Crawford Bros. Aeroplanes
Legendary member
I'm thinking having an adjustable canard would be good for trim too.
What Did You Fly Today
- Thread starter Wildthing
- Start date
Timmy
Legendary member
Wildthing
Legendary member
If the collet works lose you will know it right away , prop will stop spinning.
I have very few reverse threaded collets/motors so I spin the motors whichever way I need to and very seldom have any come loose, I tighten the heck out of them.
Timmy
Legendary member
same
slowjo
Master member
I'd just go with elevons.
Crawford Bros. Aeroplanes
Legendary member
I did a bit of planning before I start on the fuselage for the canard wing. With the wing built I can see it will definitely balance tail heavy empty, which is perfect because I need to stuff everything into the nose anyway. I have a lot of hardware that needs to go up front so having the motor further aft should help with balance.
The ESC needs to have good airflow so it goes on the ceiling behind the vent. The Rx is light enough to put pretty much anywhere, I'll put it somewhere where it's out of the way but still accessible through the hatch so I can switch it with other planes. I'm planning on using my Aura 5 which is already going in at least one other plane I own.
The hatch is a good 6" long which leaves plenty of wiggle room for the batteries. The two 1100 mah 4s from Revolectrix I have picked for it are pretty light so they'll probably need to go slightly further forward. The camera goes without saying, the VTx will go either ahead or aft of the batteries to get proper cg.
If I had the model already built I could calculate exactly where everything needs to go based on the empty cg. Seeing as I haven't built it yet I can only speculate.
For the hatch I want to use coroplast like I see a lot of FPV wings using now, it'll look nicer and be more durable than a foam hatch. I just don't have any coroplast. Does anyone know any alternatives? If not I can pick some up when I buy foam on Thursday, it just seems a bit pricey when I only need ~12 in sq.
The canards are an interesting bit. I decided to go with adjustable canards both for trim and to further increase the flight envelope. I can run them through the gear switch on my Tx to get two positions, if possible I'll run them through the flaps channel and use them in conjunction with flaperons.
My original plan called for dihedral in the canards. I'm not willing to leave it out and I'm stingy with servos so I needed to find a way to run both sides off one servo. A standard ft hinge wouldn't work with the dihedral so here's what I came up with.
Two control rods running through the fuse sides and attached to one servo horn. Since it's only running flaps it'll only be pulling, any flex in the pushrods won't matter too much.
Really I'm just posting this because I want to work on it but it's 1000 pm here and I need to go to bed, so I'll settle for talking about it instead. That's what about 70% of my posts are anyway. G'night.
The ESC needs to have good airflow so it goes on the ceiling behind the vent. The Rx is light enough to put pretty much anywhere, I'll put it somewhere where it's out of the way but still accessible through the hatch so I can switch it with other planes. I'm planning on using my Aura 5 which is already going in at least one other plane I own.
The hatch is a good 6" long which leaves plenty of wiggle room for the batteries. The two 1100 mah 4s from Revolectrix I have picked for it are pretty light so they'll probably need to go slightly further forward. The camera goes without saying, the VTx will go either ahead or aft of the batteries to get proper cg.
If I had the model already built I could calculate exactly where everything needs to go based on the empty cg. Seeing as I haven't built it yet I can only speculate.
For the hatch I want to use coroplast like I see a lot of FPV wings using now, it'll look nicer and be more durable than a foam hatch. I just don't have any coroplast. Does anyone know any alternatives? If not I can pick some up when I buy foam on Thursday, it just seems a bit pricey when I only need ~12 in sq.
The canards are an interesting bit. I decided to go with adjustable canards both for trim and to further increase the flight envelope. I can run them through the gear switch on my Tx to get two positions, if possible I'll run them through the flaps channel and use them in conjunction with flaperons.
My original plan called for dihedral in the canards. I'm not willing to leave it out and I'm stingy with servos so I needed to find a way to run both sides off one servo. A standard ft hinge wouldn't work with the dihedral so here's what I came up with.
Two control rods running through the fuse sides and attached to one servo horn. Since it's only running flaps it'll only be pulling, any flex in the pushrods won't matter too much.
Really I'm just posting this because I want to work on it but it's 1000 pm here and I need to go to bed, so I'll settle for talking about it instead. That's what about 70% of my posts are anyway. G'night.
You posted as I was in the middle of writing this, I've decided to use elevons for pitch control but still have a movable canard with adjustable angle of attack for fast and slow flight. I'm hoping it'll mean better handling at lower speeds by taking some of the load off the elevator, on canards the nose tends to drop at lower speeds.
L Edge
Master member
I would make it adjustable if you have a radio with Flightmode capabilities. In the Viggen build thread, mine has elevons in mode 1, mode 2 has my 2 axis thrust vectoring unit as well, and mode three where it contains the movable canards, the elevons and the TV unit all working.
If you like to explore, I have even flown a model where 2 servos were used in the canards as a second set of elevons, had thrust vectoring which allows for some wild manuavers. I needed 5 cups of coffee to fly this thing when all functions were working.
Wildthing
Legendary member
That's the way I would go with 4 servos and 4 channels so you could do any setup you want to try.
L Edge
Master member
Interested in your SR-71. Did you build it yourself? Are all 3 motors tied together or are the 2 upfront set up for differential thrust?
Timmy
Legendary member
You really plan things through! Also you need to put both control rods on the same hole on the servo arm otherwise one canard will move a bit more than the other. Not sure how one might solve this though. Or maybe the difference is so small that it won't matter?
Wildthing
Legendary member
It was the beta version through Parkflyers International, the original plan was just a single pusher and doing it that way would mean the battery would really have to go up front in the nose and that of course would be the weakest point. So going with the 3 quad motors and 3 micro 20A esc's the battery is just forward of the leading edge which was perfect. The front motors I did setup as differential thrust but never did get to use them. That last little hit did it in, not sure if I will build another or not.
L Edge
Master member
I built one to study the effects of loss of power with inlet ducting using 64 mm EDF's. Two things I found is 1) doesn't like sharp turns at all and turns need to be wide!!!!!!! and 2) you got to slightly power on the landings till the wheels are on the ground. The reason-- is the long nose once it goes positive, the airflow underneath just pushes up the Sr-71 and it just stalls or crashes out.
Turns needed to be started using differential thrust, but too much catches the nose and drives it up or down in yaw on the turn. So I ended up blipping the rudder in the start of the turn. Of course, it doesn't take much to roll it.
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Wildthing
Legendary member
My first flight was somewhat successful other then the landing in which it flared up and landed on it's tail. I ran only elevons but turns were like you said, soon as you started turning the nose went up so I tried moving the cg forward slightly and then I had launching problems. It would lift off but then start to roll right away.
Crawford Bros. Aeroplanes
Legendary member
With the standard ft servo arms it might make a difference, the ones I'm using are so close together I don't think it'll matter.
Crawford Bros. Aeroplanes
Legendary member
Maybe if I had a Taranis and an 8ch Rx...
Wildthing
Legendary member
No rudders right? So a 6 channel rx would work as long as you can do the mixes in your tx.
Crawford Bros. Aeroplanes
Legendary member
The issue I see is that the canards and elevons need to move in the same direction for roll, but opposite directions for pitch.
Crawford Bros. Aeroplanes
Legendary member
I started work on the fuselage for the canard FPV wing today. I played around with some batteries to see about cg, with my original layout it's far too nose heavy. The batteries need to be over the wing so I'm moving them back and turning the top of the air scoop into a second hatch. FPV gear, Rx, etc will be up in the nose, the batteries will be where the Rx was previously with the ESC mounted to the bottom of the hatch to get proper airflow.
I also moved the canards all the way forward. The cg is now almost 1" forward of where it was previously, this should give me some wiggle room on electronics placement. There's very little room that far forward however, I'll have to switch around the canard servo mechanism to push rather than pull. Shouldn't be too much of a problem though.
I also moved the canards all the way forward. The cg is now almost 1" forward of where it was previously, this should give me some wiggle room on electronics placement. There's very little room that far forward however, I'll have to switch around the canard servo mechanism to push rather than pull. Shouldn't be too much of a problem though.
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