I'm thinking of making a glassfibre mould for observatory - interested?

[skybadger]

Hi all

My dome is beginning to look a bit ratty after 20 years or so, so I want to replace it with a new one.

I've had a close look at Pulsar and ExploraDome and the others, but I don't want to spend the wonga for a large dome and then build lots of bits to make it interface to the building. Also with the dome sizes at 8ft, 10ft, etc I'd want something like the 10ft at least which is expensive even in kit form.

So I got to thinking about GRP again - I built the shutter on the dome from a mould I made and a bunch of other pieces to go with it so I feel competent about how to do this - but if I was to get the investment in, it might as well be for a mould rather than a one-off build.

Which begs the question - who else would be interested in investing in a SGL mould for a 10foot dome ?

The last time I worked out the costs of producing the mould it came out at about £800 in materials - I'll do my sums again to validate this and post it up here. This of course was without labour - that's essentially free.

I am thinking of a dome design with

• two identical hemispherical sides with raised facing lip
  
• two base annulus segment rings which form teh lower edge of the dome hemisphere
  
• two central section annulus short segments which form the lower edge of the central segments
  
• one central arc for the back of the dome joininbg the hemispheres
  
• One main shutter which rolls back along the roof line
  
• One smaller shutter which may get lost in the design stage
  

so 5 or 6 main moulds for design and build.

The moulds will be built from OSB and ply cladding before glafssfibre cladding.

The anticipated cost per dome as a kit would then be of the order of 600 ea. based on materials only.

Admittedly this is based on my requirements and glosses a lot of the details - what dooes it run on - who provides the wheels/ring/shutter hinges/motorisation etc ?

Anyone interested ?

I'd post a link to my current obsy but I need to work on the webserver. Try http://www.skybadger.net/skybadger for a pic...

Cheers

Mike

[nytecam]

Interesting project - my astro buddy and I did something similar for a 3m [9ft-10in] GRP dome awhile back but managed it with just two moulds to produce 10 GRP 'finger' panels [5 each side] at pic below with upstand to short edge [to shutter] and downstands to long edges to bolt together - the dome gore's radiant point was horizontal rather than at the top where it would have cuts through the shutter line !

The second mould served for the shutter in 5 panels all with downstand edges - 1 lower shutter hinged outwards, 2 fixed at back of dome and 2 slid back over the fixed section. The dome rotated on an angle-iron ring bolted to the base of the dome running on castors fixed to obsy roof. Ali trim weather joint where shutters met.

The obsy is fully described in P. Moore's Small Astro Observatories - Springer. When it came to my turn the cost of GRP materials rocketed so I abandoned GRP for 10ft frameless dome from marine ply

Good luck with your project.

[The Sailor]

Good luck with that Mike

Jim

[JamesF]

Making the dome out of multiple identical sections does seem like a way to reduce the cost of the mould construction.

James

[Gina]

Yes, I though that design was very clever. You tend to think of panels with the ribs radiating from the apex - nice bit of lateral thinking

[nytecam]

Yes, I though that design was very clever. You tend to think of panels with the ribs radiating from the apex - nice bit of lateral thinking

Thank you Gina