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Dome Restoration or Convert to Roll-Off

observatory DIY
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#1 tmiddendorf

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Posted 16 July 2020 - 08:57 AM

I need any recommendations you may have as to whether to restore my observatory dome or replace it with a roll-off. Here is some details. The dome is 16ft DIY made of plywood and laminated with hard board. It is in bad condition. It sits on a 16ft x 16ft cinder block  building. I plan to put a 20" Obsession in it. The location has a fair amount of wind so the dome restore is desirable, but I love the idea of the open sly with the Obsession. Also, I can install wind blocks if I go with roll-off.

 

What has your experiences been?

 

Thanks



#2 kathyastro

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Posted 16 July 2020 - 09:12 AM

We need more information.  What exactly is "bad condition"?  Leaking? Rotting?  Mechanical problems?  Is there a frame that would allow it to be re-skinned if the skin is the problem?  Would restoration require starting from scratch?

 

If starting from scratch, there is no doubt that a roll-off would be simpler.



#3 Xeroid

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Posted 16 July 2020 - 09:16 AM

Might help you to make a better decision if you can obtain estimates of a new dome vs repair/replace existing dome.


Edited by Xeroid, 16 July 2020 - 09:16 AM.


#4 tmiddendorf

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Posted 16 July 2020 - 09:19 AM

The dome has the ribs, not sure of condition, i.e. if plywood is delaminating. 90% of skin is on except at top of shutter doors. The top has huge gaps and is definitely leaking into the empty building. The 90% of skin remaining is starting to separate from the ribs.

 

The shutter doors have to be rehung with new wheel mechanisms. The base ring is warping due to weight and only 8 wheels around. My thought was to use 16 wheels to distribute the weight thus reducing the warping. 



#5 tmiddendorf

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Posted 16 July 2020 - 09:20 AM

Purchasing a new/used dome was a thought I had as well. A new dome would be upwards of $25K I would think. But need to really research that option.



#6 555aaa

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Posted 16 July 2020 - 10:19 AM

My college observatory was made in 1896 and has a wooden dome. It's survived IMHO because it is on an extremely sturdy iron ring which in turn sits on a stone building. It seems that if the ring sags over time, then you will always be fighting having the shutters close properly as the dome distorts from the ring warpage, since the ring isn't providing good structural support.How is the ring constructed? But you say you have a cinder block building which can be very rigid. How is the foundation?

 

There are some hybrid options where the "dome" is more of a conventional roof with shutters but it still rotates. That allows for a much easier shutter design using flat shutters.



#7 TOMDEY

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Posted 16 July 2020 - 10:20 AM

Well... 16-foot is getting toward the large size; working on it far from trivial. Is the ~hard board~ like Masonite or such? If so, that stuff is absolutely terrible as dome skin, would have to be 100% replaced. Add to that the warped ring, failed shutter mechanism... sure sounding like tear down and rebuild is the easiest path. Once you got it stripped down to the cinder block walls --- would also want to scrupulously examine even that, the foundation, and pier. The winds favor a dome, though.    Tom



#8 tmiddendorf

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Posted 16 July 2020 - 10:25 AM

So the design while on cinder block building didn't sufficiently account for water/snow run off at the corners. Nor did it sufficiently account for the load at the corners where the dome is over open air so to speak. Yes any sag will definitely effect the shutters. The ring is 3 layers of 3/4" plywood on top of 1/4" steel ring. The steel ring has no support rigidity, only allows the wheels to roll on it more smoothly.

The rotating roof idea is interesting. 



#9 scottsdalejohn

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Posted 16 July 2020 - 10:26 AM

From personal experience, once plywood begins to de laminate you need to replace it, and if you have a lot to replace it's generally less expensive to start over with new construction. A local framer/carpenter will be able to give you a  estimate of the cost to repair and/or replace the existing structure. With that information you can decide how best to move forward.



#10 tmiddendorf

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Posted 16 July 2020 - 10:29 AM

Well... 16-foot is getting toward the large size; working on it far from trivial. Is the ~hard board~ like Masonite or such? If so, that stuff is absolutely terrible as dome skin, would have to be 100% replaced. Add to that the warped ring, failed shutter mechanism... sure sounding like tear down and rebuild is the easiest path. Once you got it stripped down to the cinder block walls --- would also want to scrupulously examine even that, the foundation, and pier. The winds favor a dome, though.    Tom

Tom,

I agree a lot of work. I think the ribs could be salvaged and if I use 16 wheels instead of the 8 it would bring the ring flat. Yes the entire skin has to come off. On a 10' dome I built I used 1/8" plywood as the skin. It is easily bent. Over this I used MFM Peal and Seal white 36" wide rolls. It is tough and functional. So my thought was to do similar on the 16'. The cinder block walls are on a standard concrete foundation. No movement or issues there yet. Pier is solid.



#11 tmiddendorf

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Posted 16 July 2020 - 10:31 AM

From personal experience, once plywood begins to de laminate you need to replace it, and if you have a lot to replace it's generally less expensive to start over with new construction. A local framer/carpenter will be able to give you a  estimate of the cost to repair and/or replace the existing structure. With that information you can decide how best to move forward.

Very true about a local giving me estimates. One of my neighbors there used to be a manager at a truss building company before he retired so I know what his leanings will be :)



#12 DSOGabe

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Posted 16 July 2020 - 11:09 AM

Sounds like, all in all, starting from scratch will be cheaper in the long run.



#13 tmiddendorf

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Posted 16 July 2020 - 11:33 AM

Sounds like, all in all, starting from scratch will be cheaper in the long run.

That is slowly the conclusion I think I am coming to. I am appreciating all the perspectives everyone has. 

 

Also hoping to hear from those who have gone through this before and what your critical decision points were to reach your conclusion. There is no one best solution I don't think, just informed choices that satisfy ourselves that one way over the other is the way to go. Innovative ideas and solutions intrigue me.



#14 tmiddendorf

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Posted 16 July 2020 - 11:35 AM

That is slowly the conclusion I think I am coming to. I am appreciating all the perspectives everyone has. 

 

Also hoping to hear from those who have gone through this before and what your critical decision points were to reach your conclusion. There is no one best solution I don't think, just informed choices that satisfy ourselves that one way over the other is the way to go. Innovative ideas and solutions intrigue me.

I was even thinking of a rool-off dome. Best of both worlds. Open it up on calm nights and stay encapsulated on the windy ones in the dome. I should have done that with the 10'; would have been much easier relatively speaking.




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