Total Redo! Tank Placement and Frame Strength Inquires!

[Jesseaf]

Hi! Note: I have attached a diagram!!!!



First post. Longtime lurker. Ill keep it short as short as I can.



I have been Renovating a 1978 30 foot Argosy. Its completely stripped.



I need to purchase and place the holding tanks. Fresh, black water, and grey water.



I will be putting a D&M Plastics tank at the front under the seating. It is 290 litres 10" H 27"W 66"L


The back is more complicated as i have moved from a rear bath to a side bath. I will be adding much larger tanks than original (151 litres each)


They will rarely be both full but im concerned about frame strength.



Where and how should i re enforce the frame?


Cheers!

[truckasaurus]

I'm not qualified or expert enough to give out frame advice, I just remade mine from 2" x 6" box at the direction of an expert. I thought I'd just offer up https://www.pellandent.com as another source of tanks. I bought from them when I lived in Alberta and recently after my move from Saskatoon to Georgia.

[skyguyscott]

This calls for serious engineering. I am not an engineer, but recall one saying once, regarding bridge building, "Anyone can engineer a strong bridge, the trick is designing one that is just strong enough." He was speaking about the trade offs of cost, weight, and strength.

In trailers, you not only have to consider the strength of the frame but overall weight and balance and how that will transfer to the axles/tires (are they strong enough) the tongue, and how it will tow/track/brake once in motion.

[azflycaster]

If Airstream was using the same frame construction on the Argosy line that they did on their Airstream line I would have serious concerns with the weight of the size tanks you have listed. The 70s trailers had issues with the frame separating from the body in the rear bath area. Large tanks in the read would only add to the stress in this area.

[Jesseaf]

Thanks for the heads up guys, i think i will get in touch with a couple of structural guys i know.

[uwe]

Originally Posted by Jesseaf

Hi! Note: I have attached a diagram!!!!



First post. Longtime lurker. Ill keep it short as short as I can.



I have been Renovating a 1978 30 foot Argosy. Its completely stripped.



I need to purchase and place the holding tanks. Fresh, black water, and grey water.



I will be putting a D&M Plastics tank at the front under the seating. It is 290 litres 10" H 27"W 66"L


The back is more complicated as i have moved from a rear bath to a side bath. I will be adding much larger tanks than original (151 litres each)


They will rarely be both full but im concerned about frame strength.



Where and how should i re enforce the frame?


Cheers!

If your frame is an open to the center "C" channel, then your best bet is to stitch weld flat steel to the open side of the c-channel. minimum 3/16th flat stock. This will give your frame enough strength to carry your load, especially since you have it spread wide over the frame and cross members. You will have to make new cross members or modify what you have and weld them back in place onto he reinforcement stock. I would do this over the entire frame length, all the way to the front. keep in mind where you need to anchor your flooring sheets, for distancing the crossmembers. I looked at your plan, but it does not show detail on how your frame is put together from the factory.
Best,
Uwe

[jsaucier]

You indicated at least one tank would be placed "at the front". Your drawing didn't show tank placement relative to the axels and floor plan. Keep in mind that the 290 liter tank when full will hold 638 pounds of water. To state the obvious, if this weight were centered exactly between the axels it would all be on the axels. The closer to the the tank moves forward, the more the weight transfers to the tongue. This is not a static load. It is dynamic in that the water sloshes around and the trailer tires hit bumps magnifying the momentary loading. If the tanks will rarely be full, it might be prudent to consider smaller tanks. Any frame overloading will not be given a pass because it happens rarely.