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#21
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I agree with Bob ... the numbers seem very low. However I have little doubt
that a production airplane will have less rivets than most homebuilts. In general homebuilt airplanes tend to be quite complex in their construction ... there are more bits in the firewall of an RV-6 than an entire C-150 fuselage (OK maybe a little exageration but not too far wrong). There are several reasons for this: (a) Designers of homebuilts don't have access to production tooling such as guerin presses to make firewalls in a single piece. Consequently they use more, simpler to make pieces, which need more rivets. (b) In general designers of homebuilt airplanes are not as focused on refining the product for production ... if you work for C, B or P etc then you need to design lean for production. You also have the facilities, budget and extensive test programs to help refine the design. The big companies in some cases design unconservatively and then beaf up the structure where it fails. Homebuilt designers in general design conservatively and cannot afford for a part to fail during test. (c) Few homebuilts are subject to extensive structural analysis and consequently the designers has no idea what the margins are re rivet shear and inter-rivet buckling etc so they have no choice but to stick to the typical minimum rivet spacings. I think it would be safe to say that you could not produce many homebuilts economically .. they are simply over built and their crudeness, whilst good for homebuilders is not suited for volume production .... the number of rivets is a huge cost driver WRT to cost of production since the labour in any airplane will be the most significant single cost in its production. That is why stir friction welding is being used in the Eclipse business jet. There are some exceptions to my generalisation re homebuilts being more complex that factory produced airplanes. The MM-I for example is an elegantly simple airplane with a minimum number of bits - but then Dave Long was a Piper design engineer. The T-18 is also a very simple airplane ... of course John Thorp also had a background in the design of airplanes for production. I think it all comes down to the designers background. "Bob K." wrote in message oups.com... Earlier, Brian Sponcil wrote: ...I recall the builders telling me that their RV kits have around 10,000 rivets. Compared to a Piper Comanche at 3,714 and a Warrior at 1,785 that's a heck of a lot of rivets. I've seen various RVs, Cherokees, and Comanches. I've kitted rivets for HP-series sailplane kits. And I just plain do not belive those numbers for the Warrior and Comanche. Not for relatively conventional riveted aluminum airplanes with few composite components and no metal-to-metal bonding. Until it's demonstrated otherwise, I propose that someone has cooked the books on this one to make for a good story. Consider the Warrior wing: Let's guess that the rib spacing is a relatively lean 12" OC. Let's guess that the rivet spacing is an equally lean 2". The span of the metal stuff (minus fiberglass tips) is probably about 32". Taking the fuselage out probably leaves room for at least 14 ribs on a side. The wing area of 170 ft^2 over the span of 35' yields an average chord of about 58". Since the skins are riveted top and bottom, I think that there are going to be about 58 rivets per wing rib. So that yields at least 58*30 skin-to-rib rivets, and that's 1740. Admittedly, that's a pretty rough estimate, and disregards the (probably negative) contribution of the flaps and ailerons to the rivet count. But it's a start. When you factor in the rivets between the spar and the skin, between the ribs and the spars, and for the many inspection panel rings, stringers, and other local additions, you see you can easily exceed the stated rivet count for the wings alone. And you've still got an entire fuselage and set of tail surfaces to go. And also the extremely close-pitched rivets around the baseball-stitched fuel tanks, and other miscellanea. I'll change my mind if, when I next see a warrior, I see fewer than 28 wing ribs or greater rivet spacing than 2". But until then, I'm not convinced. Thanks, and best regards to all Bob K. http://www.hpaircraft.com |
#22
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On Thu, 30 Dec 2004 16:57:26 +0800, Stealth Pilot wrote:
On Wed, 29 Dec 2004 04:39:06 GMT, Ron Wanttaja wrote: 5. RVs seem to use rivets *everywhere*...perhaps the Pipers use more bolts, molded sections, etc. a piper cherokee has literally a plastic bucket full of bolts in it. ...as we found out during a restoration. Hopefully, you didn't have half a bucket left when you were done. :-) Ron Wanttaja |
#23
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On Thu, 30 Dec 2004 15:01:52 GMT, Ron Wanttaja
wrote: On Thu, 30 Dec 2004 16:57:26 +0800, Stealth Pilot wrote: On Wed, 29 Dec 2004 04:39:06 GMT, Ron Wanttaja wrote: 5. RVs seem to use rivets *everywhere*...perhaps the Pipers use more bolts, molded sections, etc. a piper cherokee has literally a plastic bucket full of bolts in it. ...as we found out during a restoration. Hopefully, you didn't have half a bucket left when you were done. :-) Ron Wanttaja no, :-) but there are two unique washers. hemispherical that sit in a hemispherical socket down in the stabilizer attach area. I think a fundamental law of physics exists that one will remain faithfully in the bucket during all cleaning, drying and sorting activities while the other must hide itself in the crack between two sections of concrete just under the stabilizer. the jones theory of special aviation fittings :-) Stealth (dont design special one-off fittings into aeroplanes!) Pilot |
#24
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Well yea, but that's what I thought Brian had a problem with, i.e., not
how many rivets are in the aircraft, but how many he personally had to set. With the QB kit, the number of rivets the builder has to set is inconsequential. MJC "Matt Whiting" wrote in message ... MJC wrote: ... or it that's a "problem" for you, do what I did. RV7-A Quickbuild kit. Poof; lot's less rivets :-) I thought the design was the same and hence the same number of rivets ... just fewer for you to set! :-) Matt |
#25
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Flush rivets are weaker so it takes more. smaller spacing between rivets,
means fewer wrinkles or puckers. "smjmitchell" wrote in message ... I agree with Bob ... the numbers seem very low. However I have little doubt that a production airplane will have less rivets than most homebuilts. In general homebuilt airplanes tend to be quite complex in their construction ... there are more bits in the firewall of an RV-6 than an entire C-150 fuselage (OK maybe a little exageration but not too far wrong). There are several reasons for this: (a) Designers of homebuilts don't have access to production tooling such as guerin presses to make firewalls in a single piece. Consequently they use more, simpler to make pieces, which need more rivets. (b) In general designers of homebuilt airplanes are not as focused on refining the product for production ... if you work for C, B or P etc then you need to design lean for production. You also have the facilities, budget and extensive test programs to help refine the design. The big companies in some cases design unconservatively and then beaf up the structure where it fails. Homebuilt designers in general design conservatively and cannot afford for a part to fail during test. (c) Few homebuilts are subject to extensive structural analysis and consequently the designers has no idea what the margins are re rivet shear and inter-rivet buckling etc so they have no choice but to stick to the typical minimum rivet spacings. I think it would be safe to say that you could not produce many homebuilts economically .. they are simply over built and their crudeness, whilst good for homebuilders is not suited for volume production .... the number of rivets is a huge cost driver WRT to cost of production since the labour in any airplane will be the most significant single cost in its production. That is why stir friction welding is being used in the Eclipse business jet. There are some exceptions to my generalisation re homebuilts being more complex that factory produced airplanes. The MM-I for example is an elegantly simple airplane with a minimum number of bits - but then Dave Long was a Piper design engineer. The T-18 is also a very simple airplane ... of course John Thorp also had a background in the design of airplanes for production. I think it all comes down to the designers background. "Bob K." wrote in message oups.com... Earlier, Brian Sponcil wrote: ...I recall the builders telling me that their RV kits have around 10,000 rivets. Compared to a Piper Comanche at 3,714 and a Warrior at 1,785 that's a heck of a lot of rivets. I've seen various RVs, Cherokees, and Comanches. I've kitted rivets for HP-series sailplane kits. And I just plain do not belive those numbers for the Warrior and Comanche. Not for relatively conventional riveted aluminum airplanes with few composite components and no metal-to-metal bonding. Until it's demonstrated otherwise, I propose that someone has cooked the books on this one to make for a good story. Consider the Warrior wing: Let's guess that the rib spacing is a relatively lean 12" OC. Let's guess that the rivet spacing is an equally lean 2". The span of the metal stuff (minus fiberglass tips) is probably about 32". Taking the fuselage out probably leaves room for at least 14 ribs on a side. The wing area of 170 ft^2 over the span of 35' yields an average chord of about 58". Since the skins are riveted top and bottom, I think that there are going to be about 58 rivets per wing rib. So that yields at least 58*30 skin-to-rib rivets, and that's 1740. Admittedly, that's a pretty rough estimate, and disregards the (probably negative) contribution of the flaps and ailerons to the rivet count. But it's a start. When you factor in the rivets between the spar and the skin, between the ribs and the spars, and for the many inspection panel rings, stringers, and other local additions, you see you can easily exceed the stated rivet count for the wings alone. And you've still got an entire fuselage and set of tail surfaces to go. And also the extremely close-pitched rivets around the baseball-stitched fuel tanks, and other miscellanea. I'll change my mind if, when I next see a warrior, I see fewer than 28 wing ribs or greater rivet spacing than 2". But until then, I'm not convinced. Thanks, and best regards to all Bob K. http://www.hpaircraft.com |
#26
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On Mon, 03 Jan 2005 02:41:38 GMT, "Cy Galley"
wrotD: Flush rivets are weaker so it takes more. A&P school was 35 years ago, but if memory serves it's the diameter and material of a rivet that sets the strength and not the head type as they are basically a shear loaded device. Spacing is set based on rivet diameter irrespective of head type. Posted Via Usenet.com Premium Usenet Newsgroup Services ---------------------------------------------------------- ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** ---------------------------------------------------------- http://www.usenet.com |
#27
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Date: 12/30/2004 09:01 Central Standard Time
Message-id: On Thu, 30 Dec 2004 16:57:26 +0800, Stealth Pilot wrote: On Wed, 29 Dec 2004 04:39:06 GMT, Ron Wanttaja wrote: 5. RVs seem to use rivets *everywhere*...perhaps the Pipers use more bolts, molded sections, etc. a piper cherokee has literally a plastic bucket full of bolts in it. ...as we found out during a restoration. Hopefully, you didn't have half a bucket left when you were done. :-) Ron Wanttaja They use buckets in their construction? Dan, U.S. Air Force, retired |
#28
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