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-   -   How strong are fence posts? Suggestions? Thoughts? (http://www.diychatroom.com/f19/how-strong-fence-posts-suggestions-thoughts-45551/)

johnluk 05-29-2009 08:31 PM

How strong are fence posts? Suggestions? Thoughts?
 
Hi, I am planning on installing pool solar panels on a wood rack. The rack measure 246 inches long by 54 inches. It is made up of a 2x4 outer frame with 2x2x51” ribs every two feet. There is ˝ inch plywood that covers the surface. The solar panels, which sit on the ˝ inch plywood, will weight an additional 43 lbs (with water flowing thru).

I am thinking of hang the wood rack on my back fence. The wood rack will span over three 4x4 PT cemented posts 8 feet apart. The fence is 75 inches high. I am thinking of hang this wood rack from the top of the fence with hinges as I need to have the wood rack at a 45 degree angle from the fence during the summer months and then hang straight down the fence during the winter months. I plan to add extra legs to support the wood rack when in the 45 degree angle.

My question is will the fence with the additional legs support this weight??? Or is there a better way??? Is there something else I should be checking???

Any input would be helpful. Thanks

rizzo 05-29-2009 09:05 PM

seems to me the static vertical weight of the panels and framing should be no problem, especially since eccentric loading is handled by the outboard supports you will add to the panels when in the 45° position. However, I suspect variable loading from wind will be the problem. If you add diagonal bracing to the 4x4 posts (boards tying the posts to ground running at 45° to vertical oriented perpindicular to the fence) you will have a stronger structure with less deflection.

Is the water being heated for a pool?

Willie T 05-29-2009 10:00 PM

Heating a pool in the Wintertime, I can see. But why are you wanting to make the water warmer in the Summer? Wouldn't the same "straight down" hanging you desire for the Winter be sufficient to take a little of the nip off Summertime water? (If your water actually gets that cold in Summer) I know our cool water is more than welcome when that ol' Summer sun is beating down.

johnluk 05-30-2009 12:12 PM

Thank you Rizzo for you feed back... I will look into our suggestions. And yes this is to heat the water for a pool.

Willie T – the world does not live just in Florida…. Welcome to Canada, we get maybe 2 - 3 months of swimming weather in a good summer. With the solar panels I could increase this to 3 – 5 months of swimming.

Ron6519 05-30-2009 12:19 PM

The quality of the fence posts will vary with time and location. To determine if your fence posts are up to the job would require you to inspect each of them to see how sturdy they are. Cedar posts buried in the ground don't seem to have much of a life span.
Ron

Willie T 05-30-2009 02:22 PM

Quote:

Originally Posted by johnluk (Post 280530)
Thank you Rizzo for you feed back... I will look into our suggestions. And yes this is to heat the water for a pool.

Willie T – the world does not live just in Florida…. Welcome to Canada, we get maybe 2 - 3 months of swimming weather in a good summer. With the solar panels I could increase this to 3 – 5 months of swimming.

You can fix that, eh? Just move down here with the rest of the Canadians. :thumbup:

Yoyizit 05-30-2009 04:29 PM

Will the panels block wind that would otherwise go through the fence?

johnluk 06-01-2009 07:31 PM

It will block some wind but I don't think it will be like a solid wall. My wood rack has 2x2 ribs with plywood on top of it but there is a 6 inch gab of no plywood running in the middle down the whole width (246 inch length) with just the 2x2 ribs showing. For the summer months the wood rack with also be on a 45 degree angle.

Yoyizit 06-01-2009 07:37 PM

With books like "Lumber Engineering" and formulas for wind force from the Web this problem could probably be figured pretty close.
I guess you'd need data on the 97.5% percentile for peak wind speeds in your area.


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