Centuri X-16 and X-7 fin patterns?

[blackshire]

Hello All,

I'm looking for the fin patterns for the X-16 single motor/two-motor cluster rocket and the X-7 single-stage/two-stage rocket from the Centuri Power System Outfit (see: http://www.ninfinger.org/rockets/catalogs/centuri_pshandbook/cenpshandbook.html ). Does anyone here have the fin patterns for these two rockets?

Semroc carries balsa versions of both rockets' nose cones, so cloning them would be easy.

Many thanks in advance to anyone who can help.

[Green Dragon]

Been looking for plans on these myself - so if anyone has em :D

~ AL

[Carl@Semroc]

Working on them ...

[STRMan]

Working on them ...

My absolute favorite 3 words I love to hear from Carl. Good enough for me!

[Mark II]

Wow, I never knew that those designs even existed. Cool! :cool:

MarkII

[blackshire]

Working on them ...

That's "as good as legal tender" for me as well!

The X-16 (with or without its optional payload section) also carried a constant-drag, falling sphere experiment for measuring the rocket's altitude at ejection. A 1.5" (38 mm) diameter ping-pong ball was ejected and fell at a constant 30 feet per second, so by timing the interval between the ball's ejection and landing and multiplying that figure by 30, the ejection altitude in feet could be computed.

This is the same principle used in the 1 meter diameter inflatable aluminized mylar "ROBIN" (ROcket Balloon INstrument) falling spheres carried by some versions of the Arcas, Loki-Dart, Super Loki-Dart, and Viper-Dart meteorological rockets, which were/are tracked by radar and timed during descent to yield atmospheric density and wind profiles.

The single-stage X-7 was the same rocket (with different decals and without the optional payload section) as the Lancer kit in the mid-1970s Centuri "Stellar Series" of kits that they sold through their "Rocket Times" newsletter. The "all up" two-stage version of the X-7 with the booster module and the payload section was the same as the Lance Corporal kit in the Stellar Series.

[BEC]

There are already Lancer fins available from Semroc: http://www.semroc.com/Store/scripts/prodView.asp?idproduct=2181 So there's your X-7 fins.

No picture, though.

[Carl@Semroc]

Centuri Power System (http://www.semroc.com/Store/scripts/ClassicParts.asp?ID=1121)

[blackshire]

BEC, thank you for the tip about the Lancer fins! I wonder if they include the Aerobee-inspired balsa strip "conduits" (used on the Lancer and Lance Corporal, but not on the X-7 from the Centuri Power System Outfit)? It's no problem if they're not included, as I'm happy to have the fin set available.

On getting the full Power System Outfit parts set available (the X-16 and X-7 *and* all of their optional modules: http://www.semroc.com/Store/scripts/ClassicParts.asp?ID=1121 )--Carl, that was *FAST*! Are the four flat "half-moon shaped" centering/sealing pieces for the motor tubes in the X-16's two-motor mount included in the laser-cut balsa parts sheet? (If not, it's no problem--I can use the old "tissue/glue putty" method to seal the spaces between the two motor tubes and the ST-16 stage coupler that they're glued into.)

Incidentally, the X-16 would also be a very good, stable booster for carrying parasite boost-gliders aloft. If you produced, say, a 3-in-1 parasite boost-glider "Combo Kit" consisting of the Firefly (www.semroc.com/Store/scripts/ClassicParts.asp?ID=128 ), the "T-tailed" glider from the Multi-Roc kit (www.semroc.com/Store/scripts/ClassicParts.asp?ID=168 ), and the canard glider from the Condor kit (http://www.semroc.com/Store/scripts/ClassicParts.asp?ID=134 ), the X-16--especially with the two-motor cluster mount installed--could carry one or more (and perhaps all three) of these gliders at a time! I know what I'll be ordering when my next state disability payment comes in later this month... :-)

[blackshire]

Wow, I never knew that those designs even existed. Cool! :cool:

MarkII

Actually, you are in a better position with respect to these classic old designs than me. I knew that they existed, but not having the money to buy them "way back when," I was restricted to catalog-gazing.

While I am a firm believer in the joys of delayed gratification (having experienced it myself many times), thirty-plus years of delayed gratification is a *LONG* time! It is sometimes much nicer to discover a rocket design when, as an adult, one has the income to purchase the kit or parts set.

[snaquin]

Are the four flat "half-moon shaped" centering/sealing pieces for the motor tubes in the X-16's two-motor mount included in the laser-cut balsa parts sheet?

I'm busy filling my cart now with RX-16 parts and noticed these .....

http://www.semroc.com/Store/scripts/prodView.asp?idproduct=1432

I know this doesn't answer your question but I believe this is the part you are referring to.

.

[blackshire]

I'm busy filling my cart now with RX-16 parts and noticed these .....

http://www.semroc.com/Store/scripts/prodView.asp?idproduct=1432

I know this doesn't answer your question but I believe this is the part you are referring to.

.

Yup, them's is the parts! Thank you for posting the link. I keep forgetting how extensive and all-inclusive their web site is.

In the X-16 (for folks who may not be familiar with this rocket), these "half-moon shaped" thick card stock parts are glued onto the ends of an ST-16 stage coupler, which (with the two ST-7 motor mount tubes nestled inside) form a removable two-motor cluster mount. This is held in place in the X-16's body tube by a motor clip that is fastened to the outside of the rocket's body tube using a glued-on thin card stock "anchor patch" (it may have been a self-adhesive anchor patch in the original Power System Outfit).

This allows the two-motor cluster mount to be quickly swapped out for the single-motor mount (and vice-versa) as desired. Also, it would enable a 24 mm motor mount to be used. For that matter (just for giggles), a four-motor 13 mm mini motor cluster mount would also fit in the X-16.

[snaquin]

Yup, them's is the parts! Thank you for posting the link.

In the X-16 (for folks who may not be familiar with this rocket), these parts are glued onto the ends of an ST-16 stage coupler, which (with the two ST-7 motor tubes nestled inside) form a removable two-motor cluster mount. This is held in place in the X-16's body tube by a motor clip that is fastened to the outside of the rocket's body tube using a glued-on card stock "anchor patch." This allows the two-motor cluster mount to be quickly swapped out for the single-motor mount (and vice-versa) as desired.

As I was happily pushing my cart down the isles at the SEMROC store I also threw one of these in:

http://www.semroc.com/Store/scripts/prodView.asp?idproduct=960

I wanted to have an option for a single "D" or "E" engine so I picked up a third engine mount.

In a rush to get to the check out line I think I forgot to add an extra hollow tube coupler to make up the base of the payload section so I'll probably have to pick one up on my next order. The suggested parts list calls for three of the HTC-16 but I forgot one is glued directly in front of the motor mount to keep the motor mount from pushing forward. I thought I'd be using the third HTC-16 to couple the payload section to the lower airframe and use a paper disc or foam board disc to close it off.

.

[Mark II]

While I am a firm believer in the joys of delayed gratification (having experienced it myself many times), thirty-plus years of delayed gratification is a *LONG* time! It is sometimes much nicer to discover a rocket design when, as an adult, one has the income to purchase the kit or parts set.Yup, that's the situation with the vast majority of classic rocket kits. I am happily cloning the OOP kits from the '60's, '70's and '80's, because they are almost all brand-new designs to me!

MarkII

[Mark II]

Centuri Power System (http://www.semroc.com/Store/scripts/ClassicParts.asp?ID=1121)Could these possibly be produced as Semroc kits someday, Carl?

MarkII

[Carl@Semroc]

... so I'll probably have to pick one up on my next order. It will not be shipped until Tuesday because of Labor Day. We will include the extra HTC-16 and the solid disc.

We do not have the PIN-16 or PIN-7 inserts.

Remember: the Power System mounts were released before the much more "energetic" ejection charges. :D

[Carl@Semroc]

Could these possibly be produced as Semroc kits someday, Carl?

MarkIIPossibly... I like the X-16, but the X-7 sustainer fins are asking for trouble. It might become the X-8 for better staging.

I have always like the educational aspect of the Power Series. The handbook is a great course guide. It is one of the best resources I have seen to bring a beginner up to intermediate level using classroom and hands-on lab exercises.

[blackshire]

Could these possibly be produced as Semroc kits someday, Carl?

MarkII

I'm not Carl, nor do I play him online, but I think a Semroc version of the Power System Outfit could sell very well to schools and scouting groups (as well as to folks like us).

In addition to the falling sphere (ping-pong ball) altitude measurement system used with the X-16 rocket, the SAM (Standard Altitude Marker [from the "Handbook of Model Rocketry"], a 1" X 12" plastic streamer with a penny weight) could be included in the outfit. It could be flown aboard both the X-16 and the X-7, and the X-16 could carry both the falling sphere *and* the SAM on the same flights for comparative studies.

Also, a simple parasite glider such as the Firefly (see: www.semroc.com/Store/scripts/ClassicParts.asp?ID=128 ), the "T-tailed" glider from the Multi-Roc kit (see: www.semroc.com/Store/scripts/ClassicParts.asp?ID=168 ), or the canard glider from the Condor kit (see: www.semroc.com/Store/scripts/ClassicParts.asp?ID=134 ) could be included in the outfit as an additional project that could be conducted using the X-16.

The Semroc Power System Outfit would appeal to Middle School and High School teachers in subjects such as Industrial Arts, General Science, Physics, Algebra, and Trigonometry. College professors teaching more specialized courses in aerospace engineering and aerodynamics would also find this outfit to be a useful teaching tool.

[blackshire]

Possibly... I like the X-16, but the X-7 sustainer fins are asking for trouble. It might become the X-8 for better staging.

What kind of trouble? Are you referring to the upper stage fins' size (too small?), or to the long, un-bonded "cantilevered" notch in the rear root edge of each fin (necessary to clear the booster module's outside #7 vented tube coupler)? If it is the latter, thin card stock stiffener strips glued parallel to the notches would strengthen the fins. (I think the "Stellar Series" Lance Corporal kit, the two-stage X-7 look-alike, used stiffener strips.) If it is the former, a little extra nose cone weight would move the CG far enough forward.

Since the early predecessor to the later Aerobee-Hi & Aerobee 150 sounding rockets (after which the X-7 and Lance Corporal were patterned) had the X-series designation of "X-8," it would be a fitting name for this rocket in the Power System Outfit.

I have always like the educational aspect of the Power Series. The handbook is a great course guide. It is one of the best resources I have seen to bring a beginner up to intermediate level using classroom and hands-on lab exercises.

Indeed! The educational steps that the manual takes the students through are incremental and build on the previous steps, and they enable the students to visualize how changes in impulse, thrust duration, rocket drag, and recovery system drag affect flight performance.

[snaquin]

It will not be shipped until Tuesday because of Labor Day. We will include the extra HTC-16 and the solid disc.

We do not have the PIN-16 or PIN-7 inserts.

Thanks Carl, I really appreciate that!

Remember: the Power System mounts were released before the much more "energetic" ejection charges. :D

I hadn't considered that. I may save the EM-9-16P and build another X-16 based on this mount with a BTC-16 plug for flying my altimeter and glue the motor mount in permanently for use with my RMS-24/40. I would think the D15 and E18 reloads would be great for altimeter flights in the X-16.

Thanks for making these parts available. I completely missed out on the Centuri Power System when it was available so I'm looking forward to building this one!

:)

.

[Carl@Semroc]

What kind of trouble? Are you referring to the upper stage fins' size (too small?), or to the long, un-bonded "cantilevered" notch in the rear root edge of each fin (necessary to clear the booster module's outside #7 vented tube coupler)? If it is the latter, thin card stock stiffener strips glued parallel to the notches would strengthen the fins. (I think the "Stellar Series" Lance Corporal kit, the two-stage X-7 look-alike, used stiffener strips.) If it is the former, a little extra nose cone weight would move the CG far enough forward.It is the latter; the notch or gap. Even with reinforcing, it has never worked for me like a good solid filleted joint.

[Green Dragon]

It is the latter; the notch or gap. Even with reinforcing, it has never worked for me like a good solid filleted joint.

Although not entirely accurate, could this not be modified with the coupler glued to the sustainer, ala Stilleto ?

Will be placing order soon myself, this one has been on the 'want list' for ages :)

~ AL

( still repairing/ restoring HPR stuff from my last craigslist find :) . )

[blackshire]

Carl's point (about the more "energetic" ejection charges of today's motors with respect to the X-16's interchangeable motor mounts) is well taken.

I wonder, though, if the two-motor cluster mount could be glued in place in the X-16 and then also be used with just a single motor if desired (when flying the X-16 with just the nose cone and no payload section, for example), by inserting a dummy motor into the unused motor mount tube? The dummy motor need not be a heavy expended 18 mm motor, but could just be one of the lightweight thin-walled yellow motor spacer tubes with thick card stock discs glued into both ends.

Since the longitudinal axes of the two motor mount tubes lie close to the rocket's longitudinal axis, the off-center moment from the single motor shouldn't be more than the X-16's large fins could handle to keep the rocket flying straight. (Also, small spin tabs could be taped or glued to the fins to roll the rocket slowly to average out the off-center thrust from the single motor.) However, I think that the "stock" X-16 was probably designed to achieve a straight and safe (lower than planned, but high enough to deploy the parachute) flight path in the event of an "engine-out" liftoff if one of the two motors in the cluster failed to ignite.

[blackshire]

It is the latter; the notch or gap. Even with reinforcing, it has never worked for me like a good solid filleted joint.

While I wouldn't at all mind building and flying a modified X-7 kit that dispensed with the notched upper stage fins and the Centuri-style outside stage coupler and instead used fully-bonded upper stage fins and Estes-style taped-together motors, I can think of two possible "fixes" that might allow the original upper stage fin configuration to be more than strong enough. They are:

[1] You could laser-cut the notch so that it would be 1/12" wider than it is now, and also extend the notch 1/4" farther forward into the fin (this 1/4" notch extension would also be 1/12" wide). The builder would glue a length of 1/12" diameter maple dowel into the wider portion of the original notch (right up against the edge of the notch) as well as into the notch extension, and this would make the fin much stronger and stiffer.

[2] If your laser-cutter can handle basswood and/or thin plywood, the upper stage fins could be made of basswood or plywood instead of balsa. The card stock stiffeners could still be glued alongside the notch to provide an extra measure of strength and stiffness.

[tbzep]

While I wouldn't at all mind building and flying a modified X-7 kit that dispensed with the notched upper stage fins and the Centuri-style outside stage coupler and instead used fully-bonded upper stage fins and Estes-style taped-together motors, I can think of two possible "fixes" that might allow the original upper stage fin configuration to be more than strong enough. They are:

[1] You could laser-cut the notch so that it would be 1/12" wider than it is now, and also extend the notch 1/4" farther forward into the fin (this 1/4" notch extension would also be 1/12" wide). The builder would glue a length of 1/12" diameter maple dowel into the wider portion of the original notch (right up against the edge of the notch) as well as into the notch extension, and this would make the fin much stronger and stiffer.

[2] If your laser-cutter can handle basswood and/or thin plywood, the upper stage fins could be made of basswood or plywood instead of balsa. The card stock stiffeners could still be glued alongside the notch to provide an extra measure of strength and stiffness.

You could always use Carl's fins as a template to cut your own thin plywood fins if he doesn't want to manufacture them.

You could also make your own balsa laminate, gluing the balsa sheets with grain at angles to each other and top it off with some paper laminating on the outside. I've done balsa laminates that were pretty dang strong, but the thinnest balsa I know of is 1/16". That would make the fins ~1/8" thick. I'm taking a wild guess that the X-7 fins are 3/16" instead of 1/8" so it would be considerably out of scale.

[blackshire]

You could always use Carl's fins as a template to cut your own thin plywood fins if he doesn't want to manufacture them.

You could also make your own balsa laminate, gluing the balsa sheets with grain at angles to each other and top it off with some paper laminating on the outside. I've done balsa laminates that were pretty dang strong, but the thinnest balsa I know of is 1/16". That would make the fins ~1/8" thick. I'm taking a wild guess that the X-7 fins are 3/16" instead of 1/8" so it would be considerably out of scale.

I think the X-7 fins (and the Lancer fins and the Lance Corporal fins, see: http://www.ninfinger.org/rockets/catalogs/centuri75rt/75rt8.html) used/use 3/32" balsa. I'm not particular about how Carl would like to configure the upper stage fins for an X-7 kit, as what works best for a quantity-production kit intended for "lay customers" often must be simplified from what experienced rocketeers can build and use successfully.

I would rather see a simplified Skill Level 2 two-stage X-7 kit that sells in large quantities, pleases its buyers, and makes a lot of money for Semroc than a Skill Level 3 "purist" kit of this design with the original notched upper stage fins that sells in smaller numbers (due to the higher Skill Level) and perhaps disappoints and frustrates many of its buyers.

With my own X-7 kit, I would notch the upper stage fins and glue copier paper to both sides of each fin, then add the outside #7 tubing coupler (with the two staging vent holes) to the front end of the booster's body tube.

[tbzep]

I think the X-7 fins (and the Lancer fins and the Lance Corporal fins, see: http://www.ninfinger.org/rockets/catalogs/centuri75rt/75rt8.html) used/use 3/32" balsa.

Oops. I meant 3/32". I have no idea why I typed 3/16". That's pretty dang thick for a little rocket. :o

[A Fish Named Wallyum]

( still repairing/ restoring HPR stuff from my last craigslist find :) . )

Well? Where is the thread with the pics? :confused: ;)

[Green Dragon]

Well? Where is the thread with the pics? :confused: ;)

ok, will start a thread :P

vintage HPR ?

not quite, but still a neat find. stay tuned ( no hijaking the thread here :D )

~ AL

[Mark II]

I've done balsa laminates that were pretty dang strong, but the thinnest balsa I know of is 1/16".Actually the thinnest balsa sheet that is readily available is 1/32". It is often used by contest fliers and scale modelers. But regardless, I think that Black Shire made a good point about sacrificing some fidelity to the original design in order to keep the kit at a moderate skill level. (Actually, I think that Black Shire is making a whole lot of very good points in this thread. So are others, too, myself excluded. Keep 'em coming; I'm enjoying reading this. :) )

MarkII

[tbzep]

Actually the thinnest balsa sheet that is readily available is 1/32". It is often used by contest fliers and scale modelers. But regardless, I think that Black Shire made a good point about sacrificing some fidelity to the original design in order to keep the kit at a moderate skill level. (Actually, I think that Black Shire is making a whole lot of very good points in this thread. So are others, too, myself excluded. Keep 'em coming; I'm enjoying reading this. :) )

MarkII

I wasn't really talking about doing it for a kit, but to do a scratch, or take a kit's fins and use them as templates for something stronger. I agree that for the average person, a modification or two would be prudent for a kit.

[blackshire]

Mark II, I very much appreciate your vote of confidence!

For the X-7 upper stage fins, three plies of 1/32" balsa (the outer two with the grain parallel to the fin leading edge and the middle ply with its grain oriented 90° to the grain of the outer plies) would be plenty stiff and strong even with the notch at the root in the rear. Taking the thickness of the glue into account, such fins would probably be no thicker than paper-laminated 3/32" fins.

With the X-16, I've been thinking about Carl's warning regarding its removable motor mounts with respect to the more energetic ejection charges in today's motors. To compensate for this, the X-16 could be equipped with two motor mount retainer clips (instead of the one used in the original) affixed to the outside of the rocket's body tube on opposite sides. These would be fastened firmly to the body tube using a 1" X 1" or 1.25" X 1.25" square of thin card stock glued down over each retainer clip.

Using the new-style motor clips with the finger tabs would allow a cord or a wire to be wrapped around the two motor mount retainer clips so that it runs in the "valley" or detent where the finger tab on each motor clip curves back upward. After inserting the motor mount in the rocket, the cord or wire would be run along the outside of the mount's motor tube(s) and then be lightly "cinched up" to pull the two motor mount retainer clips securely against the rocket's body tube.

This augmented retention system should be sufficient to spread out the ejection charge loads and keep the motor mount from being ejected from the rocket, even when using the two-18 mm motor cluster mount or a 24 mm motor mount. If necessary, three or even four motor mount retainer clips could be used.

[snaquin]

I assembled my X-16 Friday and primed the nose cone. Still needs the fin fillets and launch lugs attached.

Thanks Carl & Sheryl for including the two paper discs and extra HTC-16 to seal off the payload section. I really do appreciate that!

:)

[blackshire]

Beautiful! And don't forget--the Power System X-16 (and X-7) decals are available in the "Decals & Templates" section of Ye Olde Rocket Plans, right here at: http://www.oldrocketplans.com/decals/centuri_power_system_decal.jpg

[snaquin]

Beautiful! And don't forget--the Power System X-16 (and X-7) decals are available in the "Decals & Templates" section of Ye Olde Rocket Plans, right here at: http://www.oldrocketplans.com/decals/centuri_power_system_decal.jpg

Thanks, and I did not realize the decals were on YORP. I appreciate the link.

I sent an email to Sandman to see if he could reproduce them for me.

:)

[blackshire]

Thanks, and I did not realize the decals were on YORP. I appreciate the link.

I sent an email to Sandman to see if he could reproduce them for me.

:)

Yes! The decals for the Centuri Micron (to go on my Semroc reproduction Microns), the original Centuri Viking (Semroc and Sirius Rocketry have the parts for it), and the Centuri Power System X-16 and X-7 are at the top of my "Wish List" for decal sets I'd like to see him produce.

[Ron Bianchi]

Did you get the fin patterns? I have 3 power system kits (boxes) I could "crack" one open
and get the patterns and decal and parts list for you guys. If yes is the answer, just give me a few days to dig them out, catalog, scan, etc...

Ron

[blackshire]

Did you get the fin patterns? I have 3 power system kits (boxes) I could "crack" one open
and get the patterns and decal and parts list for you guys. If yes is the answer, just give me a few days to dig them out, catalog, scan, etc...

Ron

Semroc now has the X-16 parts set (including laser-cut fins) available, and I think Carl is also working on the X-7 booster and sustainer fin sets (as well as the other parts).

[snaquin]

Did you get the fin patterns? I have 3 power system kits (boxes) I could "crack" one open
and get the patterns and decal and parts list for you guys. If yes is the answer, just give me a few days to dig them out, catalog, scan, etc...

Ron

Ron

Any way you could get a few of the requested measurements off of one of your original decal sets for this model so Sandman can finish off the decal sets he is trying to reproduce for the power system rockets? I'm one of the users waiting for Sandman to produce these and would really appreciate it!

http://forums.rocketshoppe.com/showthread.php?t=5966

Thanks!

.

[Ron Bianchi]

Here you go. Hope this works. Sent all of the scans to Scott.

ron

[blackshire]

Here you go. Hope this works. Sent all of the scans to Scott.

ron

Thank you! I "PM'ed" a link to your dimensioned scan of the Centuri Power System decal sheet to Sandman so that he can size his duplicates of the decal sheet properly.