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Old 06-03-2016, 13:51   #1
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Water tank access

I have two 50 gallon fiberglass water tanks, each with one 4" Beckson inspection port near after end of the tank. They are small, leak, hard to open.

I am aware of the Sea Built metal inspection ports and am looking for something a little cheaper and larger.

I want to cut a hole in the tanks so I can reach in there and do periodical scrubbing (elbow grease), one access per baffled section (3 per tank)

The minimum size is 6" diameter, larger would make cleaning easier.

Has anyone made their own hatch out of fiberglass (or other material) with gasket and machine screwed it around its perimeter to the tank material (fiberglass in my case)?

I see access ports on metal tanks that machine screwed all around perimeter and am looking for ideas on how to do this with my fiberglass tanks.


Thanks
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Old 06-03-2016, 15:20   #2
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Re: Water tank access

The hole will weaken the panel it's cut out of unless reinforcing is added. One reason you have small access is to limit any loss of strength. In steel tanks where a screw or bolt on port is installed there is a welded band on the underside that is threaded for the bolts. That adds rigidity.
You epoxy a ridge of material to screw into that is epoxied in place should do the job. It could be wood cut to match the hole shape and impregnated with epoxy.
If the tanks leak, maybe you should cut the top off, epoxy another layer to cleaned surface and then reattach the top. Poly resin doesn't stick (bond) to long cured fiberglass.
I've never found the need to hand clean a water tank in 60 years. Including ship tanks mothballed for 20 years.
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Old 06-03-2016, 17:11   #3
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Re: Water tank access

Thanks Lepke,

These thanks are filthy, bought the boat a few years ago and they were filthy then. I tired cleaning them with bleach, vinegar, water, but the growth just came back.

The tanks don't leak, just the 4" beckson ports. The tanks are fiberglass (likely polyester, since they are 30+ years old) with thickneses that vary from thick 1/4" to over 3/8", with gelcoat interior. I've cleaned them over the years, but they need a good scrubbing to get the more dense, tenacious organic material removed. I've tried bleach, vinegar and water, but that doesn't get the dense material.

Maybe i can stiffen up the exterior where I cut the openings, then build a ... I don't know. I'll figure something out.
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Old 17-03-2016, 11:10   #4
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Re: Water tank access

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Originally Posted by scherzoja View Post
Thanks Lepke,

Maybe i can stiffen up the exterior where I cut the openings, then build a ... I don't know. I'll figure something out.
try a decent fabricating shop and get flange rings made up in stainless, 6" ID, 7"OD from say <1/8" thick sheet. Get full discs made up to match. A shop with a laser cutter can cut these readily. Get 8-12 bolt holes cut around the ring for clamp bolts. Pop bolts through the ring, get them brazed/silver soldered in place. Make sure once done the bolt ring slides in through the plate, and mark that orientation on both. Then cut the bolt ring at 12/6 o'clock. Cut the 6" hole through the top of your tank, and using the disc as a drill guide drill the tank top. Then put suitable goop on the two half-ring pieces and slip them into the tank then up through your drilled holes and spin the nuts down snug until the goop has set. You'll need to gasket the top plate, then drop it in place and final tighten.

You'll pay one setup charge for the ring/disc, after that it's like photocopying.
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Old 17-03-2016, 11:28   #5
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Re: Water tank access

Quote:
Originally Posted by scherzoja View Post
I have two 50 gallon fiberglass water tanks, each with one 4" Beckson inspection port near after end of the tank. They are small, leak, hard to open.

I am aware of the Sea Built metal inspection ports and am looking for something a little cheaper and larger.

I want to cut a hole in the tanks so I can reach in there and do periodical scrubbing (elbow grease), one access per baffled section (3 per tank)

The minimum size is 6" diameter, larger would make cleaning easier.

Has anyone made their own hatch out of fiberglass (or other material) with gasket and machine screwed it around its perimeter to the tank material (fiberglass in my case)?

I see access ports on metal tanks that machine screwed all around perimeter and am looking for ideas on how to do this with my fiberglass tanks.


Thanks
You can buy plastic and metal access panels and flanges.

Can also make your own access panel. The access panel and tank need to be stiffened with enough through bolts to clamp and seal a flange gasket.

We use 3/32" buna n on all our dieeel and water tanks. I make my own panels, gaskets and nut rings.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
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