Pheonix models k8b 3.5

[Kloss08]

I am a new owner a Pheonix models k8b. There appears to be quite a few hurdels to jump to make it fly correctly.

I have done the 4mm shim in the stab. I flew it for the first time last week and the thing porpuses like crazy on tug. Cg is set at 80mm.

Is there a way to fix this or must I live with it?

[Mark9]

My LE horizontal shim is 5/16" (closer to 8 mm.) CG at 80 mm aft of the LE of the wing. With that set up it required a slight amount of down trim on tow and almost neutral in normal flight. I have the trim for tow in a flight mode enabled by the switch that controls the tow release. The down trim I believe is the result of the tow airspeed being higher than the normal flight speed. The first flight was without incident, otherwise it tows very nicely once I added the slight down trim.

Also, I don't see a moustache on the nose, are you using the stock tow release? If so, that could be part of your problem. I have mine set-up for aerotow only and the release is installed in the motor shaft hole in the nose. Having the tow line come out the skid plate will result in a tendency to pitch up. If you don't plan to use a motor I would highly recommend you ditch the stock tow release. Here's what I fabricated for my Ka-8 from K&S tubing, piano wire, sheet stock and wood dowel scroll down to see the concept.. It works great.

http://forum.scalesoaring.com/forum/aerotowing-slope-scale-soaring/scale-sailplanes/21231-tow-release-help-please

[tree2tree]

I also have the tow release in the motor shaft hole. I have not had problems on tow - well except the time a cross wind . . . . but that's another story! I have 5 mm under the stab' LE. I don't have two condition modes like Mark9, but mine tracks quite well.

[Joespeeder]

Hi Noel,

Ever use a Carbon Cub to tow the KA8 ?

We have a guy putting one of these together here and i have the Cessna 170 tug which is the next plane in QQ's series. The 170 has more power (60 sized motor) than a stock carbon cub but I haven't really stressed it on tows yet. The 170 dosen't even know the Granau Baby is hooked to it and it seems like the Ka8 would be a easy tow for it.

If you get back this way let me know we'll do some flying.

Joe

[Kloss08]

Do I need to upgrade the release Or is stock serviceable?

[tree2tree]

Hi Noel,

Ever use a Carbon Cub to tow the KA8 ?

We have a guy putting one of these together here and i have the Cessna 170 tug which is the next plane in QQ's series. The 170 has more power (60 sized motor) than a stock carbon cub but I haven't really stressed it on tows yet. The 170 dosen't even know the Granau Baby is hooked to it and it seems like the Ka8 would be a easy tow for it.

If you get back this way let me know we'll do some flying.

Joe

Hi Joe,

The only tugs mine has been behind have been WAY over-kill - big gassers - so I can't comment on the 170 or the Cub. Perhaps others here have experience?

How about driving to Winamac (Aug 23 - 26). I hope to be there. It's a lot shorter drive for you than me ;-)

Noel

[tree2tree]

Do I need to upgrade the release Or is stock serviceable?

I made my own. Although it works OK, it is mounted too far back and takes more effort than it should to attach the loop for the tow rope. I am not going to change it, but also won't recommend it. Sorry - not much help!

[Joespeeder]

Hey Noel,

Hmmm..... I'd love to go. I have our PMAC Flying Circus on that Saturday so I'd have to do a banzai trip either Friday or Sunday. That would mean 4 hours one way, fly, and 4 hours home. Woof... I'm going to look at it. It's tough for me to fit something like that in these days .

Did you do the Carbon Rod mod to the Ka8 as shown on the RCG Forums?

Josh was one of the guys from PMAC that was hooked enough at our 1st Frankenmuth intro aerotow last year and bought the Ka8. I steered him toward that thread for all the secrets to the airframe.

Joe

[Mark9]

Kloss08 the stock release is not designed primarily for aerotowing. It is designed to allow the motor to be used and is as a result not optimized for towing. As I stated I believe most of your problem is because of where the tow line enters the aircraft, pulling the nose up and starting the horse to start bucking. Another option is to purchase a premade release like the one below. It is best to have it as close as possible to the front of the nose, otherwise it is very difficult to attach the tow loop as stated above. That is the reason for the design I developed. In the picture below you can see the cross bar and slider rod are just aft of the front of the nose. Keep in mind that all the stress from the tow will be transmitted into the release and the structure in which it is mounted must be able to absorb it.

https://hobbyking.com/en_us/hobbykingr-tm-glider-nose-tow-line-release-11-7x42mm.html