Fuel Tank Support

[strick]

As part of the restoration process of my 23cc I removed the fuel tank for inspection. Here is what I've found.



The support structure for the tank consisted if 1/2 inch plywood with two layers of woven roving on top. The bottom of the plywood (facing the bilge) was bare wood. When I stood on the structure it felt solid except for the ends were the rot had really taken effect. Part of the reason it felt solid was because of the keel it rests on. Notice from the pics that decay is not just limited to the ends of the wood. The wood shims that kept the tank sliding from side to side were rotton as well. They were screwed into the stringers. The fuel tank itself looked good on the top and sides however the bottom had severe pitting were it rested on the moist wood. This week I will be getting a new fuel tank built as well as rebuilding the support structure for the tank. Here is area all cleaned up .


I apologize for taking off all the pics I put in earlier posts as I'm re-doing them into web galleries and I accidently deleted the folder they were in. Here is the link for two of the folders I have up right now. John R if you want to put some on "the boat Zone" you are welcome to what ever you need.

Strick
http://www.casdvm.com/photos/Hardtop/
http://www.casdvm.com/photos/TransomCap/

[John R]

Strick - seeing that you already have your own stuff, no need for me to put them up in TBZ. However, before, I was downloading what you were posting into my "OtherProjectsInspiration" folder on my hard drive. So, if you're missing any of your other pics, let me know - I probably have them [img]images/icons/smile.gif[/img] ...

[kglynn]

Strick,

Just curious what year is your seacraft, I am in the process of stripping a 1985 down, and shortly going to inspect my tank, I have yet to look to see if my support is glassed on both sides

thanks,
KBG

[ocuyler]

KGB,

Strick has done this the real right way. Just figure on removing everything like he did and installing a new tank. I went through this this spring and removing more is better. There's no cutting corners on that job.

The only thing I would do different is have 2 tanks built instead on one 135 gallon. It would be easier to manage weight distribution.

Have fun!

[Capt Chuck]

Strick

When I pulled my 100 gal fuel tank in '95 only the rear corners of the support floor was rotted. Mine WAS glassed on both sides however. The shimms were ok also. I then Installed a new 135 gal tank which gives added weight up forward and improved the ride. I also installed a 15 gal fresh water infront of the gas tank up against the forward hold with an access hatch in the aft wall of the hold. Something for you to think about.

I made the new floor out of marine ply and glassed and gel-coated both sides. I made new shimms out of teak and screwed them between the (6) 90 degree angle supports off the tank and the stringers.

[Scott]

Strick....I can relate

What a mess under the deck ..... 27 years of slime !!! [img]images/icons/shocked.gif[/img]






But I didn’t have the fuel deck supported by the centerline stringer....Even though the deck was real rotten ...it didn't need that support apparently ....but I cant see that it would hurt I do think the brunt of the weight is loaded on the edges attached to the stringers/hull bottom where the deck is tabbed in.

Otto ... How would you do it different ??? One forward one back ??

[abl1111]

I pulled my tank and the aft edge of the wood tank platform had very little mushy. The rest of the wood seems as solid as a rock - I jumped on it a bunch - not even a creak. I'm going to leave it.

I would like to know how you re-fasten the tank back down ?

It was originally held in place by pcs of plywood being wedged between the fiberglass sides and the angled aluminum meant to hold the tank in place.

However, wherever the wood had touched the aluminum, whether the angled pcs or the tank itself - there was mild to severe galvanic corrosion. I want to avoid that in the future.

I have epoxy coated and awlgripped the tank ( probably overkill, but I had the spare supplies ). Also, I glued down 3M, 3/4", closed cell, adhesive strips on the bottom of the tank for cushioned support and to let water drain.

Once the tank is in place, how should I keep her firmly in place ?

[FELLOW-SHIP]

I went through the same thing when I did my boat. I went with a 120 gal. fit real good and I didn’t loose the hatch in front of the center consol. I moved my tank forward of the bilge area now the back of the tank is in line with where the stringers make that 90 degree angle into the bilge area. By moving it forward and increasing the size from 100 to 120 gal. plus putting freshwater tank and oil tank and batteries under the center consol and above the gas tank the boat rides much better.
FellowShip

[FELLOW-SHIP]

This is how i installed the tank, plus i also had two 90 degree plates welded to the fron and back of tank and screwed them into the gas tank deck.
http://www.yachtsurvey.com/fueltank.htm
FellowShip [img]images/icons/wink.gif[/img]

[Water Rat]

Strick:

I continue to be amazed at the amount of work you are doing and the quality of it; makes me want to take a sabatical (sp.?) from my career and go to town on my '78 23' Sceptre. If this is of any help to you and the rest of the CSC members, I had the exact same problem on my boat. After cutting out the delaminating/rotting "floor" of the fuel tank compartment, and cleaning up the mess and painting with Interlux BilgeKote, I fashioned a new "floor" out of Starboard (3/4"). However, instead of making the floor an exact replica of the original, I cut it to rest directly on top of the keel stringer, with the width varying from the aft section to forward section (wider aft, narrower forward) to conform to where it meets the inside of the hull. Also, where it meets the hull, I cut the edge at an angle to conform to deadrise, so that where the Starboard meets the hull I have two flat surfaces mating, instead of a "hard point". When I mounted the Starboard floor, I bedded it down heavily with 4200 on top of the keel stringer and where the edges met the hull. The purpose of this was to pick up rougly an additional 2-4" of height in the compartment, allowing for larger tanks. The new tanks I had fabricated (replaced a single 80 gal. with one 65 and one 45) have a "V" section at the bottom. That is, there is a flat pad at the bottom of the tank approx. 6" wide, then sections on either side that follow an angle parallel to the deadrise until they meet the vertical sides of the tank. When installing the tanks, I did not foam them in. Instead, they sit on the Starboard floor, in turn resting on the keel stringer, and lag bolted into the sides of the compartment. This design allows plenty of air circulation around both tanks, with all bilge water running underneath the now-sealed Starboard floor. It also allowed for an additional 20 gallons or so of tankage due the increased height.

I know I should have probably fabricated a proper floor out of an appropriate cor material and glassed it in, but my skills in that area are lacking. Also, I will admit, it was a major PITA measuring all the various dimensions in that compartment. However, I believe I kept all the measurements and "blueprints" I created if this would be of use to anyone.

Happy Holidays,
Chris