- This topic has 26 replies, 9 voices, and was last updated 17 years, 10 months ago by
Bruce R. Schaefer.
Bruce R. Schaefer.-
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Ed Dawson
I don’t think there is any “bashing” going on. Both PR and HM products are far better than the other options. Everything in this business will fail at some point.
I have heard some swear by one product versus to other. However, I am not yet swayed one way or the other. I have built with both and I like the “heavier feel” of the PR, but like I pointed out earlier, I’m not really convinced of one versus the other. I’ve also seen the filament wrap stuff break and when it goes – it really goes.
I suppose I’ll switch back and forth as the mood and desire to support both suppliers changes.
Supplpy has been an issue though. PR is never the most reliable when it comes to shipping (never put anything on back order) , but that might change now that Rockets is setting their stuff. I also hear that HM has been out of lots of inventory because of their recent move. It’s also been several days with no response since I sent them an email. Again, nothing is perfect.
Warren B. Musselman
From a purely structural engineering perspective, convolute wound tubing is considerably stronger than filament wound. The reason for this is that most of the load in convolute wound tubing is carried by the threads in the cloth. With Filament wound tubing, most of the load is carried by the epoxy. The question comes down to how it is fabricated. I saw Art’s convolute wound bird before and after the fracture and from all appearances, it should never have failed the way it did and was probably the result of a manufacturing defect.
However, that doesn’t mean that there is anything wrong with PF convolute wound tubing. Given the quantities and semi-hand layup used it is entirely possible that there was a dry spot or air bubble or some other problem with the individual piece of tubing he had and he should get a replacement or refund for it.
Warren
Ed Dawson
Wait, wait…. It was one of Art’s rockets that failed….
Perhaps there is a unknown trait whereby excess amounts of polish and wax can degrade the structural integrity of the glass.
Bruce R. Schaefer
Perhaps there is a unknown trait whereby excess amounts of polish and wax can degrade the structural integrity of the glass.
Can’t be serious. NOTHING on the outside of the glass will degrade it–other than a hammer. Actually, I think the paint job that Art did on my L3–nicest thing any other human being has ever done for me–made mine stronger. 😉 Why am I sounding like Rudolph Giuliani (you know, noun-verb-9-11… I’m sorry about how I keep mentioning my L3, but it was a lot of work… ‘nother issue).
Given the quantities and semi-hand layup used it is entirely possible that there was a dry spot or air bubble or some other problem with the individual piece of tubing he had and he should get a replacement or refund for it.
Well said, Warren.
Anonymous
Hawk vs. PR… here is how I see it:
–Advantage to Hawk on Customer service. You just never know with PR. While Curtiss is indeed getting better, it would be an understatement to say that he has a ways to go.
–Advantage to PR tubing when drilling holes. The filament wound is always delaminating for me. The Performance Rocketry tubing drills exceedingly cleanly
–Advantage to PR on things like nosecones. Ever try to match a cone to a HM 38mm tube? You have to build up the cone. The stuff from Curtiss is very nice, much selection
–I’d have to give an advantage to PR on strength. I have flown a LOT of miniimum diameter stuff on both, but I would never have felf comfy putting a full 98M in a HM tube. Regarding failures… SkyScraper folded during a M boost last year. That was filament wound tubing that failed. We saw another filament wound tube fail at BALLS this year. I’m going to do a 75mm minimum diameter project for BALLS next year. I’ll use PR tubing.
They are both great products. Alan does a nice job at HM, and for 95% of the projects out there, either will do just fine.
Bruce R. Schaefer
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.
Anonymous
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
Warren B. Musselman
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
Dave Tjarks
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.
Doug Gerrard
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
Ed Dawson
Warren B. Musselman
Bruce R. Schaefer
Anonymous
Dave Tjarks
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