Paul WB
member
Reged: 01/10/05
Posts: 75
Loc: Ottawa, Ontario, Canada
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Thanks, Jeff, for your pointers. To use the fiberglass, I could attach the fiberglass matt to my plywood dome frame (staple it and stretch it out) or covering a hardboard/maisonite/thin-plywood shell, and then apply the polyester resin to the matt, and adding more layers of fiberglass material (like paper mache) to give it more strength.
Paul WB
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Vixen Sphinx SXW mount
C8 SCT, William Optics 102 ED refractor
SBIG ST-2000XM camera
Edited by Paul WB (01/12/06 12:29 AM)
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 3179
Loc: Ireland
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Paul --
You'd definitely need something behind the fiberglass matt (or cloth). Otherwise you won't be able to get the fibers sufficiently impregnated with the resin. This could be a mold (ie: something that gets removed later), or a structural part of the dome.
To have enough strength on its own, the fiberglass is going to need to be on the order of 1/4" thick. That's probably 6 to 8 layers of matt & resin, which is going to take a long time to lay up.
I'd be much more inclined to use hardboard/masonite/plywood for the structural strength and to provide a suitable substrate, and then add one or two layers of fiberglass for weathering (and to improve the shear strength of the joints in the substrate). The only downside is a bit more weight.
-- Jeff.
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-100 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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Paul WB
member
Reged: 01/10/05
Posts: 75
Loc: Ottawa, Ontario, Canada
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Thanks, Jeff.
That will be plan, then. Use hardboard/maisonite as the initial skin, and then add fiberglass matt layer(s) on top. Now, I have learn about how to fiberglass. Maybe, it might be nice to have a plywood skin, and have the fiberglass on as a clear coat, like they do with some boats.
Paul WB
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Vixen Sphinx SXW mount
C8 SCT, William Optics 102 ED refractor
SBIG ST-2000XM camera
Edited by Paul WB (01/12/06 09:41 AM)
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Snow dog
Carpal Tunnel
Reged: 07/17/05
Posts: 1716
Loc: Alberta Canada
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One more Tip on the fiberglass. You need to pick up a special roller that you use to "roll out" the fiberglass and air bubbles. You can use a brush and stab at it to saturate it but I have found that if you take the fiberglass matt and lay it out on a table covered in clear plastic. Then mix up your resin and pour it out over the matt and use the brush to spread it out so it covers the whole piece you are laying up. Then pick up the plastic and matt as one piece and simply lay it over your frame. Then peel off the plastic and toss it aside and take your roller and work the matt like you would if you were painting with it. You can visually see when the matt is completely saturated and the air is out of it. It will have a "milky" look in spots that are not fully wetted out. Add more resin and roll out these areas. Be sure to have a container with Acetone in it nearby. After you get the matt all wetted out and conforming to your frame then put the roller in the Acetone to keep it from becoming unusable. This roller is an aluminum roller that has many ridges on it. They vary anywhere from 1/4 inch to 1 1/2 inches or more depending on the area that you are doing. I'd go with one around 1/2 to 3/4 inch in diameter and around 5 inches wide. I will try to find one next time I get back home and put a picture of it up for you.
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Marc
Someone get these crazy dogs off me
12" LX200 Classic
ETX-90PE
Meade DSI
Canon AE-1, EOS Rebel 350
My Home Page
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tcraig
sage
Reged: 02/19/05
Posts: 423
Loc: Northern Indiana
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Paul
I did just what you are doing last spring. I ended up hand laying fiber for my 10' dome. It ended up pretty well. I built a plywood frame and then constructed concentric circles of steel high tension cable, stapled to the plywood. The stapled sections of fiberglass matt to it then applying resin using a brush. It is time consuming but I think worth
it. Below is a link to some pictures there are 3 pages of them. If you have any questions just let me know.
dome construction
Tcraig
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LXD75-SN10
Etx-60
LPI
300D
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Paul WB
member
Reged: 01/10/05
Posts: 75
Loc: Ottawa, Ontario, Canada
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Thanks, Tcraig
I have purchased some fibreglass matt, and some cloth. I was thinking about making a wire frame, but I like your idea. Did you have to apply several layers of fiberglass?
Paul WB
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Vixen Sphinx SXW mount
C8 SCT, William Optics 102 ED refractor
SBIG ST-2000XM camera
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 Rick Needham
Vendor (ExploraDome)
Reged: 09/20/05
Posts: 1960
Loc: Fort Ann, NY
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Quote:
Paul
I did just what you are doing last spring. I ended up hand laying fiber for my 10' dome. It ended up pretty well. I built a plywood frame and then constructed concentric circles of steel high tension cable, stapled to the plywood. The stapled sections of fiberglass matt to it then applying resin using a brush. It is time consuming but I think worth
it. Below is a link to some pictures there are 3 pages of them. If you have any questions just let me know.
dome construction
Tcraig
Tcraig, What did you use to sheath your walls with? Doesn't look like plywood...but I could be wrong. Care to share this information with us? Thanks!
Rick
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Rick
Lat. 44.18 N
Long. 74.31 W
6" STAR HOC f/5 Newtonian 'Amanda'- Orion Astroview w/ dual axis drives
Celestron NexImage CCD Imager
10x50 binocs
(NSO)Northern Skies Observatory...I'm finally domed with the 8' diameter Explora-Dome!!!
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tcraig
sage
Reged: 02/19/05
Posts: 423
Loc: Northern Indiana
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I just laid up the fiber matt directly on the wire. Some of the pictures kind of show this. I didn't have any kind of sheathing. I had plywood arches around the dome. Then stapled on concentric rings of wire. Then just stapled the fiber matt directly to this. Then just wetted it down in sections with a brush. Inside and out. If I ever do it again I would probably cut plywood gores to sheath it. This would help in getting the resin to penetrate better. Also it would help hold shape better. I did have a few spots that wanted to sag a little. I just cut them out and patched them.
Also keep in mind when finished with the resin coats, that you also need a gel coat to protect from UV.
Tcraig
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LXD75-SN10
Etx-60
LPI
300D
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Paul WB
member
Reged: 01/10/05
Posts: 75
Loc: Ottawa, Ontario, Canada
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Here is one picture of my plywood frame which I assemblied temporarily in my basement. I used clamps to keep it together.
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Vixen Sphinx SXW mount
C8 SCT, William Optics 102 ED refractor
SBIG ST-2000XM camera
Edited by Paul WB (01/18/06 03:27 PM)
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Snow dog
Carpal Tunnel
Reged: 07/17/05
Posts: 1716
Loc: Alberta Canada
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Nice frame..
I found one of my Fiberglass rollers. This is well worth the 8 to 20 bucks depending on what size you get. This is much easier than stabbing at a 3 foot square matt of resin with a brush trying to work the air out of it. Just soak in in Acetone right after you do each piece and shake it out before you start the next. Carefull that you don't get the Acetone in your eye's.
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Marc
Someone get these crazy dogs off me
12" LX200 Classic
ETX-90PE
Meade DSI
Canon AE-1, EOS Rebel 350
My Home Page
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prof.2
journeyman
Reged: 01/25/06
Posts: 5
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I recently read your question and would look up "glue and stitch" boatbuilding on the net. You can use lots of different core materials. I have built quite a few items using composites and would also recommend Progressive Epoxies. They have a website and are much cheaper than most advertised brands.
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Anonymous
Unregistered
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Has anyone considered using a sandwich lamination technique for their dome?
My other hobby is a homebuilt hovercraft. The structural pieces have to be very light and are made from 1/2" and 1" sheets of 4 lb/ft^3 closed-cell structural polyurethane foam with fiberglass (polyester laminating resin with 6 oz cloth or matt + cloth) applied to either side.
If I were at a point in my life where I could build a dome (lets hope within ten years?) I would start it just like Tcraig's with wood longerons: Then I would cut long triangular pieces of 1/2" foam and hot glue them in place between the wood frames (the thinner foam is pretty flexible). Then put a layer of matt and cloth on the outside for protection, and just cloth on the inside.
If you choose to use polyester resin, check out www.mertons.com. If you buy gallon jugs you don't have to pay hazmat shipping.
If you wanted a dome that was round and not faceted you could have a few more longerons and install the foam so the edges sat a bit outboard of the wood, then sand it round before you fiberglass (this stuff sands real easy!). Another option would be to make a mold and use gelcoat.
Dan
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Pedro Scorza
super member
Reged: 07/14/05
Posts: 140
Loc: Puerto Rico
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Yes, I used cored construction in my geodesic dome. Core was 1/4 Coroplast with E-glass and epoxy resin, for a very light 65 pound 8 ft dome including ring and shutter.
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LX-90
C102HD
SN-10 on Skyscan
PST 40
WO ZS 80FD
SXVF-M7,Pictor 216,Rebel 300
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Paul WB
member
Reged: 01/10/05
Posts: 75
Loc: Ottawa, Ontario, Canada
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Hello everyone
I just thought to post a picture of my observatory, so far.
Before applying the fiberglass, I had made a few plywood gores to add some extra surface area to apply the fiberglass matt. I stapled the matt on to the frame and then applyed polyester resin and fiberglass cloth. I added another layer of fiberglass clothn and then a very thin layer of cloth (almost like tissue paper), while applying lots of resin. I find the fiberglass to be very brittle. I have applied some primer paint and have applied some laytex paint to the dome (helps to fill in the gaps). The dome seems to be alright, but I wish it was a little smoother looking. I applying some elastic paint (used for RVs). Fiberglass is a pain to work with.  (smelly, expensive, and not cheap). Oh well, it looks not too bad.
Paul WB
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Vixen Sphinx SXW mount
C8 SCT, William Optics 102 ED refractor
SBIG ST-2000XM camera
Edited by Paul WB (06/09/06 02:37 PM)
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