Flite Fest 2017: Folkerts Sk.4 -- no compromises!

[FAI-F1D]

Ok, for those who haven't seen all the footage, here is video of flight #3. I landed with more than enough power to make a 2 minute flight with a speed prop (5.25x6.25) and still had lots of capacity left (like 60% of it). I'm flying on a 3s 3500, and right now I somewhat need it for the nose weight.

This thing is still not terribly easy to fly, but it's getting better. I've got a landing mode programmed (flaps) which helps a little, and once I get more comfortable, that might become the launch mode as well. As you can see, the roll rate is absolutely insane at speed.

Eventually the flight with the speed prop will become part of a longer video detailing the whole thing, but suffice it to say that 1. It did go *very* fast and 2. I won't be using that prop on this airplane again. The prop was stalled at launch, generating massive P-factor and making it impossible to turn right. Once I got the airspeed up, the prop started working, and everything settled out and it worked fine, but the launch is just too risky with a prop that small. I'm going to try a test flight on a 6x5.5 tonight to see how that works out and will report back.

 

[FAI-F1D]

Some flying footage. The glide is pretty flat even with that 6x4 freewheeling. With the 5.25x6.25 it really didn't want to come down. I can't imaging what it would be like with the brake programmed.







Rudder installation:


The part of the rudder below the stab just hangs free, so I wanted the control horn up top. For a pure DTFB build, you could run the hinge all the way down and have an easier time of it. Either way, you get a nice buried servo install, and it only takes a few minutes. The servo is hot glued to the inside of the fuselage just ahead of the elevator servo, and I just used a piece of .061 wire to punch a path through for the pushrod. The only slop is from the servo gear train.


With the canopy framing painted and a spinner installed, she's really starting to look good. I attached some red coverite over the carbon spars to make the black go away, and it just looks that much better now. I need to do the same on the stab and add gap seals for the control surfaces. Also, I cut out scale cooling exhausts under the right wing so hopefully the motor won't heat up so much. I'll also install a flow director on the intake to force air up around the motor bell. And then time for markings and what not. After that I can finish up the plans and tie a bow on the design side of this project.

 

[willsonman]

Well, that wrapped up quickly! Just goes to show you how important a solid design, testing, flight evaluation, and adjustment plan can be! Well done!

 

[HilldaFlyer]

This plane is downright terrific.

 

[Mid7night]

So awesome! I'm quite envious of your canopy, that looks sweet!

 

[willsonman]

Plans yet?

 

[FAI-F1D]

Plans yet?

Running it down to the wire...

For what it's worth, something stopped cooperating on landing approach after a bunch of successful 100+ mph speed runs, and it punched in faster than I could react. The nose is trashed and so are the wing mounts.

It's driving me nuts that it's sitting there in need to repair because I've gotten to where I really enjoy flying this airplane.

 

[HilldaFlyer]

That's too bad... darn.
This is exactly what I'm most afraid of. I bet I can get it up, but getting it down is a different challenge ... we'll see.

 

[FAI-F1D]

That's too bad... darn.
This is exactly what I'm most afraid of. I bet I can get it up, but getting it down is a different challenge ... we'll see.

Use a good protocol and you shouldn't have a problem. I'm almost certain at this point that it was a momentary signal loss; the rx I was using is dsm2 and doesn't have a failsafe. I've had problems with those at that field in the past and it slipped my mind again. You'd think I would learn not to use dsm2 at that field given that I've had at least 4 crashes at that field caused by interference.

 

[FAI-F1D]

Does anyone know how to post dxf files here? I don't have software to convert the plans to pdf format and maintain correct sizing, so my plan is to post the dxf's so that builders can print them off correctly using a freeware dxf print program or similar. Unfortunately the forum software won't let me post the plans.

In the meantime, here's proof that the finalized plans actually exist:


End users will also need to separate the patterns out or something of that nature. Many of these parts push the limits of a single sheet of foamboard and will need to be broken up (namely the wing and fuselage).

 

[FAI-F1D]

Huh...I just realized that I never posted the photos of the finished airplane. It honestly looked pretty nice prior to the crash (and eventually it'll look pretty nice again). So here's what I ended up with:













I should add that by holding in a little right rudder as I launched it, this model turned into a real pussycat to launch. It really does have very few bad habits. Definitely not a beginner's airplane, and probably not even an intermediate, but a very good airplane nevertheless. I don't know if Dan Crews ever succeeded in getting any photos of this, but I found that it flew very nicely inverted, too.

Now all I need is a way to post the dxf's here and that'll satisfy the need for plans to be available. I'll try to put together an instruction manual for it as well.

 

[SlingShot]

Nice job Joshua. Looks like it's reasonably manageable and seems to be pretty quick. It sounded awesome with all that prop RPM!

 

[BridgeInspector]

Looks sleek!

Google Drive works well for sharing files.

 

[FAI-F1D]

Hah! Got it. The plans are contained in this zip file.

What's not in there are the decking patterns, which I scanned into a pdf which has proven a bit oversized for posting. Still working on that one...

 

[FAI-F1D]

This build thread is going to have to serve as the instructions for this model. :'(
I've been down with a virus causing high fevers, aches, and absolute exhaustion for almost a week now. Can't make myself stare at a screen long enough to finish the instructions (which I promise were coming along nicely). Next post when i can both type more and cut more foam.

 

[Fidget]

This build thread is going to have to serve as the instructions for this model. :'(
I've been down with a virus causing high fevers, aches, and absolute exhaustion for almost a week now. Can't make myself stare at a screen long enough to finish the instructions (which I promise were coming along nicely). Next post when i can both type more and cut more foam.

Feel better soon!

 

[FAI-F1D]

Ok guys I'm back. Haven't started the repairs yet, but this bird will be back in the air soon. I'm looking forward to that since I miss flying it.

 

[CaptBill]

Ok, for those who haven't seen all the footage, here is video of flight #3. I landed with more than enough power to make a 2 minute flight with a speed prop (5.25x6.25) and still had lots of capacity left (like 60% of it). I'm flying on a 3s 3500, and right now I somewhat need it for the nose weight.

This thing is still not terribly easy to fly, but it's getting better. I've got a landing mode programmed (flaps) which helps a little, and once I get more comfortable, that might become the launch mode as well. As you can see, the roll rate is absolutely insane at speed.

Eventually the flight with the speed prop will become part of a longer video detailing the whole thing, but suffice it to say that 1. It did go *very* fast and 2. I won't be using that prop on this airplane again. The prop was stalled at launch, generating massive P-factor and making it impossible to turn right. Once I got the airspeed up, the prop started working, and everything settled out and it worked fine, but the launch is just too risky with a prop that small. I'm going to try a test flight on a 6x5.5 tonight to see how that works out and will report back.

I have read before and elsewhere on this forum the term "prop stalling", it has me confused. Would you Ming explaining what the term means and what is actually going on when a prop stalls?

 

[FAI-F1D]

The Folkerts is back in action.


I did a big rebuilt with fiberglass and what not, took the model outside, and launched it. Away it went, and as soon as I punched full throttle it went completely bezerk and slammed into the top of a pine tree.

I scabbed it back together, added a balsa sub fin under the tail and tried again. And yeah...the problems went away!

And I promptly went out and ordered a bigger motor. Time for a 7x10 prop folks!!!

 

[rockyboy]

Glad you've got her controllable and able to go where you point her!! :applause:

I've heard from a couple sources of experience (and it sounds like yours too now) that these golden era racers often need a little larger tail surface when scaled down to model rc sizes.