Hello,

I'm planning to buy a QQ Yak 102" III and was curious if anyone already has field results with this combo. After reading through the forums i read that the Da85 would deliver nearly the same power as a DA100 an weights less. I'm a little bit concerned about the CG .....

I'm considering this combo mainly because of the price. Since I'm a student this would be a welcome help to the wallet compared to a DA 100.

Thank you,
David

David,
I talked to Reza from QQ about using a DA-85 on the 102" Gen III YAK. He said it would not work. By the time you got through adding weight to the nose to get the CG right, it would weigh the same as a DA-100 and not perform well with the 85.

Thank you,

I feared this answer.....

Hi Guys,

Just to make this a little more clear. Right now plane balances with 1.5” stand offs on DA100 and receiver battery in the fuse. Given the DA85 is a lighter engine, I would think you need to move all your receiver batteries forward on the engine box and even then you might not be balanced! We’re not sure because we have not done it but if you are thinking about having a plane at 24-25 lbs using DA85 this may or may not become a reality! Your elevator servo and rudder servo still stay where they should, all you can play with is receiver battery to make up for the weight difference on the nose.

Engine performance I have never made a comparison. From what I have read, engine performs extremely close to DA100, so I’m almost sure engine will pull the plane around with authority but again you may not save as much as you want on the total weight if you have to stack up on receiver batteries to balance or add nose weight.

If anyone wants to give this a shot, you guys need to know that you need to be more patient and go through mods to make it work. I do not have an answer how this can be done because I have never tried it!

Hope this helps.

Thanks guys,
Reza

check out the testing Tom did at WildHare on the DA 85 and 100 page 13

https://www.flyinggiants.com/forums/showthread.php?t=17798

I had a Gen I QQ Yak with a BME 115 up front and it balanced fine. I think the DA 85 is a bit lighter with one less muffler but it could probably be done. I also believe the Gen I was a bit lighter in the tail. When I changed to a 3W 106 I had to move the batteries all the way back behind the rudder servos. I am sure with a little bit of work it could be balanced with a DA 85.

DB what does your 115 plane weight est or actual

How much did the qq 102 and the 115 wiegh?

Dan J and I are converting an oooollldddd Radiocraft 35% Extra 330LX for the 85. This was one of the lightest airframes produced in its size. 1950 wing area. The wieght will not be a problem, we are worried about drag. This plane is alot larger then the 2.6 extra that was flown at the Shootout with the 85.

It looks like we are going to be less then 23.5 lbs. We rebuilt the motor box make it 3/4" longer and 2.5 degrees of right thrust for a flush mount engine.

way to go r-thunder

If I remember correctly it was 24lbs. 11 oz. with the 115. As far as I undertand it, the Gen I was a bit lighter than the newer versions.

Hello,

I think i might have found a solution!

The 3W 85 XI CS !!! It is heavier than a DA 85 an more powerfull than a DA100!

Yep you heard right... Based on actual field results: The DA 85XI CS turned 200rpms more than the Da100 on exactly the same prop an on mufflers like the 100 and it wasn't broken in yet!

So to summ up, the extra weight of the 3W 85 will help to get the correct CG an an the extra power.... well you understand.

I will try this combo and report it here, but you will have to wait until spring for a flight report. I will order thge plane for christmas.

Best regards,
David Lepore

Dave,
It will be interesting to hear your results. It is funny all of the reports on the 3W 85 just fizzled away. The only concern I would have with this combo. The QQ Yak has by far the most vibration out of any airframe I have had. The reports I have read on the 3W 85 are that it vibrates alot. IMHO you will need to use alot of Locktite with this setup.

At the Houston DOD fly-in last month I saw a QQ 102" Yak with a DA 85 and slimline pitts. Motor was brand new and it pulled it around pretty darn good.

@dbcaster : I already planed to softmount it a little bit, thank you for the tip.

@ Flyinrazrback: is there any video out there of the plane? Do you know if the plane had major centering probllems?

I hope it works because I'm putting a DA-85 on the 102" Yak right now. My Yak with the DA-100 balances with the batteries behind the wing tube, so if I shift them to the motor box, it should work, we'll see. Should be done by next week.