Grand Designs (and general silliness)
This is the story of a dream... or perhaps a flight of fancy, to build an observatory to look at the stars - a latter day cathedral of light! Most sensible people discount dreams as random nonsense thrown up by the thinking prune during yawny-sleepy-snoozie-snooze time... With hindsight, there might just be something to that!
To be read with a large whiskey in handThis is the story of a dream... or perhaps a flight of fancy, to build an observatory to look at the stars - a latter day cathedral of light! Most sensible people discount dreams as random nonsense thrown up by the thinking prune during yawny-sleepy-snoozie-snooze time... With hindsight, there might just be something to that!
and an even larger pinch of salt...
for that is how it was written!
Irationale:for that is how it was written!
Peed off with burning so much petrol driving to and from dark sites; loading and unloading the car; setting up and breaking down the telescope, and lugging all my equipment half way around the country, only to have the clouds roll in just as I'm ready to start observing (sound familiar?) I figured the only way I would get any good observing done was to have the scope permenently set up and ready to go.
This meant having an observatory.
Need & Avarice:
Now, my main instrument at the time was a 20" f/4 Newtonian, but I figured that if I was going to have to build a mount (equatorial, motor driven and computer controlled, of course) capable of carrying this beast, I might as well make it bigger so that I could mount a few other bits'n'bobs as well.
Now, what I really, really wanted was a high contrast planetary scope for doing solar system photography, photometry and astrometry, and as I kinda liked the idea of having an odd-ball instrument I designed and built a 14" f/15 unobstructed Folded Stevick-Paul tilted component reflecting telescope (phew!)... (which gives amazingly sexy images with a total lack of aberrations that is just to die for!) and used this as the basis for the dimensions of the observatory. Also, with a little jiggery-pokery, I could turn my 20" f/4 Newt into a 20" f/24 Loveday... just for a giggle! This would mean extending the tube a tad to accommodate the extra reflective surfaces needed for this Frankenstein transformation.
Here's the optical path layout for my 14" f/15 Folded Stevick-Paul
(make of it what you will - wierd, huh?)
(make of it what you will - wierd, huh?)
Form and Function:
Now, the 14" Folded Stevick-Paul instrument is about 10’ long, and with the 20” Newtonian piggy-backed on that, (ha! nice throw-away line, that!) I reckoned the observatory needed to be about 5m in diameter (don't you just love it when I mix Lbs, Shillings and inches like that!) so as to give me enough room to move around comfortably and not have my body heat create the dreaded ‘dome effect.’ Did I mention I always wanted a domed observatory? No? Well, it was a given as far as I was concerned. Technical aspects aside, I always wanted a dome, so a dome was what I was going to build. Domes are cool, and a 16' dome would elevate my ego well above the unimaginative poxy little garden-shed-run-off-roof-DIY jobs that most amateur astronomer wannabees fertively aspire to with their miserable "Oh-I-haven't-got-enough-money-for-a-real-observatory-and-what-little-I-do-have-I-have-to-spend-on-the-wife-or-she-won't-shag-me" dream castrating negativism. Me; I don't have that problem (no wife, no kids (that I know of), no worries) though my ego has been known to over-inflate occasionally and I try not to cramp its style... especially when I'm half sloshed and drugged up to the gills, like now! A little room for expansion (for the telescopes, of course) is always a good idea! Ok, ok, I realise that in the real world other factors have to be considered when designing your dream star-palace. Space is usually at a premium (ironic, or what?!) and 'er indoors needs room to string a washing line to hang up her undies, but I can't help thinking that compromise is the cancer of creativity. I mean, come on, can't she use the laundro-mat? Not that she *needs* to wash any clothes... judging by the credit card bills and it's not as if *she's* going to build anything in the back yard, and anyway, the less grass that has to be mown, the better... mutter...mutter... Come on, grow some balls, men. Just who pays the mortgage in your house anyway? Hmm... on sober reflection, life is short and taking a stand like that might just shorten it a lot more! Best stick with a converted garden shed. After all, what sane woman would deprive her man of his shed?
Location, location, location:
Casting around for a suitable location to site the observatory was not as straightforward as I thought. Although I have a large garden and lots of land around the house, the best (aesthetic) locations were either swamped by flood lighting from a neighbouring waste recycling centre (vermin and scum of the universe – not recycling in general, just this particular lot) or had too much of the sky obstructed by the very tall, mature trees surrounding the property, or were compromised by the boiling plume of heat rising from the totally un-insulated stately pile I call home. Bummer.
My environmentally friendly neighbours (a.k.a. Scum of the Universe)
To be fair to the Scum of the Universe, they did take (some) action when, after arriving home after 1am one night, I found that I was able to read the newspaper in the light from their plant *reflected* off my house! I totally lost it and fired off a super snotty letter to their general manager cc'd to the EPA. To their credit they were knocking on my front door at 9am the following morning! Grudging respect for this one instance aside, they remain the Scum of the Universe as long as they continue their antisocial activities and string along the local residents with false promises. Varmints!
Throwing your rattle out of the pram really gets results... sometimes!
That left a small plot bang in the middle of the flower garden. I anticipated some resistance from the family. Then a cunning plan began to form in my devious little mind.* I could sell the idea if I lied outrageously about the true size of the observatory and told them it could double up as a garden summerhouse – you know; nice place to sit out; tea in the garden; tweetie-birds; flowers; the whole nine yards. Once it was built and they saw the actual physical size of this monster; if they still didn’t like it, well… yaa-boo-sucks!
[* It’s not often you come across a small, or indeed devious little mind residing in the same head as such a large ego. The universe is a truly wonderful place!]
Where did all the peanuts go?
(or... reality revisited!):
A fairly major part of my cunning plan was to equip the observatory with a really cunning disguise, a sort of cloaking device that would render it almost not entirely blindingly obvious to the casual glance by a half blind person enjoying the garden after sunset... and to the CIA with their pesky little satellites flying overhead... by covering the dome in sheet copper treated with carbonic acid to turn it green. I reckoned that this would help it to blend seamlessly into the background, (yes, I know – it was a lame idea thinking I could hide an elephant under the carpet and hope no one would notice) but the real show stopper for this idea was the price of copper. I nearly had a heart attack when I priced the amount I would need – it still gives me the willies now, just thinking about it!
Ok, arse to that idea – it was going to stick out like a sore thumb and there was nothing I could do about that. Perhaps I can camouflage it with vines or something. Whatever.
Mine, all mine!
Anyway, the site I selected offers a 360°, mostly unobstructed view of the sky down to 20° above the horizon – not bad at all – and I put a mental CPO (compulsory purchase order) on that particular bit of the garden real estate… which was unused and a bit overgrown anyway. I’d be doing everyone a favour by tidying it up :-)
360° panorama from the observatory location in my garden. Note: the sun is at 19°51' above the horizon (11h51m on 9th November 2006)
Just to make doubly sure that no one else got any ideas about that part of the garden, I dug it up in the dead of night and hid it!
To build an observatory: First dig a big hole... then fill it with your money, dreams and sweat!
The only thing going against this site was a brace of pesky street lamps… but I had another cunning plan up me sleeve (which I’m not going to share, ‘cos it’s a bit naughty!) All I’ll say is: Here’s to the Glorious 12th!
There are two ways to extinguish street lights: legally... and with fire arms!
Architectural Merits:
Right, time for a bit of design work. What form was this monstrous edifice going to take? Although I wanted a dome (domes look good – or did I mention that already?) I really didn’t want one of your traditional looking domes made up of curved ‘gores’ riveted together, and as for fibreglass – well, I suppose it burns nicely, but the less said the better. Sorry if that offends anyone, but these are my prejudice that are getting an airing here, so ya, boo, hiss and jumpety-jump! Go write your own web page!
I know, I thought, let’s go geodesic! Cool!! I cast around the net for info on geodesic structures, and lo and behold I got more hits than a 16 year old deb in a skimpy dress! Whittling down my search criteria, I did come across a few other geodesic observatories built from (amongst and of all things) expanded polystyrene covered with stucco plaster! I mean, why go to all the trouble of creating a really sharp looking geodesic structure... and then hide it under a layer of dried mud? I wanted mine to look sharp enough that you could cut yourself on it!
I decided to design my own, and plumbed for a 6v Icosahedron made up of 360 individual triangles… each of which would have to be cut by hand to sub-millimetre accuracy and with each of the three sides of each triangle bevelled to a unique angle to make it all fit together snug as a bug. You may (rightly) surmise that, as the prospect of all this masochistic work didn’t actually frighten me (too much,) I had loooong since ceased taking my medication. Sanity was now officially away on holiday with the faeries!
Oh, just in case you were beginning to get the (false) impression that I am in fact a mad genius whose brain is bulging from mathematical ability, let me disabuse you of that notion immediately. I didn’t do any mathematical calculations (no, not one, I tell you) while drawing up the plans for the geodesic dome (geodesic maths sucks!) I did try, but my nose strted to bleed when I couldn't find the 'ON' button on my calculator, so I gave up. Maths makes my head hurt somethin' rotten. No, I happened upon a most splendid piece of CAD software, Cadre Geo, that does all the hard work for you. I just plugged in the dimensions of the dome I wanted and the program spat out all the numbers followed by an error dialogue that simply said “Nutter!” It even drew me lots and lots of pretty pictures of the dome and the individual panels. Excellent!
Another useful web site dedicated to geodesic domes is Desert Domes which has an excellent calculator and collection of graphics. Yet another page http://obs.nineplanets.org/obs/obslist.html lists hundreds of dome and run-off observatories from which I pinched various ideas.
Quantity Surveying:
Ok, now I knew how big the dome was going to be, and its shape, it was time to work out just how much material I would need to construct it… and thus how expensive it would get. With polystyrene and fibreglass (cough, gag, spit!) out of the equation, I decided to use ¼” Baltic Birch Ply for the dome, covered with 0.7mm aluminium foil which I would glue onto the ply before marking and cutting out. Now ¼” may seem a bit thin and flimsy, but ½” ply would have been twice as heavy and twice as expensive (well, duh!) Anyway, some other fool had already successfully built a smaller geodesic dome from 4mm ply and it seemed to work just fine! Mine was going to be a whole 2mm thicker - I was guaranteed success!
Out came the graph paper, pencil and ruler and I started filling drawings of 4’x8’ ply with lots and lots and lots and lots of little triangles. When I was done, I reckoned I could get all 360 triangles out of 22 sheets of plywood. Uugh... the costs could get ugly!
Above: To lay out the panels on graph paper I first measured and cut out a template of each triangle using thin card and used this to work out the best rotational position of the triangles to achieve the best fit. Some sheets have several different triangle sizes on them, as above - 18 x H-type triangles on one sheet of ply with another 6 x H-type each on the space left over on sheets E and F. Pack 'em in and stack 'em high!
Another fly in the ointment:
Plan B was (note, past tense, for the unobservant) to glue sheets of aluminium to the plywood before slicing it up and then gluing and welding the ply and metal sandwich into hexagons and pentagons before assembling the whole caboodle on site. Unfortunately (again) my experiments in welding aluminium glued to wood did not yield the splendid results I had hoped for. Getting enough heat into the aluminium sheet tended to burn the wood and glue beneath it… weakening the whole structure. The best (and way the coolest) method I came up with is a welding technique called ‘Friction Stir Welding’ but, alas, it required tools somewhat more sophisticated than the router I was armed with and with which I had conducted a few experimental welds. The technique does work… but it was slow and the finish was not all that pretty. Anodising 22 sheets of 4’ x 8’ aluminium was also proving to be a bit of a problem. I could get it done commercially for LOTS of extra cash, but not in the colours I wanted. Realistically that meant the aluminium weather cladding was also out. Drat and double drat!!
Solution [preferably something that won't dissolve in water]:
This tactical setback meant that I was going to have to settle for a fall back solution (Plan C) to protect the dome from the harsh nasty Irish weather and the even nastier effects of the Sun’s UV radiation, both of which would dissolve Baltic birch and ordinary outdoor paints in short order, so out went the cheap nasty Baltic Birch and in with the most excellent (but much more expensive) Marine Ply. Swings and roundabouts, folks; with aluminium and baltic birch out of the equation and marine ply and uber-paint back on the menu, the costs added up to about the same.
An Interesting Statistic:
Now, Marine Ply (best illegally-logged Malaysian hardwood from virgin rain forests, of course, with free baby Orangutan with every ten sheets - I've now got three of the buggers swinging out of the lights and crapping all over my home!) has a density of 0.00511g/sqmm*, and the dome has a total surface area of 38,936,759.5sqmm (give or take a bit) which means that the outer skin alone is going to weigh in at 198.96kg… not including the ribs, the 4mm inner skin, dome ring and paint. Woah - that’s heavy - but at least the wind won’t blow it away!!
[ * yes, I really did cut out a 1sqmm piece and weighed it veeeeeery carefully using a tiny cocaine balance!]
Buckminster-Fuller meets Paintball
(or how to protect a Bucky-ball):
The reason for all this palarva (plans A & B - the copper and aluminium route) was that I didn’t fancy the chances of modern paints duking it out with the Sun. The Sun is big and hot and has a secret weapon (UV) that crisps most paints over time… even UV resistant paints and ghastly fiberglass! This unpleasant fact was repeatedly demonstrated to me every time we had the woodwork on the front of the house painted. Within just a few months of all that nice shiney, expensive paint going on, it would start to blister and crack and fade. Repainting it with the same modern 'UV proof' synthetic paints was just pouring good money after bad. It was also deeply depressing. So a few years ago I stripped all the paint off the house - right back to the wood (which was dry as a bone and gasping for nourishment) and applied my secret weapon!
I had read in Country Life Magazine that the Holkham estate in Norfolk, in the UK, was experiencing the same problems with their paintwork and had taken a gamble by going back to linseed oil based paints. The results were astonishing. After five years the paint was as good as new and by wiping it down with a fresh coat of plain linseed oil the paint would recover its original gloss and luster. I tried it on my house and got the same results! After several years, the paintwork is still in top condition and only needs a fresh coat of oil to brighten it up. The wood (which absorbed the initial treatments of plain linseed oil like blotting paper) has been given a new lease of life! One of the greatest benefits of linseed oil paints is that not only is it waterproof but it allows the wood to breath. So now you know; linseed oil is my secret weapon... it also smells great and leaves your hands beautifully soft too!
Walls, Doors and Floors:
After going to all that trouble to design and build such a splendid dome, it felt a shame just to leave it lying on the ground where it might get kicked and wet (and overgrown in my garden!) Lifting it off the ground with walls seemed to be a sensible idea... but how many? I thought about building just one wall (circular, you dummies!) but felt that was a bit predictable and boring. Two walls would certainly be different, but a bit draughty. Eight walls seemed a nice compromise - four for north, south, east and west, and another four to fill in the gaps.
The next major decision was how tall should they be? Silliness aside, I checked the local planning laws which permit an erection without requiring a planning application to be lodged as long as it is not more than 25 square metres in area and not more than 4m high. I was safe with the observatory's footprint, but with the dome rising 7.5' (with a 6" overhang of the walls) I was limited to a wall height of just over 5.6' unless I sank the floor below ground level. That actually worked out very nicely as the doors to my small greenhouse and the fern-house are both just over 5' high and require you to stoop a little to enter. It lends a quaint old-world feeling to the garden. The observatory walls and doors would be in keeping! I planned to build the walls out of 4x2" studs clad in T&GV planking on the outside and thin cedar strip on the inside. The floor would be T&G planking over 2x6" floor joists on 20" centres.
Bill of Materials:
With all the major dimensions worked out I could now draw up a list of materials needed to build this monster and work out just how much it was all going to cost me. This is where things get ugly and I began to get a crimping sensation in my sphincter!
Dome Construction Materials:
€431.73 for 8 x sheets 4'x8' x 18mm Marine Ply (for dome rings)
€460.53 for 22 x sheets 4'x8' x 6mm Marine Ply (for dome panels)
€ 83.73 for 4 x sheets 4'x8' x 6mm Marine Ply (for telescope tube)
€110.72 for 3 x sheets 4'x8' x 12mm Marine Ply (for dome ribs)
€110.72 for 3 x sheets 4'x8' x 12mm Marine Ply (for telescope tube)
€115.20 for 8 x 4.8m lengths of 6"x2" floor joists
€207.36 for 18 x 4.8m lengths of 4"x2" studs
€470.40 for 56 x 4.8m lengths of 5" T&G planking (floor + walls)
€ 40.00 for 8 x 600mmx600mm concrete paving slabs (foundation load spreaders)
€174.24 for 150m or 1"NG polythene tube for underground cable duct.
€14.31 for 2 rolls of orange builder's twine for cable duct pull-thru.
€39.95 for 5 litres of waterproof wood glue.
€257.95 for 22 sheets of 4'x8' x 4mm WBP Ply (cladding for inside of the dome)
€39.95 for another 5 litres of waterproof wood glue - gotta stop sniffing this shit!
€272.90 for another 13 6"x2" floor joists, 30 joist hangers and nails. I forgot about these!
€46.21 for nuts, bolts and screws.
€9.68 for 16 300mm galvanised steel straps to hold the perimeter joists together.
€67.20 for 4 more 6" x 2" x 4.8m joists.
€70.62 for 10 litres of Protim wood preservative, brushes and floor brads
€19.44 for floor brads (for nailing the walls and floor.)
€19.40 for a roll of heavy duty builder's plastic for lining the walls and under floor.
€16.95 for welding rods - for the telescope tube assemblies.
€5.97 for 40 M4 x 20 machine screws for mirror cells.
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€3085.16 + blood, sweat, tears, labour and bananas for the bloody Orangutans!
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Control Hardware & Software:
€89.78 TheSky 6 (Serious Astronomer's Edition) Software Bisque ($129.00)
€56.00 Vellman USB Interface Kit
€00.00 Relays for dome motors
€30.00 Lesve Dome Driver Software
And so to work...
Now, the 14" Folded Stevick-Paul instrument is about 10’ long, and with the 20” Newtonian piggy-backed on that, (ha! nice throw-away line, that!) I reckoned the observatory needed to be about 5m in diameter (don't you just love it when I mix Lbs, Shillings and inches like that!) so as to give me enough room to move around comfortably and not have my body heat create the dreaded ‘dome effect.’ Did I mention I always wanted a domed observatory? No? Well, it was a given as far as I was concerned. Technical aspects aside, I always wanted a dome, so a dome was what I was going to build. Domes are cool, and a 16' dome would elevate my ego well above the unimaginative poxy little garden-shed-run-off-roof-DIY jobs that most amateur astronomer wannabees fertively aspire to with their miserable "Oh-I-haven't-got-enough-money-for-a-real-observatory-and-what-little-I-do-have-I-have-to-spend-on-the-wife-or-she-won't-shag-me" dream castrating negativism. Me; I don't have that problem (no wife, no kids (that I know of), no worries) though my ego has been known to over-inflate occasionally and I try not to cramp its style... especially when I'm half sloshed and drugged up to the gills, like now! A little room for expansion (for the telescopes, of course) is always a good idea! Ok, ok, I realise that in the real world other factors have to be considered when designing your dream star-palace. Space is usually at a premium (ironic, or what?!) and 'er indoors needs room to string a washing line to hang up her undies, but I can't help thinking that compromise is the cancer of creativity. I mean, come on, can't she use the laundro-mat? Not that she *needs* to wash any clothes... judging by the credit card bills and it's not as if *she's* going to build anything in the back yard, and anyway, the less grass that has to be mown, the better... mutter...mutter... Come on, grow some balls, men. Just who pays the mortgage in your house anyway? Hmm... on sober reflection, life is short and taking a stand like that might just shorten it a lot more! Best stick with a converted garden shed. After all, what sane woman would deprive her man of his shed?
Location, location, location:
Casting around for a suitable location to site the observatory was not as straightforward as I thought. Although I have a large garden and lots of land around the house, the best (aesthetic) locations were either swamped by flood lighting from a neighbouring waste recycling centre (vermin and scum of the universe – not recycling in general, just this particular lot) or had too much of the sky obstructed by the very tall, mature trees surrounding the property, or were compromised by the boiling plume of heat rising from the totally un-insulated stately pile I call home. Bummer.
My environmentally friendly neighbours (a.k.a. Scum of the Universe)To be fair to the Scum of the Universe, they did take (some) action when, after arriving home after 1am one night, I found that I was able to read the newspaper in the light from their plant *reflected* off my house! I totally lost it and fired off a super snotty letter to their general manager cc'd to the EPA. To their credit they were knocking on my front door at 9am the following morning! Grudging respect for this one instance aside, they remain the Scum of the Universe as long as they continue their antisocial activities and string along the local residents with false promises. Varmints!
Throwing your rattle out of the pram really gets results... sometimes!That left a small plot bang in the middle of the flower garden. I anticipated some resistance from the family. Then a cunning plan began to form in my devious little mind.* I could sell the idea if I lied outrageously about the true size of the observatory and told them it could double up as a garden summerhouse – you know; nice place to sit out; tea in the garden; tweetie-birds; flowers; the whole nine yards. Once it was built and they saw the actual physical size of this monster; if they still didn’t like it, well… yaa-boo-sucks!
[* It’s not often you come across a small, or indeed devious little mind residing in the same head as such a large ego. The universe is a truly wonderful place!]
Where did all the peanuts go?
(or... reality revisited!):
A fairly major part of my cunning plan was to equip the observatory with a really cunning disguise, a sort of cloaking device that would render it almost not entirely blindingly obvious to the casual glance by a half blind person enjoying the garden after sunset... and to the CIA with their pesky little satellites flying overhead... by covering the dome in sheet copper treated with carbonic acid to turn it green. I reckoned that this would help it to blend seamlessly into the background, (yes, I know – it was a lame idea thinking I could hide an elephant under the carpet and hope no one would notice) but the real show stopper for this idea was the price of copper. I nearly had a heart attack when I priced the amount I would need – it still gives me the willies now, just thinking about it!Ok, arse to that idea – it was going to stick out like a sore thumb and there was nothing I could do about that. Perhaps I can camouflage it with vines or something. Whatever.
Mine, all mine!
Anyway, the site I selected offers a 360°, mostly unobstructed view of the sky down to 20° above the horizon – not bad at all – and I put a mental CPO (compulsory purchase order) on that particular bit of the garden real estate… which was unused and a bit overgrown anyway. I’d be doing everyone a favour by tidying it up :-)
360° panorama from the observatory location in my garden. Note: the sun is at 19°51' above the horizon (11h51m on 9th November 2006) Just to make doubly sure that no one else got any ideas about that part of the garden, I dug it up in the dead of night and hid it!
To build an observatory: First dig a big hole... then fill it with your money, dreams and sweat! The only thing going against this site was a brace of pesky street lamps… but I had another cunning plan up me sleeve (which I’m not going to share, ‘cos it’s a bit naughty!) All I’ll say is: Here’s to the Glorious 12th!
There are two ways to extinguish street lights: legally... and with fire arms!Architectural Merits:
Right, time for a bit of design work. What form was this monstrous edifice going to take? Although I wanted a dome (domes look good – or did I mention that already?) I really didn’t want one of your traditional looking domes made up of curved ‘gores’ riveted together, and as for fibreglass – well, I suppose it burns nicely, but the less said the better. Sorry if that offends anyone, but these are my prejudice that are getting an airing here, so ya, boo, hiss and jumpety-jump! Go write your own web page!
I know, I thought, let’s go geodesic! Cool!! I cast around the net for info on geodesic structures, and lo and behold I got more hits than a 16 year old deb in a skimpy dress! Whittling down my search criteria, I did come across a few other geodesic observatories built from (amongst and of all things) expanded polystyrene covered with stucco plaster! I mean, why go to all the trouble of creating a really sharp looking geodesic structure... and then hide it under a layer of dried mud? I wanted mine to look sharp enough that you could cut yourself on it!
I decided to design my own, and plumbed for a 6v Icosahedron made up of 360 individual triangles… each of which would have to be cut by hand to sub-millimetre accuracy and with each of the three sides of each triangle bevelled to a unique angle to make it all fit together snug as a bug. You may (rightly) surmise that, as the prospect of all this masochistic work didn’t actually frighten me (too much,) I had loooong since ceased taking my medication. Sanity was now officially away on holiday with the faeries!
Oh, just in case you were beginning to get the (false) impression that I am in fact a mad genius whose brain is bulging from mathematical ability, let me disabuse you of that notion immediately. I didn’t do any mathematical calculations (no, not one, I tell you) while drawing up the plans for the geodesic dome (geodesic maths sucks!) I did try, but my nose strted to bleed when I couldn't find the 'ON' button on my calculator, so I gave up. Maths makes my head hurt somethin' rotten. No, I happened upon a most splendid piece of CAD software, Cadre Geo, that does all the hard work for you. I just plugged in the dimensions of the dome I wanted and the program spat out all the numbers followed by an error dialogue that simply said “Nutter!” It even drew me lots and lots of pretty pictures of the dome and the individual panels. Excellent!
Another useful web site dedicated to geodesic domes is Desert Domes which has an excellent calculator and collection of graphics. Yet another page http://obs.nineplanets.org/obs/obslist.html lists hundreds of dome and run-off observatories from which I pinched various ideas.
Quantity Surveying:
Ok, now I knew how big the dome was going to be, and its shape, it was time to work out just how much material I would need to construct it… and thus how expensive it would get. With polystyrene and fibreglass (cough, gag, spit!) out of the equation, I decided to use ¼” Baltic Birch Ply for the dome, covered with 0.7mm aluminium foil which I would glue onto the ply before marking and cutting out. Now ¼” may seem a bit thin and flimsy, but ½” ply would have been twice as heavy and twice as expensive (well, duh!) Anyway, some other fool had already successfully built a smaller geodesic dome from 4mm ply and it seemed to work just fine! Mine was going to be a whole 2mm thicker - I was guaranteed success!
Out came the graph paper, pencil and ruler and I started filling drawings of 4’x8’ ply with lots and lots and lots and lots of little triangles. When I was done, I reckoned I could get all 360 triangles out of 22 sheets of plywood. Uugh... the costs could get ugly!
Above: To lay out the panels on graph paper I first measured and cut out a template of each triangle using thin card and used this to work out the best rotational position of the triangles to achieve the best fit. Some sheets have several different triangle sizes on them, as above - 18 x H-type triangles on one sheet of ply with another 6 x H-type each on the space left over on sheets E and F. Pack 'em in and stack 'em high!Another fly in the ointment:
Plan B was (note, past tense, for the unobservant) to glue sheets of aluminium to the plywood before slicing it up and then gluing and welding the ply and metal sandwich into hexagons and pentagons before assembling the whole caboodle on site. Unfortunately (again) my experiments in welding aluminium glued to wood did not yield the splendid results I had hoped for. Getting enough heat into the aluminium sheet tended to burn the wood and glue beneath it… weakening the whole structure. The best (and way the coolest) method I came up with is a welding technique called ‘Friction Stir Welding’ but, alas, it required tools somewhat more sophisticated than the router I was armed with and with which I had conducted a few experimental welds. The technique does work… but it was slow and the finish was not all that pretty. Anodising 22 sheets of 4’ x 8’ aluminium was also proving to be a bit of a problem. I could get it done commercially for LOTS of extra cash, but not in the colours I wanted. Realistically that meant the aluminium weather cladding was also out. Drat and double drat!!
Solution [preferably something that won't dissolve in water]:
This tactical setback meant that I was going to have to settle for a fall back solution (Plan C) to protect the dome from the harsh nasty Irish weather and the even nastier effects of the Sun’s UV radiation, both of which would dissolve Baltic birch and ordinary outdoor paints in short order, so out went the cheap nasty Baltic Birch and in with the most excellent (but much more expensive) Marine Ply. Swings and roundabouts, folks; with aluminium and baltic birch out of the equation and marine ply and uber-paint back on the menu, the costs added up to about the same.
An Interesting Statistic:
Now, Marine Ply (best illegally-logged Malaysian hardwood from virgin rain forests, of course, with free baby Orangutan with every ten sheets - I've now got three of the buggers swinging out of the lights and crapping all over my home!) has a density of 0.00511g/sqmm*, and the dome has a total surface area of 38,936,759.5sqmm (give or take a bit) which means that the outer skin alone is going to weigh in at 198.96kg… not including the ribs, the 4mm inner skin, dome ring and paint. Woah - that’s heavy - but at least the wind won’t blow it away!![ * yes, I really did cut out a 1sqmm piece and weighed it veeeeeery carefully using a tiny cocaine balance!]
Buckminster-Fuller meets Paintball
(or how to protect a Bucky-ball):
The reason for all this palarva (plans A & B - the copper and aluminium route) was that I didn’t fancy the chances of modern paints duking it out with the Sun. The Sun is big and hot and has a secret weapon (UV) that crisps most paints over time… even UV resistant paints and ghastly fiberglass! This unpleasant fact was repeatedly demonstrated to me every time we had the woodwork on the front of the house painted. Within just a few months of all that nice shiney, expensive paint going on, it would start to blister and crack and fade. Repainting it with the same modern 'UV proof' synthetic paints was just pouring good money after bad. It was also deeply depressing. So a few years ago I stripped all the paint off the house - right back to the wood (which was dry as a bone and gasping for nourishment) and applied my secret weapon!
I had read in Country Life Magazine that the Holkham estate in Norfolk, in the UK, was experiencing the same problems with their paintwork and had taken a gamble by going back to linseed oil based paints. The results were astonishing. After five years the paint was as good as new and by wiping it down with a fresh coat of plain linseed oil the paint would recover its original gloss and luster. I tried it on my house and got the same results! After several years, the paintwork is still in top condition and only needs a fresh coat of oil to brighten it up. The wood (which absorbed the initial treatments of plain linseed oil like blotting paper) has been given a new lease of life! One of the greatest benefits of linseed oil paints is that not only is it waterproof but it allows the wood to breath. So now you know; linseed oil is my secret weapon... it also smells great and leaves your hands beautifully soft too!Walls, Doors and Floors:
After going to all that trouble to design and build such a splendid dome, it felt a shame just to leave it lying on the ground where it might get kicked and wet (and overgrown in my garden!) Lifting it off the ground with walls seemed to be a sensible idea... but how many? I thought about building just one wall (circular, you dummies!) but felt that was a bit predictable and boring. Two walls would certainly be different, but a bit draughty. Eight walls seemed a nice compromise - four for north, south, east and west, and another four to fill in the gaps.
The next major decision was how tall should they be? Silliness aside, I checked the local planning laws which permit an erection without requiring a planning application to be lodged as long as it is not more than 25 square metres in area and not more than 4m high. I was safe with the observatory's footprint, but with the dome rising 7.5' (with a 6" overhang of the walls) I was limited to a wall height of just over 5.6' unless I sank the floor below ground level. That actually worked out very nicely as the doors to my small greenhouse and the fern-house are both just over 5' high and require you to stoop a little to enter. It lends a quaint old-world feeling to the garden. The observatory walls and doors would be in keeping! I planned to build the walls out of 4x2" studs clad in T&GV planking on the outside and thin cedar strip on the inside. The floor would be T&G planking over 2x6" floor joists on 20" centres.
Bill of Materials:
With all the major dimensions worked out I could now draw up a list of materials needed to build this monster and work out just how much it was all going to cost me. This is where things get ugly and I began to get a crimping sensation in my sphincter!
Dome Construction Materials:
€431.73 for 8 x sheets 4'x8' x 18mm Marine Ply (for dome rings)
€460.53 for 22 x sheets 4'x8' x 6mm Marine Ply (for dome panels)
€ 83.73 for 4 x sheets 4'x8' x 6mm Marine Ply (for telescope tube)
€110.72 for 3 x sheets 4'x8' x 12mm Marine Ply (for dome ribs)
€110.72 for 3 x sheets 4'x8' x 12mm Marine Ply (for telescope tube)
€115.20 for 8 x 4.8m lengths of 6"x2" floor joists
€207.36 for 18 x 4.8m lengths of 4"x2" studs
€470.40 for 56 x 4.8m lengths of 5" T&G planking (floor + walls)
€ 40.00 for 8 x 600mmx600mm concrete paving slabs (foundation load spreaders)
€174.24 for 150m or 1"NG polythene tube for underground cable duct.
€14.31 for 2 rolls of orange builder's twine for cable duct pull-thru.
€39.95 for 5 litres of waterproof wood glue.
€257.95 for 22 sheets of 4'x8' x 4mm WBP Ply (cladding for inside of the dome)
€39.95 for another 5 litres of waterproof wood glue - gotta stop sniffing this shit!
€272.90 for another 13 6"x2" floor joists, 30 joist hangers and nails. I forgot about these!
€46.21 for nuts, bolts and screws.
€9.68 for 16 300mm galvanised steel straps to hold the perimeter joists together.
€67.20 for 4 more 6" x 2" x 4.8m joists.
€70.62 for 10 litres of Protim wood preservative, brushes and floor brads
€19.44 for floor brads (for nailing the walls and floor.)
€19.40 for a roll of heavy duty builder's plastic for lining the walls and under floor.
€16.95 for welding rods - for the telescope tube assemblies.
€5.97 for 40 M4 x 20 machine screws for mirror cells.
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€3085.16 + blood, sweat, tears, labour and bananas for the bloody Orangutans!
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Control Hardware & Software:
€89.78 TheSky 6 (Serious Astronomer's Edition) Software Bisque ($129.00)
€56.00 Vellman USB Interface Kit
€00.00 Relays for dome motors
€30.00 Lesve Dome Driver Software
And so to work...
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