I an anxious to see some answers. I to am getting ready to leave
paper on a future rocket.

I hope to hear from Art. H. During Oktoberfest He had an air
frame failure. I do not know what His was. But it did split.

I use Hawk Mountain tubing, never PR. I found the quality is much better with HM and Art's rocket is an example that many of you saw first hand. The PR tubing may be thinner walled which results in lighter weight but the tolerances are not as consistent resulting in frustration and more work.

Doug

You make an interesting point about the tolerances. I ordered a couple of replacement 4" PR couplers and they really don't match the original dimensions. I though it was just related the the moves to "thick wall" couplers.

Hawk Mountain airframe, filament wound airframe, convolute wound… All great products.

Performance Rocketry convolute wound airframe… Not so sure about. I had a 4” Performance Rocketry airframe crack and the crack went up the airframe a foot and a half. My failure WAS a fracture along the overlap of the inner layer of cloth. It was a week spot in the airframe (a defect). It was not a zipper, the shock cord didn’t cut the airframe, and there wasn’t even a charge or a parachute on the cracked side of the airframe.

The same kind of thing happened to a rocket that Dave Tjarks flew (D2). It was the same kind of airframe that I had but the incident was under different circumstances. Dave’s rocket hit the ground hard. The Performance Rocketry airframe cracked and split along the length of the airframe, while the Hawk Mountain would have just spiral fractured wherever the greatest stress was or where the weakest pint of the rocket was (EX. the empty space above the upper centering ring).

When I redo my rocket, I will use Hawk Mountain airframe or something that is not Performance Rocketry fiberglass airframe.

Art

Art and Others, Any and I repeat Any manufacture can and does make products that are defective from time to time. It happens. I have used LOTS of Hawk Mt/Giant Leap filament wound glass (BTW Hawk Mt last I knew only did filament wound and not convoloute) I have also used Lots of PR Convolute tubing Including My 6" diameter L3 rocket. I have abused them all and they all have breaking points. Heck my L3 rocket came in from 14K under a small drouge only and cracked a body tube in a weak spot I created as well as breaking the nose cone collar/coupler. But the heavyest part I thought that would break is the booster and not a crack anywhere. In fact I remeber when I had the motor melt into the rocket and I used the booster section like a fence post driver over a 4x4 piece of wood to pound the casing out for 2 hours strait and let me tell you I abused it every way i know how. Not a crack or issue. Again its PR tubing.

Now I will agree with Doug on one thing. Yes the tollerances are sometimes off. But not always. I would think this is to be expected with a "more so hand constructed" product then a mass produced machine made product like filament wound. If youve never seen the process of making either I higly recomend it. Very cool stuff. Past testing by rocket materials(a web site for the purposes of testing stuff to see their strengths) of Convolute has shown it is stronger for what we use it for in most cases. But again anything can fail and anything can have the abillity to be defective. The issues with Filament wound is spriral fractures. these are in essance a kink and cause a week spot in the air frame if severe enough I have seen it look like a bend. Ive also seen them not be visable and upon the next flight the rocket shreds. Filament has its limits as well.

I have had good luck with both and bad luck with both. I would not make any hasty desicions based on one or two issues anyone has had. 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.

Things I like about filament wound are its nice easy to finish product, Smooth inside thats seamless. (its there but you wont find it) works good with piston ejection set ups. Handle sizeable BP charges, comes in many sizes (but up to only so large in diamter it seems) pretty strong but nothing is bullent proof.

things I like about Convolute, Its stronger then filament. Will not spirial fracture, Comes in larger sizes, easy to finish like the filament, handles very large BP charges, again pretty strong but not bullet proof.

Whatever you chose I find glass to be the way to go. Ive pretty well left behind cardboard/phenolic or laminated air frames (except in super sizes) and do only Fiberglass airframes. They live longer handle more transportation abuse and seem to be less work.

Conway

My L3 was PR convolute G-10. No problems. I'm using it again on a similar but different rocket. Only time and abuse will tell. The difficult thing is finding any weak points BEFORE you fly. As Conway said and we all know, NOTHING is indestructible. We all saw Eric D's carbon fiber Tower of Power I absolutely disintegrate at Oktoberfest '06, and he came back a year later and made a fantastic and perfect L3 flight with Tower of Power II. Personally, I prefer convolute over filament wound, only because it seems to have "some" give to it. It's more resilient. However, what happened to Art makes me question PR now.

My L3 was PR convolute G-10. No problems. I'm using it again on a similar but different rocket. Only time and abuse will tell. The difficult thing is finding any weak points BEFORE you fly. As Conway said and we all know, NOTHING is indestructible. We all saw Eric D's carbon fiber Tower of Power I absolutely disintegrate at Oktoberfest '06, and he came back a year later and made a fantastic and perfect L3 flight with Tower of Power II. Personally, I prefer convolute over filament wound, only because it seems to have "some" give to it. It's more resilient. However, what happened to Art makes me question PR now.

Its understandable to question things when stuff happen. BUT I cant say as that I have heard that this is an issue all around the world with everything PR sells. I see plenty of their kits/parts fly and not a problem. Im not saying it just for the benefit of PR but in general for all products made. If the same thing happened with Hawk Mt tubing I would still be there to comment. Things happen and it seems in rocketry Boy do they. Lets just not have a knee jerk reaction to a situation is all. I mean that is why they have things called warranty and defective replacement all the time. Art have you contacted the Vendor/ and or Manufacture and asked for their help. I would put more of my decision based on how they handle this part of it then a single bad experience on a product. Just my 2 cents.

Good point, Conway. Art, it is CLEAR your PR tubing had a flaw, and if PR stands behind their products, they will not only replace it but will want the sample of tubing that failed, so they can prevent that from happening again. After this next rocket, I'm going to try a two stage Hawk Mtn rocket, only because I need a bird to fly J's & K's and want to do two stages. I have a GLR filament wound Rocky Mountain Thunderbolt that I've flown successfully, but I'm really going to stress it out next year. Notice that I'm not bashing Curtis of PR; very few people have had a good experience with him, and that's his fault. If his products weren't substantially good, he would have been long gone, for quality and for customer service. I deal with people who SELL his products, not him, personally. That wasn't a bash, just fact.

P.S.
Slipstick, you did well getting the PR G3 for your L2. Don't worry about it. And, I wish that JamesR would see this and post. He told me something about filament wound (FW), and I "think" it was that long FW tubes can snap. James didn't have a problem with C (convolute) G-10. I'll let him correct that. JW--who never does anything in long tubes did his 98mm O flight in FW, I believe, and it went perfectly at Balls. I'll let JW correct that. 🙂

I have built 2 hawk mountain airframed kits and the quality was exceptional. They are AMAZINGLY strong and everything fit beautifully. I have no experience with PR stuff.

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.

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

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.

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.

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.