FF2017 Int. Racers: Caudron C.460

[rockyboy]

Step 4: Foam Cutting

Progress! I have a pile of sliced foam and plywood!



Love using the laser cutter at TechShop for this stuff - only downside is the slightly concave melting of foam around the cuts, and the 18x24 bed size.



And there are some interesting other projects to gawk at every time I go in - including one of the local manager's full size kit plane project. He's been making slow progress over the last two years, but it's up on wheels now and no longer scooting around on a shop cart.



I've also got a PCB based spar coming on from a forum member to try out in the wing. Really like the idea of simplifying the wiring and wing removal with this.

http://flitetest.com/articles/wing-spar-pdb-power-distribution-board-project


To do:
- Build the prototype
- Crash
- Adjust plans (scale up to true 1/6, switch to rounded formers for fuse)
- Prepare skin with flattened shapes
- Build prototype v2 (the pretty one)
- Fly!

 

[rockyboy]

Taranis project is at a holding point until I get down to the laser again, so it's time to clean up the shop a bit and get back to the Caudron!

This prototype was cut at about 1/7 scale - wingspan about 4.5" too short to meet the build rules. So the PCB spar isn't fitting so well in this wing, but it should be great in 1/6 scale version coming next.

 

[Michael9865]

Nice!

 

[rockyboy]

More progress on the first prototype tonight. Concerned about the tail weight of the double layer elevator and rudder - will probably try a single layer setup at some point in the testing process.


The first plans tweak is to put some tabs on these power pod rails to align them to the fuse easier.



Using a temporary foam spacer to hold the hooks at the right place while the glue dries.




Should have plenty of surface on the elevator (and rudder - it's similarly sized)


Starting to look like a plane!


Just kidding! The wing isn't glued together yet.



I am thinking I have a disconnect between the size of the tail control surfaces - all very large and good for slower speeds, and the wing control surfaces which are much smaller and sized for high speeds. One or the other is going to need to change, but hey - this is all about learning, right?

So far I'm up to about a dozen plans tweaks I want to make for the next prototype. My goal is to get this built, balanced, tossed, powered up and crashed a couple times before closing the book on it. All by the end of this weekend - weather and 'honey-do list' willing.

 

[AkimboGlueGuns]

Looks like it's going pretty quick! For your elevator, just try a ton of expo, and set up some low(ish) rates. I think that will work OK, but you may just want to try down sizing the tail.

It's weird that you have that problem. I think most of us will have to increase the tail surface just to get our racers flyable, and you might have to do the opposite.

 

[HilldaFlyer]

Excellent progress. I'm liking how the pieces fit together.

Like you, I'm finding it tricky to get the tail the right thickness. I was going to do two layers, but I also was concerned with the weight. Two layers is just about right for my 1/4 scale prototype (funny - the prototype is huge) but I think it will be too thick for the 1/6 scale. I think I've settled on one thickness and using fiberglass skin to give it the structure it will need for the high G forces - I'm guessing that one thickness of foam board will fold.

 

[rockyboy]

Looks like it's going pretty quick! For your elevator, just try a ton of expo, and set up some low(ish) rates. I think that will work OK, but you may just want to try down sizing the tail.

It's weird that you have that problem. I think most of us will have to increase the tail surface just to get our racers flyable, and you might have to do the opposite.

I proactively scaled the tail up 15% from scale based on saiga556's experience, but then I also increased the control surface sizes too. That second part was probably overkill.

 

[rockyboy]

Excellent progress. I'm liking how the pieces fit together.

Like you, I'm finding it tricky to get the tail the right thickness. I was going to do two layers, but I also was concerned with the weight. Two layers is just about right for my 1/4 scale prototype (funny - the prototype is huge) but I think it will be too thick for the 1/6 scale. I think I've settled on one thickness and using fiberglass skin to give it the structure it will need for the high G forces - I'm guessing that one thickness of foam board will fold.

A couple of Nerdnic's speed planes seem to do well with the double layer rudder/elevator at this size, but I'm really not crazy about how heavy it feels right now. Once I get the power pod and electronics up front we'll see what it does to the balance. But I think you're on to the right idea with fiberglassing a single layer for these 1/6 scale racers if we want to avoid dead weight balancing up front, or extending noses.

 

[rockyboy]

Almost ready - wing went together smoothly, everything lines up close enough for government work.

Just need to attach the wing, wrap some poster board on the fuse lid, build a power pod (I have a power pack C motor here that was heading towards a Bushwacker), figure out battery and balance concerns, install rudder/elevator servos, and put control horns everywhere.

I think she'll be in the air this weekend. Don't know how long she'll stay in the air, but at least she'll get a toss or two I can learn from.

 

[rockyboy]

More progress - wing mounted - flat incidence - and poster board worked out for the fuse. Also cut a hole in the bottom of the vertical stab to hang it up with the rest of the fleet for a minute. Need to do up the power pod and electronics next. Still hoping to get in the air with it this weekend.

 

[rockyboy]

Abbreviated power pod and servos all installed - not in time for a weekend maiden though. Lots of learnings to update the plans for the next build. I really messed up the power pod sizing somehow, and need to completely reconsider the front end. Thinking of moving to just a firewall for build simplicity on the next version. I also ended up with two fuse top lids, so I did one with poster board and left the other bare. Will probably try flight with the lighter weight flat lid first just to help out with the wing loading. And I should probably do some calculations and see how the loading and thrust ratios look.

And it looks like the weight is going to balance out with double layer tail surfaces after all. It's a pretty heavy motor. Need to velcro in a battery and head out for some glide testing, and then put in some power and see if she flies!

 

[rockyboy]

Hooray for v1 Maiden Flight!

TLDR; It flew!! Briefly, and without much control, but she flew!!



So the longer story of the day.

I started with glide testing in the waist high weeds (this is the only time waist high weeds are something I appreciate). At first she went in nose first, then she stalled, and then I finally figured out the proper battery placement. As expected, the CG is almost 1/3 of the chord distance back from the leading edge. And I didn't have to add any dead weight to get a balance, so I'm all happy about this - I'll be able to keep the extra strength of the double thickness vertical and horizontal stabilizer in the plans for v2.

Then I went up to the flight line and recruited a couple helpers. My friend John H. for the hand launch, and a cute little girl for video camera work who was at the field with her family enjoying an FT Storch, a DTFB F-22, and a DTFB wing. Great group - and really good to see mom, dad, and both kids engaged in building and flying. But I digress.

I started to go wrong as I was doing the final CRAP check before takeoff. Namely, I started to worry I wouldn't have enough control surface movement to pull up if launch speed was too low. So I flipped the switch up to max throws. That wasn't a good idea.

Blipped the throttle and she pulled well - hand launcher called for full throttle and she pulled really well. Plenty of thrust.

Then came the launch. And the torque roll. And the wild over correction. And the lawn dart manouver. And the realization many days later on the bench that I had the aileron controls reversed. :black_eyed:

I do have about 2-3 degrees of right thrust (courtesy of a washer after reading Mid7night's maiden flight experience). I'm not sure that's enough, but I think I'm going to try control surface / throw fixes before moving the thrust angle any more.

So I have a little body work to repair. Everything crunched that was supposed to crunch - even snapped a bamboo skewer - so the motor is safe and straight. Even the prop survived - the angle at impact must have been really close to straight in.





For the next maiden (unless I get any other good ideas) I'm going to dial the rates way back down, and install a gyro with variable sensitivity set low. Hopefully that will help me get it up a couple mistakes high, where I can turn the gyro off and start learning how it behaves and what other design changes I might need to make.

 

[Aviator08]

Progress!!! great job! It will be flying before you know it.

 

[Mid7night]

I hope you understand I mean no malice when I say, your flight report makes me feel better about mine.

It's clear the thrust angle helped your first maiden go about as well as my second one, and it's also nice to see your initial CG was aft too. Solidarity, my friend!

At least your motor and prop survived - your weeds are a lot more forgiving than my hard-pack dirt. People (even locals) tend to forget that southern California is still a desert, no matter how many trees you plant here.

You've also made me reconsider not-posting my maiden videos. I'll cut them together and post them in my thread this evening. Hopefully we can help whoever is next in the air, stay in the air.

 

[rockyboy]

@Aviator08 - Thanks!

@Mid7night - Glad to help through sharing my pain Let's both show all the smashy - crashy parts - all the cool kids are doing it

So with a gyro on order from Headupshobby.com (should arrive by Thurs) my plan is to be ready to re-maiden again this weekend.

When are you looking to sacrifice foam next? :black_eyed:

 

[wilmracer]

These small, high-speed planes definitely pose a real challenge, particularly for those first few seconds of flight until they get up to speed. I've had more than a few close calls with the Rare Bear and it has AS3x. A bit firmer hand launch and some lower throws (and maybe a bit of CG adjustment) and she'll be flying great!

 

[Mid7night]

@Aviator08 - Thanks!

@Mid7night - Glad to help through sharing my pain Let's both show all the smashy - crashy parts - all the cool kids are doing it

So with a gyro on order from Headupshobby.com (should arrive by Thurs) my plan is to be ready to re-maiden again this weekend.

When are you looking to sacrifice foam next? :black_eyed:

It'll be a while longer before I'm able to sacrifice racer-foam again ... need to find room in my hobby budget for a new motor.

Meanwhile, I'm hoping to test out my redesigned A-4 Skyhawk, now with a 70mm EDF. I'll be back in the air one way or another!

 

[rockyboy]

@wilmracer - thanks for the encouragement! With luck on the weather and health fronts, the next maiden will be Saturday with you and Joshua to help out

@Mid7night - what size motor are you using in your beastie? I didn't see that in the thread.

 

[saiga556]

Just my opinion which I have drawn from my experience with AS3X, but I wouldn't trust an unproven gyro on an unproven airframe. A gyro may offer some help in the future. Seems like another unknown variable in the system. Hope it works for you.

The C460 is a very high performance bird, as such it has very high performance problems.

Good luck

 

[rockyboy]

Yeah, I'm not a fan of AS3X either - had one plane with that and it always felt funny in the air. I have been having good luck using the Hobby Eagle A3-L units and the remotely variable sensitivity. I assign a Slider pot near the momentary switch to control gyro so that when it's at the middle position the gyro is off. Then I can gently bring in the effect just enough to fight the wind of the day or whatever airframe weirdness.

But I do hear you on the idea of so many untested items all being together - and the risk of changing too many variables at once. Bad scientific method.