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J&H Aerospace Micro BOT build

speedbirdted

Legendary member
#1
I won this kit months ago in a soaring competition but only now do I have the time to actually start on it. I've always loved the full size Bird of Time but have just never got around to building one (though that will one day change) and also I don't have the space for a 3 meter ship at the moment so this is a nice compromise. The version I got by pure random chance was also the V-tail, but I honestly would've been fine with either as at the event I won the kit at I had the opportunity to fly the prototypes of both the V-tail and conventional tail versions of the aircraft, and they both flew very nicely.

It's a very nicely made kit. All the parts popped out of the sheet nicely and none were excessively charred or anything. No parts were broken either, but that's probably because this kit never touched the US postal service :p It's very complete too. Just about everything except the electronics and glue is included. Hell you even get doculam to cover it with!

PXL_20211006_041559820 (1).jpg


Both high-start and motorized configurations are advertised and I think I'll do this as the latter. It'll give me an opportunity to test some ideas for 3D-printed folding prop hubs I've had.

Speaking of the electronics I currently have none suitable. I think what will happen here is I'll get this framed up and possibly covered and then it'll sit for a bit until I get electronics that will fit in it. Right now all I've done in terms of progress is getting the basic fuselage structure framed up, and pictures of that will come soon enough.

Stay tuned...
 

speedbirdted

Legendary member
#4
Well, I overestimated how much time this would take to get framed up. I pretty much finished off the basic construction today! The wing took most of the time to build since the whole fuselage is built from like 5 pieces of balsa. No formers even, it doesn't need them. The only bits that still need to go on are the pegs for the rubber bands and the firewall, which I'll install once I get drilled to fit the chosen motor. The tail will get glued on permanently once the covering goes on. I also have to sand the wing trailing edge down but that'll get done once the filler cures after 24 hours.

There's nothing real outstanding in terms of construction technique here. The laminated leading edge is nice because it cuts down on the amount of sanding you have to do. Having run out of Super Phatic I used ambroid to bond the laminations because it sands very well.

PXL_20211007_023542314.jpg


However it was during the wing construction that I encountered a design error in the kit. Can you spot it?

PXL_20211006_065023938.jpg


The shear webs are cut with the incorrect grain direction! Instead I adopted to cut out my own with the grain going in the correct direction, that is between the spars instead of parallel to them.
 
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speedbirdted

Legendary member
#7
Is this a 'V' tail BOT?
Are you on drugs? That's clearly a conventional tail installed. :p

As I wait for the electronics to show up I thought about ways I could make this airplane more user-friendly. I have never really preferred rubber banded wings, and the only reason I ever did like them was when I was a crappier pilot than I am now and dragged wingtips on landing, it helped save the fuselage from potential damage. So, I made the decision to convert to a bolted wing mounting. I used just one 2-56 bolt with a blind nut and a basswood tab on the leading edge which fits into a slot. Normally the forward fuselage is made more secure by the front rubber band mount, which is a carbon rod that gets glued in, but instead I made a little basswood former that the tab slots into, and it does the job instead.

I also decided to magnet mount the hatch instead of using a rubber band to keep it shut. I used a couple of little magnets that came from a broken outrunner motor. They work perfectly for the task.

With no rubber bands, it does also look a lot sleeker, and I'm sure the L/D is just a little better too. :)

PXL_20211008_022856188.jpg
 

Piotrsko

Master member
#9
Well, I overestimated how much time this would take to get framed up. I pretty much finished off the basic construction today! The wing took most of the time to build since the whole fuselage is built from like 5 pieces of balsa. No formers even, it doesn't need them. The only bits that still need to go on are the pegs for the rubber bands and the firewall, which I'll install once I get drilled to fit the chosen motor. The tail will get glued on permanently once the covering goes on. I also have to sand the wing trailing edge down but that'll get done once the filler cures after 24 hours.

There's nothing real outstanding in terms of construction technique here. The laminated leading edge is nice because it cuts down on the amount of sanding you have to do. Having run out of Super Phatic I used ambroid to bond the laminations because it sands very well.

View attachment 209249

However it was during the wing construction that I encountered a design error in the kit. Can you spot it?

View attachment 209250

The shear webs are cut with the incorrect grain direction! Instead I adopted to cut out my own with the grain going in the correct direction, that is between the spars instead of parallel to them.
Built them both ways, doesn't seem to make any difference, it's the stress spreading that's important. Vertical webs are easier to cut using scissors or paper shears. Important only on a plane that used a hundred of them front and back
 
#10
Mail came today, and covering went on. I bought all the electronics from willy nillies so I figured I would get covering there too. I suppose I could have used the doculam but I didn't want a clear finish and didn't feel like having to paint it.

Nothing too elaborate. I prioritize visibility over flashiness anyway. Just solid red on the fuselage with the exception being the canopy in silver, with white on the top of the wing and tail.

PXL_20211013_064516616.jpg


Underside of everything was done in checkered red/white. It'll probably just fade to pinkish at high altitude but either way it'll help visibility.

PXL_20211013_064753853.jpg


You may notice I did not build the tailskid. I honestly think it serves no purpose other than just to be dead weight. I think it might actually be carryover from the standard tail BOT where it functions as a sub-fin, and in that case I'm not sure why it wasn't gotten rid of.

This covering is a tad heavy on shrinkage, especially on a lighter built airframe such as this one, but overall it worked pretty well. There are some wrinkles in a few places that I didn't want to get rid of because of associated warping but overall it came out good enough for my standards.

Next up is to glue the tail and mount all the electronics. I'm hoping this will not need ballast, and CG totally empty seems to be pretty tail heavy, so that's promising. There is not much room in the nose to shift the battery. I'm going to have to do some thinking to get everything fit in here...
 
#11
Back in the day with big heavy servos, there was some success putting the servos where the reciever sat and relocating the reciever to the back, but we also used a 4 aa pack nicad rock to power the electronics since electric motor power was unheard of. The state of the art has advanced a lot and your kit is a much different animal from the '80's stuff I knew.