pcastine

My Feedback: (8)

Darrinc,

The plane is a 3.3m Composite-ARF yak. Scale-wise, it's something like 42-44%, not 35%.

Pete

as722

My Feedback: (1)

Bodyworks, can a crystal stop working? I've had crystals go bad, it can happen. As a matter of fact I'm surprise crystals don't fail more often.

I tape my crystals, use a piece of dental fluss around the plugs so they don't come apart and use two layers of foam around my receivers! I've heard people say (" I which I would've had two receivers" ) after the only receiver they had failed but I've never heard anyone say " I'm going back to a single receiver" after landing their airplane safely with one receiver after the other one failed.
Can anyone tell me the disadvantages of two receivers and I don't care what horizon says and yes I use JR equipment.

Albert Santiago

pcastine

My Feedback: (8)

Disadvantage: "It's more expensive!" (ok - you just spent $X,XXX on your plane, but an extra $300-400 is too expensive?!?)

JR claims that you have a reduced range when using two receivers. It may be true, but I haven't noticed it.

jpmcclary

My Feedback: (6)

PARA NOY YA.........Use an isolator.....They provide all the safty you can get...

PaulBK

pete:

the way it was explained to me by "someone in the know" - and I am not talking the field expert, this is someone VERY close to center of JRs testing -was that the testing proved that there was a possibility of reduced range in one of the receivers when using two, and that was the reason that JR began warning of dual receiver systems. In addition, the engineers also proved that the fear of excessive battery load was nonsense, that receivers were more than capable of handling the several times the maximum load of a 40% airplane with digital servos. A little later, Horizon published one of QQs setups in their quarterly flyer that showed him using a single receiver, and a matchbox with a 7.2v battery dedicated to the rudder servos. By that time, however, an awful lot of IMAC pilots had been and were using two receivers, had never had any problems, and did not feel comfortable going back to one - research be damned. The feeling within IMAC - which was pretty understandable - was that if the dual receiver equipped planes weren't having problems doing low altitude rolling figures that apexed 1500' or more from the pilot - then there was no need to change anything.

What are the downsides to running dual receivers....except for the cost, I don't think the concerns raised by JR have been proven to be a real issue - and Horizon/JR knows that. They also know that there are still plenty of JR systems out there using two receivers...including their own pilots. But the inability for the receiver to withstand the current needs - one of the original reasons for using two receivers - that has pretty much proven to be bunk, but still surfaces as a reason to have two. so do people who claim that you have to have isolators, power distributors, and all kinds of other plumbing..even though those devices weren't available until long after 35% and 40% airplanes became popular.

I know lots of guys that run one, and lots of guys that run two. It isn't worth a debate, but it does help to know the facts.

PK

Priority RC
Professional RC Building
Corona CA

Rcpilot

My Feedback: (78)

I'm only running dual RXs because I simply don't have enough ports in a single RX to plug in all my servos and dual batteries.

With 2 RXs--I can plug in the servos I need, and dedicate 2 ports to battery input. I'll have 1 port left over.

It's not that I don't think the RX will handle the load of 8 digitals--not at all. The power buss is plenty big.

My problem is the connectors from the switch that plug into the RX. If you believe that a connector is good for 3 or 3.5 amps--then IMO--you don't have enough power going INTO the RX by only using 1 battery input connector. Thats not enough input amperage to handle the servo loads.

I wanted to be able to put 6 or 7 amps into a RX. I needed to be able to plug in 2 battery connectors in order to get that much power INTO the RX.

It's just a matter of supplying the RX with ENOUGH power to handle the servo loads on the system.

Thats why I'm using a switch with an 18ga lead coming in and dual 22ga leads going out.

rcamp

"The whole argument about the second rx just doubling the chance for failure (with a resultant crash) is basically complete BS. There is no way to rationalize it and it has been proved to me twice!"

It's hard to understand your attitude about failure modes. If you use two receivers, you are twice as likely to experience a failure. It's probability and not BS. As to crashing or not, with two receivers you might recover, as you did and then again the failed receiver may just cause a crash anyway. It depends on the failure mode of the failed receiver. I'm glad you had good results and you should continue to do what makes you feel comfortable.

PaulBK

rc, i am sure you are aware that you can put a Y on any servo connection and use the port for both the servo and battery. 90" wing seems awful small to have these kinds of set-up issues.

OnTheEdge

"...then it could have been avoided...."

Perhaps yes, perhaps no. People are human. Things happen. Because people are human and because things happen, dual Rx's will give you a better chance of getting the plane back down. It's that simple. The best set-ups and the best pre-flights can catch a lot, but you can't catch them all. Albeit rare, receiver failures can and do occur. Look at this post. Two days old and already three reciever failures. Just ask the techs at Horizon, Hobby Services (Futaba) and Radio South what the most failed receiver components are. Crystals and filters. Either of those fail in the air, the rest of the receiver is useless up there.

A couple years ago this topic came up on one of the Yahoo Giant Scale Groups that I'm a member of. One guy said receivers never go bad and he never even heard of a receiver that went bad. With in two days, there were about six posts of folks who had a receiver or crystal go bad AND landed the plane safely and intact with the remaining functioning receiver. (The actual guy who landed the plane posted, not someone who once heard of someone who once landed a plane with only one Rx working).

Do what makes you feel comfortable, but every time I hear of a pilot who landed a dual receiver plane the with the remaining receiver, it just increases my comfort level.

............Mark

Leardriver

My Feedback: (12)

Well said Mark!

PaulP

Rcpilot

My Feedback: (78)

I don't use Y-harness' on Giant Scale planes. Thats a failure waiting to happen.

Every servo gets plugged into it's own port and mixed properly with the radio or a matchbox.

I got 2 rudder servos--not gonna run 2 8231 digitals on a Y-harness. They'll just fight each other--and one needs to be reversed anyway.

2 elevator servos--one needs to be reversed.

2 ailerons servos--I need to be able to dial in differential--not gonna happen with a Y-harness.

Everything needs to be "tuned" and mixed for 0 resistance in the linkages. No binding allowed. No ganged servos fighting each other. No running down a battery with servos fighting each other. Not allowed.

So, ya see, I can't use a Y-harness. Not if I wanna do it right. And I'm not gonna cheat with a Giant Scale plane worth well over $2200. Thats just askin' to kill someone. Safety first.

My attitude totally changed this year--and not for the worse.

I used to just build my planes and fly them without bothering to install kill switches or some other positive means of shutting it down. I used to put Y-harness' on aileron servos on smaller planes. I used to not worry about a lot of stuff. Don't get me wrong--I build a tight plane--and I'm proud of how they turn out. I use good solid 4-40 linkages and H9 Titanium Pro Links everywhere. I use heavy duty (overkill) control horns and heavy duty servo horns.

But, I just never worried about kill switches or servo loads going through a Y-harness. Not to say that I took it lightly--I just never thought that my planes were big enough to justify certain items. And I certainly never thought one of them could get away from me and hurt someone. I NEVER fly anywhere NEAR the flightline or the pits. ALWAYS way the heck out there--away from everyone else. I've put planes into the dirt to keep them from heading over the flightline before. More than once. I'd rather crash it than crash it into someone.

But, I saw an airplane get away from a guy and it was a great big 100" plane. Big ole gas engine. Lots of weight in this bird. 25+ pounder. That sucker went in HARD as a cannon ball hitting a brick wall. WHAM!!!! Full throttle Guys were scattering too. Like cockroaches in the bright lights. Barely missed the flightline and a couple other pilots who really couldn't move too fast because they were trying to fly their planes and run away at the same time. It was out of control--and the guy had no way to shut it down.

That right there was it for me. Scared the crud outta me and I was 150' away watching it happen real fast--but slow motion at the same time. We all know that feeling.

My planes get kill switches now. I plug 1 servo into 1 port on the RX. I use redundant batteries and/or switches. I use heavy duty servo leads.

I don't need to kill somebody. Heck, I don't even want to have a near miss with someone and have him whining about his soiled shorts afterwords. Just not worth it.

It may seam like overkill to you. It is--afterall--only a 90" plane. But, to me, it's justified. It's redundant. It's safe (safer). And it's proven. I ain't the first guy to use 2 RXs in a plane that most people would deam as only requiring 1 RX. But, I can't see any other way to plug all these servos in and provide them with enough amps to make the work correctly. To me--it's justfied. Heck, it's only another $50 for the 2nd RX and a little bit more work to install it. Justified--totally.

Hammbone is the guy who got me to thinking right about this situation. I was all ate up about using 2 RXs in a 90" plane.[sm=confused.gif]

I thought,

"No one ever uses dual RXs in a plane this size. People will think I'm stupid. People will say that it's overkill. People will say this and people will say that. Guys just don't use dual RXs in a 90" plane."

Ya know what Jim told me?

"If YOU need it to set the plane up properly--then it's justified. If YOU feel it will give you an edge--in the way of redundancy and safety--then it's justified. If you don't mind spending the extra $50 to achieve that level of confidence in your setup and the safety it provides--then it's justified."

And then he said the most important thing of all.

"Who cares what someone else thinks of your setup?"

"Is it safer" yes

"Is it worth the expense?" yes

"Will it allow you to set the plane up the way it needs to be setup and provide all the amperage that you need for the digital servos?" yes

"Then it's justified."

That was all it took for me. I was worried about what people would SAY. And Jim got me to thinking about what was the best way to set it up and not worry about what people think. I owe him a tremendous debt--for making that little light come on in my head. [sm=idea.gif]

If it's functional and it's safe--then do it. Don't worry about what people will say. It's your money flying around up there--and if it's worth the extra $50 for the 2nd RX--then do it.

I feel like I've hit a new personal level in my hobby. My attitude has changed. Yeah, they are fun. But, if ya kill someone--it ain't gonna be much fun anymore. Safety first.[sm=thumbup.gif]

Hammbone

My Feedback: (309)

Well said RCpilet,
I have to agree.

Jim

Hammbone

My Feedback: (309)

Interesting.... I did not know about this.
The fact still remains though (as RCpilet stated) that these standard plugs we all use going into a RX will only pass about 3 amps of current. For this reason we still need to use multiple plugs from our batteries going into two RX's (to get enough ports to plug into), or some type of power distribution device.

Using one RX only (with no power distribution device) simply will not provide adequate power to your servos on larger planes with lots of servos.

Jim

bodywerks

My Feedback: (4)

You can run a Y harness off your throttle servo and ignition cutoff or choke servo to get two extra outputs for your battery packs, if need be.
I personally have never had a crystal just plain "go bad". In my 15-20 years of flying, I have had several fail do to being in too many slope combat collisions, or from improper mounting of the receiver, but never "just because". I could always trace it back to something I did wrong. The only way a crystal stops working is if it cracks or if the little conductive filaments seperate from it - all of which have to do with excessive vibration or hard impacts. I have also had the ceramic filters take a dump, too, but always because of how/where I used the receiver (slope combat).
Also, don't get me wrong - I'm not debunking the validity of using two receivers where it is necessary for the added servo ports, in leau of a powerbox, on 37-50% aircraft. But it simply is not necessary on a 35% planes and smaller where you are only using a maximum of 8 high-powered servos, often less.

Rcpilot

My Feedback: (78)

Thats your opinion. You may be totally comfortable using a Y-harness along side a servo so that you can run the battery plugs into the RX. I'm not. Simple as that.

I have had a lot more Y-harness' fail than switches--batteries--and RXs. The idea of running my battery power through a Y-harness makes me cringe. No way I'd ever do that. I've NEVER had a battery failure. I've NEVER had a RX failure. I have had 1 switch fail, and it was caught on pre-flight inspection. I replace my batteries and switches every year though. So, that explains why I've never had one fail. Cheap insurance. Overkill--maybe? But worth every penny. With as many Y-harness failures as I've had and seen--no way I'd ever trust my plane to one if it meant pushing battery voltage through it.

Saying that dual RXs isn't necessary on anything smaller than 37% is just limiting yourself.

I always though it wasn't necessary--untill I came across a situation that totally lends itself to dual RXs.

Never say never.

We have so many pre-conceived notions about how it should be done in this hobby. Most of us get downright nasty about brand loyalty. I think that we are so opinionated sometimes--that we can't see the forest through the trees.

I'll bet that 10yrs ago--if you'd mentioned dual batteries--all the guys whould have said that you were crazy. They would have said that it wasn't necessary and that there were other ways to power a RX.

I'll bet--at some point--somebody even made the argument that dual servos on a surface was overkill. Anybody thinking about putting 2 aileron servos on a wing panel was an idiot and the idea was rediculously overkill.

Each situation is different. Every plane is different. Every person is different. Just because someone decides to do something different that you wouldn't do--doesn't make it wrong. Just different.

PaulBK

Jim, I was heavily involved in IMAC when a lot of what turned out to be nonsense was being touted as plane saving gospel - trust me...these connectors will easily handle well in excess of 5 amps and no one that i know has run dual receivers because they won't use a Y on a single receiver. It's about preference, nothing more.

But hey, what do I know?

Paul K

Contest Director, JR SCAT Series scale aerobatic championship, 1999, 2000, 2001 (seven contests per year for three years...average attendance 40+)
Former Scale Aerobatics columnist, Model Aviation
1999 IMAC Sequence Committee Chairman

Hammbone

My Feedback: (309)

Sorry Paul, I don't believe for one minute that these standard connectors can handle 5 amps.
That's what's great about this hobby though. You can use one RX on your planes and I'll use two RX's on my planes.

Happy flying, Jim

RTK

My Feedback: (1)

I will throw in my .02 cents,,,,and I think Paul has a good handle on this.
Good connectors will handle 5 amps+ no problem,, in bursts,,,,The problem is they will only handle 3-4amps continuous, any more for an extended time and they get hot, then the plastic melts. This information was from a well known manufacturer by the way...

How long and how many amps do these planes pull???? Not sure, but I know someone with a data logger could tell you. I just know what I use and what works for me and my friends.

I am running 8 digitals thru (1) Futaba receiver with multiple inputs from (2) batteries on a 35%er. No problems have been encountered to date. I always use the KISS principle,,,lighter and less failure points in my minds eye.

Now I am not saying there is anything wrong with 2 Rx's or power boxes, I have not yet had a need for them.

Darrinc

My Feedback: (5)

Why do you need more than one reciever and one battery in a 35%?

Are they falling out of the sky all the time?

bodywerks

My Feedback: (4)

No.
I put an 8611 into a full stall and it pulled 1.9 amps, to give you an idea. I believe that you most definitely need more than one power lead going into your Rx on these larger aircraft. Not really for piece of mind, but to excersize the full potential of your servos. I would be more concerned with power loss due to voltage drop across one lead than melting wires...
Jim, were you running dual Rx's on your Cap?

Darrinc

My Feedback: (5)

When have you ever stalled a servo in flight?

RTK

My Feedback: (1)

I use 2 batteries for redundancy, higher amperage load and for longer flight times. Anything smaller fly's on 1 Li-.

Thunderbolt47

My Feedback: (8)

MY Sukhoi would still be with me If I hadn't taken the extra battery and bat-backer out. I was told by Duralite that the 4 cell packs have redundency built in to them. BUT, Not went the wire breaks loose from the pack.

I still use one RX, but I will never fly a Giant scale with out 2 batts and a batt-backer.

I'm in the prosess of out fitting a 37% Ultimate. I will be using one RX with a Smart-fly Power box and super reg. and two 2400 fromeco batteries. The reason for the power box is the long distance of the top Aileron lead. I hope this will be sufficient.

BTW I've seen JSM77777s setup. he explained it to me at the field last summer. Looks very K.I.S.S to me.

Darrinc

My Feedback: (5)

I like simple, heres my 35% CA Yak. The 4 cell 2800 mAh pack is for tail weight. The 1200mAh Li-Poly for ign can be seen up in the corner.

Thats it, my whole system.

Hammbone

My Feedback: (309)

Yes.

Jim