You know, Ed, the more I think about it, you may be right. Art's finish was so slick it had to take a lot of rubbing to get it that way. Probably heated up the epoxy and caused it to fail. You know, the thing that's really sad is all the work Art put into it. Just getting his money back won't come close to covering it, not to mention doing what he was intending to do.

JW, the things you said are true. I'd forgotten about the difficulty of drilling into FW. I still have a loose filament where I drilled a vent hole on one of the rockets I mentioned earlier. And, there are those that may remember this, when I was sanding the upper airframe (of that rocket I ended up flying in June) trying to loosen the nosecone fit, all PR G-10, I joked that when I hit my leg I'll stop. I mean I really took a lot off from the inside, where the harness was going to (and did) rub and stress it out. It was amazingly strong stuff. Even picked up a few rocks as it was dragged across the grasslands. Only minor scratches, no dings, no gouges, all structurally sound. Also, what you mentioned about FW folding is probably what James was talking about. And, I certainly didn't have ANY problems with the fit of all the PR tubes, bulkplates, engine mount centering rings, and couplers. All perfect.

All good comments. They both make terrific products. I've used HM on several J570 minimum diameter boosts and never had a failure. This is a 25 oz rocket, minimum diameter, and a J570. LOTS of stress. SkyScraper was a lot taller and it had some "slop" after several flights which no doubt contributed to the failure.

The drilling thing (on filament wound) is a mess. I have tried drilling at different speeds, types of bits, taping before drilling, etc. The danged delamination is a mess.

Incidentally, it seems like HM 38mm tubing has the same wall thickness as the 98mm, which seems a bit odd to me? You'd think it would scale up?

Also, in the neener-neener-neener dept 🙂 I scored some 29mm glass tubing. Very rare stuff. I'm going to use it on a dart. It, too, has the thick wall. Very, very nice.

JW

HM makes two grades of 98mm tubing. The thin wall stuff you have is generally assumed to be for motor mount tubes. There is a heavier wall product meant for high performance airframes.

I've got a piece of 29mm HM FWFG as well... Saving it for an I200 bird.

Warren

As far as Daves failure it was nothing more then a failure of the recovery harness that was past its due date and a booster section that came in from a pretty high altitude ballistic and was broken on impact. It happens and most rockets that come in be it partially or whole ballistically dont survive.

Conway

Yes, my failure was due to the harness not holding up its end of the bargin and yes it did drop in from quite a ways up. But it wasn't ballistic, it was falling flat the way a good section should. Splintered the daylights out of it. Not really what I was expecting. With other types of tubing I would have been able to whack off the bad section and glue on a replacement.

The drilling thing (on filament wound) is a mess. I have tried drilling at different speeds, types of bits, taping before drilling, etc. The danged delamination is a mess.

I had to get the right tools but I don't have a problem drilling holes in the tubing.

Doug

Well don't keep us in suspense - What are the right tools for drilling clean holes in filament wound fiberglass?

Warren

If you've worked with G10 you are probably already aware that toothed instruments such as saw blades, and drill bits, absorb almost all the heat generated since the G10 is such a great thermal insluator. So you burn up a lot of blades and bits. However, you can sand or grind G10 just fine.

I use Diamond bits for cutting slots and drilling holes in the tubing.
Here is a link for diamond cutoff wheels for your Dremel tool:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=31501

Here are two links for some diamond drill bits
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=36252
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=32351

There are other places to get these but they frequently go on sale at Harbor Freight. Often I may start a hole if a smaller size twist drill bit but then use a the diamond bits for the correct size you want. Since they sand the tubing it leave smooth holes. For very large holes use a sanding drum.

Doug

But, Doug, filament wound isn't G-10. I thought only convolute is G-10. Or did I just learn something new?

G-10 and G-11 (Glass Cloth / Epoxy Resin)
These glass-epoxy laminates are specified for their extremely high strength and high dimensional stability over temperature. G-10 and G-11 are used for terminal boards, high humidity applications, electrical and electronic test equipment and electric rotor insulation. G-10 and G-11 are difficult to cut or machine and may require special equipment. G-10 is slightly stronger while G-11 is a better insulator and can take higher temperatures. FR-4 is a fire-retardant G-10 glass-epoxy laminate that is used primarily in the printed circuit board industry.

The thing I like about cutting it is that it smells like a circuit board. I guess I can assume that both FW and C both are/ or can be G-10?

I guess I can assume that both FW and C both are/ or can be G-10?

I guess I have made that same assumption as well. I know it has fiberglass and epoxy and the best way I found to cut that is with the diamond bits. BTW, they work very well on carbon products too.

Doug

What makes a material G10, G11 or G12 or their corresponding fire ratings of FR4 FR5, etc. is the epoxy that forms the substrate and the way they are manufactured. It has to do with fire rating so the epoxy has EVERYTHING to do with it. Also, typically G10 circuit board material at least is compressed during layup with several thousand PSI of pressure.

Warren

Actually G10 comes in many forms be it Sheet/FW/CW products. G10 is a rating of the glass its strength and temperature abillities. So all the above can be G10 or other ratings dependant on the materials used. Normally G10 is tougher and has higher heat abillities. Its also harder to cut drill and ect.

Thanks, guys! Doug both you and Chris LaPanze mentioned the right diamond cutting wheels for fiberglass. I finally went out today, in the snow, and bought the right ones. I used #409 before and while that one works, you'll chew 'em up. Diamonds aren't just for our girls. 😉