Diesel fuel tank inspection port sourcing?

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slowgoesit

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Vessel Name
Muirgen
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50' Beebe Passagemaker
I am going to have to open up one of our fiberglass diesel fuel tanks. I doesn't currently have any inspections ports. The tank is 650 gallons, no baffles, integral on the outside with the hull, and 1/2" to 3/4", braced FRG everywhere else. They are 43 years old, and the starboard aft fuel tank seeps fuel into the bilge when filled over about 200 gallons. I have an idea of where the leak is on the outside, but feel the best solution would be to access the inside of the tank, thoroughly clean the fiberglass, and use an aviation type fuel tank sealer to seal the seep.
I have found only one source for diesel fuel tank inspection ports, and am considering the following port, 14" diameter (12" usable), in aluminum. Has anyone had experience with this company, or can they recommend another company?


I'm also considering the use of the following to seal the tank:

Pilot Supplies and Aircraft Parts | Aircraft Spruce seal the tank. Does anyone have any PERSONAL, FIRST HAND experience with this product? (No offense, but I'm not interested in what your wife's boyfriend's cousin's hairdresser has to say)
 
Insurance concerns aside, not tthat hard to make one. $543 ???
2 pcs of alum, one like letter "O" with a slot in it , one matching flat plate. Drill holes, tap slotted plate &. "Spin" it in. Make gasket etc. That big makes it easy
 
I’ve used Flamemaster 3204 on steel tanks which Pilot Supplies sells. I bought mine through SkyGeek. Cleaning the tank is critical. Wear gloves and throw away clothes. I used the B2 which has a 2 work time and about 48 hour(?) cure time. The stuff is as advertised. Here’s a thread.

 
Scot - When I had my tanks replaced in fiberglass, I added inspection ports made in fiberglass. Turns out fiberglass pipe fittings are used in oilfield applications, especially fracking as it is very resistant to hot, caustic liquids. I wanted to avoid the dozens of screw penetrations necessary to install aluminum SeaBilt plates. For the life of me I cannot find the source I used - they were not cheaper than the aluminum ones but I was able to have the assembly glass-in so there are zero through-tank penetrations for fasteners (even the end plate is outside the tank). Here is an example (make sure you go with 50psi rating is half the price of 150psi) FRP Stub Flanges. Note the holes are 1" diameter so pretty dang big - I seem to recall getting them from McMaster and they were expensive.

Any idea why your fiberglass tanks are weeping? Wrong resin? I forget what resin was used on my tanks but I know I did some research (I think Steve D'Antonio provided some input). For a fiberglass tank, coating may be more of an epoxy coating vs the "airline coating" that I think is used on aluminum.

Good luck -

Peter
 
Scot -
Any idea why your fiberglass tanks are weeping? Wrong resin? I forget what resin was used on my tanks but I know I did some research (I think Steve D'Antonio provided some input). For a fiberglass tank, coating may be more of an epoxy coating vs the "airline coating" that I think is used on aluminum.

Good luck -

Peter
Peter,
Only one tank is having any issues. I think there was damage to the tank itself, It's just a really tiny seep, and from an isolated area, not accessible without removing a lot of cabinetry/flooring . I halfway suspect that a long screw had possibly been screwed through the tank where the floor adjoins the tank. Still possible, but I can't find the screw if that what it is. The rest of the tank exterior is bone dry, and none of the other three tanks have any issues whatsoever. It's not an immediate problem, as we can still carry about 900 gallons without using that tank. It's just something that I want to eventually fix.
 
I’ve used Flamemaster 3204 on steel tanks which Pilot Supplies sells. I bought mine through SkyGeek. Cleaning the tank is critical. Wear gloves and throw away clothes. I used the B2 which has a 2 work time and about 48 hour(?) cure time. The stuff is as advertised. Here’s a thread.

Larry, that's the kind of material I'm looking at, but in the instructions it states under preparation it states:

"To obtain good adhesion, surfaces must be free of all traces of oil,
wax, grease, dirt or other contaminants"

Always a good idea, with ANY surface application, but I'm not sure it is actually possible to remove ALL traces of oil from the inside surface of a fiberglass tank that has been used to store fuel for the last 43 years . . . . Some of the other preparations I've looked into are more forgiving of oil contamination . . .

If I knew beyond a shadow of a doubt I could clean the inside fiberglass surface to remove all trace of oil, I'd just epoxy a couple of layers over the the suspect area, assuming it's visible.
 
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Insurance concerns aside, not tthat hard to make one. $543 ???
2 pcs of alum, one like letter "O" with a slot in it , one matching flat plate. Drill holes, tap slotted plate &. "Spin" it in. Make gasket etc. That big makes it easy
Sibernut,
I thought about this as well. It wouldn't be difficult. I could cut it out on my CnC plasma cutter the next time I head to KY for another load of household goods. Then a couple of Nitrile gaskets, and away we go. Just looking at options right now. I'll need to explore the liability aspects though.
 
I put one in my port tank. I settled on the seabuilt after talking to a local tank repair company who said that is all they use. Also Seabuilt is the only one I could find that stated it was ok to install on the sides of a tank. Seabuilt - Access Plate Systems

The design of the Seabuilt is unique and it would be hard to duplicate in such a way that would provide equal sealing ability.

As far as sealing, I am sure you will be able to adequately clean the area, maybe scuff it a bit too, and find something that will flow and stick well enough to last for years. I would recommend Pro-Seal Fuel Tank Sealant 890 A2 6 Oz Cartridge / 3.5 Fl Oz Material Kit | Aircraft Spruce
The A2 flows well and can be brushed on. Cure time is lengthy though and it just said adheres well to common aircraft substrates and did not specify fiberglass. I have used most of the fuel tank sealants that are sold on Aircraft Spruce...but always on aircraft fuel tanks. Its important to seal well past the suspected leak point, maybe 6 to 10 inches back, all around.

If its at all helpful, I covered my install here https://youtu.be/Y-dXjrmaW9Q?si=YYTYL3HjW2JNVXMR
 
I put one in my port tank. I settled on the seabuilt after talking to a local tank repair company who said that is all they use. Also Seabuilt is the only one I could find that stated it was ok to install on the sides of a tank. Seabuilt - Access Plate Systems

The design of the Seabuilt is unique and it would be hard to duplicate in such a way that would provide equal sealing ability.

As far as sealing, I am sure you will be able to adequately clean the area, maybe scuff it a bit too, and find something that will flow and stick well enough to last for years. I would recommend Pro-Seal Fuel Tank Sealant 890 A2 6 Oz Cartridge / 3.5 Fl Oz Material Kit | Aircraft Spruce
The A2 flows well and can be brushed on. Cure time is lengthy though and it just said adheres well to common aircraft substrates and did not specify fiberglass. I have used most of the fuel tank sealants that are sold on Aircraft Spruce...but always on aircraft fuel tanks. Its important to seal well past the suspected leak point, maybe 6 to 10 inches back, all around.

If its at all helpful, I covered my install here https://youtu.be/Y-dXjrmaW9Q?si=YYTYL3HjW2JNVXMR
Thanks Allen. I'm pretty sure I used that sealant on a Mooney wet wing many years ago. It would be pretty pricey though, especially for the volume I'd need if I decided to coat the bottom 1/3 of the tank!
 
Scott, if your tanks are fiberglass, why not use a piece of G10 as the cover.

you could make any size or shape you prefer. Imbed captive nuts or insert captive studs and use a gasket material to seal.

On the inside since it's fiberglass it seems like the perfect application for a epoxy like Westsystems Gflex. You could paint on a layer to provide good crack sealing, and then use a thickened mixture to fill any voids.
 
Thanks Allen. I'm pretty sure I used that sealant on a Mooney wet wing many years ago. It would be pretty pricey though, especially for the volume I'd need if I decided to coat the bottom 1/3 of the tank!
Ahhh..I thought you were just going to do the suspected area. Yes it would be pricey. The link you gave in your OP just takes me to aircraft Spruce and not the particular product. What was it? Btw..if you have time and are not usung the tank, you can always do a test patch to check adhesion after installing the port.
 
Allen, I WAS initially thinking of just coating the suspect area. Still haven't made any decision on that. I scoped and photographed, as well as reached my arm up to the elbow into the tanks with a white cloth the inside to see what wiped off the bottom of the tank. Nothing except wetness from fuel residue. That was on both aft tanks in 2023 when I replaced the sump gaskets. That's also how I know there are no baffles. The insides of both tanks were pristine. They're slightly sloped on the bottom down to the sump which is located in the center, forward third of the tank, with the pickup (from the top) centered directly over the center of the 8" sump. The original gaskets were brown 1/4" cork, and were well past their service life, and seeping. I replaced them with high conforming 1/4" nitrile, cut to fit. No leaks there since.
According to the previous owner of 32 years, those sumps had never been off the tanks. There was about 1/4" to 1/2" of . . . well, almost a jello consistency material in the rounded, very bottom of the sump, except where the fitting for the drain valve was installed. Probably about 1/2 cup total in each tank. That's not half bad for a boat that was completed in 1982! I've sumped the tanks several times since we've owned the boat, and never gotten anything out except clean fuel.

The original product I was looking at was:


Then I looked at this one, but discounted it because it doesn't state it adheres to fiberglass

 
Keven, I've never used G-10. First blush says it might be a great material for the inspection plate!
 
G10
24" x 24" x 1/2" is $358.75!

OUCH! Maybe back to Aluminum . . .
 
Allen, I WAS initially thinking of just coating the suspect area. Still haven't made any decision on that. I scoped and photographed, as well as reached my arm up to the elbow into the tanks with a white cloth the inside to see what wiped off the bottom of the tank. Nothing except wetness from fuel residue. That was on both aft tanks in 2023 when I replaced the sump gaskets. That's also how I know there are no baffles. The insides of both tanks were pristine. They're slightly sloped on the bottom down to the sump which is located in the center, forward third of the tank, with the pickup (from the top) centered directly over the center of the 8" sump. The original gaskets were brown 1/4" cork, and were well past their service life, and seeping. I replaced them with high conforming 1/4" nitrile, cut to fit. No leaks there since.
According to the previous owner of 32 years, those sumps had never been off the tanks. There was about 1/4" to 1/2" of . . . well, almost a jello consistency material in the rounded, very bottom of the sump, except where the fitting for the drain valve was installed. Probably about 1/2 cup total in each tank. That's not half bad for a boat that was completed in 1982! I've sumped the tanks several times since we've owned the boat, and never gotten anything out except clean fuel.

The original product I was looking at was:
I mean...if it adheres, makes a layer, and is diesel resistant then in theory it would work. Sealing a wet wing on a large jet is MUCH more precarious with thousands of individual holes..lol. And it is usually succesful..lol. And it essentially follows the same principles. Coat the ever-loving h*ll out of it with good quality material after a very good cleaning to bare material. I would probably still do a test patch before committing. The only thing I worry about is that you haven't fully identified the area. If it is a screw partially protruding through or putting pressure on the tank causing a crack..and then you seal it, further flexing may compromise the newly sealed area. I suppose when you get the access hole you might get a better look and may be able to form a plan. I would think that if the tank is not currently in use, I might commit to the seabuilt access port and get that behind you to create a real access hole. Once thats done it may open up additional options if you can really identify the offending area.
 
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G10
24" x 24" x 1/2" is $358.75!

OUCH! Maybe back to Aluminum . . .

$132 from McMaster (plus shipping)

Sheets, 24" Wide x 24" Long, 1/2" Thick


Peter
 
The above pricing seems to be on 2 different products. G-10 is not GP03. I have no idea if either is resistant to diesel fuel or suitable for use.

I also think that the internal picture frame shaped plate is Stainless Steel on all of Seabulit's access hatches. The reason is that the stainless steel stud to the picture frame connection needs to be leak proof. You could goo up a threaded connection here but then how do you stop the stud from turning when you tighten the outer plate. Slot the end of the stud?
The solution to this issue that I used when I built my 20" x 21" rectangular access hatches was to thread the studs into the picture frame and plug weld them in. That is easiest done if the picture frame is also stainless.

No clue how you would seal and secure the stainless stud to G-10 connection.

This way although you still need to be accurate with the drilling and gasket making, it is much easier to affect a seal on the flat surfaces and not have the diesel run the threads & leak.

My tanks are 0.188" Alum. and as a result have a reasonably flat & smooth gasket sealing surface.

Are your FRP tank surfaces smooth?

If you are going to make them, fabricate them big enough, if possible to allow you to crawl inside.
 
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I’ve worked with G10 and it’s heavy. The specs say 1/4” sqft = ~2.5 lbs. Cutting it is ok with a fine tooth blade but dusty, you’ll need a good mask.

If you want to look at GP03, I have some 1/4” but nothing wider than 8.5” but I’d be glad to send you a piece.

I’d go with Al since it’s easy to work with and everything is gasketed so minor imperfections, in the tank shouldn’t be an issue. If the are, you could always flatten the small area.
 

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Call Seabuilt directly and talk to them about your specific application. They are nice folks. The products are not cheap, but as you can see, neither is coming up with your own fab.
 
Do you need or want an inspection hatch.
I guess you do if exterior is not accessible.
Has an outside patch over been ruled out.
 
I have Seabuilt inspection ports (which I think are SS) and a coating of Splash Zone over the corroded/pitted bottom and several inches up the sides. Inspection once the port holes were cut showed that only the bottom of the tank was corroded. Sides and top was still perfect. Steam cleaning (with some kind of solvent like Simple Green) followed by wet vac and it was ready to coat.

My contractor used a fairly small port (8 inches?) so not as costly. My tanks have two baffles, so three ports. He guestimated baffle location by tapping, then drilled a small hole. Inserted a "L" bent wire with a 4" bend. That way he could rotate it around and make sure that his 8" hole wouldn't be too close to a baffle should the tapping method not be accurate. If too close, he could move and drill his big hole. Good idea.
 
Steve, I want inspection hatches. Or rather hatch, since I plan on only one. It will be in the aft end of the tank approximated 1/3rd of the way down from the top. I've verified that there are no baffles present, so I can see/access the entire tank from the one port. I'm looking at the 14" port, which will give me 12" of access to the interior of the tank.
 
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