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DIY $80 Grunjet

Grifflyer

WWII fanatic
#1
Introducing the Grunjet, a two sheet foamboard performance jet flying fast and sporty, and slows down to a solid run on landings, and is packed with amazing vertical performance, all only costing 80$ built to BNF standards

-Video

-Parts list
two sheets of adams readi-board

FMS 50mm 11 blade EDF 4s version

4s 1300mah 45C

40a esc

three 9g servos

-Review

-Speed
I would say roughly 70mph

-Handling

smooth but fast roll rate with the same tendencies on the elevator which makes a great introduction to jets

-Slow speed
This is one of the strongest points for the design, so it comes in really slow compared to other jets in its class.

-Stalls
A little rough but I have yet to drop a wing

-Aerobatics
This plane doesn't have a rudder so you're limited to basics: rolls, loops, and inverted flight.

-Take offs
You can either do an underhand launch while holding the thrust tube, or my favorite, just plop it on the grass and give it full throttle and off she goes!

-Vertical
Nearly unlimited

-CG

4.5 to 5 in/11.5 to 12.5 cm from leading edge

-Gallery

a.jpg

b.jpg

a (1).jpg

b (1).jpg

c.jpg

-Plans

Grunjet Plans V1.0

-Decals

Grunjet Decals
 
Last edited:

jaredstrees

Well-known member
#13
Afternoon Grifflyer! I’m going to start my build on this tonight. Any tips? The batteries and esc I have are a little big at 1500mah and 60 amp esc, but I’m using gorilla glue to shave a little and I’ll probably shave a little more weight where possible. Looks like a great plane and am looking forward to the build/flight!
 

Grifflyer

WWII fanatic
#14
Afternoon Grifflyer! I’m going to start my build on this tonight. Any tips? The batteries and esc I have are a little big at 1500mah and 60 amp esc, but I’m using gorilla glue to shave a little and I’ll probably shave a little more weight where possible. Looks like a great plane and am looking forward to the build/flight!
Personally....I think you'll be fine, I run on a 1300 and a 40 amp with NO regard to saving weight and it comes in SO slow. So, I think you might not come in as slow, but you'll get a bit more power and make the ground takeoffs even more fun! The only tip I've got is make sure your thrust tube is straight,

And I should probably mention control throws.
Ailerons Low=~15 degrees | High=~24 degrees
Elevator Low=~11 degrees | High=~20 degrees
 
Last edited:

jaredstrees

Well-known member
#17
Probably not the decals, I'll add some color to it, most likely just a little colored packing tape for orientation. After the maiden and I get a handle on it's flight characteristics I'll most likely build another and really dress her up. Seems like it should be pretty straight forward and quick build. If you get a chance though, could you take a pic of the bottom so I have a 360 view for the build? If not I'm sure I can figure it out.
 

Grifflyer

WWII fanatic
#18
Probably not the decals, I'll add some color to it, most likely just a little colored packing tape for orientation. After the maiden and I get a handle on it's flight characteristics I'll most likely build another and really dress her up. Seems like it should be pretty straight forward and quick build. If you get a chance though, could you take a pic of the bottom so I have a 360 view for the build? If not I'm sure I can figure it out.
sorry I'm a little late but here are some pictures from lots of different angles
a.jpg

b.jpg
make sure the tail tapers down to one sheet of foam thick.

c.jpg

d.jpg

e.jpg