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New Build, 2-stage Mini Max, using Fin Wizard
#1
I started this build thread on another new forum, but there has not been a lot of traffic.  I thought I'd add it here.

I bought several Mini Max kits several years ago at Hobby Lobby, getting them for around $6 with a 40% off coupon. It seemed like every time I went into the store, there were two more Mini Max kits hanging up.  I think I quit at 4, although I just could not resist the urge to buy them every time I saw them ...   Smile

I had decided I probably would not build all of them the same, and in fact, I decided that the first build should be a 2-stage, so the booster section is made from parts of a second kit. I decided to kitbash a second kit since the booster will use the kit decals to duplicate its looks with the lower part of the upper stage. 

The booster is much longer than the small, mini "T" motors, so it will employ gap staging. Here are the parts on my workbench. I've used one of the kit's body tubes, as-is, for a booster tube. I have punched two gas ports in the top of the booster tube, as well as clearance notches in the coupler, where it would have partially covered the ports. The booster's motor tube is slightly longer than the standard motor tube, to more directly aim the booster's burnout blast at the upper stage motor's nozzle. I also decided to use a longer BT-50 for the upper tube, rather than the short tube supplied with the kit.

I'm using an "old-style" engine hook for the booster, rather than the newer style hook included in the kit, for minimal overhang at the tail end of the rocket. The upper stage will use the standard hook. 

Next up, attaching the fins with Fin Wizard, a product I offered a few years ago.

   
Lee
NAR 55948, L2
In Build: Mars Snooper
Next: upscale Sky Hook (Panavia kitbash)
In Finishing:  Estes Honest John, Red Nova, Super Cobra
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#2
What the heck is 'fin wizard'?
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#3
Next step, dragging my Fin Wizard out to add fins. I marketed this product a few years ago, but my friend that was doing the machining separated from his wife and went thru a divorce, and had to focus on projects that provided a paycheck. I have one of 3 we produced before discontinuing production. This product works beautifully, but does have its limitations. First, it only works for BT-20, BT-50, BT-55, and BT-60, by using special table legs for sized for each tube. (It also works for corresponding Centuri tubes). Next, it only works for 3-finned or 4-finned rockets. No tube marking is required -- Fin Wizard automatically places 3 or 4 fins equally about the body tube.

Anyway, back to the Double Mini Max, hereafter referred to as the "DMM". The picture shows the first fin added to DMM's upper stage body tube. The body tube is layed in the cradle, and the fin with glue is layed on the table, touched to the body tube, and allowed to dry. Sometimes a body tube extender is required during gluing, depending on fin profile. I just keep a set of short body tube sections with a coupler for doing this.

A small piece of tape, or a weighted object like a small beanbag can be set of the tube and fin to keep it from shifting, although this is usually unnecessary. If you look at the picture, a very narrow gap shows between body tube and table. This is by design, to keep any glue seepage from touching the table, or wicking under the fin and leaving a mess on the fin's surface.

Next up:  adding the second fin, and more info on how the Fin Wizard automatically aligns the next fin.

   

(08-19-2015, 07:56 PM)rstaff3 Wrote: What the heck is 'fin wizard'?

I got sidetracked, and you jumped in before I could add another post! See above.

First picture below shows adding a second fin. One of the two "legs" on the Fin Wizard has tapered slots for both 3-fin and 4-fin alignment. When the first fin joint is dry, it is indexed into a slot, so that the second fin can be glued on. 

Depending on fin profiles, either the leading edge, or the trailing edge, can be used to hold the glued fin. The legs slide into slots on the bottom side of the table, and are held in place, correctly aligned, with a recessed cap screw, loosened or tightened with a hex wrench. 

Once the second fin joint is dry, the body tube is rotated again, capturing two fins. The third fin can then be glued on. This same procedure is used for 4-fin rockets, but the 90 degree slots are used instead of the 120 degree slots.

Here are pictures of two fins attached, and then the third fin. Also shown is a picture of the Fin Wizard with leg sets for the other body tube sizes. Each leg set is inscribed with the BT designation. 

               
Lee
NAR 55948, L2
In Build: Mars Snooper
Next: upscale Sky Hook (Panavia kitbash)
In Finishing:  Estes Honest John, Red Nova, Super Cobra
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#4
I completed the priming of the booster. The cheap HomeShades Primer I bought a Walmart works great. Sands very easily. It looks like Duplicolor is going for close to $7 a can at automotive stores, so this cheap ColorShades primer may become my new standard.The picture below is after a 3rd coat. There is a little bit of a body tube seam showing at the top, but usually when the final sanding is done, these disappear as you get to a point where paint in the seam is level with the surface of the tube. 

After the booster dried, it was lightly sanded, then painted. My color choice for the bodies/fins is white undercoat, followed by a red topcoat. I used my favorite paint -- Rustoleum Lacquer. It only comes in red, black, and white. Works for this one just fine. 

Second picture is the painted booster.  Since the cans of spray paint were old (~ 5 years), I concentrated on prepping the booster, and will complete the upper stag prep afterwards.  I sprayed on a coat of white lacquer, and it looked a little bumpy. I forgot how quickly lacquer dries, especially when it is hot outside. I gave it a second, wetter coat, and allowed it to dry. I then lightly wet-sanded it. Lacquer just dries so fast, you need to put it on pretty wet, so I also held the can a little closer to the rocket.  I've found that runs are almost non-existent when using lacquer. The red topcoat picture is after 3 coats.  It came out pretty smooth and very glossy. The 3rd picture is after decal application, and a clear coat of Krylon UV-Resistant Acrylic Gloss Clear.

               
Lee
NAR 55948, L2
In Build: Mars Snooper
Next: upscale Sky Hook (Panavia kitbash)
In Finishing:  Estes Honest John, Red Nova, Super Cobra
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#5
The "fin wizard" looks interesting! Any possibility of it being offered again in the future? Might be interested in obtaining one for myself if I can finagle the "budget" a bit *LOL*
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#6
(08-20-2015, 04:57 PM)sanderj Wrote: The "fin wizard" looks interesting!  Any possibility of it being offered again in the future?  Might be interested in obtaining one for myself if I can finagle the "budget" a bit  *LOL*

sanderj,
Yes, there is a possibility the product will be offered again (really, a "new and improved" version).  The timing was lousy when I did this before, with my friend having some personal issues.  All that is long behind him, and he now has a new Haas CNC machining center that automates all the tool changes that were manual before. And we had to do a lot of hand de-burring of parts, which his Haas could automate.  Very little manual intervention other than feeding in more material would be required. Finally, it is 10X the speed of his previous CNC, which all help contribute to making a Fin Wizard easier and more economical to build.

Now that I've used it for a number of rockets, I'd change a few things -- making the table bigger and getting it higher off the work surface so bigger fins fit.  Currently I move it to the edge of my workbench if the fins hang down too far, and touch the workbench.

The four leg sets I offered -- BT-20, 50, 55, and 60, cover the vast majority of builds for the intended use of this product.  I could see possibly adding BT-5, and maybe some Centuri/Semroc sizes that aren't a direct drop-in into one of the Estes-sized legs.

Here are the close/identical tubes from Estes and Centuri/Semroc:
BT-5 is .543"OD, ST-5 is .543"OD  (existing leg set works for both)
BT-20 is .736"OD, ST-7 is .759"OD (existing leg set may work OK for ST-7, I need to verify)
BT-50 is .976"OD, ST-9 is .998"OD  (existing leg set may work OK for ST-9, I need to verify)
BT-55 is 1.325"OD, ST-13 is 1.34"OD  (existing leg set may work OK for ST-13, I need to verify)
BT-60 is 1.637"OD, ST-16 is 1.64"OD (existing leg set will work for both)

I would possibly want to offer ST-9 and ST-13 leg sets (and ST-13 would work for BT-56, which is 1.346"OD).  I cannot imagine a great demand for ST-7.  Likewise I am unsure about other intermediate sizes like ST-8, ST-10, and ST-11.

Fin spacing on small rockets is critical -- getting a fin a bit away from a pencil line when gluing fins on manually really stands out.  The Fin Wizard nails this.  On larger body tubes like BT-70 and BT-80, I think missing the line just a bit is considerably less noticeable. The biggest issue is getting a fin placed perfectly perpendicular to the tube, and something like the Guillotine by Ted Macklin really works well for this.
Lee
NAR 55948, L2
In Build: Mars Snooper
Next: upscale Sky Hook (Panavia kitbash)
In Finishing:  Estes Honest John, Red Nova, Super Cobra
Reply
#7
(08-20-2015, 06:07 PM)Trident Wrote:
(08-20-2015, 04:57 PM)sanderj Wrote: The "fin wizard" looks interesting!  Any possibility of it being offered again in the future?  Might be interested in obtaining one for myself if I can finagle the "budget" a bit  *LOL*

sanderj,
Yes, there is a possibility the product will be offered again (really, a "new and improved" version).  The timing was lousy when I did this before, with my friend having some personal issues.  All that is long behind him, and he now has a new Haas CNC machining center that automates all the tool changes that were manual before. And we had to do a lot of hand de-burring of parts, which his Haas could automate.  Very little manual intervention other than feeding in more material would be required. Finally, it is 10X the speed of his previous CNC, which all help contribute to making a Fin Wizard easier and more economical to build.

Now that I've used it for a number of rockets, I'd change a few things -- making the table bigger and getting it higher off the work surface so bigger fins fit.  Currently I move it to the edge of my workbench if the fins hang down too far, and touch the workbench.

The four leg sets I offered -- BT-20, 50, 55, and 60, cover the vast majority of builds for the intended use of this product.  I could see possibly adding BT-5, and maybe some Centuri/Semroc sizes that aren't a direct drop-in into one of the Estes-sized legs.

Here are the close/identical tubes from Estes and Centuri/Semroc:
BT-5 is .543"OD, ST-5 is .543"OD  (existing leg set works for both)
BT-20 is .736"OD, ST-7 is .759"OD (existing leg set may work OK for ST-7, I need to verify)
BT-50 is .976"OD, ST-9 is .998"OD  (existing leg set may work OK for ST-9, I need to verify)
BT-55 is 1.325"OD, ST-13 is 1.34"OD  (existing leg set may work OK for ST-13, I need to verify)
BT-60 is 1.637"OD, ST-16 is 1.64"OD (existing leg set will work for both)

I would possibly want to offer ST-9 and ST-13 leg sets (and ST-13 would work for BT-56, which is 1.346"OD).  I cannot imagine a great demand for ST-7.  Likewise I am unsure about other intermediate sizes like ST-8, ST-10, and ST-11.

Fin spacing on small rockets is critical -- getting a fin a bit away from a pencil line when gluing fins on manually really stands out.  The Fin Wizard nails this.  On larger body tubes like BT-70 and BT-80, I think missing the line just a bit is considerably less noticeable. The biggest issue is getting a fin placed perfectly perpendicular to the tube, and something like the Guillotine by Ted Macklin really works well for this.

Thanks for the info!  I have been looking at the "Guillotine" by Mr. Macklin myself, been leaving lots of hints with my better half and the kids that Christmas is coming and it would be nice to see "Santa" leave one for me under the tree!  *LOL* Tongue   In the mean time I will do what I can with the Mk 1 eyeball and a ruler
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#8
I think a Guillotine will be part of my tool kit at some point.  Until we redo the Fin Wizard and possibly add leg sets for bigger tubes, the Guillotine would be my choice.  And realistically, I am not sure one Fin Wizard for all tube sizes makes a lot of sense anyway.  Perhaps an "XL" model with really big table, and the larger tube leg sets, would be a better choice.

I think I may be talking myself out of offering a solution for large tubes!
Lee
NAR 55948, L2
In Build: Mars Snooper
Next: upscale Sky Hook (Panavia kitbash)
In Finishing:  Estes Honest John, Red Nova, Super Cobra
Reply
#9
(08-21-2015, 12:02 PM)Trident Wrote: I think a Guillotine will be part of my tool kit at some point.  Until we redo the Fin Wizard and possibly add leg sets for bigger tubes, the Guillotine would be my choice.  And realistically, I am not sure one Fin Wizard for all tube sizes makes a lot of sense anyway.  Perhaps an "XL" model with really big table, and the larger tube leg sets, would be a better choice.

I think I may be talking myself out of offering a solution for large tubes!

*LOL*  I understand, the dilemma of having one tool that does "all" sizes versus separate devices for each....

Like Alton Brown on Food network says it is better to have a "tool for multiple uses than multiple tools for single uses" (or some such thing)

Would still be interested in yours if you offer them for sale again in the future though
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#10
Back to the building of my 2-stage Mini Max.  I really struggled with paint on the upper stage.  A combination of heat/humidity, and spraying with an old can of lacquer, gave me some bumps on the first coat of red.  I wet-sanded it to smooth it, let it sit a couple days, and sprayed again today.  It was early in the morning, so weather cooperated much better.  But I was still getting some little bumps in spots, so I sprayed a final coat very heavy, making it pretty wet.  Since I paint rockets on a dowel, I rotated the dowel for a minute or so, to allow the lacquer to dry, and prevent any sags or runs.  It ended up looking pretty good.  Maybe not as good as the booster, but smooth enough for providing a good base for the decals.

I threw away the can of paint, it was getting a little low anyway.  I think I first used this lacquer 5 years ago, and decided it was foolish to try to use it up if its age is what is gave me the issues.  I'll wait a couple days before I add the decals, which will basically be similar to the booster, plus the big black band with skull decal.  The booster got fewer decals due to its size. I also need to add motor mounts, which I usually add last, and then I'll post the final picture of the completed rocket.

   
Lee
NAR 55948, L2
In Build: Mars Snooper
Next: upscale Sky Hook (Panavia kitbash)
In Finishing:  Estes Honest John, Red Nova, Super Cobra
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