Thinking of a giant scale project...

[DMA, IN]

hey all, I have been thinking of getting into giant scale for a while. I fly all electric so I would have to do a conversion. The model I'm looking at is the 160 version of the Richmodel Long-Ez: http://www.avia-richmodel.com/Product/LONG-EZ-160-(30-Days).html I have always been a fan of Rutans designs so this will fit right in.

I'm guessing pretty much anything can be converted to electric but i would like to see some recommendations for a budget setup, I'm not really looking for unlimited vertical but good sporty performance.

Let me know what you think.

Darren

[Ed Lyerly]

Darren,
What is the largest diameter prop tou can use with the stock landing gear ?
Ed

[DMA, IN]

I really don't know as I don't actually have the plane. I am assuming that I would probably have to go with a 3 blade prop for clearance during take off and landing being that it is a pusher.

[Ed Lyerly]

It will make a significant difference, in that the 3 blade prop will be considerably less efficient than a two blade "E" prop.
I'm thinking something like an AXI 5330/18 on 10S turning an 18x10 APC-E Prop.
Ed

[jrb]

Three balders are not “considerably less efficient” than two; in fact they are far more efficient Po/Pi when operated at the same rpm.

Selecting the correct effective Kv will let you use them very efficiently!

Using a different motor (than for 2) or a geared solution will get you to the correct Kv

[Ed Lyerly]

jrb,
I stand corrected :).
Perhaps it is the efficiency of the 2 blade APC "E" props vs the "non-E" 2 and 3 blade props I have tried that gave me that distinct impression.
I have been running some APC 3 blade glow props on several of my planes (8-10 cell),
and while they are quieter and require less compensation for the P factor when flying .... the power output is not as good (with the same watts in). If it's motor inefficiency I'm experiencing, (due to wrong KV) post flight temp checks don't show it.
Ed

[jrb]

How did you measure Po Ed?

When comparing an APC 15x12x4 and an APCE 16x10, they ran virtually the same (Pi & rpm) on the exact same motro/GB, ESC, & pack.

In addition to running "smoother" the x4 made more velocity off the back of the prop and thrust -- note velocity time thrust is Po.

Jim

[Ed Lyerly]

Hi Jim,
The only things I'm measuring are WOT static watts, and motor and pack temps at the end of a flight.
I have tried 10S on a AXI 5330/18 and 8S an E-Flite Power 110. I used a 18x12 APC-E and an Xoar 18x12 "E" prop. I compared them to APC 3 blade "glow props" ... a 15x13.5 and a 15.75x13. The 15x13.5 pulls a few less amps, and the 15.75x13 pulls a few more than the APC 18x12E prop (which pulls a few more than the same size Xoar).
In the air, I'm looking at what kind of vertical "punch" I have with my 9 lb Venus II when going from a horizontal pass at 1/4 to 3/8 throttle. I'm looking at the ability to accelerate vertically and hold or increase speed as I go. I'm looking at the ability to do a snap about 200 feet up and continue vertically without running out of punch.
In these cases the larger diameter 2 blade "E" props do a much better job ..... that's why I think they are more efficient.
Your numbers say otherwise, but my field results are what really matters to me.
I will definitely give the nod to 3-4-5 blade props in looks, quietness and smoothness.
Ed

[jrb]

Gotta fly what you like Ed!

For your measure of success you need in-flight thrust – fundamentally a bigger diameter with less pitch for the same motor load will do that.

An 18” two converts to a 16.6” three blader of the same pitch and motor load (DiaN=D2/(2/N)^.2) – yours were smaller than thisl not a true indictment/comparison.

Just shows a blanket statement can’t be applied to all.

I fly all APCEs, except for a 4 blader VarioProp (swapped to this from a APC x4), and had a very bad experience when trying a wooden Zinger.

Though, I do wonder if a bit less flutter & flex of the APCEs would be a better solution.

Jim

[jrb]

PS: multi bladers made from APCE seem to work very well!

Even if your use two set at 90 degrees -- snue.

[Ed Lyerly]

You are right ..... it's what works in your application, and how happy you are with it that really matters :).
OK, then maybe a pair of APC-E props set at 90 degrees would give Darren what he needs for the Long-EZ (prop clearance, thrust and smoothness). It would be interesting to see how that would perform.

[jrb]

Quotes and photos:

http://www.rcgroups.com/forums/showthread.php?t=376743

Another test yesterday--3600 watts or 4.75 hp on a "stacked" 4 blade APC 27/13. Battery is a 10 amp/hr 12S pack. Runs very smooth and quiet. Next stop is the plane. 85 amps measured with the Schulze controller--also up for running test is the CC110 HV controller on this setup.

The BAM has finally found it's way into Ray's new plane. Here are some pictures from his shop. I don't know about the model but it weighs in at around 22-24 lbs RTF. Should be a lively perfromer with nearly 4000 watts--I measured actually a little over 3900 with the 4 bladed prop. It should be around 170 watts/lb.

If all checks out ok the first flight should be tommrow.

Steve

[DMA, IN]

2 props on the same shaft was something I hadn't thought of but should give me enough prop and ground clearance. Would be a bit of work to get a spinner to fit on but not to bad.

As far as motors go, What do you guys think of either of these two:
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=3890

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=4188

Nothing against AXI, just trying to watch the budget a bit.

Another thing I'm wondering about is with the smaller version of this model they put the battery up in the nose. I would have to probably do the same to balance it but I have always heard to keep the battery and ESC wires as short as possible, would this be a problem? If this all comes together I'm looking at using A123 cells and their slightly heavier weight should help in that respect.

Thanks for all the help!

Darren

[Ed Lyerly]

Darren,
I suggest:
(1) Get the model
(2) Determine the prop clearance.
(3) Check size of battery location.
(4) Choose motor, battery, and prop to provide the power needed.
In short ..... too many unknowns until you have the plane in hand.

Yes, short leads are best .... but ..... longer leads can be made to work just fine.
Ed

[VODOOFIXER]

Darren
The 63-64-B runs real good. We (me and the guy that owns the plane) have been flying the RCGUYS Super Decathlon. This has a 98" wing span and is about 15lbs.
This flys great, streight up if you want most of the time its at 1/2 throttle or less.
Runing a 20-11apce and 10 HXT 4100. A cheep way to go and it flys fine.
Al Messer

[DMA, IN]

sounds like a logical order to me, the model will be ordered around mid to the the end of this month. Then once i finalize everything get the rest on order.

Darren


Darren,
I suggest:
(1) Get the model
(2) Determine the prop clearance.
(3) Check size of battery location.
(4) Choose motor, battery, and prop to provide the power needed.
In short ..... too many unknowns until you have the plane in hand.

Yes, short leads are best .... but ..... longer leads can be made to work just fine.
Ed

[DMA, IN]

Thanks for the comments on this motor as this is the one I'm leaning towards. With these Chinese motors sometimes you just cant trust their reported figures....

Darren



Darren
The 63-64-B runs real good. We (me and the guy that owns the plane) have been flying the RCGUYS Super Decathlon. This has a 98" wing span and is about 15lbs.
This flys great, streight up if you want most of the time its at 1/2 throttle or less.
Runing a 20-11apce and 10 HXT 4100. A cheep way to go and it flys fine.
Al Messer