Frame reinforcement needing for new holding tank location

[Jeremy9107]

Hoping for advice from the knowledgeable. I am adding gray water tanks to my previously tankless Caravanner and moving my black water tank. I would like to put the 2 gray tanks in the bays directly over the axles and the black tank in the first bay to the rear of those. What would be the best method for supporting them? They will essentially occupy the entire bays. Much appreciated.

[Chatthayer]

When I had the rear floors out, and wanted to add a grey tank, I also wanted to strengthen the rear end and add a hitch. I took it to a experienced welder who created a nest for the 40 gallon tank and beefed up the rear end. '72 tradewind 25 footer

[Chatthayer]

I also moved the black tank to over the axels. As I converted to a rear bed and side baths

[Bubba L]

On my 55 frame, there was a bay directly above the axle. So I placed my two tanks fore and aft of the axle. I bolted 4-inch and a half by 3/16” straps to the bottom of the cross member. I used SS bolts with locknuts. In the future if I have to drop the tank, I can remove the bolts from one side of the strap and turn the strap parallel with the cross member and drop the tank. This drops the belly pan profile down the depth of the strap. But I don’t think that matters. Hope this helps. Good luck, Bubba

[Jeremy9107]

Thanks for replies. If you have any photos of the mod that would be helpful. Bubba I had envisioned something like what you did but have no room to spare between the top of the axle and bottom of the cross member and wasn't thinking I could get strap with bolts to fit in that space. How were you able to do that?

Bubba was one of your tanks over the axle a black tank? What were its dimensions? Chatthayer what are dimensions of your black tank?

[StevenD]

If this file downloads, here's a pic of the gray tank installed in our Safari. Our support straps were formed from 1/8 thick by 2 inch steel stock. These were bent into "C" shapes and bolted to the cross members. One quirk with our trailer was that when our frame was originally welded together, the crossmembers were not quite parallel and the spacing between the crossmember varied about 1/2 inch between the left and right side so each strap had to be measured individually to fit the space.

[57Vintage]

My situation doesn't match yours as I have an older AS with leaf springs and axle, but I will caution you to watch clearances. I found my first design didn't clear the spring perches and bolts very well. Also keep in mind you want to be able to access and remove the tank once the trailer is done. If the tank is directly above the axle tube you need more clearance fore/aft to slide the tank out at an angle. I assume you will use the torsion axles which places the axle tube fairly close to the bottom of the frame rails.

As far as support I took a different approach. To keep the tank in place I took some scrap .032 aluminum I had left over from the belly pan and made a strap 6" wide that runs side to side and bolts to the frame rail. It is not meant to support a full tank, just empty. The cover to enclose the tank provides support when in use. It is 1/4" aluminum plate (I know it's overkill but the price was right, 1/8" would be more than sufficient). The cover and strap both bolt to the frame rails and crossmembers. Rivnuts were installed in the frame, my new crossmembers are rectangular tubing, no access to the back side.

If you plan on using seelevel tank monitors be sure you have adequate clearance away from frame members.

"Determine where to mount the senders on the tanks. They
will need to have a flat area on the side of the tank large
enough so the whole width of the sender is in contact with
the side of the tank, all the way from the top to the bottom
of the tank. Make sure that any metal is at least an inch away
from the sender. "

Hope this helps

[Bubba L]

Originally Posted by Jeremy9107

Thanks for replies. If you have any photos of the mod that would be helpful. Bubba I had envisioned something like what you did but have no room to spare between the top of the axle and bottom of the cross member and wasn't thinking I could get strap with bolts to fit in that space. How were you able to do that?

Bubba was one of your tanks over the axle a black tank? What were its dimensions? Chatthayer what are dimensions of your black tank?

Jeremy, if you go to “Tale of a 55FC Whale Reno” and look at posts 41 and 46. These may show the spacing. Since I had to do some welding anyway, I adjusted and added a 14ga C-channel purlin to accommodate the tanks. Like you, there was not enough clearance above the axle tube. These tanks are from VTS and they measure 50 x21 x4 and are 16 gallon tanks. In running the PVC drain pipe, I cut holes thru the cross members and placed split plastic tubing as grommets. Also, the holes I cut were reinforced with a couple strips of steel straps above and around the holes to bring back the structural integrity of the cross member. I did have room on the end to place the Sea Level monitor strip with required clearance. We will not have a black tank, but a composting toilet instead. Good luck. Bubba

[Jeremy9107]

After a lot of thought I think I am going to stick with the original Airstream design for holding tank support. The black water tank was sitting in a sheet metal box that rested on 2 pieces of angle iron running side to side bolted to the frame. I am going to copy that design for both the black water and gray water tanks. I have already welded the new tabs to bolt the angle iron on to. It should make for easy removal if needed. Photos to come later...