Thread Tools
Jul 25, 2009, 06:29 AM
Registered User
Prop stitches's Avatar
Quote:
Originally Posted by dz1sfb
Gary,

The airfoil I am using is the 4-40 Undercamber. Used by GPW and Tony65x55. I am under the impression that GPW developed it. I have not been a fan of the KFm wings on these birds, however many have met with success with them. I really enjoy keeping these birds light, and have been richly rewarded in doing so. I do not know if it could get more efficient than it already is. She will jump off the ground if you need to, glides superbly (not a sailplane in the least), If you hold full up in the glide she just seems to slow down and very gently descend with just a hint of a bob, can go vertical as long as you have the battery, and has excellent duration on the battery specified. It has met every design criteria that has been asked of it and then some. To top it all off, it uses among the lowest cost components, making it very affordable to build and fly.

Just finished the remainder of the planes this afternoon. I'll post some pics of the finished fleet tomorrow night.

Ken
I am definately going to use my wing baking jig. I really want to surprise and impress my pals at the field. Thank you so very much for your design, and advise. I'll post pix and video in a couple of days.
Thank you again.
Gary
Sign up now
to remove ads between posts
Jul 25, 2009, 10:00 PM
Ken's CAD Models
dz1sfb's Avatar
Thread OP

Which color scheme do you like best!


Finally got the pics uploaded. I had to change some of my browser setting to get it right.

Hope you enjoy. Let me know what color scheme you think is most attractive.

Ken
Jul 25, 2009, 10:22 PM
AKA Don
Wow! What a fleet. There's going to be a lot of happy campers.

I like them all, but orange trim on white has always been a favorite of mine.
Jul 26, 2009, 12:27 AM
where did my wings go?
estlin76's Avatar
Awesome, Ken!! those look great!!! Wish i was gonna be in Wisconsin in August to see those flying about, but i bet you are gonna get some sweet video. Oh, its a toss between the purple and the orange, but they are all beautiful!

Shawn.
Jul 26, 2009, 01:26 AM
Ken's CAD Models
dz1sfb's Avatar
Thread OP
Quote:
Originally Posted by rbrown3rd
Monoblock ready for gluing. Coming along nicely.
Woo Hoo! Congratulations on a great start Bob.

Ken
Jul 26, 2009, 01:29 AM
Ken's CAD Models
dz1sfb's Avatar
Thread OP
Thats 2 for orange and 1 for purple.

Don and Shawn, I appreciate your comments and opinion here.

Thank you,
Ken
Jul 26, 2009, 09:16 AM
Registered User
Prop stitches's Avatar
I kind of like green, and like the looks of it on the plane. I vote green, in fact I think I will make mine green.
I baked the wings yesterday (made two left panels) so now I have to make two planes.
Props
Jul 26, 2009, 09:29 AM
AKA Don
Quote:
Originally Posted by Prop stitches
...
I baked the wings yesterday (made two left panels) so now I have to make two planes.
Props
OH, been there done that!
Well, can't have enough spares, or PLANES.
Jul 26, 2009, 11:10 AM
Addicted to flight since 1944
rbrown3rd's Avatar
I like them all. What a great sight it would be to see them all in the air at the same time.
Last edited by rbrown3rd; Jul 26, 2009 at 08:08 PM.
Jul 27, 2009, 07:35 AM
dizzy yet?
Kap'n Karl's Avatar
Ken,
That fleet looks awesome! (I guess I'll vote for purple) Try and get some video of them in flight!

I finished my Oshkosh Special build this weekend. 10 min here...10 min there... she's finally done! I can't wait for her maiden flight! Hoping for some good weather this week.

This was my very first scratch build and your pre-cut template really made things easier on me. I made a few rookie mistakes along the way, but I'm hoping that it won't cause too many problems. I wish I would've found this Oshkosh thread before I started building it! Probably would've saved me from myself. I think I got a little caught up in too many outside suggestions and I have also crashed and repaired my trainer so many times this year that I made a few modifications as a pre-attempt at strengthening up the design, when I should've perhaps kept her as light as possible to start with. Still... fully loaded she's weighs in under 15 ounces and balances out pretty well. There's also a different motor/battery combo in this plane which I had pre-purchased before I got this design from you at our SEMFF meet, and it was built with 2" monobloc.

Thanks again for all the info. Here are some pics. I wasn't going for anything historically accurate, just wanted an Army plane since I am working on an Army contract at my job.

Karl
Jul 27, 2009, 07:50 AM
Ken's CAD Models
dz1sfb's Avatar
Thread OP
Karl,

I love the paint scheme! The sky blue of the foam looks natural against the olive drab. What is the extra material on the bottom of the wing? Also see that you have opted for a E prop over a SF. Do you know what your finished RTF weight is? One other note. Not alot of dihedral there. Turns may feel a little sluggish.

She looks reallly nice.

Ken
Jul 27, 2009, 08:37 AM
dizzy yet?
Kap'n Karl's Avatar
Ken,

You're good! You called me out on almost all of my concerns! ha ha.
1)There is indeed extra material under the wing. Kind-of an undercambered KF-3 thing. 2 strips of foam centered under the CG. The first layer starts at the LE of the wing giving it double thickness for about 1/2 the wing. 2nd is a skinny strip of foam centered at the CG. You may call it crazy, I'll just call it Army-strong.

2) The prop: I don't have a lot of gear yet. When I went to the LHS he suggested this and said it was a good slow-fly prop. Honestly, I don't even know what an "E prop" is.??? I was hoping to either meet with SGTalon or one you guys from SEMFF for some final suggestions before the maiden flight. I'd actually prefer someone a bit more skillful than myself to fly it the first time. I put the prop on for the pics but wasn't sure if that would need to get swapped out right away.

3) The dihedral. You're good! Were you measuring my pics on your monitor?! ha ha. Before I found your Oshkosh thread I started following the original BB design plans which called for less dihedral. (1 1/2 " at the wingtips) But I didn't account for the extra long wings of the Oshkosh, either.

Good thing I still have some green paint leftover. I might be building a 2nd set of wings.

Karl
Jul 27, 2009, 10:24 AM
Ken's CAD Models
dz1sfb's Avatar
Thread OP
Quote:
Originally Posted by Kap'n Karl
Ken,

You're good! You called me out on almost all of my concerns! ha ha.
1)There is indeed extra material under the wing. Kind-of an undercambered KF-3 thing. 2 strips of foam centered under the CG. The first layer starts at the LE of the wing giving it double thickness for about 1/2 the wing. 2nd is a skinny strip of foam centered at the CG. You may call it crazy, I'll just call it Army-strong.

2) The prop: I don't have a lot of gear yet. When I went to the LHS he suggested this and said it was a good slow-fly prop. Honestly, I don't even know what an "E prop" is.??? I was hoping to either meet with SGTalon or one you guys from SEMFF for some final suggestions before the maiden flight. I'd actually prefer someone a bit more skillful than myself to fly it the first time. I put the prop on for the pics but wasn't sure if that would need to get swapped out right away.

3) The dihedral. You're good! Were you measuring my pics on your monitor?! ha ha. Before I found your Oshkosh thread I started following the original BB design plans which called for less dihedral. (1 1/2 " at the wingtips) But I didn't account for the extra long wings of the Oshkosh, either.

Good thing I still have some green paint leftover. I might be building a 2nd set of wings.

Karl
Karl,
A good indicator of how well the prop will work is to put it on a wattmeter. Maybe Dennis has one. You need for three components, the ESC, battery, and motor. You then use as much prop as your lowest rated component can handle.

The E prop is simply a designation that APC uses to identify it as Electric use. These are usually for higher Kv applications. They have a SF or Slow Flyer series as well. Given the Kv of your motor, I suspect you will want to run a 9 x 4.7 SF type prop.

Give that wing a try. It will fly, but may not generate as much lift. You will be able to turn okay with the given dihedral, but rudder rolls may not be possible. That is not entirely bad for a new person.

One other thing that crossed my mind is this. By going with the 2" monoblock and tapering from 1-1/2" at the rear of the wing, you are bound to loose a little incidence due to the support point being further outboard on the front of the wing relative to the back of the wing. You have a mitigating factor working for you in this case, and that is with the lower dihedral angle the difference is not as much. I have not taken the time to trig out the difference. There would be a greater impact if you had more dihedral though.

I hope you are not discouraged by my comments. I am not criticizing your work. Just letting you know how different changes can effect the geometry of the plane. Theoretically, if spread the front support very wide while leaving the rear as is you could result in negative incidence which would be quite unstable.

Lets see if we can meet after work sometime this week and fly, I also have a wattmeter.

Ken
Jul 27, 2009, 12:06 PM
dizzy yet?
Kap'n Karl's Avatar
Quote:
Originally Posted by dz1sfb
I hope you are not discouraged by my comments. I am not criticizing your work. Just letting you know how different changes can effect the geometry of the plane. Theoretically, if spread the front support very wide while leaving the rear as is you could result in negative incidence which would be quite unstable.

Lets see if we can meet after work sometime this week and fly, I also have a wattmeter.

Ken
Your input is always welcome. Like I said, this is my first build and I was grateful to have one of your Oshkosh Special templates to use. I should've contacted you or searched the threads for more input beforehand but I just started my project one weekend with a "let's get 'er done" attitude and started building while using the BB build designs as a reference. I'll be very happy to see her fly, period. If we could get together after work one day I'd be happy to let you fly her and get your input for tweaks. And if I end up having to build another set of wings so be it. This whole project has been a good learning experience from cutting/glueing the first piece all the way to hardware and paint.

Karl
Jul 27, 2009, 12:12 PM
Ken's CAD Models
dz1sfb's Avatar
Thread OP
Karl,

USAirNet is showing Thursday morning with windspeeds of 2 mph. The remainder of the day is not displayed yet. Likely that the afternoon will be respectively lower and probably a good day to shoot for. I would love to see the field at 25 mile rd.

Ken


Quick Reply
Message:

Thread Tools