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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

-feel
very sporty in the air

-slow speed
incredible

-stalls
a little rough but I have yet to drop a wing

-aerobatics
slow, fast, and hesitation rolls, plus inverted

-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 of 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 sheet 1
Grunjet plans sheet 2

-Decals
follow link
 
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#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 basically in other words, 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! I've got a quick tip just 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
 
#15
Awesome! Thanks again! I'll post some pics when she's done. Parts are cut and ready, if I have a chance tonight I'll put it together and hopefully maiden this weekend.
 
#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
 
#20
I finished her up Saturday, but I wasn't braving those winds! Went together well. Hope to maiden this evening, as the rest of the week looks wet. Thanks for the plans, can't wait to see how she flies!

GRUNTOP.JPG GRUNBOTTOM.JPG