1.45X Upscaled Jet Freak

[Rktman]

This isn't exactly a build thread since…well…it's already been built. But I’ve attached the templates, parts, and build notes below as a pdf file if you're interested in a fast, easy build of what turned out to be a surprisingly great flyer. I know, looks unlikely, especially considering the original wasn't much to get excited about. Turns out in this case, looks are deceiving.

What was totally unexpected was this upscaled foamie’s more than decent 1 minute 38 second flight on a C6-3 (intended to use a B6 but ran out; all I had left in my range box was the C). I honestly had much lower expectations because of its basic, sort of chunky design, and was realistically expecting a 25 or 35 second flight…if it didn’t disintegrate on the way up.




Flight Report

Plus #1 — It didn’t disintegrate.

Plus #2 — While 1 minute 38 in dead air may not put it in the competitor's circle, it's pretty darned respectable for something not contest-optimized.

Plus #3 — There was no tendency to roll even without any dihedral (I’ve been experimenting with swept wing and delta winged designs lately because they exhibit a “built in” dihedral effect). Best part was seeing it confirmed.

Plus #4 — My hand trimming attempt actually resulted in it being perfectly balanced and stable. It usually takes an actual flight or two to fine tune things.

Plus #5 — Although it boosted high enough that I lost sight of it at first, it thankfully circled in about a 25’ radius and I eventually got eyes on it. Also fortunate that it was 10:00 a.m. and the thermals hadn’t started to form yet. (I’ve lost quite a few to the park’s always-hungry perimeter trees or beyond the park boundaries. A B-motor would probably have been better for this initial flight, and for smallish to medium soccer field-sized flying areas).

So why the upscale? Well, since my original cloned balsa version was destroyed by what I now think must’ve been a motor CATO in late 2019, I decided to celebrate its demise by building an upscaled version on its 1-year “departure” anniversary. Had to wait over a year, but finally got to fly it the week before last.

Okay having problems attaching the pdf file. Back in a little bit…

 

[Rktman]

That pdf problem is going to take longer than I thought. In the meantime here's the parts list and build notes. Will put up the pdf files with templates and the info below when I get the problem sorted out.

Parts list

• (1) 1/8” polystyrene foam sheet
• (1) eRockets or BMS BNC-50J nose cone sanded down to 1.07” in length and rounded to match original BNC-20A shape
• (1) 4.5 ” length of BT-50 (Main Boost Pod)
• (1) 3” length BT-20 (Motor Eject Pod)
• (1) Engine Hook
• (1) 18mm Engine Block
• (3) 20/50 Centering Rings
• (1) Streamer
• (1) 1/8” Hard C-grain Balsa Hard Balsa (9 – 14 lb) recommended
• (1) Launch lug

Build Notes:

• I built the upscaled version’s wings from 6mm (1/4”) Pro-Formance foam (sadly no longer available since Great Planes seems to have been swallowed by Horizon Hobby). The 1/4” pink Owens Corning extruded polystyrene foam insulation board available from Lowes, Menards, etc. could possibly be a workable substitute once the paper sheathing is peeled off to lighten it.
  
  
• All balsa parts are 1/8”. I added a keel since the pylon, rudder and wings needed something solid to attach to.
  
  
• Lay the keel and both wings on a flat surface and use wood glue or foam-safe CA to join them to the keel at their root edges. The top edge of the keel needs to be flush with the glider’s wings. This side will be the top of the glider where the pylon/motor pod are glued.
  
  
• Probably the key to getting a decent glide is the addition of flaps (elevons?) to the outer half of the wing’s trailing edge. Using the template pattern, carefully cut partway through the foam where indicated by the dotted line, then gently bend the flap’s trailing edge upward 1/16”. (Using the flap angle guide provided helps to position the flaps correctly). Lock both flaps in position with glue.

• It’s strongly advised that you protect the foam wings with self-adhesive aluminum tape or aluminum foil, as the motor’s exhaust plume will definitely melt or severely damage the wings otherwise.
  
  
• Glue the engine hook 2.5” from the exhaust end of the motor eject tube, then glue the motor block ahead of the hook, pushing it in from the front.
  
  
• Glue a centering ring to both ends of the motor eject pod and attach the streamer.
  
  
• Add glue and place the 3rd centering ring 3” up inside the main boost tube (use the motor eject pod to shove it in, stopping when the end of the eject pod is flush with the end of the boost tube). This will leave a small cavity up front where the vent holes will be punched.

• Using the vent and pylon marking guide, mark the main boost tube where the pylon will be glued and the vent holes need to go. Use a paper punch to make the two 1/8” holes 180° apart on either side. (This is optional, but I’ve had the shotgun Estes ejection charge snap pylons and/or damage boost tubes severely. This will vent enough pressure to prevent that but will still spit the eject pod/streamer and motor.

• Glue the pylon even with the end of the main boost tube and glue the launch lug in the space between the tube and pylon. When dry, glue the unit so that the front of the pylon is flush with the front of the glider’s keel.
  
  
• Like the original model, the design of the Jet Freak tends to be nose-heavy. It’ll need some aft weight. If you use harder, denser balsa for the keel and rudder, it shouldn’t take much. My glider only required 1.84 grams of clay added to the rudder tip. Otherwise add weight as needed to trim.

 

[J Blatz]

Nice job man. I have a built from scraps Jet Freak that is a great performer on 1/2A and A class motors.

 

[Rktman]

Nice job man. I have a built from scraps Jet Freak that is a great performer on 1/2A and A class motors.

Thanks J. appreciate that! I miss my original too, flew really great on an A until the CATO destroyed her. (She was also "purtier" than my current upscale IMHO).

 

[Rktman]

Finally got the upload kinks worked out for the pdf (was far too big for some reason). Templates at 100% scale are in the pdf below.

 

[Aeronerd]

This isn't exactly a build thread since…well…it's already been built. But I’ve attached the templates, parts, and build notes below as a pdf file if you're interested in a fast, easy build of what turned out to be a surprisingly great flyer. I know, looks unlikely, especially considering the original wasn't much to get excited about. Turns out in this case, looks are deceiving.

What was totally unexpected was this upscaled foamie’s more than decent 1 minute 38 second flight on a C6-3 (intended to use a B6 but ran out; all I had left in my range box was the C). I honestly had much lower expectations because of its basic, sort of chunky design, and was realistically expecting a 25 or 35 second flight…if it didn’t disintegrate on the way up.

View attachment 486791


Flight Report

Plus #1 — It didn’t disintegrate.

Plus #2 — While 1 minute 38 in dead air may not put it in the competitor's circle, it's pretty darned respectable for something not contest-optimized.

Plus #3 — There was no tendency to roll even without any dihedral (I’ve been experimenting with swept wing and delta winged designs lately because they exhibit a “built in” dihedral effect). Best part was seeing it confirmed.

Plus #4 — My hand trimming attempt actually resulted in it being perfectly balanced and stable. It usually takes an actual flight or two to fine tune things.

Plus #5 — Although it boosted high enough that I lost sight of it at first, it thankfully circled in about a 25’ radius and I eventually got eyes on it. Also fortunate that it was 10:00 a.m. and the thermals hadn’t started to form yet. (I’ve lost quite a few to the park’s always-hungry perimeter trees or beyond the park boundaries. A B-motor would probably have been better for this initial flight, and for smallish to medium soccer field-sized flying areas).

So why the upscale? Well, since my original cloned balsa version was destroyed by what I now think must’ve been a motor CATO in late 2019, I decided to celebrate its demise by building an upscaled version on its 1-year “departure” anniversary. Had to wait over a year, but finally got to fly it the week before last.

Okay having problems attaching the pdf file. Back in a little bit…

Very cool. I got some poster board (I think its called fomecore) that I'm going to try this with. looks like a simple build with not very many parts. Just my speed.

 

[Rktman]

Very cool. I got some poster board (I think its called fomecore) that I'm going to try this with. looks like a simple build with not very many parts. Just my speed.

Foam core is too heavy IMO. If you can strip off the outer paper covering it might be light enough to use. You might have to use something thicker than 1/8", foam core may not be as strong. Or maybe reinforce it with thin carbon rods or something. It's also open-cell foam, so it may not be as smooth.

 

[TheAviator]

Foam core is too heavy IMO. If you can strip off the outer paper covering it might be light enough to use. You might have to use something thicker than 1/8", foam care may not be as strong. Or maybe reinforce it with thin carbon rods or something. It's also open-cell foam, so it may not be as smooth.

Adams Readiboard ($1/sheet @ Dollar Tree) works really well for super cheap builds. It's less than 1/2 the weight of regular Elmer's foamcore.

 

[waltr]

Nice upscale. I did a half-scale Jet Freak for MMX motors. Fun build and flights. Gave one to a club member and it flew away on his first flight so this design does fly well.

When I was glide trimming also found the wing needed a little 'up elevator'. I did this on the balse wings by sanding an away the bottom trailing edge.

 

[Rktman]

Nice upscale. I did a half-scale Jet Freak for MMX motors. Fun build and flights. Gave one to a club member and it flew away on his first flight so this design does fly well.

When I was glide trimming also found the wing needed a little 'up elevator'. I did this on the balse wings by sanding an away the bottom trailing edge.

Sanding in some elevator on the trailing edge is an excellent idea (vs adding tail weight), especially with a smaller, lighter downscale tlike yours that doesn't need a whole lot of correction.