The Shrike is a new design and experiment in combat models for the SEMFF group. The prototype was completed and tested this week (04-JUN-2013). The sucessful testing including multiple midairs and flying out of each one, proves this is one tough bird.

Most flights were conducted with an 850 or 950 mAh 2s battery, and a couple of flights with a 750 mAh 3s battery.

Airframe Specifications;

Wingspan - 32"
Over all length - 15"
RTF Weight - 8.2 oz

Equipment Specifications;

Motor - 1700 Kv 2730 KEDA (24g)
Propeller - HK 7x6 APC like
ESC - 15A HK SS
Servos - two 10g HK analog
Rx - HK R610

Notable characteristics -
The FSW design fabulous pitch response and requires very little stick pressure to hold inverted flight. Loops are tight and straight. Rolls are crisp, fast, and predictable.

The only habit it had that took some getting used to was kind of flopping around when gotten into a full stall, especially inverted. Recovery was simple, with releasing the aileron/elevator stick and applying throttle she flies right back on the wing.

All in all I am very happy with its performance, and will combat it quite a bit this summer.

I have just finished the production prototype, which moved the aileron servos aft 2" and covered the esc/rx pocket that now includes some areas for stuffing wires. Will have this one out for testing on 11-JUN-2013. The only reason for the second prototype was to work out better component arraignment for CG considerations and to tidy up the design for production.

What follows is a pictorial build guide.

Ken

Here are a couple of videos as well.

Shrike demo (0 min 47 sec)

http://www.youtube.com/watch?v=gDTH6KmujbE

Finished the production prototype this evening.

Although this one is much cleaner, the AUW is still the same at 8.2 oz.

Here they are.

Ken

Finally finished, I think!

The pdf file for the Angry Bird eyes is in the above post now also.

Ken

This is a really cool design. I find it interesting that you went with a tractor setup and not a pusher that you would usually see on a flying wing. Is there any reflex in the elevons?

Ben

Originally Posted by bhoov128

This is a really cool design. I find it interesting that you went with a tractor setup and not a pusher that you would usually see on a flying wing. Is there any reflex in the elevons?

Ben

No reflex. The tractor configuration works well for cutting streamers and achieving center of gravity without additional ballast.

Ken

Originally Posted by dz1sfb

No reflex. The tractor configuration works well for cutting streamers and achieving center of gravity without additional ballast.

Ken

Facepalm! I guess I completely missed the "combat" in the thread name! Still, really cool design!

Ben

Nice concept Ken! If you want to keep the air flow on the KF steps without using fences or a straight wing, the forward sweep will do that for you.

Jack

OK it looks like I found my next (quick but it always seems so before one starts ) project:

Evolving this into a Shrike Slope Combat Wing. More western sloper dedication in honor of our eastern brethren. After the OSG it is nicely befitting.

Out of MPF of course! Thanks for the concept and original design, I love it.

Few questions:
1- I develop my planes out of sketchup, it looks like you may have a file. Would you mind sharing or should I redraw from PDF (not a huge effort to redraw anyhow)
2- Have you found all the reinforcement to be necessary, especially with such thin stock of CF? I am thinking 5mm LE, splitting and lower profile for the vertical fin (now fins)? And laminating film cover. Any thoughts?
3- How difficult was it for CG? Slopers have much less battery, and no motor nor prop, so weight forward is somewhat an issue.
Is it sensitive to CG location?
How far back can it go?
What do you think about less wing neg sweep? Another option could be straighter LE while keeping the neg sweep.
4- Hinges? What did you use?
5- What cover material did you use? It looks like just tape, is that it? I plan on laminating film, that gives a lot of strength and some rigidity too to MPF.
6- I'll know as soon as I have the design in sketchup, but do you know the wing loading and WCL by any chance?

Thank You, Michael

Hi Michael,

Lots of questions. I will try to answer succinctly.

1. I am a bit reluctant to send out the file since I am selling kits and it represents my hard work. It is a prettty simple design and tracing it in Sketchup will be easy. The wingspan is 32" for referencing the size. Email me at kenscadmodels@aol.com and I will send you the 3D model.
2. The reinforcements are for the benefit of streamer combat. It really helps it survive those head to head mid airs.
3. The CG tends to build nose heavy, so that should help you. CG range is much like any other model, but she can get nasty quick if it's too far aft. This plane is more pitch responsive, but that does not twitchy. A little aft CG and it glides very well. For power it likes it better more forward. Wide flight envelope even with forward CG. Certainly there would be no problem in playing with the wing sweep.
4. Hinges are clear thin packing tape on both sides.
5. Colored and clear packing tape.
6. Gotta clue me in on WCL. The wing area and weight are listed in the plans.

Ken

Ken,

Thanks so much for all the info, and so quick too

No worries for the plan, it'll take me only a few minutes in SU to make them and since I may modify it's probably just as much work to trace originally than modify existing.
I know it's your hard work, and I know how you feel, it's already very nice of you to share what you did. If you want to sell the kits of the slope version once developed, we can talk.

WCL: Wing Cube Loading (sorry to use the acronym), I use just as much as wing loading for comparison, but in this case it's almost irrelevant. It's to compare planes, also with their full size versions and birds (if one wants) and for that comparison to be meaningful. In this case no real plane so it's just to populate the comparison database.
http://www.theampeer.org/CWL/jaffe.htm

But like I said as soon as I have the SU rough design, those compute, so I'll let you know anyway.

Tracing done, so here are the info (8.2 oz version)

Wing Loading: 5.8 oz/ft2
WCL: 3.68
AR (Aspect Ratio): 4.16
Aileron ratio: 18.8%
Tail Volume Coefficients:
Vh: 0.19 (low in theory but there could be a mistake, I haven't checked how wings are supposed to be computed, so that is an airplane like computation based on where your CG is positioned. A theoretical plane calculation should give 0 in this case, but your CG is significantly forward than 25% MAC)
Vv: 0.012

Michael,
Great contribution to this thread.

On CG, there are so many calculators out there. What has worked well for me is, and easy in SketchUp, is to have the wing planform as a simple polygon, right click on info once the surface is selected. As you know this gives area. Then I start dividing the area with a balance line until I get 25% /75% balance point. Seems to work well.

Would be interested in kitting a sloper. Always thought my StingRay would be a good sloper as well.

Thank you,
Ken

Originally Posted by dz1sfb

On CG, there are so many calculators out there. What has worked well for me is, and easy in SketchUp, is to have the wing planform as a simple polygon, right click on info once the surface is selected. As you know this gives area. Then I start dividing the area with a balance line until I get 25% /75% balance point. Seems to work well.

Would be interested in kitting a sloper. Always thought my StingRay would be a good sloper as well.

Now that's interesting, I have to think about it. The way I do it is the same way except I divide the wing area (with a longitudinal line) into two equal parts, that is then the MAC, then take 25% of it. That should result in the exact same place, yet it seems that it didn't.

I'll look at the stingray.

Originally Posted by dz1sfb

Hi Michael,

Lots of questions. I will try to answer succinctly.

1. I am a bit reluctant to send out the file since I am selling kits and it represents my hard work...

Ken

Is there a website selling this kit yet?
Thanks