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#1576 B.C. Arnot

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Posted 08 September 2020 - 01:01 PM

Hi, what is the process for sealing with fiberglass and resin? Is this a cloth that you wrap around the cardboard tube?

You get a mat of fiberglass (not the woven type but the one with strands), Bondo sells them. Get Bondo Fiberglass resin and poor the resin into a disposable cup and add the appropriate amount of drops of liquid hardener in the cup. Take a Disposable chip brush and with the fiberglass laid on top of the concrete form tube, work it into the fiberglass. You have 15 minutes of work time to get everything in that cup onto the fiberglass, so work In small portions. Once you’re done, let it cure and then sand with 80 grit. After sanding, use Bondo Glass filler to fill in the voids. Sand smooth with 120 grit, then 220. Fill any fine holes from the bondo with regular Bondo then sand again with 220 and finally 400 grit and apply etching primer and spray paint with whatever color you want, I chose white. 


Edited by B.C. Arnot, 08 September 2020 - 02:34 PM.

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#1577 macdonjh

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Posted 08 September 2020 - 09:51 PM

You get a mat of fiberglass (not the woven type but the one with strands), Bondo sells them. Get Bondo Fiberglass resin and poor the resin into a disposable cup and add the appropriate amount of drops of liquid hardener in the cup. Take a Disposable chip brush and with the fiberglass laid on top of the concrete form tube, work it into the fiberglass. You have 15 minutes of work time to get everything in that cup onto the fiberglass, so work In small portions. Once you’re done, let it cure and then sand with 80 grit. After sanding, use Bondo Glass filler to fill in the voids. Sand smooth with 120 grit, then 220. Fill any fine holes from the bondo with regular Bondo then sand again with 220 and finally 400 grit and apply etching primer and spray paint with whatever color you want, I chose white. 

Thanks for that.  I didn't know Bondo made resin.  I might do that to repair an OTA I've made too many holes in.  It sounds like you'll get a fairly thin layer of fiberglass.  My OTA is damp-proof and structurally sound, just reminiscent of Swiss cheese.



#1578 B.C. Arnot

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Posted 08 September 2020 - 10:32 PM

Thanks for that.  I didn't know Bondo made resin.  I might do that to repair an OTA I've made too many holes in.  It sounds like you'll get a fairly thin layer of fiberglass.  My OTA is damp-proof and structurally sound, just reminiscent of Swiss cheese.

Yeah Bondo makes fiberglass kits. There are two kinds, mats and cloths. The mats are loose strands weaved into a thin mat where the cloth is woven into a thick fabric. Whichever you get they are sold separately with the Bondo Resin and Bondo Resin Hardener. For you, I would just use Bondo Glass to fill in any drilled holes and then sand flush. If you put a fiberglass mat down on your scope just to cover a few holes, the body of your scope will no longer be flush. The fiberglass job is for layering or fixing large holes, say if you are sealing up a 2” bored hole to make a 1.25” hole. Also keep in mind fiberglass repair works well on composite materials, especially ones where the resin can soak into, but not so well on metal surfaces.



#1579 musicengin

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Posted 10 September 2020 - 08:29 AM

If you put a layer inside as well as outside, fiberglass repair works nicely for metal. Feather the edges and primer, paint or clearcoat over to make sure the fiberglass doesn't lift away from the metal.


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#1580 B.C. Arnot

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Posted 11 September 2020 - 02:47 AM

If you put a layer inside as well as outside, fiberglass repair works nicely for metal. Feather the edges and primer, paint or clearcoat over to make sure the fiberglass doesn't lift away from the metal.

I would make sure the metal surface is scuffed with 120 grit so the fiberglass resin has something to bite into and not have any chance of lifting. It will allow for a stronger bond and have a solid foundation to work with. Make sure to clean the surface with denatured alcohol after sanding before applying the resin with the fiberglass mat.

 

I would still recommend just using the regular Bondo or Bondo Glass if all Macdonjh needs to do is fill in a few drilled holes if they aren’t that big in diameter, then sand smooth and repaint. It’s easier to use, cheaper and less labor intensive. I would only go with the fiberglass method if the affected area was big. 


Edited by B.C. Arnot, 11 September 2020 - 03:32 AM.


#1581 macdonjh

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Posted 11 September 2020 - 08:17 AM

If you put a layer inside as well as outside, fiberglass repair works nicely for metal. Feather the edges and primer, paint or clearcoat over to make sure the fiberglass doesn't lift away from the metal.

 

 

I would make sure the metal surface is scuffed with 120 grit so the fiberglass resin has something to bite into and not have any chance of lifting. It will allow for a stronger bond and have a solid foundation to work with. Make sure to clean the surface with denatured alcohol after sanding before applying the resin with the fiberglass mat.

 

I would still recommend just using the regular Bondo or Bondo Glass if all Macdonjh needs to do is fill in a few drilled holes if they aren’t that big in diameter, then sand smooth and repaint. It’s easier to use, cheaper and less labor intensive. I would only go with the fiberglass method if the affected area was big. 

Thanks to both of you.  My OTA is phenolic-impregnated paper (a Proto-star Blacklight tube).  Since it already has flocking/ light trap on the inside, I don't want to completely line the inside if I don't have to.  I thought about simply using Bondo (I used that as filler for the spiral grooves), but was concerned about it falling out of the holes, since it would really just be a plug in each hole.  The holes aren't big, 1/8" - 1/4" (3mm - 6mm) diameter.  What I had decided on was using some flocking (perhaps with some fine wire mesh) inside the OTA as a backer and then using Bondo to fill the holes.  Sand, prime and repaint. 

 

I might even sand all the existing paint off so I can fill the spiral grooves again because I didn't get them to quite disappear when I painted the first time.



#1582 B.C. Arnot

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Posted 11 September 2020 - 11:00 AM

Thanks to both of you.  My OTA is phenolic-impregnated paper (a Proto-star Blacklight tube).  Since it already has flocking/ light trap on the inside, I don't want to completely line the inside if I don't have to.  I thought about simply using Bondo (I used that as filler for the spiral grooves), but was concerned about it falling out of the holes, since it would really just be a plug in each hole.  The holes aren't big, 1/8" - 1/4" (3mm - 6mm) diameter.  What I had decided on was using some flocking (perhaps with some fine wire mesh) inside the OTA as a backer and then using Bondo to fill the holes.  Sand, prime and repaint. 

 

I might even sand all the existing paint off so I can fill the spiral grooves again because I didn't get them to quite disappear when I painted the first time.

You have a pic you could show us of your telescope with these holes? I could take a look and use my best judgement to see what would work well for it. 



#1583 cuzimthedad

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Posted 11 September 2020 - 11:28 AM

We should get back on topic here as this is not really a discussion thread. Maybe starting a new topic would be in order now.


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#1584 Matej

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Posted 11 September 2020 - 12:10 PM

This is the telescope I build for my son a few years ago. The objective is 90/900 Meade bought for some 20$ on eBay. There is a prism hidden in the tube as could be seen on pictures. I like to use paper rolls for the tube as they are cheap, easy to be get and wrought, being available in dozens of lengths and diameters. I have been using this material since the sunny days of my childhood when nothing seemed to be a problem until the present day to my full satisfaction; most of those telescopes being in service even nowadays. This is a kind of telescope anyone could afford, while the moments underneath the clear skies offering bottomless ocean of beauty could not be bought for any money.
https://refraktorian..._lll/1301546818

Edited by Matej, 11 September 2020 - 12:12 PM.

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#1585 macdonjh

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Posted 11 September 2020 - 06:01 PM

You have a pic you could show us of your telescope with these holes? I could take a look and use my best judgement to see what would work well for it. 

PM sent.



#1586 jvrsluys

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Posted 14 September 2020 - 06:57 AM

Hi Folks,

 

this one took 16 years to complete, but last weekend I finally managed to get it assembled: a 125mm f/8 doublet refractor. 

 

The tube is entirely made of wood: small strips of pine, glued together to form a perfect cylinder. 

The baffle is made out of airplane plywood.

The rest is a mix of different DIY techniques: laser cutting for the internal baffles, 3D printing for the lens cell and the focus adapter, CNC milling of different flanges, tube rings and mounting plate, and of course good old fashioned planing, sanding and drilling.

 

There is still some work left, like varnishing the tube and finalising the baffle. But at least I could have first light yesterday on the sun (she is boring these days...) and perform a star test last evening. Stars looks nice, just need some fine tuning on the collimation.

Oh well, just a few more years to go...  wink.gif

 

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Edited by jvrsluys, 14 September 2020 - 06:57 AM.

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#1587 dawsonian2000

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Posted 14 September 2020 - 05:41 PM

Homemade 6" f/8 Newtonian Reflector out of concrete form tubing and weather sealed with fiberglass and resin, coated with oil-based paint. The mount is a homemade tripod mount using schematics from Vega Sky Center with some personal liberties taken, using a combination of redwood, pine and hickory, with the base and cradle made from 3/4", 1-1/2" and 2" cabinet grade plywood. The GEM is made of 1-1/4" pipe fittings with PVC bushings bored to allow PTFE sleeve bearings to accommodate the 3/4" pipe.

Awesome job, Brian! I am truly appreciative that you used my design and added features to make it your own! It makes me so amazed that the North Star II field tripod designs are being utilized by others within the ATM community. I could not be any happier!

 

I see that you designed your tripod for your homemade 6" f/8 Newtonian and pipe GEM. And they look fantastic sitting atop your tripod! Congratulations!!!

 

Well, strangely enough, I just completing building a 10" f/4.7 Newtonian for my friend, brother and colleague Gary Barabino. I just completed it on Saturday 09/12/2020, which I built and gifted to him while he was visiting. And it is seen here in this photo with Gary looking through it sitting atop the actual North Star II Field Tripod I created and showcased on the Vega Sky Center website; for which you designed yours from!

 

Congrats and thanks again for sharing your wonderful tripod to the astronomical community and for using my design! What a blessing!

 

If possible, please send me some photos and some details on its construction. As time permits, I would love to feature it on the VSC website. It can only be inspiring to other amateurs looking to build a tripod of their own.

 

 

Thanks a million!!!

Mel

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Edited by dawsonian2000, 15 September 2020 - 05:11 PM.

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#1588 dawsonian2000

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Posted 14 September 2020 - 06:01 PM

Awesome job, Brian! I am truly appreciative that you used my design and added features to make it your own! It makes me so amazed that the North Star tripod designs are being utilized by others within the ATM community. I could not be any happier!

 

I see that you designed your tripod for your homemade 6" f/8 Newtonian and pipe GEM. And they look fantastic sitting atop your tripod! Congratulations!!!

 

Well, strangely enough, I just completing building a 10" f/4.7 Newtonian for my friend, brother and colleague Gary Barabino. I just completed it on Saturday 09/12/2020, which I built and gifted to him while he was visiting. And it is seen here in this photo with Gary looking through it sitting atop the actual North Star Field Tripod I created and showcased on the Vega Sky Center website; for which you designed yours from!

 

Congrats and thanks again for sharing your wonderful tripod to the astronomical community and for using my design! What a blessing!

 

If possible, please send me some photos and some details on its construction. As time permits, I would love to feature it on the VSC website. It can only be inspiring other amateurs looking to build a tripod of their own.

 

 

Thanks a million!!!

Mel

BTW!!! - The Newtonian I built for Gary is comprised of a genuine Cave Astrola fiberglass main tube (with aluminum end rings) and rotating rings, which I customized to attach to an ADM D-Series dovetail bar with radius blocks utilizing the original 3/8" studs on the rings. The optics are 10" f/4.7 primary and 2.27" secondary installed inside the main tube using a hybridized Synta spider assembly modified with Kenneth Novak spoke tips and the primary mirror mount made by Optical Supports; a company once owned by an old friend Kurt Walker.

 

First Light was performed under windy conditions as Hurricane Sally was making her move into the Gulf of Mexico. Nevertheless, the views of Jupiter, Saturn and Mars where spectacular during moments when the winds died down.

 

 

Thanks, and Congrats again on the tripod build Brian!

Mel


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