BJ-J3 Cub - NOT a Failure Story - Plans and Build Instructions

[jpot1]

Servos inside the fuse.



Put everything together and this is actually nose heavy without the battery. I only have a 75g 1100 kv motor which is the problem. I need to use a 1300 or 2200 mah 3s centered under the opening in the fuse top. Will have to see how this flies as I am not keen on taking the wing on and off to change the battery.

 

[jpot1]

Built this to get my daughter to come flying with me...so she got to pick the color!



Maiden tomorrow and then some more decals.

 

[CaptBill]

Nice.
I just finished borrowing your landing gear idea. I did it just a tad differently. I laced or sewed the steel rods to the plywood mount. Also lashed where the axle and side legs come togeather. After I level it all up I'll epoxy the threading and lashing. My thread is 92 weight dacron, used normally.for marine exterior canvas covers.picture to follow

 

[jpot1]

Maiden was not terrific as I guessed at the cog being about 1/3rd of the chord but it flew a bit tail heavy. Trimmed in a ton of down to compensate. Also was a bit windy. Got it down in one piece and am moving cog about a half inch forward.

 

[CaptBill]

alt landing gear



I have never been very pleased with my landing gear. This is actually for a Storch but as I am planning a cub for my next build (remembering that all things are subject to change) I have been following this thread as well.

I still need to do a little adjustment to make it all balanced out, then epoxy the lashing there the supports and axle wire come together. I used one pc of continuous wire for the two axel pieces. The wire runs across the plywood base and between the plywood and the main support legs.

btw, the plywood is salvaged from a Clementine fruit box, why its so colorful

 

[Strix]

Nice one, Jpot! That color looks great!

Mine flew perfectly with the CG right on the spar, which is about 25% of chord.

 

[ranger351]

Finally flew my BJ J-3 Cub! What a great plane if it's not on your build list it should be!



I built this plane during the winter the of 2015/16 with skis. But never had the right condition to try it out. So the other day I took the skis off and installed the wheels.



Today the weather was decent here in Minnesota so I gave it a Go! I set it up with a C pack I had laying around and a 9x6 prop running off a 3s 1600 mah battery. I built it a steerable tail wheel so it cruises around on the ground as good as it does in the air. The take offs can be scale or super short how ever you like em. The plane will fly fast or slow down to crawl and seem to just float in mid air. I was even able to do some simple rolls and loops with out any effort. I highly recommend this plane to anyone weather your a beginner or experienced pilot. The way this plane handles reminds me of the FT Storch but in a bit smaller package.

 

[FPVology]

glad you enjoy the design!
those skis look awesome. If i didn't live in AZ i would have to give those a try lol.
love the steerable tail wheel as well.
Nice build!

 

[ranger351]

glad you enjoy the design!
those skis look awesome. If i didn't live in AZ i would have to give those a try lol.
love the steerable tail wheel as well.
Nice build!

THANKS! Wish I was able to give the skis a try! The plan was to try to fly off the frozen lake at my brother in laws house. It's been either to windy or super cold here in Minnesota. Yesterday was the first time I'd been able to fly in about two month and it was still only 37 degrees!

 

[Oske]

I couldn't find a weight range for the motor on hobbyking to compare to the motor i have but i have a park 300, will that work? I dont want to have to buy new electronics.

 

[Strix]

I couldn't find a weight range for the motor on hobbyking to compare to the motor i have but i have a park 300, will that work? I dont want to have to buy new electronics.

Honestly, I don't believe that's enough motor for this model, which has an all-up-weight (with 2200 3s) around 20 ounces or a bit more.

E-flite's page on the Park 300 (http://www.e-fliterc.com/Products/Default.aspx?ProdID=EFLM1150) says "Ideal for 3D models 6–9 oz (170–255 g) and sport and scale models 8–12 oz (225–340 g)"

You could probably get away with it, but the plane would certainly be lacking power. A 370 or 400 size motor is a much better fit.

 

[yuhuyu]

do you think an emax 2212 980kv with a max thrust of 880gr will be enought for this plane, maybe a little more of weight ?

i've made a remix between this and an Armin wing <..< havent had time for maiden flight

 

[FPVology]

as wilsonman might say.. it'll fly... probably!

 

[Strix]

I'm loving this plane, so I'm bumping this thread!

This is #2. #1 went down in the woods behind my club's runway, never to be seen again (BEC failure). :black_eyed:

 

[jpot1]

Strix, nice looking cub. This bird is such a gentle flyer. It's many times what I fly first to loosen my thumbs up. Built this one for my daughter to learn on. She got to pick the color.

 

[Wingding]

Nice flying Strix, good seeing you out at the field yesterday. I look forward to building this Cub myself.

 

[varg]

I liked your J3 design so much (it's a simple Cub, but not that simple Cub), that I built one of my own so I'd have something proven to fly and enjoy while I work out the kinks in my Curtiss. Of course I couldn't leave well enough alone and had to modify it, that's just my nature.

Flat takedown wing, basswood spar, internal servos, C power pack, removable sprung undercarriage, nose doublers. Here's hoping it isn't too heavy with all of those mods.

I'm aware that the prop is on backwards in these pics, I put it on hastily for the pictures and didn't realize it was backwards until I took it off again.

(edit 6-22)
Maidened it today and it flew great. It was a bit gusty but with the flat wing and extra weight it handled just fine. With the 8x4 prop it could barely maintain a walking pace in the headwind at times but with the 9x6 it pitched up with the application of throttle. Needs some down thrust to go with the right thrust. A great airplane with a lot of roll authority.

 

[Wingding]

Well I have the plans for this Cub, and the FT Simple Cub is coming out any day ... decisions, decisions.
I've decided to go ahead and build this one because I keep seeing Strix flying his and it looks great and flies great.

 

[varg]

This design is a little more scale looking than the simple cub and it's a little bigger and heavier. A little bigger and heavier is good in my book because of wind handling. It's also fairly aerobatic, probably moreso than the simple cub though we can't be sure.

 

[alan0043]

Hi Everyone,

I have a question about the plans. Are the plans for the J3 up to date with all of the modifications ? I think it will be fun to build the J3 and also the Tubby Cubby. That way you can compare the two planes side my side. I have paper in the printer and I am ready to go. Please let me know about the plans.

Al