Homemade Carbon Fiber OTA Tubes?

[KenMiller]

[quote=Bob_riggs;1839]How do you come up with this stuff, anyway...lol?/quote]

www.Google.com

[Gary Beal]

Originally Posted by Bob_riggs

Gary, I certainly agree with Jim. You did a fine job, indeed! Jim mentioned the need for end rings for support. Do you feel they would be helpful, or is your tube sufficiently rigid?

Jim, thank you for your input, and suggestions.

Ken, the article you shared along with Gary's encouraging success story is just what I needed. Making a female mold is something I had not considered. And, there is a lot of good information in it which I, and others, will find most helpful.

It sounds very "doable". Thanks, guys!

Clear Dark Skies!
Bob

Bob,
I ended up with an extra layer inside on both the ends, so effectively a layer of fiberglass, a layer of Kevlar, and a layer of Carbon Fiber, from the inside out. I actually had a strip of alloy perhaps 25mm x 3mm, and bent this into a hoop, with the idea of fiberglassing this into place as "inside end stiffeners". In the end (ha, no pun intended), I just used the fiberglass strip (maybe 75 wide??), and that gave it enough stiffness. Yep, if you sit on it, it will bend and or break, but I am happy with it. The interior ring baffles I suppose stiffened the whole lot as well.
I haven't read the article, but in my case the mold was male, not female, although I don't want to get into a battle of the sexes here.
Gary

[Drkxrider]

Bob,

Being somewhat of a newcomer to the forums, this is my first post. I see that the last one to your question was in March. If you have started project I wish you good luck, If not maybe I can offer you some insight from my experience (experiment) with carbon fiber.
I too was looking for a lightweight alternative to the more common aluminum and sonotube telescope tubes for my 10" mirror, carbon fiber seemed like the the way to go because of It's strength and rigidity.
Searching the internet for premade tubes produced no results, they were to small, except for one http://www.dreamscopes.com. At almost a $1000.00 for a 12" diameter x 48" long tube, I decided to give it a try myself.
There is a wealth of information on Shane's site about advanced composites. The most important being that strength comes from the fiber not the resin. If you have to worry about drips by letting your project be stationary, then you have to much resin applied. The idea is to wet it out just enough to get it wet throughly with resin and then squeeze out as much as you can, the whole purpose of vacuum bagging.
I wanted something simpler than having to make molds or bagging here's what I came up with.
I bought a Blacklite tube from Protostar http://www.fpi-protostar.com/blite.htm. It is a phenolic (impregnated kraft paper) tube that is pre flocked. Three yards x 50" of carbon fiber and resin came from Ebay. Foam paint rollers and paint tray from Home Depot.
I started out by making a couple of supports from plywood that I could slide inside of tube. They were 2" wide x the inside diameter. I then drilled a 1 3/8" hole in the center of the supports with a holesaw for a 1" pipe. I used two reel jacks (we electrican's use them to hold large spools of wire for pulling) to support the pipe and make it easy to spin the tube. Once tube was supported on the jacks I mixed up some resin and applied it to the tube with the foam paint roller. I let that set until tacky and applied another thin coat. Once tube was coated the second time, I started with the carbon fiber dry. I just layed it on tube, straightened it out, loaded paint roller with resin and as my wife turned tube I painted down the fiber with the roller. I did this for two layers with just the one load of resin and alot of pressure on the roller. After curing, tube weighs in at just under 8 lbs.
Total weight of telescope with mirror, cell, spider, secondary and focuser under 20 lbs.
I hope some of this helps you. Here are a couple of pics of finished telescope.

Good luck and clear skies.
Don Reed

[Bob_riggs]

Hello Don!

A hearty welcome aboard AstroClassifieds to you! You'll find we are not as large as some but what we lack in quantity, we have in quality, and we are growing in both catagories.

Thank you for your information. Using a form which doesn't have to be separated from the finished tube makes great sense. The Protostar link is a winner!

Gary Beal's fine project had me really fired up to go for it, but smoothing out the butt of the edges of a linoleum male mold was vexing me. So, I've held off doing the project, looking for a better solution. Clearly, you seem (pun intentional) to have my answer.

Also, appreciate your pic's. That's some sweet setup you have there. Well done, sir!

Did you find the need for end rings or baffles for increasing ridgidity with your approach?

Thanks again, and CDS!

Bob

[Drkxrider]

Bob,

The phenolic tube is already quite rigid, much more than sonotube. The application of the carbon fiber only increases the rigidity. I found no need for any type of additional supports.
As far as baffles go, with the tube being flocked, I also saw no need for them.

Don Reed

[Gary Beal]

Hi Don
welcome aboard, like Bob said, a small but great bunch.
Nice looking tube, very nice. I took the approach that anything other than the C/F itself only added to the weight, so used the formica awkward method, but I must admit to having thought about a few smaller ones, and using your method of coating the former.
Gary

[Bob_riggs]

Originally Posted by Drkxrider

The phenolic tube is already quite rigid, much more than sonotube. The application of the carbon fiber only increases the rigidity. I found no need for any type of additional supports.
As far as baffles go, with the tube being flocked, I also saw no need for them.

Don Reed

Excellent, Don! Thanks again for your input. Did you happen to weigh the phenolic tube prior to adding the CF and after?

BTW, your quote from Einstein is so right on, great choice!

Cheers, and CDS!

Bob

[Drkxrider]

Bob,

No, I didn't weigh the tube before. I looked at the spec's on Protostars site and took that as what it was.
The BL-12 tube shows it at 1.8 lbs per foot X 4ft. = 7.2 lbs., which is what I bought. My mirror is a older Coulter that I had re-figured by Alan Raycraft,
10.1" F/4.46 so the 48"L Blacklite tube was perfect for me. As far as weighing it after, I did it the old fashion way. I got on the scale to see what I weighed , and then did it again holding the tube. The difference was almost 8 lbs.
I've attached a pic of thier weight comparison chart.

Don Reed

[Bob_riggs]

Excellent input, Don. Thanks again. I'm ready to get mine going.

CDS!

Bob

[Gary Beal]

Originally Posted by Bob_riggs

[font=System][color=blue]Excellent input, Don. Thanks again. I'm ready to get mine going.

Good one Bob, do what I didn't, get someone to take some pictures,
Gary