area of the tank

A call to Ospreys might well sort you out with a GRP tank if you want an "off the Shelf" ready made unit.

I am thinking I may make it as part of the structure under floor
with baffle plates and on the out side of the tank continuing the line as the width stringers
and the same with the centre string as well.

Ian M · 28 March 2010, 16:05

Quote:

Originally Posted by Sonar

I am thinking I may make it as part of the structure under floor
with baffle plates and on the out side of the tank continuing the line as the width stringers
and the same with the centre string as well.

There has been a thread on here before about fibreglass tanks. I have not made one, and am not an expert, but beware, from what I have read normal polyester resins are a no no for fuel tanks. Over time the fuel degrades the resin leading to blocked fuel lines etc.

tonymac · 28 March 2010, 18:07

Quote:

Originally Posted by willk

In addition, and I'm not judging, but you might consider not pooing in your new tank

If he really wanted to tell us he could tell us WHY he pooed in his tank - then again if he REALLY wanted to push the boat out he could tell us HOW he pooed in his tank but NO pictures please!!

Sonar · 28 March 2010, 18:28

Quote:

Originally Posted by Ian M

There has been a thread on here before about fibreglass tanks. I have not made one, and am not an expert, but beware, from what I have read normal polyester resins are a no no for fuel tanks. Over time the fuel degrades the resin leading to blocked fuel lines etc.

Yes there is a special resin you have to use to make a petrol or ethanol fuel tank
it's called crystic-199 resin.

BogMonster · 28 March 2010, 19:05

I thought at least somebody would have said

Have you fellas never heard of a wide-necked funnel? And it's illegal to do it over the side in inshore waters

Anyway I never said it was me. Back into the realms of reality, thanks for the sensible replies

So all the Osprey underfloor tanks are GRP are they? For some reason I had assumed it was s/s but looking at the original quote it doesn't say.

Ian M · 28 March 2010, 19:30

Yes, Osprey tanks are GRP. So no problems bonding them in!