Brenner

Hey Brian,

Your Midrex is certainly a work of art. The whole package is breathtaking, and the purple Contra looks absolutely sensational! You have definitely set an impossibly high standard for the rest of us to try and follow.

Brenner ...

serious power

Hi Brenner,
Thanks, it is the least it deserves.
We've been 'staying out of your hair' a little lately, knowing that you guys are busy.
I've had a vary enjoyable season this year flying the contra - thank you.
Will be in touch soon.

Brian

serious power

Hi Christian
I had a few flights on Sunday.
It was quite windy so not great for trimming observations.
Anyway I flew it at CG = 112mm back from the LE bottom wing.
A small pull out at the bottom of downlines - 3% thr to elev mix made it push hard - so _1%.
It pulled to the canopy on both knife-edges.
The mix to sort this out is/will be very small- less than .25mm elevator movement.
I can't give a % as I wes reducing my normal/low rate rudder flight by flight.It was at 7% AFR and 50% Expo for the last two flights and I still had to be very careful.
If I brought the nose up at all in knife-edge the model would climb.
I have a single elevator servo with pull pull.
I also do have extra weight in the front due to the re-work.
The rear end of the batt,, pack (tp5000) was at the wing LE former for this CG. So lay out your components before installing to check.

Brian

Brenner

Mike's working on a set of molds for a new 22x22 set of front and rear props. Here's a picture of the the mold halves fresh from being CNCed.

Now they have to be polished and plated.

RC_Pattern_Flyer

My Feedback: (1)

Now thats beautiful!

pattratt

My Feedback: (1)

Brenner
I know that longer blades are more efficient but 22" is too long for most of the current designs. [mine works on grass at 22' but not on concrete or asphalt] We are all looking for a wider speed envelope at a higher top speed so what is keeping us from going over square on the prop such as a 21x22 or 21x21.5? Would this not solve both goals of higher top end speed and better prop clearence. There would be a slight loss in prop efficiency but the benefits might out weigh the loss? Just a thought!
Dick

serious power

Hi Dick,
The existing contra props are also 22in dia,, .
It is easy to put on longer legs,extend existing ones and/or put on bigger wheels (we use Mk 70mm).

Brian

Brenner

Hey Dick,

You're definitely right. a 21x22 prop coupled with a 9.89:1 gearset has very similar performance to a 21x22 with a 10.56:1 gearset. the only differences are a slight increase in prop rpm, and a very slight loss in efficiency for the 21" prop vs the 22" prop.

The reason we're starting with a 22x22 set of props, is that we want to be able to mix and match them with the props we already have, and we know mixing and matching same diameter props with different pitches works.

However, this is not to say that we won't make a set of 21x22 props, I just want to see how the 22x22 props fly first before we commit to our next prop size.

Brenner ...

pattratt

My Feedback: (1)

Hey Brenner
Thanks for the explanation. What type of prop combinations and gear sets would you project to give increased top speed, down-line breaking, and acceptable battery load on a F-13 sequence?
I have pretty well settled on the 10.15 and 22x20 as my all around set-up but have not tried any split prop set-ups.
I know several others have experimented with mixing the props but I have not seen any definitive results on what was or was not sucessful. If anyone has any feedback on this I would appreciate reading about it.
Thanks
Dick

Brenner

Hey Dick,

This is what we're trying to work out right now.

Right now we are getting feedback (from North American flyers primarily ...) that we need to save about three hundred mah or so in order to get through F13 without being too hard on the packs, so we are looking for a combination that will trade off vertical performance for more horizontal speed so that the plane has the potential to get through the pattern a little quicker at a lower throttle setting.

What we're trying to do is trade off various engineering compromises in order to get the best mix of performance characteristics, and this is what we're hoping to see with the new props. We are going to try a set of 22x22 props with a 10.56:1 gearset, and a mixed set of 22x22 and 22x21 props with a 10.33:1 gearset. Both setups should be quicker while compromising a little vertical performance, and with slightly less downline braking.

Keep in mind that the guys who are asking for this are already flying 22x21 props with the 9.89: gearset. They probably wouldn't have a problem with mah usage if they flew your 10.15:1 setup, but they want to maintain the speed that the 9.89:1 gearset gives them so that they have enough speed margin to adjust for wind conditions in maneuvers like the rolling circle.

I remember watching Dave Lockhart fly a rolling circle when I judged the last unknown sequence in the Nats f3a final, and he demonstrated this principle perfectly. At the time there was a heavy wind blowing, but Dave was able to adjust for the upwind and downwind speed difference and match his roll rates around the full circumference of the circle, while many other pilots were not able to do this.

Brenner ...

pattratt

My Feedback: (1)

Hey Brenner
Thanks for the info. I was not aware we had a 22x21 set of props available.
Chip is sending me a new 45C TP G6 pack that he wants me to try on the Contra De Ja Vu. He said it was like adding additional HP. I think I would like to try the 22x21 set of props.. I will call tomorrow.
Dick

underdw

My Feedback: (2)

You'll make weight with that pack Dick? TP website says 655gm

Brenner

Oops! I made a mistake...

Sorry, I meant 22x20, not 22X21. Too many sizes for me to keep everything straight .

Brenner ..

pattratt

My Feedback: (1)

Ok, no problem.
Dick

serious power

Hi Dick,
We have been using the 22x18 front and 22x20 rear with the 10.15 gear set all season.
We are flying both monoplanes and biplanes on this set up.
Only in very strong winds (25mph+) we put on the front 22x20.
We are using 3300 to 3700 mAh per P sequence.
We do all the horizontal stuff at 1/2 to 2/3 power, and the vertical stuff at 2/3 to 4/5 early in the flight and at 3/4 to full later on.
Headwinds just have to be managed,to maintain a constant speed, regardless of power plant.
Crosswinds are a different matter. I feel vertical performance is critical in crosswinds, much more so than horizontal speed.
Before the contra I flew YS then Plettys with 20x15 and 20 x14.5.
With the Contra I had to learn to 'save it for the verticals'.
I have to say that this is one of the most manifest advantages the Contra offers. You can continually adjust power for eg all the way around a loop without disturbing the model and the models speed response is almost instant.
I agree that for more forward speed ,battery limitations allowed for, more pitch and less diameter is the way to go.
However prop stall speeds will likely start to play a role - we will just have to wait and see.
I believe the current mixed props are better in this regard. I found that 'picking up the model' with power after a pull or push out is better. This is at relatively low speeds (Euro style).

Brian

Angus Balfour

Exactly what Brian said. I almost exclusively use the mixed props, 22X20 rear, 22X18 front, 10.15 gears and Neu motor. For all but the strongest of winds this is a seriously awesome combination. For high winds I simply put on the 22X20 front which makes a big difference to the speed of the plane but you really need to nurse your pack through the first half of the schedule or you will be struggling by the end. At this stage I never change the gear ratio, always 10.15 gears.

Not that it is a big issue but impression does help and the noise you get off the mixed props is also really nice to listen to (I think). Very different to the two 22X18's which themselves are very different in sound to the two 22X20's. Wonder what these new props will sound like.

pattratt

My Feedback: (1)

Hey Brian and Angus
That was exactly the info I was looking for. I will immediately try the 22x18 front on the 22x20 rear with the 10.15 gear-set. I will also report my impression of the TP 45C when I get it in my hands. Chip said I would have it this week!
Thanks again for the info.
Regards
Dick

Brenner

I've been flying with Thunderpower G6 65C packs, and I like them a lot. The only downside is they are about 5 ounces heavier than the equivalent 25C packs.

Brenner ....

pattratt

My Feedback: (1)

Hey Brenner
I think the 45C is the weight compromise between the the two. What was your first flight impression on the 65C? I am hoping that the 45C will allow me a "Broader" power band without increasing mah usage for a given sequence.
Regards
Dick

Brenner

Hey Dick,

That's pretty much what I experienced. more power when needed, without a significant increase in mah useage.

Brenner ...

pattratt

My Feedback: (1)

Brenner
Thanks, that is what I was hoping to hear.
Dick

Angus Balfour

I should have also mentioned that I have started using a TP 5000 65C battery in the wind which takes my Valiant right up to 5050g. It is approx 4930g with the F3A Unlimited packs. This high C combo does give a bit more power but not as much as what I thought. I think this is because the F3A Unlimited packs are still able to provide the amps on the 10.15 gears and 22X20 props. If I moved up to the 9.89 gears, or moved up to the new 22X22's I'm sure there would be a much larger difference. 22X22's on high discharge packs will be crazy power! I think a 22X20 front and 22X22 rear would be a really interesting combo to try.

OhD

I'm installing a Contra Drive/Neu and thinking about using the 1.5mm mounting plate and bulkhead supplied with the contra drive with Budd Engineering rubber isolators. I would put the rubber isolators on the mounting plate as opposed to the bulkhead as suggested by the drawing in the instructions. Any comments or recommendations? Are the 1.5mm parts stiff enough? Are the Budd isolators too soft or too hard? Anyone used this combination successfully? Any suggestions are welcome.

Thanks, Jim O

Dsnow

Hi Jim, not sure it really makes any difference, post #116 & #118 page 5 show how I've been running mine. You may need to reinforce the carbon plate because there is not much material after drilling the larger hole, I did not reinforce mine.

Dave

patternflyer1

My Feedback: (11)

Jerry has 2 different strength isolators Jim. I think the one's for the c50 are the soft ones. The outrunner are much stiffer.

Chris