Skin material for dome

[Earl]

the advantage of a dome is the smaller footprint, this has been my deciding factor.

[cloudnine]

SWMBO prefers a dome, and to be honest, I do too from both an aesthetics perspective and also because I've spent 34 years as an amateur astronomer wanting one.

I take the point that a roll-off shed is better for so many reasons, and am wading through yesyes's build (up to page 18 out of 36!) admiring the ingenuity and attention to detail. I'll be gleaning as much as possible from the many threads here, as well as the two Patrick Moore Small Astronomical Observatories books and David Arditti's book. There are so many options it's untrue, so while I'm deciding the exact details I'm clearing the site and putting in retaining walls and an oversized concrete base (with block for the pier). The oversizing allows me to change my mind over dimensions as the plan comes to fruition ... the exposed concrete will have a nice layer of decorative pebbles and maybe a few plant pots to 'break' the lines a little. 

Ultimately the dome needs to look 'nice' which may be the most difficult aspect to address. A functional dome is just a matter of careful engineering/construction. A beautiful dome is going to be a challenge.

I need to do a lot of thinking and a little experimenting methinks.

Martin

[olawelin]

On a practical level I mostly agree with Olly that small(-ish) domes aren't that practical, but life doesn't always have to be about what's practical and if I were going to build a dome I'd love to make a geodesic one.  I want two piers in mine though and that really does make a dome rather more awkward (and far too interesting to the planning authority).

James

A small dome is ok if you make the walls under it high enough, mine is 2.4m and the walls around 150cm, I am about 180cm and having no problems standing straight in there anywhere. Just remember to get the pier high enough as well.

That geodesic design looks great, would be fun to try building one.

//Ola

[ollypenrice]

Interesting stuff. What about the technology used in the construction of concrete boats?

I can understand the charm of the dome, don't get me wrong. They do have a certain something.

Olly

[SnakeyJ]

Ferrocrete is used for boats - would work but too heavy practically for a small dome.

[nytecam]

I've built 6 domed obsys for friends, groups and self over the years with either fold-aside (early on) to up 'n over. My current 6' dome has a lift-off shutter that's parked inside the dome see my homepage links.

An up 'n over shutter is split into 5 - 2 fixed at the back where a 2 section shutter is parked - the final 5th section beneath the shutter is hinged forward. Full access to the zenith is possible!

My last dome for a friend was octagonal in plan (see Ron's dome in link) using 4 cylindrical panels including the shutter and 4 cylindrical gores to the 'corners' - all in painted ply. If I were to do again I'd repeat the latter for relative easy of construction. Good luck in your project :-)

[nytecam]

Here's the 2.2m octogonal dome dims and lift...

[cloudnine]

Thanks, nytecam, thats really interesting. That's the kind of obsy I have in mind. Can I ask how thin is the ply that you used to clad the dome and did you use a special ply (e.g. marine) or just bog standard ply with appropriate treatment/painting?

If (from what I can work out from your 'discovery' link in your signature) you are Maurice Gavin, I have to say that I really liked your idea of having more than a hemisphere as a dome. I've also read with interest the obsy plans on the website and taken much inspiration from them.

Cheers,

Martin

[nytecam]

Thanks, nytecam, thats really interesting. That's the kind of obsy I have in mind. Can I ask how thin is the ply that you used to clad the dome and did you use a special ply (e.g. marine) or just bog standard ply with appropriate treatment/painting?

 

If (from what I can work out from your 'discovery' link in your signature) you are Maurice Gavin, I have to say that I really liked your idea of having more than a hemisphere as a dome. I've also read with interest the obsy plans on the website and taken much inspiration from them. Cheers, Martin

Thanks Martin - yes that's me! It's a decade since Ron's obsy was built and I'm a bit vague on detail - I see him tonight at the club meeting and will quiz him and get back here. ;-)

ps: just seen on my homepage...The 18mm framework and 4mm cladding is in waterproof ply for painting. but will get more details. ;-)

[nytecam]

Hi Martin - got this response from RonJ over the weekend...

"I used 4mm marine ply for the dome which was glued and screwed to a 12mm ply framework. It was then primed with a wood primer and given two coats of acrilic paint.

The lower [hinge forward] shutter is bolted to the adjacent vertical frame of the dome in four locations (two at the top and two at the bottom). It is very rare for me to need to lower this shutter. The main shutter is tied internally above the lower shutter to the adjacent vertical frame of the dome and at the top to the timber cross member. This has proved adequate even during the high winds of last winter.

Hope this helps."

[michaelmorris]

Many years ago Astronomy Now (or possibly Sky at Night Magazine) did a series on buliding your dome. This used a wooden frame with hardboard segments glued and screwed in place, This was then waterproofed using a few coats of fibreglass resin.

see http://stargazerslounge.com/topic/219445-hilltop-observatory/page-3

[Horwig]

I'll add my twopence worth to this thread. Built my dome a couple of years ago, ribs were glued 12mm ply, skin was 3mm ply gores, glued and pinned to the ribs, and then fibreglassed. Here are some pics of mine, plans came from Midland Stargazers. Found a gore calculator on the web, will look for it if you'r interested.

BTW, the timber two part shutter was a disaster, it warped and would not slide, so was replaced with a fibrglass moulding

Best of luck with the build

Huw