Originally Posted by davereap

[B] watch your %ages

Steve I think this could apply a lot to your builds, as you have to make thick wings because of your materials.. What are your %ages for the good wings, and have any turned out poor?
BTW... an excellent build thread for your Vesper

My previous wings that did work well are
.... a sloper with ...same 30mm thick wing at 14% depth/chord at the tips down to 10% at the roots ..tips 210mm root 280mm ...glides very well
.. and Zagnutz 25mm thick wing......10% at tips ..8% root.... flys and glides very well.
So I thought 30mm would be ok again....BUT it wasnt...I must admit I looked at the ends and wondered if it would be ok, because they looked too thick and out of proportion...

Vikings work shows a 10% wing is good as a guide target...less = faster ..more = slower..

So Ive got to chop the wing to reduce the %ages and fly again..

Considering how far off my %ages are its a wonder it flew as well as it did..

Dave,
As you have figured out I don't go to a lot of trouble when designing or building. When it comes to building: "Fast is good!" My KFm4s seem to be slow and acrobatic and my KFm2s are a bit faster flying but don't seem to be any less acrobatic but have better lift. At low speeds they are about the same. The edge may go to the KFm4 here but it's slower because the frontal area is greater and produces more drag. They lose speed in a throttle-off dive better than the 2 and that is desirable in my small landing area surrounded by trees!

KFm4: Typical... about 20% at the tip and 12% at the root.
KFm2: Typical... about 14% at the tip and 8% at the root.

Low AR deltas and flying wings are a bit lower percentages I suppose. The above numbers I would guesstimate are around +/- 20%

My KFm2 is lighter and faster and a snap to build but I use the I-Beam so the build is a bit more complicated. The KFm4 has no internal stiffening or sticks and uses the tape only for strength and stiffness. I have built more of the 4, but now I may mix them up a bit more. The 2 is quite good also.

One KFm4 I built I used the EPE foam on the outside wrapped around the leading edge. It flies fine, is equally at home inverted as right side up and it's thinner so it flies fast like a KFm2. Internal stiffening is complicated in my opinion so I'm not crazy about the building complexity with this construction for the KFm4.

All my KFs have flown well. I have had problems with CG sensitivity with the KFm3 and now I don't use it because of the build complexity. I'm a lazy bastard I have built several planes with it and it flies fine. Only one time did I make one that didn't' fly well. I put that same wing on a different fuselage and it flew OK. Go-figure???

My problems seem to come when I get the wing loading well above 5oz/sq ft. I like light and nimble not heavy and sluggish.

Wing tips are another matter. I use them to give directional stability and control vortex losses but I think it seems that they have a very minor effect. The KF wings seem to fly well with or without them.

All the above nonsense is subjective and based on my feelings when I fly. I have garnered enough experience to make my instincts pretty good now. At least I think so. I can say I know what I like pretty well and I can imagine pretty closely what a plane will be like by looking at the design parameters. I guess I'm moving from Klutzy to Competent in my flying skills too.

Jack,
Dave is the expert not me. He has the builds and the flight time on his resume and he's been a bit of a mentor for me. Encouraging me in this insanity, we all seem to be infected with and patiently making suggestions as I clumsily stumble forward. I'm a bit like you in that I enjoy the technical reads and analyzing the numbers but it's building and flying that tells the real story. It's nice to quote stuff and be able to spew out the rhetoric but the important thing to me is to have the instincts to really understand this mess. Not just to be an observer but to be part of the equation.

I'll just finish-off by saying that this whole thing is a "Zen" like experience that is best when you lose yourself in it. I want a full-house pane with retracts, flaps, dive-breaks and lighting. "Make me one with everything..."

Mabuhay,
Steve.

PS.
I got a bit of stick time in the other day with Tata. Not flown together yet but we're flying the Buzzard on TX #2 and I flew the Vesper on TX#1. Wind picked up and the Vesper managed to find a tree but no damage luckily.

Windy session with Buzzard and Vesper (4 min 7 sec)

Next calm morning I will maiden the new Vesper and see if Tata and I can manage to get two planes up at the same time. Edna will have to video for us. Hope it works out. Will post here.

Edit: Oct. 28, 2009, 21:52.
Because of problems, today, between Grandma and Tata concerning his work and his behavior, Tata is not with us anymore. I don't know if that will change so, it seems that for the moment, I'm flying alone. It's an unfortunate situation.

Grandma is jealous. Build her an airplane...

Jack

Originally Posted by jackerbes

Grandma is jealous. Build her an airplane...

Jack

Not Grandma's fault this time so never mind. I will just look for a nice, cute, 18 to 20 year old helper with big "totoys" and a fine "lobut" then Edna will think: "OH ! Maybe we need to give Tata another chance?????"

Looks like I need to fix the helmet cam at least for a while. I want to maiden the new version of the Vesper today but I'd like to get video and Edna is going to the Market for our weekly shopping.

New bird on the building board. Started last night and have the basic airframe done in 1 hour. Will share when it's far enough along for pictures.

Typhoon "SANTI" (MIRINAE) is heading this way. Just now getting light and we have wind! Sheesh!

Steve.



Edit: October 29,2009 16:43
Threads stripped out in helmet cam adapter but the typhoon is headed straight at us so I'm not gonna sweat the buggered threads too much. We could get nailed this weekend. Didn't get to fly, too much wind.....

Tried 2 new ones out today (been a while!) both KFm2. One worked one didn't. I need to review my calcs and see where I went wrong

One was a 48"ws Cub, which worked great. The other was a 24"ws 4F-51-KF (working title for now) which is basically a Delta... It must have too small of a step, as I couldn't get enough nose weight on it to be frisky and not pitch sensitive I will rebuild it with more step height.

good luck with the weather steve ...you are getting more than your fair share of the bad stuff..

Originally Posted by Gene Bond

...The other was a 24"ws 4F-51-KF (working title for now) which is basically a Delta...

That 4F-51 has been a workhorse for some time now, hasn't it, Gene? You should be able to side-by-side the KF with any number of previous models and see if there is something else buggered, like the motor pitch or some other alignment issue. Eh?

Originally Posted by davereap

good luck with the weather steve ...you are getting more than your fair share of the bad stuff..

Dave,
I remember the weather in Houston back in the late '60s. We used to say: "If you don't like the weather in Texas just wait 5 minutes." Here it seems like it's been one typhoon after another. Between the losing Tata, having wind every day and the problems with the Helmet cam it's been a bit unsettling. The older I get the less I like changes.

Anyway I have a new bird on the board. Its a radical variation of the Vesper Which I'm leaning towards calling the "Pagan". I'm enjoying the new build and it's helping to keep my mind off the recent disturbances and gives me something to focus on. I'll post pictures when It's fully evolved. It will make two planes to maiden and 2 to fly that have been repaired and modded. I'm hoping the Pagan will bring some things together in a cohesive way. I have a good feeling about this one.

Anyway! At least we are all healthy and reasonably fit!

Gene,
I just Googled your "4F-51" I like it. Have you got the KF wing problems sorted out yet?

Steve.

Originally Posted by A Useless Geek

That 4F-51 has been a workhorse for some time now, hasn't it, Gene? You should be able to side-by-side the KF with any number of previous models and see if there is something else buggered, like the motor pitch or some other alignment issue. Eh?

It's just I was hoping to have one I could fly fast or slow... I didn't make it thick enough. I just added more V-Stab/rudder area, which helped part of the issue, but pitchiness can only be cured one way (cg) without fixing the wing thickness.

The new bird is up and flying well with the same BW motor but I added a 1300mah Lipo to get the correct balance.

The maiden can be seen at the following URL with some details in post #7 third video.
https://www.rcgroups.com/forums/show...0#post13384020

I'm currently trying to finish up the Vesper MK2-Sport, which I call the "Pagan".
I'll post details and pictures when she's ready to fy. Just getting the gear installed currently and may be able to maiden tomorrow. At least, that's the plan...

Steve.



Edit: November 1, 2009 19:03
The Pagan is ready to maiden. I have a new retriever named Nugnug. We'll see how he does. I miss Tata though.
Edna hired this guy to help around here and he'll be my chaser. We'll see how it goes.
Pictures below and I'll be posting a few more of them on the Vesper site.



Maiden Successful. at 8am this morning. additional flights just got better. Landings are fantastic with D/R set to low. It glides beautifully.
More details and additional video on the Vesper thread.

PaganMaiden (1 min 40 sec)

I built a little flat foamy 3d type plane. I am not satisfied with it as the flat wing is very pitchy especially with down elevator!. Plane flies ok but that about it. It rolls good loops not so good.

I was thinking adding a Kfm2 top step to the wing.

The wing is 13 root and 6 tip chord. Straight LE. 2.25 ailerons include in the dimensions.

So would my step need to be 6.5 tapered to 3 for the top with a thickness of 1 inch step at root tapered to ½ inch at the tip?

I am using ¼ thick blue core.

What do you guys think? Will this make my plane fly better?

Where should the CG be?

Grant: what's the span? I built three planes off the parkflyer Pete planform, and all three with simple kfm2 (just double thick top step at 50%) They are 30-36" span and 7" chord oval plan view wings. Fly super. great glide, really soft stalls, inside/outside loops, axial rolls. Very accomodating airfoils. I maintained constant thickness all along the span, just rounded at the tips. CG wants to be just forward of the 50% step for starters, maybe 40%.

The span is 31.75 on the plank.

Originally Posted by grant31781

The span is 31.75 on the plank.

Do you have a picture you could post? Springer is right the KFs like a more rearward CG on a conventional plane with a non-stepped foil. 40% is recommended I fly mostly wings now and the KFm2 likes around 18 to 20% MAC.

If it,s a conventional plane with a standard tail then start about 33% and move it back, bit by bit, until it's got the performance you like without being too twitchy. Wing thickness can affect CG to some extent too.

Good luck,
Steve.

grant31781 wrote:

"..So would my step need to be 6.5 tapered to 3 for the top with a thickness of 1 inch step at root tapered to ½ inch at the tip?..."

You have the step locations right but a step height of 1 inch tapering down to 1/2 inch is not a good idea At least I don't think it is. The steps are normally 1/4" to 3/8" or so high (one layer of blue core or FFF will work fine) and the step is the same height from the root to the tip.

You should be able to basically just cut the KFm2 strip and glue it to the top of your wing with Gorilla Quick PU. Use a piece of 60 or 80 grit workworking sandpaper glued to a flat board like the one seen in the photo to straighten and round the leading edge. With two layers, just make it like a 1/2" half round shape, you don't need a sharp leading edge.

Take a piece of clear or colored package sealing tape and wrap the leading edge to strengthen it smooth the air flow.

Jack

what Jack said. The critical dimension we didn't have is the span. With that small a wing, just double the thickness for the top step as he shows and don't bother to do a taper in thickness out to the tip. Keep the step at 50% of the chord as you go out from center to tip though. (6.5 tapering to 3 as you noted earlier) If you want to get fancy, you can carve the leading edge of the top step to make a sortof airfoil leading edge, or just leave it blunt. If you're doing slow speed 3d type stuff, the blunt may be just as effective. If trying for some speed and more flying "on the wing", then the contoured surface may be a little better.