Bilge Tank for West Coast Tritons

[Triton106]

I have posted a couple of threads related to this project last year -
1. Built-in tank integrated to hull vs. stainless steel tank
2. Bilge location and dimension
3. Is fiberglass a suitable material for potable water tank?

Well, like a lot of my projects it takes me a while to get to it. Today I got out my saber saw and cut into the teak and holly veneered sole (over fiberglass substrate). This is what I found -



I cannot believe Aeromarine considers this a potable water tank! Look what gem the Aeromarine worker left in the water tank! Oh my, I hope the PO's never drank from this tank. I had my doubts so I never drank anything that came out this tank.



Here is the cutout opening -



Here is my dilema and question -



As you can see in the middle of the inclined section of the bilge there is what appears to be a lifting eye which has been glassed over. I am not sure what purpose it still serves since the bilge is entire glassed in. If you can think of use for the glassed in lifting eye please let me know.

The lifting eye is right in the middle of where I was going to have a custom stainless steel water tank built. Before I opened up the sole I was thinking that the water tank will probably be an inverted L shape. The upper section will reast on the incline portion of the bilge and the lower portion will sink into the deep part of the bilge. Now with the lifting eye in the middle I am at loss as to what is the best thing to do here. I think my options are:

1. Cut out the lifting eye and continue with my plan.
2. Settle with a smaller tank that will sit in the deep part of the bilge but I can only get approximately 15 gal.
3. Use the bilge for battery storage as Tim has done for Circe which I think is an excellent idea. The only problem is that my future plan involves offshore sailing and I really need the water storage space.

What are your thoughts?

[Rachel]

Thoughts:

1) What IS that thing?!?

2) I'm glad you bit the bullet and cut into your teak and holly sole; but I know that must have been a difficult first cut!

3) I think the lifting eye might actually have been a "lowering eye" that was used to set the ballast pig in the boat. I would probably get rid of it, if it were in the way, as I can't think of any purpose it serves now.

4) I think a stainless water tank in the bilge is a great idea. I wouldn't want batteries down that low (in the deep bilge), and a water tank seems like a great thing to put there. As a side note, I think that stainless tanks are typically put on some sort of runners or supports, so that they don't sit in water and to allow water to pass under them, so that might allow your eye to stay there (can't tell how high it is).

5) Geez, that ... thing. Yikes.

[Triton106]

Thanks Rachael!

I am leaning that way too (i.e. cut out the lifting eye). Your explanation of the lowering eye makes sense to me. I thought Aeromarine used steel punches or some other cheap weights for ballast. A cast lead or iron ballast is a nice discovery that offsets the ugly "thing".

The "thing" appears to be some dried up goo that Aeromarine used to seal off the ballast. Why they did not remove it before they sealed the tank with the fiberglass sole is entire a mystery. I checked before I installed the teak and holly veneer about 3 years the fiberglass sole appeared original. I don't think any PO left the "thing" in there.

[Rachel]

Its...... THE BLOB!!!

[mitiempo]

I'd second a stainless tank in the bilge. I also think it is too low for batteries. I'd also remove the lifting eye. As far as the "blob" I guess it was cheaper to leave it there rather than remove it. Who would ever see it anyway?

[Hirilondë]

As far as the "blob" I guess it was cheaper to leave it there rather than remove it.

I bet it had nothing to do with money. The worker just found it easier to leave than to clean up his mess

Who would ever see it anyway?

Exactly!

[Triton106]

I just got my first quote back for a custom stainless steel tank (see below diagram - note drawing is not to scale). It's $850! I am waiting for a second quote tomorrow. Looks like I need to start the discussion with Triple M Plastics folks that Bryon and other others recommended on this forum.

[mitiempo]

Doesn't sound too out of line. I paid about $500 a year ago for a SS diesel tank custom made and it was a lot smaller than your water tank - 14 gallons actually.

[Rachel]

A few thoughts:

1) I'm not that good at reading drawings, but is that tank a dog-leg shape to take advantage of your bilge space? Or is it a gradual slope?

2) I would have thought it would have been more than 20 gallons in that space? Unless your bilge it just looks larger than it is. Or maybe it's because of the missing dog-leg?

3) I might like to have a pickup tube for the water with the fitting on top of the tank, rather than an outlet at the bottom of the tank (again, if I'm reading that correctly).

4) If it's a well-made custom tank, that doesn't seem like too outlandish a price, to me.

5) On the other hand, Bryon did seem very happy with his Triple M tank, so that might be worth looking into. I would place a high value on stainless over plastic for drinking water, but then you could just about drink out of old arsenic bottles and be a step ahead of that factory tank ;)

[mitiempo]

Rachel
It looks like a gradual slope, but every dimension is smaller at one end or the other.
Top 12" to 10" wide, bottom 10" to 8" wide, and height 6" to 12". By not having fittings on top the tank can be a bit taller. I checked the capacity because I thought it would hold more but it is correct.

[Triton106]

I got my second quote back and it is...........$1,400!!!

Triple M Plastics quote..........$436 (not including shipping)! I think I am going with them.

Rachael wrote -

1) I'm not that good at reading drawings, but is that tank a dog-leg shape to take advantage of your bilge space? Or is it a gradual slope?

2) I would have thought it would have been more than 20 gallons in that space? Unless your bilge it just looks larger than it is. Or maybe it's because of the missing dog-leg?

3) I might like to have a pickup tube for the water with the fitting on top of the tank, rather than an outlet at the bottom of the tank (again, if I'm reading that correctly).

1. My drawing is poor and not to scale. But there is no dog-leg in the design because I do not want the lower half of the bank sit in the bilge water which could be damaging to even stainless steel tanks. I know this does not take advantage of the extra space (about 6 gallons). It does increase the deep bilge capacity (after I open up the bulkhead that separates the bilge from the current built-in tank) which helps if a boarding wave ever gets in the cabin.

2. Yes, the total capacity should be about 26 gallons if I take advantage of the dog-leg. However, my friend Rob reminded me that by flaring out the topside of the tank to take adavantage of the keel shape I can add a few more gallons. I looked at Bryon's drawing (see below) and it does make a difference. I am guesstimating the added capacity to be about 2 gallons in my case.



3. What is the advantage of pickup tube vs. outlet at the bottom? I know the coast guard banned bottom drain from fuel tanks. As Mitiempo stated by not having fitting on top I am trying to maximize the tank size. The top of the tank sits about a little over one inch from the bottom of the sole so that I can install floor joists (not the correct technical name I am sure) to hold down the tank and support the sole.

[Rachel]

What is the advantage of pickup tube vs. outlet at the bottom?

Keep in mind that I am only a tank amateur, but I'm thinking a couple of things:

1) Any sediment or etc. in the very bottom of the tank would be less likely to get into my drinking water (yes, of course you will clean the tanks periodically, but between times).

2) If a hose or fitting fails you will not lose all of your potable water (because gravity will keep it in the tank).

I wonder if you could have a fitting that is near the top of the tank but on the side, with an elbow in the pickup tube inside the tank? I don't know if that's possible or desirable, but maybe you have more leeway there, space-wise.

Rachel

[Skipper Dan]

Ray have you thought about one of these. http://www.defender.com/product.jsp?pat ... &id=120943 I am thinking of putting two in the cockpit lockers one on each side. That way if I am not using them I still have space for other things. Plastimo Flexible Water Tank from defender in case the link did not work.

Dan

[mitiempo]

And they don't need a vent. But make sure the compartment is well padded. I have a small one and will probably get another.

[barrybrown]

Ray

On my last Triton (east coast) I installed a stainless tank in the bilge shaped to fit the space. I placed the pick-up tube much as Rachel has suggested about half way up, this compromise protected some of the water in case of hose or fitting damage but allowed me to drain more than half into the bilge at the end of the season then pump the remainder.
On this boat I installed a 13 gal Plastimo flexible tank in the same area, it holds only 8 gal, I don't recommend it because of the low volume and it does not give the same secure feeling as the stainless. I will probably change it for either stainless or plastic.

Barry

[Triton106]

Thanks everyone for your input.

Rachel wrote regarding pickup tube -

1) Any sediment or etc. in the very bottom of the tank would be less likely to get into my drinking water (yes, of course you will clean the tanks periodically, but between times).

2) If a hose or fitting fails you will not lose all of your potable water (because gravity will keep it in the tank).

I think it is a good idea especially for polyetheylene tanks as the fittings on these tanks are more susceptible to breaking under stress (vs. stainless steel tanks). Installing the fitting close to the top sound like a great compromise. I am not sure if I agree entirely on the sediment point. I plan to install a filter in the line and prefer to have the sediments come out of the tank and catch them at the filter rather than having them sitting in the tank for a long time.

I also considerred bladder tanks and ruled them out because of longivity and capacity considerations (none of the mfg makes one that fits the Triton bilge area).

[Rachel]

Ray, you have a point, and maybe the sediment reason was not a good one.

Rachel

[Hirilondë]

3. What is the advantage of pickup tube vs. outlet at the bottom? .

For holding tanks I always recommend pick up tubes and every hole in the tank being in the top. Leaks in the fitting or connection developing in the top have a slightly different result than those on the bottom.

[Triton106]

I stopped by my boat today and took some additional measurements in order to design a more flared topside. Here is my revised drawing. I estimate that the added space is 1.5 gallons. Triple M Plastics said that there is no additional charge for adding this feature. There maybe additional shipping cost. So this is what I will go with. Am I missing anything else?

[Rachel]

How do the two baffles work with the two inspection hatches? I mean, if there is one inspection hatch in each section, wouldn't that be one baffle? Or, if two baffles, three inspection hatches? (If I remember correctly, Bryon had a baffle mix-up when he got his tanks.)

Edit: I went back to Bryon's thread, because I didn't want to say something potentially negative without looking it up. Here are a couple of excerpts indicating that he did have a baffle issue, so maybe that is something to carefully check.

Before getting the tanks:
I asked about the baffles and wether they add an additional layer of plastic in the area where the fittings mount. They said yes to both. They add baffles every 16" and the entire mounting surface is double thickness.

After receiving them:
I was told that they put baffles in ever 16" but neither tank has a baffle. The tanks are 27" overall. This would be the only thing they said they would do that didn't happen...

He did seem very happy with the tanks and service except for that though.
They are heavily built and fit perfectly. Their service was excellent

The thread
http://plasticclassicforum.com/viewtopi ... +M+plastic

[Triton106]

How do the two baffles work with the two inspection hatches? I mean, if there is one inspection hatch in each section, wouldn't that be one baffle? Or, if two baffles, three inspection hatches? (If I remember correctly, Bryon had a baffle mix-up when he got his tanks.)

Edit: I went back to Bryon's thread, because I didn't want to say something potentially negative without looking it up. Here are a couple of excerpts indicating that he did have a baffle issue, so maybe that is something to carefully check.

Before getting the tanks:
I asked about the baffles and wether they add an additional layer of plastic in the area where the fittings mount. They said yes to both. They add baffles every 16" and the entire mounting surface is double thickness.

After receiving them:
I was told that they put baffles in ever 16" but neither tank has a baffle. The tanks are 27" overall. This would be the only thing they said they would do that didn't happen...

He did seem very happy with the tanks and service except for that though.
They are heavily built and fit perfectly. Their service was excellent

The thread
http://plasticclassicforum.com/viewtopi ... +M+plastic

Rachel, excellent observation. When I first spoke with them I was going to put in one baffle and two inspection hatch. They told me that for that size tank I need two baffles. Today, I called them again to iron out some details. When I asked about the inspeciton hatch they told me that the baffle has a large openning in the middle and will allow me to reach over to the next compartment. I am not sure in practice how easy it can be done since it is one thing to reach over it is something else to be able to clean the corners which will be difficult. Since their tech guy is out until after the Labor Day weekend they said he will call be back on Tuesday.

I also asked them about Bryon's baffle issue (did not use actual names) they explained that it depends on the actual size of the tank. In some cases when they deem that the tank is structurally solid they don't add baffles. But I did not get into details with them why they told Bryon they would add and did not.

Some additional cost information -
Packaging - $25
Shipping (to SF Bay Area) - $73
Pickup Tube - $25
Customer supply and install fittings (they double wall and drill and tap the holes)

[Rachel]

It does seem like it would be harder than necessary to reach in, over the top of a baffle, and then down into corners. After all, it's usually enough of a challenge cleaning tanks when it is "easy." Unless there is something about it I don't understand (like the baffles are very low, or..?). I think I would be asking about having three inspection ports, each one in the center of its own "compartment." (Which is probably what you will be doing when they call you back :)

Thanks for keeping us updated.

Rachel

[Figment]

This tank really isn't all that large, and the fore and aft free surface effect shouldn't matter to the boat at all, would the baffles really add anything meaningful? Other than stiffening the sidewalls and possibly making the assembly a bit easier?

[Rachel]

Annoying sloshing when your head is on the berth?

(I don't know that the tanks need baffle(s), but just thinking aloud.)

[mitiempo]

With a tank that long I would want baffles. With a half full tank and the boat rising to waves the water will rush from one end to the other. Baffles will quieten the tank as well as protect it from destroying itself by this movement.

[Triton106]

The tank arrived from Triple M on Friday. Upon initial inspection I found a couple of minor nuances and a fairly material issue.

1. They said that the tank needs two baffles but the actual tank came with only one. This is a similar issue that Bryon ran into. Not a big deal since I initially thought the tank only needed one.
2. They said the pickup tube would be copper (same as the house water pipe) but the actual product is made of pvc. Furthermore it does not appear that they cleaned it well before installing.
3. The acces hatch plate is quite thick and the massive hex bolts (1/2"-13) which they used to bolt down the hatch added approximately 3/4" height to the tank which I did not anticipate. The bolts are now standing proud of the cleats that supports the sole hatch plate.



The only way I can think of to address the height issue is to replace the hex bolts with other lower profile head bolts. After prusing McMaster-Carr website I found three potential substitutes: (1) flathead, (2) roundhead, (3) sockcap.




I bought a flathead screw from a local hardware store and it seem to fit (the picture shows it without the countersink) but I worry that it may crack the hatch plate. The roundhead bolt head is actually taller than hex bolts but it is easy to grind them down. The sockcap seems to have the lowest profile and could work but it only comes with 18-8 stainless steel.


Any advice?

[mitiempo]

I don't think there would be a real problem with the countersunk flat head machine screws. There should not be much if and expansion like there would be with plexiglas ports as the bilge won't have the heat of the sun to deal with. If you don't want to do that the socket heads should work well. Nothing wrong with 18-8 in this situation I wouldn't think.

One question - what kind of gasket is under the inspection plates? I can't see them but maybe you haven't put them on yet.

[Hirilondë]

There should not be much if and expansion like there would be with plexiglas ports ....

I don't understand why people say there is much expansion and contraction in port lights. Polycarbonate is extremely stable through a vast temperature range and acrylic is almost as good.

If you are concerned about using flat head machine screws Ray you could use a forstner bit to create a countersink with a flat landing and use the same fastners again or the socket head ones. There will be very little pressure on the inspection ports, so drilling the countersink should not be a structural or leak issue. You can also add a recesses in your sole panel drilled with a forstner bit that line up with the bolt heads allowing it to sit on the cleats without hanging up on them.

I wouldn't be bothered by a PVC pick up tube. Although it is annoying that a company tells you one thing then does another.

[Triton106]

Thanks Dave, Mitiempo for your input.

I spoke with Triple M this morning. They were very nice and asked me to ship the covers and bolts back to them and they will counter sink the covers and ship flathead bolts back to me overnight. That will provide me with an opportunity to thoroughly clean out the tank before installing it "permanently".

I am very pleased with their customer service. Like Dave said I am not too bothered with the pvc pickup tube.

Mitiempo, they used silicon to seal off the cover plates.