VELLUM PAPER BODY TUBES FOR MODEL ROCKETRY This is a collection of rec.models.rockets discussion about making body tubes out of vellum paper. Vellum tubes are sometimes used to create very light-weight rockets for use in NAR competition. However, their usefulness is not limited to NAR competition, and a creative "scratch builder" will find that the tips and ideas presented here can be extended to other uses. Enjoy, Wolfram von Kiparski NAR 28643 ************************************************** Article: 16756 of rec.models.rockets From: mckiou@cbnewse.cb.att.com (kevin.w.mckiou) Subject: Re: Vellum rockets for Altitude... Date: Thu, 24 Mar 1994 19:04:10 GMT Message-ID: References: Lines: 32 In article billw@glare.cisco.com (William ) writes: >A while ago I asked about vellum rockets typically used by "serious folk" in >altitude and (small engine) parachute duration. One of the interesting >things was that the vellum tube was taped together rather than glued. > >Is the reason for tape structural or just convenience? I'm working on >something for which it would be more convenient to glue up a vellum tube. > >Thanks >Chops > mckiou@cbnewse.cb.att.com (kevin.w.mckiou) answers: I can't say for sure why the poster taped his/her rocket, but I suspect it was easier construction. It might even be lighter. For what it's worth, I did some experiments with vellum tubes prior to NARAM-33 to determine the strongest way to make them. Taping turned out to be quite a bit weaker than thinned yellow glue. So, what I did was cut the vellum so it would make two complete wraps around a form (BT-5 size brass tube) and then brushed thinned yellow glue on half (vertically) of it. I wrapped the vellum (actually Mike Jungclas and I did this) around the form and waited a few seconds for the glue to set, pulled it off and let it finish drying. We made up a bunch of these for PD/SD and Alt models. The glue tends to dry unevenly and warp the tube. So, what I did was to put the tubes back on the form and iron them with a Monokote iron. It worked great. They were straight light and strong. I never weighed the tubes to see which method was lighter. But the glued tubes were definitely much stronger. Kevin cujo@sage.cc.purdue.edu (Ryan Woebkenberg) answers: I knew a guy that used white glue to make paper tubes for scale models. I would think that using glue would make the tape joint nonexistant, therfore decreasing drag. maybee using a bunch of glue would add weight, the person that made the scale tubes soaked his in white glue, so that might add undesired weight. -- Ryan "Changing his major to drama." Woebkenberg jcr0599@ritvax.isc.rit.edu (John Viggiano) answers: I use the double sided tape normally supplied with the thin film covering for windows from 3M. It is narrow, holds very well, and is more convenient than glues. ************************************************ Article: 22947 of rec.models.rockets From: alway@tarle3.physics.lsa.umich.edu Subject: Vellum construction Date: 13 Sep 1994 16:34:16 GMT Lines: 205 Message-ID: <354ka8$qf1@srvr1.engin.umich.edu> lynell@cco.caltech.edu (Lynell K. Jackson) wrote: An aside. I have been collecting unwanted vellum lamination folders (used to protect the laminating machine from excess goo extruded from the edges of the transparencies) for experiments with rolling vellum rockets. Any tips to help get started? (please change the subject line if you respond to this question :-) Lynell Pete Alway (alway@tarle3.physics.lsa.umich.edu) answers: Here's something I pulled out of an old T Minus 5 file: Development of the Paper Tiger The Paper Tiger owes its origins to some good luck. By chance, I was able to obtain a state-of-the-art S6A model constructed by Ukrainian Yuri Gapon (see photo on page 10). This ship follows the current vogue of molding the entire airframe from fiberglass cloth and some sort of resin over a machined mandrel (form). This produces a very light and smooth model. However, the stiffness of the body tube leaves something to be desired, bearing more resemblance to a plastic bag than a rocket airframe. The valuable lesson I learned is that standard rocket construction materials are the moral equivalent of cast iron and boiler plate. The average model rocket is many times heavier than it needs to be to withstand the loads imposed on it during flight. I set myself the goal of matching Gapon's airframe weight of 4.14 g. This brings up another important point: a good scale is an invaluable tool for assessing the weight of new materials. Without accurate weight data, it's difficult to know if progress is being made toward lighter models. The other key ingredient is a notebook to record your observations and ideas. Initially, I intended to use balsa tubing rolled from 1/32" sheet as the basis of my airframe. This material is very easy to make and much lighter than kraft paper tubing. It has the additional advantage that it can be covered with Japanese tissue to produce a smooth, colorful, and lightweight tube. Next, I decided to cut down Apogee Nova egg capsules to produce nose cones and tail transition cones. This works, but is awfully expensive and HEAVY. Such a nose cone weighs 1.68 g, with the tail cone at 1.49 g. That's 68% of the target weight in just the cones. Next I decided to eliminate the weight and expense of the tail cone by replacing it with paper. Drafting vellum looked like a nice candidate, since it is very smooth, water resistant. and readily available. I produced a vellum tail cone, bonding the seam with Scotch Magic Transparent mylar tape. This was a remarkably strong, lightweight component (0.23 g). At this point the light bulb went off, and I decided to make a 30 mm body tube in the same way. This proved to be very strong, light (1.38 g), stiff (it holds its shape much better than the fiberglass tubing on Gapon's model), and easy to make. The final problem was the nose cone. The cut-down nova cone was now just too heavy to justify, given the ultralight nature of the rest of the airframe. I had neither the time nor the inclination to try molding fiberglass cones. Again, the inspiration was Soviet: If conical nose cone is good enough for their launch vehicles, it should be good enough for me. The Chinese get honorable mention in this regard as well, since skyrockets had conical paper nose cones a thousand years ago! The final design uses a 3:1 taper with a balsa tip produced by "machining" soft 1/4" balsa stock in an electric pencil sharpener. The base is made from balsa tubing, with a 1/32" balsa bulkhead to hold it round (0.24 g). A loop of Apogee Kevlar line is bonded with CA to the back of the bulkhead and routed through the bulkhead/tube joint for recovery system attachment. Total nose cone weight is 0.69 g. Paper Tiger I, flown at MSC, has a rugged tail cone assembly which includes an Apogee Blackshaft core tube, and a rolled balsa ring and bulkhead similar to that of the nose cone at the body tube/tail cone interface. The conical paper tail shroud extends back only as far as the fin leading edges, with the fins bonded directly to the core tube. This produces an absolutely bulletproof tail assembly which should survive unlimited launching. The body tube is attached to the balsa ring with a turn of Apogee 1/2" wide mylar tape, and can be removed and replaced. Wadding is from 1" thick white styrofoam "beadboard" (1 lb cu.ft density) cut with a hot wire, as on the Ukrainian model. This provides excellent protection of the recovery system and airframe. The body tube is still serviceable after three launches, but is beginning to show some distortion. The weight of Paper Tiger I less rigging and recovery system is 4.14 g, dead even with Gapon's model, thus achieving my initial goal. A test flight on the then contest-illegal A3-6T at MSC yielded a duration of 90 seconds without the aid of a thermal. The model boosts without tipoff from a 13 mm 4 12" piston, and deploys the recovery system exactly at apogee. The drawing on page 14 shows Paper Tiger II, which is an attempt to build the lightest possible airframe using these techniques. Experience has shown that fins can be bonded directly to a vellum airframe tube and have adequate strength (Al and Buzz did this on their NARAM-33 winner). I have had good success with cardstock fins cut from a manila folder. While substantially heavier than 1/32" balsa fins, these are much thinner and smoother, requiring only a few coats of clear dope for a finish and offering less drag. Paper Tiger II therefore employs cardstock fins bonded to a vellum tail cone which extends to the rear of the airframe. The blackshaft core tube has been reduced to a 1/2" ring to which the engine is taped. The external shock cord mount is also bonded to this ring with slow CA. The balsa ring at the tube/tail cone joint has been eliminated, and the bulkhead is laminated from two thicknesses of 1/32" balsa with their grains crossed for stiffness. A single thickness bulkhead inside a 1/4" balsa ring might be a better alternative, resulting in easier assembly and the possibility of body tube replacement as on Paper Tiger I . The bulkhead is perforated with 4 holes to serve as an ejection baffle, offering additional protection for the upper airframe and recovery device. Paper Tiger II weighs in at 3.5 g and represents a breakthrough in lightweight construction, since 4 g seems to be the international standard for lightness. A prototype has been constructed and is ready for test firing. I am confident that it will withstand flight loads. The remaining question is how well the unprotected tail cone stands up to ejection. My guess is that most of the burning debris will hit the baffle plate and not the cone wall. If the cone does suffer significant burn damage, a vellum tube can be inserted in the end of the engine casing or attached to the blackshaft tail ring to focus the ejection forward and prevent it from striking the cone wall. Vellum Construction for NAR Models The drawing on page 15 shows one approach to vellum construction applied to produce a 14 mm diameter NAR model. By using a blackshaft tail assembly, a very robust model results. The vellum tubing can be replaced in the event of burn damage. This approach is midway between the old "boilerplate" and an all-vellum airframe. Blackshaft tubing of 14 mm diameter has a linear mass density of 0.127 g/cm, while vellum tubing is only 0.042 g/cm, a factor of 3 difference. Replacing 7" of blackshaft with vellum in the design shown saves 1.5 g, and makes the difference between a 2.4 g model and a 3.9 g one, a savings of 39\% for almost no effort. The vellum tube is attached to the tail unit with Apogee chrome mylar tape, and can be replaced in minutes if damaged. Compare the 2.4 g final airframe weight with the 3.5 g for an expended 13 mm engine casing. The model is now 29% lighter than the spent engine! Construction Hints The new skills and materials required for these models are minimal. For material I am using Crystalene vellum produced by Keuffel and Esser. It is approximately 0.003" thick and has a surface mass density (useful to know for weight estimates) of 0.0069 g/cm2. A pad of 50 sheets 17"x 22" sells for around $15.00 at Ulrich's in Ann Arbor. While not a trivial expense, this is enough material for perhaps 100 models if care is taken not to waste it, and the actual cost per model is pennies. Vellum models aren't just light, they're CHAD (CHeap And Dirty)! To produce vellum tubing you need a suitable mandrel. For the NAR model shown, just use a piece to blackshaft tubing as your form. For the Paper Tiger I roll the balsa tubing for the nose cone shoulder first and then roll the vellum tubes around it, ensuring a perfect fit. Cut a blank from vellum, allowing 1-2 mm of overlap at the seam. ***end article excerpt Perhaps this is of use Peter Alway (editor's note - plans for the Paper Tiger can be dowloaded from the NAR website - http://www.nar.org) owens@cookiemonster.utd.rochester.edu (Bill Owens) adds: Very interesting article. Reminds me, I have to subscribe to that newsletter... I don't have a lot of experience with vellum rockets, but working from John Viggiano's presentation at the 1993 MARSCON (proceedings may still be available) I was able to get 44 seconds in 1/2A SD at NYSPACE this year. This was my first vellum rocket, and it had the 6th best individual flight of the day; would have been better, but the wadding jammed so it was a little heavy coming down. It was also a NAR minimum diameter model, not one of those loony FAI things (which is obviously what the article describes). >I >produced a vellum tail cone, bonding the seam with >Scotch Magic Transparent mylar tape. This was a >remarkably strong, lightweight component (0.23 g). I had a lot of luck with white glue and a monokote sealing iron; I made mandrels for the body tube out of perfectly sized plastic tubing found at the hardware store and for the nose cone out of manila paper, coated the overlapping paper with glue, allowed it to dry and heated it in place to melt and fuse the glue into the joint. This technique is not only quick but reliable; the first tube I made is the one I used! The nose cone was simple, a vellum cone with a vellum tube glued into the bottom, and after some experimenting I found that the easiest way to do this was to make the tube slightly larger than the body tube, so it slips over the outside. This also makes the entry of the external shock cord much nicer. >Experience has >shown that fins can be bonded directly to a vellum >airframe tube and have adequate strength (Al and >Buzz did this on their NARAM-33 winner). I have >had good success with cardstock fins cut from a >manila folder. While substantially heavier than >1/32" balsa fins, these are much thinner and >smoother, requiring only a few coats of clear dope >for a finish and offering less drag. I used laminated cardstock (two pieces with yellow glue) for more stiffness, but it probably wasn't necessary for 1/2A. Mine didn't appear to require any finish other than a little magic marker for visibility. I used an external shock cord mounted to the fin root, but unfortunately it wasn't strong enough and the rocket separated on the second flight... The best trick from John's article, I think, is to use chrome trim Monokote inside the tube just ahead of the motor. It prevents burn through and makes the chance of reuse much higher. I didn't have any at the time I was building so I used very thin aluminum foil (from a stick of chewing gum ;) I'm still tempted to try vellum for C SD this weekend, but I don't think I'll rely on it! Bill. jsvrc@rc.rit.edu (J A Stephen Viggiano) adds to Bill Owen's comments: >I don't have a lot of experience with vellum rockets, but working from >John Viggiano's presentation at the 1993 MARSCON (proceedings may still >be available) I was able to get 44 seconds in 1/2A SD at NYSPACE this >year. [stuff deleted] >The best trick from John's article, I think, is to use chrome trim >Monokote inside the tube just ahead of the motor. It prevents burn >through and makes the chance of reuse much higher. I didn't have any >at the time I was building so I used very thin aluminum foil (from >a stick of chewing gum ;) Let's give credit where credit is due. Bill wasn't at MARSCON '93 (though he was at MARSCON '94), where the vellum workshop was held. Dr. Andy Tomash was given credit for inventing the technology, even though it was for those clunky FAI birds, and Al and Buzz were given credit for many ideas that make Vellum a viable option for our more streamlined contest models. Their contributions include heat sealing the seam and the trim Monokote reinforcement. Have fun and fly 'em high! -- Having fun at NARAM-37 should be easier than pronouncing "Geneseo". ======================================================================== John Viggiano, jsvrc@rc.rit.edu or sjvppr@ritvax.isc.rit.edu NAR 25615 I'm the NAR, and I vote! billw@glare.cisco.com (William ) adds this about vellum paper: An interesting revelation from perusing a paper catalog is that Vellum comes in multiple weights! The (not free) sample books from the people at 800-A-PAPERS include both an "average weight" vellum and also a heavier weight vellum. With patterns on them... BillW mark@fnbc.com (Mark Bundick) answers Lynell's question: lynell@cco.caltech.edu (Lynell K. Jackson) wrote: >> experiments with rolling vellum rockets. Any tips to help >> get started? Chicago FAI flyers have done this for about 4 years now. We used vellum based models for FAI PD and SD events. They consisted of: a. 4"-5" of BT-5 tube b. a 1/16" balsa centering ring c. 8.5" of vellum tube made of the same paper Andy T's article posted by Peter Alway; we made them around a 29mm HPR engine tube covered with waxed paper, seams glued with thin CyA. d. three large-ish swept 1/32" balsa fins e. balsa nose cones turned from scrap and hollowed out. f. Kevlar shock cord anchored to the fins. g. a transition section of vellum material between the 30 mm vellum tube and the BT-5. To assemble the pieces parts, we'd: - build the vellum tube - attach the centering ring to the BT-5 - build the transition section on the BT-5/ring combination, gluing the edges with thin CyA. - slip the tube over the completed transition-tube combo, aligning carefully before gluing together - attach the fins - attach the shock cord. We originally thought they'd burn up after one flight, but found them to be incredibaly durable. They're also duck soup simple to build and cheap, cheap. Even if we'd gone with fiberglass for the actual contest, paper was an excellent alternative to getting some really good practice models quickly. After we developed the 29MM tube to roll tubes and built a fixed fin jig to slap on the fins, we could probably have made about 10 models a hour or so. Try this if you're into large diameter PD birds with enormous chute volumes. ========================================================= Mark B. Bundick "Running a NARAM will never be harder NAR President than building a nice scale model" roger.wilfong@umich.edu (A. Roger Wilfong) answers Ted Apke's question about Mark Bundick's vellum rocket technique: In Article "tha@akanano.wh.att.com (-T.APKE)" says: > > Mark, > When you say you attached the shock cord to the fins, could > you be more explicit? That is, does the shock cord run outside the airframe? > > Ted > External shock cord attachment is common in competition duration models. It keeps the inside of the body clean so you can pack as large a chute as possible inside and not have it snag the shock cord attachmnet, also since the attachment is to the rear (or side - see below) of the model, it virtually eliminates snap back problems. The external cord does produce more drag, but in duration the slight loss of altitude is made up for by a larger recovery system. The attachment is usually by CA-ing the end of the shock into a fin root. Usually a wrap of mylar tape (or chrome trim Monocote) is wrapped around cord and body tube so that the model hangs horizontally with a spent motor casing in place. Just streach the cord along the body tube and past the shoulder of the nose cone. _ | \ /- Mylar tape | \ / ------------------ | | ------------------ | / \- GC with expended motor, no nose cone and no recovery system. |_/ \ \- CA here I should point out that the shock cord in this case is a piece of Kevlar or braided nylon fishing line (I usually use 30# on small models, 50-70# on larger models). The Kevlar is stronger, but may need a small bunge to absorb the shock - a couple of feet of 30# nylon is usually springy enough to absorb the shock by itself. - Roger