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Old 05-22-2013, 12:19 PM   #1
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1981 31' Excella II
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Rear Cross Member Rear Bath Hole Pattern

Does anyone know what the hole pattern is for the tank feedthrough's in the rear most crossmember on the rear bath late 70's trailers. It is 4 small holes surrounding one big hole. I expect the big hole is something like 4 inches and the small ones are probably 5/16" or something like that. I am assuming the tank valves mount to the crossmember.

Perry
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Old 05-22-2013, 09:42 PM   #2
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Pics always help. But I am guessing the 4" hole is for the drain coupler for your black tank, and the smaller holes are for the bolts that hold the coupler in place.
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Old 05-23-2013, 06:53 AM   #3
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Trying to help someone else make a new beam for back there.

Perry
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Old 05-23-2013, 08:44 AM   #4
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Just did this.... I originally tried to measure from the remnants of the old cross beam. I've attached a pic of those measurements- when I had the new cross beam fabricated, I was going to have the guy cut the holes where they were. But I chickened out.

I ended up mocking everything up first, then marking where the holes go. I used 4.5" hole saw, based on what I could guesstimate the old holes to be. I'm not quite sure what the 4 surrounding holes were for, but I would guess they may be to access the screws on the Thetford valve body- for service, repair, replace??

I'm not going to put the surrounding holes back in. I switched to Valterra- cheap and easy. I found some 1/8 rubber squares at Lowes in the plumbing section for making your own gaskets. I will ultimately cut that to fit tightly over the plumbing that exits the rear crossmember, and also cut some aluminum to rivet, screw or bolt over it to hold it tight against the crossmember. I've attached a pic of someone's rearend I found searching around trying to figure out what it is supposed to look like.

I dont believe the valve attaches to anything except the tank. Although, I'm with you... wondering if my entire plumbing assembly is going to be unsupported (or supported by the tank connection?? Theres a youtube video from a guy that redid his with Valterra here: Airstream valterra conversion - YouTube

I'm also going to delete the bumper plate to avoid future water intrusion. Instead I'm going to leave a gap for water to drain, but will insert an additional piece of aluminum to help shed the water away from the rear crossmember. Attached a pic of a design I found on AForums.
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Old 05-23-2013, 08:45 AM   #5
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more coming as soon as my phone catches up.
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Old 05-23-2013, 11:02 AM   #6
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FYI- just a thought on one of those previous pics... I would probably not go by those measurements on my drawing.. It is probably pretty close to what "I" had, but may not be a standard for "any"...

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Old 05-23-2013, 11:11 AM   #7
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Perry- I just re-read your original post, which I thought was asking for the "pattern for all the holes in the rear crossmember".... I see now you're just asking what the 4 holes are for...

Oh well- hope that info helps.
Mic
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Old 05-23-2013, 01:04 PM   #8
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No I am trying to figure out how to make a whole new crossmember so the more info the better. So what goes in the the tank. It looks like some sort of nipple section coming off the valve that is hose clamped to the tank. I would think that connection would be prone to leak with that pipe just hose clamped on.

Thanks for the pics and the video. Those will come in handy.

Perry
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Old 05-23-2013, 10:24 PM   #9
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Ha- funny you say that.... I'm getting ready to assemble everything tomorrow, so had a last minute thought.... maybe I ought to fill up those tanks and make sure there are no leaks.

Ummm... BOTH those freakin hose clamps that hold the valves leaked! I pulled them off and coated the inner surface with some plastic joint sealant and trying it again overnight. Although, now I'm VERY concerned, and thinking maybe I should have used some sort of industrial sealant, but now they are all coated in that plastic sealant, so I may have just made a mess. I really hope this doesn't affect my assembly day tomorrow!
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Old 05-24-2013, 08:37 AM   #10
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I would use Silicone around the pipe nipples that go in the tanks. Clean both surfaces of oil or sealant residue. It won't hurt to roughen the surface a little. HDPE is hard to get anything to stick to. I would fill them with water and see if you have leaks and go from there. If it ain't broke don't fix it.

Perry
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Old 06-05-2013, 02:18 PM   #11
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So how is everyone making or buying these crossmembers? Are they available from Airstream or Inland RV etc?

Perry
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