Kit Observatory - not for chickens

[jimmywrangles (James)]

Originally Posted by jenchris

snowyskies is quite right.
The better you make the plug the longer it lasts.
I used to work for Haines Hunter - their boat plugs lasted for years and often made a boat a day from them.
Swimming pools are made the same way, but you don't need to go to those lengths for a one off.
What's a good diameter for a dome?

Good question, 3 meters perhaps.

[netwolf]

2.4m is the stock standard, 3.0m would be nice. Just wondering though how the 3m would fit in with Council laws. I think the keep it 2.4m to be safe.

Glad to see some fiberglass experts on here, i have no experience with this at all. Just passing on what my friend told me and what i gathered from the web.
A curved plug would be ideal, but a Geodesic one maybe easier to make.

I am told there is some sort of special chemical mix you can use to make expanding foam that cane me made to any shape by carving it. My friend has used this to make body parts for his 4wd. You just mix two chemicals together and you get a volume of foam instantly. You then carve this up to the shape you need and then make a Fibergalls plug from this.





Regards
Fahim

[ballaratdragons (Ken)]

I used to own a Fibreglass business, and built 42' boats and fuel tanks for Carribean, and as simple as you all make it sound, it isn't.

Mold making is critical as the heat and curing forces of the part will distort the mold, putting every piece out of alignment.

A Mold must be laid up thick, reinforced with Wood (preferably steel), and it HAS TO HAVE tooling gel for its gel coat or you will damage it, and really wasting your time and money if you don't.

And speaking of money, bulk fibreglass resin is very expensive and so is the matt (and you need more than 1 type of matt).

Tooling gel is very expensive!
Then there is the 20+ litres of Acetone (which you will definitely need).
You can lay Fibreglass without the proper metal hand rollers, but I'd hate to try.

Do you know how to make the Talcum Bog you will need.

These are the reasons I've never done this myself.
It just isn't cost effective.

And all this is just for the Mold!

If you want to make a fibreglass Dome, go for it.
I'm just letting you know some points so you can't say "no-one said so".

[netwolf]

Ken, I was not suggesting it was easy. Indeed I think the intial stages would require people with expertiese in Fiberglassing. And we would use that experties to learn from. People could be taught the proper process to make there own final pieces. This is what they have done in the UK as per my links.

And of course there are probably much easier ways to build an observatory.

Indeed Ian Sharp sent me a link to another fellow in there group who has gone a diffrent path. And he said this might be the better way to do it, taking less time to do than his one.

http://www.astralweeks.org/observatorybuild/index.html

Similar to a few others I have seen like this one
https://home.comcast.net/~bronson321...n321/home.html

[MrB (Simon)]

Originally Posted by netwolf

I am told there is some sort of special chemical mix you can use to make expanding foam that cane me made to any shape by carving it.

Sounds like Polyurethane foam. The same stuff surfboards have been shaped from since the 60's, before being glassed over.

Link:
http://www.sprayfoamnation.net/product/twocompgrp
https://secure.solidsolutions.com.au...cts.php?cat=23

I do not endorse those suppliers, they're just the first links I found.
I'm sure some digging around would yield better suppliers.
Fiberglass suppliers should stock it.

[jenchris (Jennifer)]

Oh I know the difficulties working with glass.
I've built several boats (when I lived in Bermuda) and worked for Haines for a while.
My partner is the accountant for an epoxy manufacturer and I have used all their products at some time too, including triax cloth which is as flexible as a frozen bearskin.
Yes I can make talcum bog - yes I can use a chop gun.
I don't want to make domes - I want someone else to make them!
I can even use those awful staplers which we stuck the halves together with.
Which is why I recommended making a foam sandwich dome - it's less stressful and less expensive than a mould!
Airex foam or similar is useable - also end grain blasa can be bought in flexible panels and stuck onto the frame then filled with fairing compound (resin mixed with microspheres) and shaved or sanded to a reasonable contour.
Modern free form epoxy glass structures are not hard to make - but it can get expensive.
Highly insulative honeycomb panels can be used for the skin of the walls - they don't absorb moisture and weigh nothing

[ballaratdragons (Ken)]

Originally Posted by jenchris

Oh I know the difficulties working with glass.
I've built several boats (when I lived in Bermuda) and worked for Haines for a while.
My partner is the accountant for an epoxy manufacturer and I have used all their products at some time too, including triax cloth which is as flexible as a frozen bearskin.
Yes I can make talcum bog - yes I can use a chop gun.
I don't want to make domes - I want someone else to make them!
I can even use those awful staplers which we stuck the halves together with.
Which is why I recommended making a foam sandwich dome - it's less stressful and less expensive than a mould!

I have no doubt you would be able to lay up a dome, but many people seem to think it is just a matter of slap it on, brush it down and let it set.
You and I know it ain't that way

My points were made to the uninitiated.

There is an easier way to make a Fibreglass dome, and it consists of making a sectional cardboard, styrofoam or plywood dome first, then cover it with 1 single layer of 225 chopped matt.
The strength is in the original structure. The Fibreglass is just to protect the structure from the elements and add 1 more minor layer of strength.

If using cardboard panels a very thin layer on the interior is also recommended

Or just cover it with weatherproof plastic like this one: http://www.bearcreekobservatory.com/construction.htm

Here is a panel style dome:

[netwolf]

The wodden dome seems like a great idea, but how do they make the plywood bend into a curve? I dont understnad this. How would you even cut it out of flat plywood accurately when it has to fit a sperical triangle. I have seen domes like this and people are using diffrent materia like massonite etc but still how do they cut that out of a flat surface to fit a spherical one.
I must be missing something simple here.

Yikes I did not realise the fiberglas made you itch, yikes brings back bad memories moving false ceelings in the office lab to put up cable. I was itching for a week.

[pmrid (Peter)]

Originally Posted by netwolf

2.4m is the stock standard, 3.0m would be nice. Just wondering though how the 3m would fit in with Council laws. I think the keep it 2.4m to be safe.
...
Regards
Fahim

I just had a look at the Brisbane City Council web site on planning approvals for sheds (see: http://www.brisbane.qld.gov.au/plann...heds/index.htm ) where they say:

"Sheds are 'Class 10a' (non-habitable) structures under the Building Code of Australia. According to the Building Regulation 2006, you do not need building approval if your shed is:

• no more than 10 square metres in area after building work is completed
• no more than 2.4 metres high (with an 'average mean height' of no more than 2.1 metres)
• no longer than 5 metres along any side

If your shed does not fulfil all of these requirements, you will need to lodge a building application and have it assessed by a building certifier."


So you could build up to 3 x 3 metres square or with a 3.5 metre radius for a round structure. The height issue is the greater problem though. OK with a roll-off but not a dome.


Peter

[jimmywrangles (James)]

Originally Posted by ballaratdragons

If you want to make a fibreglass Dome, go for it.
I'm just letting you know some points so you can't say "no-one said so".

Thanks for the constructive advice.

[jenchris (Jennifer)]

a five sided building with 2.4m sides is 9.91m^2
The peak is 900 over but the wall height is ok, the average height would be over 2.1.
so it's on a hiding to nothing unless you get planning permission
Then they'll want 2000 dollars worth of concrete floor and a portaloo in place while you build it. Witches hats and traffic patrols and scaffolding may be called for and a shakedown area at the gate to get rid of soil from truck axles.
Yellow flashing lights and high visibility jackets must be worn -site safety with hard hats and boots and a site manager's office.
3 inspections at a costof 500 dollars each to be done at flooring, roof on and lock up. Completion to be assessed under W42 loading, tie downs 100mm from each vertical member.

I wouldn't get Council involved ina fit.

[wasyoungonce (Brendan)]

A little OT but the new dealer advertisement on the right of the IIS page for Astro Domes.

Reasonably cheap for the steel dome...no prices for the fibreglass versions.

Has anyone noticed that they look like the EVA pods out of "2001 a space odyssey" ....so you really let your imagination run free when inside one...

"Open the pod bay door HAL...."

[netwolf]

I was digging around and came accros this company Dome Incorporated. That make kits Geodesic Domes. Most of the kits are for large Domes, but the do make some 8' and 10' version in Steel and wood.

http://www.domeincorporated.com/geod...me-photos.html

http://www.domeincorporated.com/geod...Wood_Frame.jpg

http://www.domeincorporated.com/geod...s/wood_hub.jpg

The last link shows something similar to the Starplate discussed earlier, for the kit gazebo's.

All that reamins is to workout how best to canvas this. Ply sheets with some fiberglass finish or Alumnium sheets. Many options.

Regards
Fahim