149 replies to this topic

[kmcintyre]

Not me... ok, maybe 1/4".

 

Kevin

Question:

 

Those you with tin canning noises and with a single top sheet....have you ever had a snow load on that roof?

 

Thanks...Phil

 

[Reason for question to follow.... ]

[Wallowa]

New Information:

 

First FWC says that tin canning almost always is associated FWC that have had a snow load.  Take that at their word.  I guessed that the top sheet on my '16 Hawk is about 88 sq/ft.....using the table in this article [scroll down for chart] you can see that any appreciable snow of a variety of types [water content/density over time] can quickly exceed the FWC statement that "the top can take 1,000 lbs of snow".  Hypothesis, WAG, is that too much snow either bowed the top sheet and or top frame and stretched the aluminum top sheet creating bowing in areas between roof framing.   https://roofonline.c...weight-of-snow/

 

Recent Observations and Clue For A Fix:

 

The top of my Hawk has 6 length wise aluminum frame members [look location of these above the inside liner wooden strips].  The obvious areas of bowing/flex from distorted top sheet on my top was between these frame members.  A lot of convex bowing of top sheet between those frame members.  Bracing laterally across these frame members did not stop the tin canning, but putting weight [used 2"x 4"x 3ft for area and weight test] longitudinally and centered between these 6 roof frame members did dampen or eliminate the movement up and down of the top sheet in those spaces and tin canning.

 

My 2 solar panels [on Yakima Rails] cover about 30 sq/ft of the top sheet and while top sheet does flex more in uncovered areas of top sheet the 'why' tin canning can occur under the solar panels is a puzzle.  Perhaps the weight on Rails caused top sheet distortion.

 

I have been skiing with the Hawk and have had up to 12" of fresh [powder, low water content] overnight on top sheet before I scraped the top off with a rubber snow remover rake.  Never did the snow sit long on the top and most of the other times I had a maximum of 6" snow for brief periods on top sheet.   Never ice or "Sierra Cement".

 

So, all this and $3 with get you a cup of crappy coffee....My next move will be to purchase aluminum flat bar and using 100mph tape place sections of the bar between the longitudinal frame members of the top sheet while seeing if I can replicate wind produced tin canning with my hand. 

 

Phil

 

Weight of my two Zamp panels [160 & 170w] and mounting frames about 55lbs; no idea of weight of rails or two power roof vents.

Edited by Wallowa, 04 June 2023 - 05:43 PM.

[Wandering Sagebrush]

FWIW, my camper never had a snow load, it occurred on our very first trip.  That dog don’t hunt…

[Wallowa]

FWIW, my camper never had a snow load, it occurred on our very first trip.  That dog don’t hunt…

 

 

Take that to FWC...

 

Regardless of the 'why', right now my money is on weighting down the loose/distorted sections on the top sheet between the top longitudinal frame members...I will try aluminum bar, unless someone has a better idea of how to lessen or stop the TC.

[pvstoy]

Don't have a suggestion.  I used Orange Aluminum for some Z bar and was pleased with them.  Just another shopping comparisons

 

https://orangealuminum.com/

 

Patrick

[Wallowa]

Thanks Pat...shipping costs are through the roof for 6 foot lengths....nominal cost for 2"x1/4" is $6+ per foot....right now Amazon seems the best bet...

 

Question for Collective Wisdom:  Is the bar length or the bar weight the most significant factor in reducing tin canning ?

 

Perhaps there is an optimal combination?  FYI...2"x1/4"X6ft aluminum bar weight is 3.51lbs.

 

Phil

Edited by Wallowa, 05 June 2023 - 03:00 PM.

[pvstoy]

Just thinking out loud here so don't take it a known value.

 

If using flat bar then weight and surface area might gain the most benefit.

 

If using a angle piece (like a "L") taped down then weight may not be a issue as long as the length is ridged enough to keep the roof from popping up and down. Angle is strong and can be smaller and lighter than flat stock.

 

If a piece of angle is run east/west the full width of roof, 90 degrees to the roof trusses with bonding material, then the slop that goes up and down with as with your tape pulling example would be controlled.  I might be tempted (and If it was my roof I would) screw it to the trusses as it crosses 90 degrees at each truss.  By having the angle captative at the truss locations, the bonded space between has no place to flex up and down to.  

 

I have no issue screwing it down to the truss as the full length roof tracks are done that way but running north south.  If you have truss up front that is not covered by roof rack tracks that would be a good starting place.

 

Long winded but just some thoughts.  Patrick

[Rocklobster]

I'm picking up my new 2023 Grandby in July. It's a full build out, and as everyone on the discussion knows, I'm forking out a pretty penny. Ya'll have got me a little worried now. I will definitely be asking a lot of questions to the rep when I pick it up. He better have the answers.

[Vic Harder]

Phil really doesn't want to make any holes, I think.  

 

Phil, I wonder if you are open to pulling off the ceiling liner and tackling this problem from inside/below?  I bet that attaching the East West frame members with VHB would help, as would (re)glueing the rigid insulation to the one piece top sheet.

[JaSAn]

..... Question for Collective Wisdom:  Is the bar length or the bar weight the most significant factor in reducing tin canning ?.....

For vibration damping: 

placement is the most important factor.  At the peak or trough gives maximum attenuation.  At a node gives no attenuation.

Second is mass for low frequencies (1 to 250 hz), friction for mid range (250 to 2000 hz).

 

If you can reliably reproduce the oil canning, experiment with weights to find correct placement.

 

Instead of Macgyvering a solution why not use a product engineered to attenuate vibrations?