A.S.P. fin thickness?

[blackshire]

Hello All,

(Before I ask my question about the Estes A.S.P. Semi-Scale kit below, take a gander at Chris Timm's "UK missile pics" thread on this forum section!)

Now to my question: I was just looking at the mini-motor powered Estes A.S.P. Semi-Scale kit (Cat. No. #0862, see: www.ninfinger.org/rockets/catalogs/estes82/82est26.html ). The plans are online here: ( www.spacemodeling.org/JimZ/est0862.htm and www.spacemodeling.org/JimZ/estes/est0862.pdf ).

What thickness of sheet balsa (1/16", 1/8", or 3/32") did it use for its fins? (John Brohm's Body Tube/Kit Index says that it used an 18" length of BT-20 for its body tube, and it had a BNC-20N balsa nose cone, for which the PNC-20A nose cone in the Wizard and Viking kits is a plastic direct replacement.) The Estes A.S.P. would make a nice "fun scale" kitbashing project.

Many thanks in advance to anyone who can help.

[CPMcGraw]

Hello All,

(Before I ask my question about the Estes A.S.P. Semi-Scale kit below, take a gander at Chris Timm's "UK missile pics" thread on this forum section!)

Now to my question: I was just looking at the mini-motor powered Estes A.S.P. Semi-Scale kit (Cat. No. #0862, see: www.ninfinger.org/rockets/catalogs/estes82/82est26.html ). The plans are online here: ( www.spacemodeling.org/JimZ/est0862.htm and www.spacemodeling.org/JimZ/estes/est0862.pdf ).

What thickness of sheet balsa (1/16", 1/8", or 3/32") did it use for its fins? (John Brohm's Body Tube/Kit Index says that it used an 18" length of BT-20 for its body tube, and it had a BNC-20N balsa nose cone, for which the PNC-20A nose cone in the Wizard and Viking kits is a plastic direct replacement.) The Estes A.S.P. would make a nice "fun scale" kitbashing project.

Many thanks in advance to anyone who can help.

I think we've touched on the ASP fins somewhere on this forum, but it's been a couple of years ago...

Using the 1974 Parts Catalog as a guide, the part number for the fin sheet is 32257, which falls between the fin sheets for the HoJo (32256) and the TEROS (32258). Both of these sheets were 3/32" .

Using the first page of the plans as a guide, however, you would be inclined to think 1/16" [BFS-20]. These fins have a paper (cardstock) tab attached on the bottom edge, and the thicknesses for both seem to be drawn proportionally to each other.

If I were to build a clone today, I'd stick with [B]BFS-20. Estes did not seem constrained to keep part numbers entirely consistent, so following with the Parts Catalog numbers might not be the best way to go on this one. Only someone who has an original kit (built or NIB, Scigs30, you doing this one?) can say otherwise.

[blackshire]

Craig, I thank you for this information. I was inclined toward the 1/16" thick BFS-20 myself (that's what I used in my BT-5 size Nova Hobbies ASP kits (see: www.rocketreviews.com/reviews/all/oop_nova_asp.shtml ). 3/32" just seems too thick, including for how the Estes A.S.P.'s fins look in the kit card photograph.

For the larger BT-20 size Estes A.S.P., I'll probably "paper" the 1/16" thick fins for extra strength and to obviate the need for sanding & sealing (my same reason for using a plastic PNC-20A nose cone instead of a balsa BNC-20N nose cone). Unlike my ASP kit (which put on a fair imitation of the U.S.S. Enterprise's transporter [now you see it, now you don't!]), the larger Estes version should be slow enough (although probably *just*) that I can actually follow the powered portion of its ascent.

[barone]

I built a scale model of the A.S.P. for NARAM 49 so it wasn't exactly like the Estes kit but you might be able to use these ideas.

I used 1/16" balsa. Attaching the fin tabs is a pain and they usually get taken off in the first flight. The scale data shows the tabs on a side of the fin and not centered on the bottom. So, I made card stock overlays of the fin and tab to go on one side of the fin and just a fin for the other side. If you plan on attaching flares to the fin tips, the overlay helps to keep them secure (I had one break off on landing but it was an altitude event and I used a streamer instead of going with a small parachute).

I used ST-7 tubing and nose cone from Semroc. I cut the tip of the nose cone off to install the antennae and then used squadron putty to re-build and shape the nose cone around it. You can use the extra weight because it's initially a little unstable on a C motor but straightens out and flys straight. Fin tabs create quite a bit of spin..... ;)

Anyway, here's a picture of it........

[blackshire]

Don, thank you for posting the photograph and description! I'll stick to the "stock" Estes A.S.P. for now. I noticed, though, that Semroc has what they call "Deci-Scale" (1/10th Scale) 5:1 tangent ogive ASP nose cones and conical (11 degrees, I believe) Nike-ASP nose cones on their web site. Maybe kits incorporating these will follow soon?

[sandman]

I just finished the decals for the ASP.

[ghrocketman]

The fins on the Estes ASP kit were NOT balsa of any thickness.
I built an original MANY years ago that I still have.
They were fibreboard like Centuri used in many of their kits including all the Super Kits.

[blackshire]

The fins on the Estes ASP kit were NOT balsa of any thickness.
I built an original MANY years ago that I still have.
They were fibreboard like Centuri used in many of their kits including all the Super Kits.That may have been a later production run of the kit, as the one on JimZ's web site definitely has balsa fins.

[blackshire]

I just finished the decals for the ASP.Wow--thank you very much for the fast service! The PayPal payment has been sent.

[CPMcGraw]

That may have been a later production run of the kit, as the one on JimZ's web site definitely has balsa fins.

And the plans specify a balsa sheet in the parts list.

But, that's a thought if someone was willing to try it -- a laser-cut set of matteboard fins, 0.02" thick. Carl's material is far superior to what Estes used in the past, so it might hold up longer once it's been sealed and painted.

[mojo1986]

Just checked my ASP kit (Estes #0862)..................1/16" die cut balsa.

Joe

[blackshire]

And the plans specify a balsa sheet in the parts list.

But, that's a thought if someone was willing to try it -- a laser-cut set of matteboard fins, 0.02" thick. Carl's material is far superior to what Estes used in the past, so it might hold up longer once it's been sealed and painted.I heartily agree! Structurally, the long-chord, short-span, right-triangular A.S.P. fin is probably the strongest possible fin planform for use with *any* kind of fin material, so such "fibre" fins should hold up very well. If Carl brings out an A.S.P. kit (either Deci-Scale or a reproduction of the BT-20 size Estes A.S.P.), I would have absolutely no objections to fibre fins in the kit.

[blackshire]

Just checked my ASP kit (Estes #0862)..................1/16" die cut balsa.

JoeThank you, Joe! Up to now I was 99% certain of this, but it's always best to have definite confirmation.

[CPMcGraw]

... If Carl brings out an A.S.P. kit (either Deci-Scale or a reproduction of the BT-20 size Estes A.S.P.), I would have absolutely no objections to fibre fins in the kit...

Carl, there you have it -- straight from the horse's mouth! :D

Sorry, 'shire, couldn't resist... :o

[blackshire]

Carl, there you have it -- straight from the horse's mouth! :D

Sorry, 'shire, couldn't resist... :oYou've nothing to apologize for--I am pleased to (rhetorically speaking) be ridden thusly!

[Ez2cDave]

A little data on the A.S.P. . . .

[blackshire]

A little data on the A.S.P. . . .Ah--thank you for posting all of those! I'd never seen that...cardstock? red-and-black "roulette round" ASP (I've seen that round, but not that cardstock model). Being made for 13 mm motors, I presume the rolled body tube is BT-5 size (I used to have a mold master for a BT-5 size 5:1 tangent ogive, from which I cast solid polyurethane resin [with "investment cast" screw eyes] nose cones, for my Nova Hobbies ASP kit www.rocketreviews.com/nova-hobbies-asp-mike-goss.html [I never sold kits with those, because I had so many balsa 5:1 ogive nose cones]). Today, one of the 3D printing folks could make such 5:1 BT-5 ogives. Also:

Those "super-caliber cone" ASP rounds look like the pictures in Dr. Richard Morrow's book, "Small Sounding Rockets" (which--the last I'd heard--he was working on reprinting, perhaps via POD [Print On Demand] publishing [here www.google.com/search?ei=9UKNXPbjBoGe8AO70LjABQ&q=small+sounding+rockets+richard+morrow&oq=Small+Sounding+Rockets+by+Richard+Morrow&gs_l=psy-ab.1.0.0i22i30.3426.19897..26586...1.0..0.147.4539.1j39....2..0....1..gws-wiz.....6..0i71j35i39j0i131j0i131i67j0i10i67j0i67j0i131i10j0j0i13j0i13i30j33i299j33i22i29i30.VEJK4p7cMxM is his book]). He also covered a two-stage sounding rocket that used that mushroom cloud sample-collecting nose cone, called the ASCAMP (see: www.google.com/search?source=hp&ei=8UCNXJvfMs-Dk-4P5tCKMA&q=ASCAMP+sounding+rocket&btnK=Google+Search&oq=ASCAMP+sounding+rocket&gs_l=psy-ab.3..33i299l2.1173.9260..14772...0.0..0.146.2740.1j22....2..0....1..gws-wiz.....0..35i39j0i131j0j0i10j0i30j0i5i10i30j0i5i30j0i10i30j0i22i30j0i22i10i30j33i160.Xuu7eh_FuMw ), and:

The ASCAMP used the delta-finned ASP as its first stage. The SCAMP second stage, which had Aerobee 350-like fins (although much smaller) and the "super-caliber cone," used the same "Baby Sergeant" rocket motor as that used for the Jupiter-C/Juno I and Juno II high-speed solid propellant upper stages.

[Ez2cDave]

Ah--thank you for posting all of those! I'd never seen that...cardstock? red-and-black "roulette round" ASP (I've seen that round, but not that cardstock model). Being made for 13 mm motors, I presume the rolled body tube is BT-5 size (I used to have a mold master for a BT-5 size 5:1 tangent ogive, from which I cast solid polyurethane resin [with "investment cast" screw eyes] nose cones, for my Nova Hobbies ASP kit www.rocketreviews.com/nova-hobbies-asp-mike-goss.html [I never sold kits with those, because I had so many balsa 5:1 ogive nose cones]). Today, one of the 3D printing folks could make such 5:1 BT-5 ogives. Also:

Those "super-caliber cone" ASP rounds look like the pictures in Dr. Richard Morrow's book, "Small Sounding Rockets" (which--the last I'd heard--he was working on reprinting, perhaps via POD [Print On Demand] publishing [here www.google.com/search?ei=9UKNXPbjBoGe8AO70LjABQ&q=small+sounding+rockets+richard+morrow&oq=Small+Sounding+Rockets+by+Richard+Morrow&gs_l=psy-ab.1.0.0i22i30.3426.19897..26586...1.0..0.147.4539.1j39....2..0....1..gws-wiz.....6..0i71j35i39j0i131j0i131i67j0i10i67j0i67j0i131i10j0j0i13j0i13i30j33i299j33i22i29i30.VEJK4p7cMxM is his book]). He also covered a two-stage sounding rocket that used that mushroom cloud sample-collecting nose cone, called the ASCAMP (see: www.google.com/search?source=hp&ei=8UCNXJvfMs-Dk-4P5tCKMA&q=ASCAMP+sounding+rocket&btnK=Google+Search&oq=ASCAMP+sounding+rocket&gs_l=psy-ab.3..33i299l2.1173.9260..14772...0.0..0.146.2740.1j22....2..0....1..gws-wiz.....0..35i39j0i131j0j0i10j0i30j0i5i10i30j0i5i30j0i10i30j0i22i30j0i22i10i30j33i160.Xuu7eh_FuMw ), and:

The ASCAMP used the delta-finned ASP as its first stage. The SCAMP second stage, which had Aerobee 350-like fins (although much smaller) and the "super-caliber cone," used the same "Baby Sergeant" rocket motor as that used for the Jupiter-C/Juno I and Juno II high-speed solid propellant upper stages.

HERE YOU GO . . .

https://rocketry.files.wordpress.com/2007/07/downscale_asp.pdf

Dave F.

.

[blackshire]

HERE YOU GO . . .

https://rocketry.files.wordpress.com/2007/07/downscale_asp.pdfDownloaded and saved with appreciation--Thank You! As it shows, the 4:1 tangent ogive from the NC-5 nose cone pack isn't "off-scale" enough to look glaringly wrong. This could easily be the simplest, easiest-to-build scale model rocket.

[Ez2cDave]

Downloaded and saved with appreciation--Thank You! As it shows, the 4:1 tangent ogive from the NC-5 nose cone pack isn't "off-scale" enough to look glaringly wrong. This could easily be the simplest, easiest-to-build scale model rocket.

You are entirely welcome . . . I believe that data should be shared, not hoarded.

A little more "FUN", from the same source . . .

https://rocketry.wordpress.com/ultimate-paper-rocket-guide/paper-rocket-partial-builds

Dave F.

[blackshire]

You are entirely welcome . . . I believe that data should be shared, not hoarded.

A little more "FUN", from the same source . . .

https://rocketry.wordpress.com/ultimate-paper-rocket-guide/paper-rocket-partial-builds

Dave F.*Nods* I let Peter Alway keep the scale data I sent him, because it would probably be dumped post mortem when the building management cleans out my apartment. Also:

Looking at the paper nose cones in the plans links that you posted, I think it would be easy to make curved-sided ones (tangent ogive, secant ogive, rounded-tip conical, etc.) and other such nose cones--as well as transitions and boat-tails (tail cones)--out of paper or card stock, by using papier-mâché construction methods (see: https://en.wikipedia.org/wiki/Papier-m%C3%A2ch%C3%A9 ). The mold could be 3D printed or made of polyurethane resin, with the white or yellow glue/paper mixture being pressed into place in the mold cavity. The nose cones or other parts could be either hollow-cast or solid-cast (in the latter case, a screw eye could be "investment cast" into the wet glue/paper mixture).

[Ez2cDave]

*Nods* I let Peter Alway keep the scale data I sent him, because it would probably be dumped post mortem when the building management cleans out my apartment. Also:

Looking at the paper nose cones in the plans links that you posted, I think it would be easy to make curved-sided ones (tangent ogive, secant ogive, rounded-tip conical, etc.) and other such nose cones--as well as transitions and boat-tails (tail cones)--out of paper or card stock, by using papier-mâché construction methods (see: https://en.wikipedia.org/wiki/Papier-m%C3%A2ch%C3%A9 ). The mold could be 3D printed or made of polyurethane resin, with the white or yellow glue/paper mixture being pressed into place in the mold cavity. The nose cones or other parts could be either hollow-cast or solid-cast (in the latter case, a screw eye could be "investment cast" into the wet glue/paper mixture).

That's a very interesting idea . . . The idea of molding nose cones caught my attention.

With a 3-D printed mold ( I don't have a 3-D printer, but I have a friend that does ), it might be possible to "injection mold" nose cones, using epoxy in a syringe.

The two halves of the mold would be clamped together and the syringe attached to a threaded nipple on the mold . . . Of course, there would have to be a small hole to allow air to escape and the resin to completely fill the mold . . . . Once cured, the mold is unclamped and the sides are separated . . . Presto !

Thoughts ?

[Doug Sams]

That's a very interesting idea . . . The idea of molding nose cones caught my attention.

With a 3-D printed mold ( I don't have a 3-D printer, but I have a friend that does ), it might be possible to "injection mold" nose cones, using epoxy in a syringe.

The two halves of the mold would be clamped together and the syringe attached to a threaded nipple on the mold . . . Of course, there would have to be a small hole to allow air to escape and the resin to completely fill the mold . . . . Once cured, the mold is unclamped and the sides are separated . . . Presto !

Thoughts ?If you can mix in some fiberglass matting, that might enable making it lighter and also less brittle. I would mold it with the bottom open to facilitate inserting the matting. But some experimentation will be required to find a way to keep the wall reasonably thin.


Doug


.

[blackshire]

That's a very interesting idea . . . The idea of molding nose cones caught my attention.

With a 3-D printed mold ( I don't have a 3-D printer, but I have a friend that does ), it might be possible to "injection mold" nose cones, using epoxy in a syringe.

The two halves of the mold would be clamped together and the syringe attached to a threaded nipple on the mold . . . Of course, there would have to be a small hole to allow air to escape and the resin to completely fill the mold . . . . Once cured, the mold is unclamped and the sides are separated . . . Presto !

Thoughts ?Yes, that works just fine. Spray-on (in aerosol cans), wax-based mold release prevents the polyurethane casting resin from bonding to the 3D printed plastic mold. (Some resin casters even use molds made out of the same resin--such as, say, Alumilite--that's used to cast the parts themselves! As long as the mold cavity [and any places where the mold halves fit together] is sprayed with wax-based mold release, the cast part [and any excess resin] doesn't glue itself to the mold.) In addition:

Epoxy casting resins are also available, but they're more expensive than polyurethane (they do produce slightly more dimensionally accurate cast parts than polyurethane casting resin, but the difference is very small, and the mold cavity size can--if desired--be very slightly "nudged" in order to compensate for that). But even at the very worst, a cast resin duplicate part is just a tiny bit looser in the body tube than an original injection-molded or blow-molded styrene or ABS plastic part (or a properly sanded, sealed, and painted balsa nose cone that's used as the mold master part). Also:

Another method, which I used, is to create an RTV--Room Temperature-Vulcanizing--rubber mold (the platinum-cure rubber molds last longer and produce more dimensionally accurate parts, but I've used the cheaper tin-cure rubber with entirely satisfactory results), and produce solid-cast nose cones in it, and:

The rubber molds can also be made in two halves, and single-piece molds--which I used--also work fine. The nose cones can be lightened if desired (although small, solid resin BT-5 and T15 nose cones aren't too massive) by mixing microballoons (micro-bulb filler) into the resin, to lower the density of the cast part. Such single-cavity RTV rubber molds can also produce hollow nose cones, transitions, and tailcones by rotating the mold, even by hand (although roto-casting tables can be bought or built for casting such parts in quantity. This (see: http://www.ninfinger.org/models/rms_tips/resin_cast.html ) article that I wrote, "Resin Casting for Rocketeers," covers the various resin casting methods.

[blackshire]

If you can mix in some fiberglass matting, that might enable making it lighter and also less brittle. I would mold it with the bottom open to facilitate inserting the matting. But some experimentation will be required to find a way to keep the wall reasonably thin.


Doug.What is preferable to use depends on the part size, and the flight stresses it's expected to undergo. Kevlar veil (it's rather like panty hose--in fact, actual panty hose might be fine for some applications) or the equivalent glass or carbon fiber cloth, and a long-curing (an hour or more) epoxy, or polyurethane casting resin, should be fine for model rocket nose cones, transitions, and tailcones (and fins, which could use foam cores). One "wets" the mold cavity with the resin (after applying an appropriate mold release), then presses the cloth into it (a gel coat can also be applied if desired--as is often done with molded fiberglass boat hulls--to give the finished part a shiny surface). Toward the top of that size range (BT-70 or so and up), more layers of the Kevlar, glass, or carbon fiber could be built up in the mold, to provide additional strength. Also:

For LMR/mid-power rockets, using heavier glass, Kevlar, or carbon fiber cloth would ensure ample thickness and strength. Another option that could be implemented along with the heavier cloth--although it would be best done outdoors--would be to use polyester resin. It stinks abominably until it has cured, but it is very strong and also has a little flexibility, which is good for such large rocket parts (the pre-made fiberglass R/C model airplane and R/C model sailplane fuselages--and R/C powerboat and sailboat hulls and racing car bodies--are made of heavier glass cloth and polyester resin). If you have neighbors with whom you are feuding, making such rocket parts in the yard or on a balcony or deck (when the wind is blowing toward them) could serve two purposes at once... :-)

[Ez2cDave]

I've been looking at molding techniques and I am intrigued by the use of a "Compression Mold" . . . The two parts could easily be 3-D printed . . . Still doing research . . . Basic concept below.

[teflonrocketry1]

). Today, one of the 3D printing folks could make such 5:1 BT-5 ogives.

I could easily 3D print 5:1 ogive nosecones (including the integral A.S.P. antenna or at least one with a flat truncated or open tip) in any BT size up to BT-80. The estimated cost in material for ABS plastic (at $15/Kg) is the diameter times the height (both in inches) times $0.30 . Mass production of more than one nosecone at a time will save on time and hence production cost. I have been printing 9 to 25 BT-20 sized ABS nosecones in a single batch.

[Ez2cDave]

I could easily 3D print 5:1 ogive nosecones (including the integral A.S.P. antenna or at least one with a flat truncated or open tip) in any BT size up to BT-80. The estimated cost in material for ABS plastic (at $15/Kg) is the diameter times the height (both in inches) times $0.30 . Mass production of more than one nosecone at a time will save on time and hence production cost. I have been printing 9 to 25 BT-20 sized ABS nosecones in a single batch.

Can a large 3-D printed nose cone ( BT-70 and larger ) be thin-walled, hollow, durable, lightweight, and shock resistant ?

What would the cost be to do a 5:1 BT-80 Ogive with .060"- .125" wall thickness ?

How much would it weigh and how long would it take to print ?

Thanks,

Dave F.

[teflonrocketry1]

A large BT-80 nosecone can take up to 8 hours to print at 0.2mm resolution, (or as little as 4 hours if I change the diameter of the print nozzle), the print would use about 100 grams of material with a 3/32" wall thickness (for ABS, or about 110 grams for PLA) At $15/Kg the plastic material cost is about $1.50.

I have made nosecones like this visit: https://forums.rocketshoppe.com/showpost.php?p=221129&postcount=35 for my Estes Panavia to Cherokee D clone http://forums.rocketshoppe.com/showthread.php?t=17244 .

I am currently limited to printing nosecones that are 400mm long (not including the shoulder which can be printed separately). I would only be able to print 4 of these larger nosecones at one time. I actually modified one of my printers with a 900mm high Z axis; however, there are still a lot of issues to work out and I have not been able to print anything over 600mm long.

Attached are pictures of a BT-20 size scale ASP nosecone I just printed. It took me minutes to draw the cone in RockSim, another few minutes to slice the exported 3D model with CURA software, and the 3D print took 3 hours and 2 minutes at 0.12 mm resolution and used about 7 grams of ABS plastic filament. The antenna is a bit flimsy but I think it will be OK for flight. I guess I will have to build and fly the scale ASP model to prove this.

[Ez2cDave]

A large BT-80 nosecone can take up to 8 hours to print at 0.2mm resolution, (or as little as 4 hours if I change the diameter of the print nozzle), the print would use about 100 grams of material with a 3/32" wall thickness (for ABS, or about 110 grams for PLA) At $15/Kg the plastic material cost is about $1.50.

I have made nosecones like this visit: https://forums.rocketshoppe.com/showpost.php?p=221129&postcount=35 for my Estes Panavia to Cherokee D clone http://forums.rocketshoppe.com/showthread.php?t=17244 .

I am currently limited to printing nosecones that are 400mm long (not including the shoulder which can be printed separately). I would only be able to print 4 of these larger nosecones at one time. I actually modified one of my printers with a 900mm high Z axis; however, there are still a lot of issues to work out and I have not been able to print anything over 600mm long.

Attached are pictures of a BT-20 size scale ASP nosecone I just printed. It took me minutes to draw the cone in RockSim, another few minutes to slice the exported 3D model with CURA software, and the 3D print took 3 hours and 2 minutes at 0.12 mm resolution and used about 7 grams of material. The antenna is a bit flimsy but I think it will be OK for flight. I guess I will have to build and fly the scale ASP model to prove this.


Hmm . . . Very interesting, Bruce !

What are the structural properties of the nose cone ?

Is is brittle and easily damaged ?

Are there different plastics that can be used ?

Advantages and disadvantages of each type ?

Sorry for the barrage of questions . . .

Thanks ,

Dave F.

[teflonrocketry1]

ABS is very similar to polystyrene since ABS is mostly that polymer (about 50 to 60%), its fairly strong and not that brittle. Another, more common filament, for 3D printing PLA (also the cheapest at $10/kg) is much more brittle and more sensitive to warping at higher temperatures, and difficult to sand.

ABS sands easily and can be bonded with most plastic cements. I typically treat my ABS 3D prints with acetone which relieves stress in the plastic and strengthens it. Almost all the ABS items I have 3D printed passed a 4ft drop test to a cement floor, the same cannot be said of 3D prints made with PLA filament.

While I am fairly good at printing with ABS, there are other polymers available, that are even stronger, at even higher price points. Kevin Cespedes at Aerobotix ; https://www.shapeways.com/shops/cespedesign-multimedia , uses a white nylon polymer and charges accordingly.

There are many other polymers available such as simulated wood, glow in the dark, and PET which I have yet to try. There are also highly flexible polymers available; even custom 3D printed running shoes can be made, just search the internet.

I purchased two Ender 2 printer kits for $175 about 1 year ago and they both have more then paid for themselves with all the high quality parts that I made.

[Ez2cDave]

ABS is very similar to polystyrene since ABS is mostly that polymer (about 50 to 60%), its fairly strong and not that brittle. Another, more common filament, for 3D printing PLA (also the cheapest at $10/kg) is much more brittle and more sensitive to warping at higher temperatures, and difficult to sand.

ABS sands easily and can be bonded with most plastic cements. I typically treat my ABS 3D prints with acetone which relieves stress in the plastic and strengthens it. Almost all the ABS items I have 3D printed passed a 4ft drop test to a cement floor, the same cannot be said of 3D prints made with PLA filament.

While I am fairly good at printing with ABS, there are other polymers available, that are even stronger, at even higher price points. Kevin Cespedes at Aerobotix ; https://www.shapeways.com/shops/cespedesign-multimedia , uses a white nylon polymer and charges accordingly.

There are many other polymers available such as simulated wood, glow in the dark, and PET which I have yet to try. There are also highly flexible polymers available; even custom 3D printed running shoes can be made, just search the internet.

I purchased two Ender 2 printer kits for $175 about 1 year ago and they both have more then paid for themselves with all the high quality parts that I made.

Bruce,

Which 3D printer do you have ?

Dave F.

[teflonrocketry1]

I have two Creality Ender 2's which still cost $175 at: https://www.3dprintersonlinestore.com/creality-ender2-mini-kit

These are kits, so some assembly is required. Chris Taylor (of Naramlive.com) has an excellent YouTube channel on 3D printing, T3DP, and has some very detailed videos on how to put these kits together and adjust the printers to get high quality results https://www.youtube.com/watch?v=SAMPanw2am8.

I routinely get 0.1mm resolution or better with PLA and ABS filaments. I have posted pictures of my 3D prints next to actual the blow molded parts and it is difficult to tell them apart https://forums.rocketshoppe.com/showpost.php?p=220736&postcount=2.

The newer model, the Ender 3, is supposedly an even better 3D printer, it costs $199 from the same vendor. I get the filaments on sale at Amazon for $10 to $15 per kilogram. If you are not into learning a CAD program, I also wrote an article on how to generate 3D printer files from RockSim https://www.apogeerockets.com/educa...wsletter476.pdf

[Ez2cDave]

I have two Creality Ender 2's which still cost $175 at: https://www.3dprintersonlinestore.com/creality-ender2-mini-kit

These are kits, so some assembly is required. Chris Taylor (of Naramlive.com) has an excellent YouTube channel on 3D printing, T3DP, and has some very detailed videos on how to put these kits together and adjust the printers to get high quality results https://www.youtube.com/watch?v=SAMPanw2am8.

I routinely get 0.1mm resolution or better with PLA and ABS filaments. I have posted pictures of my 3D prints next to actual the blow molded parts and it is difficult to tell them apart https://forums.rocketshoppe.com/showpost.php?p=220736&postcount=2.

The newer model, the Ender 3, is supposedly an even better 3D printer, it costs $199 from the same vendor. I get the filaments on sale at Amazon for $10 to $15 per kilogram. If you are not into learning a CAD program, I also wrote an article on how to generate 3D printer files from RockSim https://www.apogeerockets.com/educa...wsletter476.pdf

Bruce,

I'll check that unit out . . .

I know Chris Taylor . . . I'll shoot him an email.

No, I don't want to have to learn CAD . . . LOL !

Thanks,

Dave F.

[blackshire]

I've been looking at molding techniques and I am intrigued by the use of a "Compression Mold" . . . The two parts could easily be 3-D printed . . . Still doing research . . . Basic concept below.David Merriman, a well-known modeler and diver (see: www.google.com/search?source=hp&ei=I-aRXIGDBI7B0wKx667wDA&q=Modeler+David+Merriman&btnK=Google+Search&oq=Modeler+David+Merriman&gs_l=psy-ab.3...6523.19234..22642...0.0..0.283.2771.2j20j1....2..0....1..gws-wiz.....0..35i39j0i131j0j0i10j0i13j0i22i30j33i299j33i160.4TqoEZK9cBs ) has written several printed and online "How-To" articles on vacu-forming and resin casting (which involve--and can optionally involve, as there are several methods--the same types of molds and techniques that you described in your white paper. I avoided "re-inventing the wheel" in my resin casting by reading his articles. Another trick that I learned about vacu-forming parts came from PSS (Power Scale Soaring [R/C slope-soaring scale glider models of powered aircraft, including jet and rocket planes]):

While this problem seldom occurs in model rocket vacu-formed parts, it can occur in larger ones. PSS modelers (and "regular" scale sailplane builders) often make their own vacu-formed canopies, usually using the male mold process that you covered. PSS models (and many scale model sailplanes) often have green- or gray-painted canopies, to give the impression of transparency (because it obviates the need to include a detailed cockpit interior), while other PSS and scale sailplane modelers vacu-form transparent canopies. Also:

Because the heated plastic sheet--whether opaque or transparent--is pulled down over the male mold, the cooled plastic canopy retains internal stresses that soon form cracks, especially after bumpy landings, even on grass (which can be stopped by drilling holes through the canopy at each end of each crack. But the formation of such stress cracks can be entirely prevented by gently heat-treating the cooled canopy, before removing it from the male mold, as this provides relief of the internal stresses.

[blackshire]

Bruce,

I'll check that unit out . . .

I know Chris Taylor . . . I'll shoot him an email.

No, I don't want to have to learn CAD . . . LOL !

Thanks,

Dave F.I can confirm Bruce's results, having several examples of duplicate Centuri and MPC nose cones, transitions, tubing connectors, and even 5 mm diameter MPC simulated booster nose cones and nozzles from the MPC/AVI/early Quest plastic parts set (used in the MPC/AVI Taurus-1 Miniroc kit), which he 3D printed.