Hooked-On-RC

My Feedback: (16)

Gentlemen and Ladies,
We are all on the quest to find the great flying light weight airplanes but have we reached a point in the design and assembly process where things have become a lot weaker (strength and durability wise) in order to save a few pounds? With the innovation of CNC and computer aided design, the engineering of airplanes has never been easier, Laser cutting has given us accurately cut parts that fit together perfectly square and tighter than a duck's backside however are the new designs just to light weight and therefore give up the ability to fly with heavy G loads? Everyone wants a plane that will "hover" at 1/3 throttle and that requires either power or lightweight planes, however have those lighweight planes become to fragile to fly the heavy G loads found in agressive 3d Manuevers?

Your thoughts on this guys and gals....

camss69

My Feedback: (46)

I vote no.

I'm in the process of assembling (not building) an EF YAK and it's very light, built with the laser cut parts you are describing and I have to say that sucker is strong, you can attempt to twist the wing, twist the fuse, it just doesn't budge.

I've pretty much punished my H9 extra 260, which isn't the lightest build ever but it's still a modern design, tons of snaps, walls, blenders, you name it I've tried it at least a hundred times and it's still going strong.

I've had 2 fliton electrics, if there is a plane that fits your description it's them, couldn't break either of them, one died due to a low knife edge pass, the other, still going.

If they aren't designed right, or the guy at the assembly plant doesn't get enough glue on that all important joint, sure it'll fail, and the rest of the plane might not survive a failure, but they are built to fly.

I'm sure there may be some bad ones out there, but for the most part I think the current selection of planes are the best we've ever seen for any type of flying.

krayzc-RCU

My Feedback: (31)

i use to fly fun fly planes in 2k that were a piece of plywood for a fuse now today its light and i love it. They all tear up if you just flat out wreak it but in the air all have proven to be strong as ever. I 2 have the EF Yak that is an eng. master piece.....

BaldEagel

I fly a QQ Yak 85" modified to incorporate a cannister tunnel and its still only just over 16.5Lb, with no modifications it could have been 15.5Lb, this is impressivly light for an all out 3D plane some of my flying according to my peers looks at though I am trying to break it, no problems so far so I have to say if its constructed properly and has sufficient glue my answer would be NO.

Mike

Jake Ruddy

My Feedback: (40)

COnsidering we are using a lt of CF gear now I dont really think we are getting weaker.

When I go into a dive and slam full El. tostop the plane and float down in an Elevater most people who havent seen it cringe... however having done it 100 or so times on my frames without any damage I would say they are up to the task.

I don't see the point of making them super strong.. if you hit the ground fast enough it's still going to break.

sensei

If designed properly, and bond and glue lines are sound; the lighter airframe will sustain just as many G loads as the heavy one, and in many cases more. the difference is; the lighter one will not see as high a loading due to the lower weight per G induced upon it.

Bob

bodywerks

My Feedback: (4)

No. Because of the high-tolerance fit of assembled pieces of a structural component, the strength has improved tremendously. Also, with the aid of CNC and CAD engineering over the past decade or so, the structural designs have improved. Sure, you hear of planes blowing apart in the air still, but the planes are built in china and there are humans working on them. It also happens to be a human that chooses and installs the radio equipment and engine. Human error will always exist.
Now, in addition to that, building a heavier plane or beefing up a plane (which also increases weight) just to "make it stronger" can have an adverse effect in the air, since the heavier weight will have more inertia in a high-G turn or other high-stress maneuver, thus putting more force against the structural components of the plane. Same goes for when you dork a landing or whatever. You know the old saying "the bigger they are, the harder they fall"? Well, one could say " the heavier they are, the harder they hit" - meaning more momentum on impact and thus more damage.
Personally, I am a weight freak, but 97% of my weight savings is in the form of equipment selection. On a 100CC plane, I can save a good 2 pounds over conventional setups by using CF accessories, one servo on the rudder, lighter wheels, and no bells and whistles for electronics. By doing this, I actually increase the strength of my plane since there is less overall weight acting against, say, the wings in a high-G turn, for example.
If ARF companies started building heavier just to make planes more idiot-proof and damage-tolerant, I'd go back to building for myself...

bodywerks

My Feedback: (4)

How do you say exactly the same thing I am trying to say, but in only one or two sentences???[8D]

Rcpilot

My Feedback: (78)

There's 2 ways to build an airframe:

1-Build it to fly. That means light.

2-Build it to crash. That means heavy.

I haven't crashed a plane yet that survived the impact, and trust me when I tell you that I've built some HEAVY planes in the past. The simple fact is--if you crash it, you're gonna break it. There isn't a "crash-proof" airplane yet. When they hit the ground, no amount of reinforcing and beefing up will help it survive the impact.

So, given that, there's no point in bulding it to survive a crash. It won't survive anyway. It's just heavy.

So, build it to fly. Build it light and punish it in the air. Most of them are actually overbuilt. I watched my buddy do some nasty blenders with MY plane a couple days ago. I admit, I tensed up and cringed when he threw it into the flat spin from a blistering aileron roll. But, it held together. He did that 3 times on 2 consecutive flights and the plane is happy as can be.

When you look at the construction of this particular plane, your initial thought is, "Better not dork that one on the landing. It'll explode." Typical of ARFs today. All laser cut. Even the balsa. Light as an eggshell.

I've done full throttle inverted snaps and it's holding together. I come in at full throttle and then back off to idle--immediately give full down elevator and full right aileron and rudder. BLAM!! The air around it actually makes a creepy "whhoooooshing" sound when I snap it hard like that. Not a scratch on it.

I just discovered the benefits of light airframes about 3yrs ago. My entire build/assembly process is concentrated on finishing a light model. As light as possible.

I agreew with Bodyworks and Sensei. Lighter planes actually incur lower G loads. That means you can punish them even more.

I vote NO.

checkride

This might sound stupid but what about using 3mm depron
for sheeting it is light and strong. I think it could be stronger the balsa.

you not really sacrificing strengh for wieght. There are some lovely kits
out there that are strong and light.

Hooked-On-RC

My Feedback: (16)

some great analysis gents and gets a guy to think when he is in the process of building that if a plane is designed and engineered correctly (that is the key) and then built light, it can in fact endure a greater "G" load than one that is built heavier. Continue your thoughts boys....

sensei

Now thats funny.

gooseF22

Look at the Dalton/Troybuilt/Scarfo models versus the cardens. Both good, but the dalton is alot lighter. I can personally attest to the 35% TBM original 260. It floats on wings of angels. It is ballistic with an OLD 3W80 twin on it. I think last I checked it was around 22 pounds. NOt bad for a 35% er. Scarfo and Dalton still build em, but they are a little heavier due to the core wings versus the foam rib from Gene/Bill's days. John and I are working on covering both a carden and a dalton at this time. The difference is pretty dramatic. You just have to be careful not to ding the dalton up or grab it by the ribrunners. There is probably 4-5 pounds difference in finished product, but thats a guess because we havn't finished them identically with eletrons.

Now to a nearer story. Remember the old sukhoi from H9? It was constructed old school and with a GT80 it advertised about 26 to 28 pounds depending. I bought it used and it had a BME102 in it with about 2 pounds of lead in the nose. It was not set up very well. It did not fly well either. It flew heavy.

I sort of followed TBM's rebuild and talked to Bill Hatcher and did the following: ZDZ Super 80, wood prop, carbon spinner, pull pull rudder tray with one 5955, otherwise as advertised, used a 3.5 ounce ignition batt, 2 6 ounce main batts, two miracle regs, and the AR7000 reciever. I left the original gear, but put a carbon tail. Removed the pilot and lightened the canopy. With the aluminum spar and gear, and reglued the wing spar/webs. it came in less than 24 and it completely transformed the aircraft into a total monster. It is rock stable at high alpha. There is a magic point where an airframe flies great. I dont know if it would fly better with carbon gear/spar, but that would save about 12 ounces, along with lighter batteries, one pound. I will try it a little later and see if I can see one pound, but I hate to touch anything cause it is sweet. To get it to balance, I put the motor 2 and 1/4 inches forward

No weight added Ma!! Thank you TBM!! good coaching.

T. Bob

My Feedback: (9)

I vote "It's a dumb question".

sensei

Yah right T Bob, like you would even know if that was a valid question or not. Seems all of your inputs are the same; year in and year out, just alot of the same BS. I guess that is why they keep you on a short leash on F/G, LOL.

camss69

My Feedback: (46)

I'm a little surprised at the number of yes votes yet none of the yes people are posting their reasoning.

Aside from some structural failures in flight due to bad glue joints/and or building errors (from the factory) can anyone think of a plane that "couldn't take it" and outright failed due to design flaw? I'm talking failing in flight when flying the type of maneuvers the plane was designed to do?

The only one that comes to my mind is the stab on the TT rare bear, maybe there are others I have missed but I think even that one, people were putting bigger engines than were recommended on the plane. I don't want to get caught up on that one plane, it's just an example so forgive me if the particulars are not correct.

canavanbob

My Feedback: (20)

I voted yes because it's true. I designed full size airplanes for Boeing for 40 years and we sacrificed all the strength we could. I'm sure we did allot more stress calculations than any of the model companies. Commercial airplanes have to have the highest payload capability possible. We designed the parts based on flight loads encountered in service and added a safety factor. Like someone said before we designed the planes to fly not crash. The model makers are taking advantage of the better technology. The airframes are now more vulnerable to errors in assembly that compromise the strength. Yes, it's good thing to sacrifice as much strength as you don't need.
Bob

T. Bob

My Feedback: (9)

My point is "who cares� build the way you want to build.
If you build it to light (sensei) it will fly poorly.
To heavy (AeroTech) it will also fly poorly.
The point is WHO CARES
Do what you want to do
This is America.

canavanbob

My Feedback: (20)

If you don't care, surely you you can find something better to do with your time and quit wasting ours. I'm like you, I build what I like, it doesn''t have to be super light, but, I don't want a pig either. Some people like their planes as light as they can make them. Let them have their fun.
Bob

Rcpilot

My Feedback: (78)

After reading that, I might want to change my vote to YES.

I AM willing to sacrifice strength for weight. As long as it's weight that I don't necessarily NEED. Like additional gussetts and formers that were designed to help the airplane fair better in a crash. We don't need that weight. It won't survive anyway.

Interesting discussion. I wish CF was cheaper.

I used to take the view on ARFs that there wasn't much you could do in order to lighten them up. I mean, the airframe is built and covered. None of us is going to strip it and hog out a pound with the Dremel. Thats not why we bought an ARF.

So, I used to just build them and it ended weighing whatever it weighed. That was before I realized just how thin the air is up here at 6000' That was before I actually got my hands on a 35% plane with low wing loading and felt how light they fly.

Now, I spend countless evenings designing and building lightweight servo trays and figuring out ways to drop weight. A sandwich of balsa and CF is lighter and stronger than a piece of lite-ply. Even if it's only a few grams or an ounce. An ounce here and an ounce there makes up for 1/2 pound or more. Thats a significant weight savings on a 15--20 pound model. I dropped 3/4 pound out of a 28% plane just by switching out my batteries. 3/4 pound in batteries!! Thats HUGE in a 16 pound plane. The airplane flew a lot better after I did that.

I'm just starting to really get the hang of building and assembling light. As I mentioned, I only REALLY discovered the merits of lightweight planes a few years ago. It took me another year of reading these forums and looking at products on the web to figure out how to build and buy light on a budget.

This is a picture of a rudder tray I built recently. It's 1/8 x 1/4 spruce sandwich with a piece of CF tape in the center. This was glued together with 2hr finishing resin and compressed as tight as I could get it without actually smashing the wood. All excess glue was wiped off, of course. It's extremely light and should easily take the 300oz of torque these servos can put out.

If I'd had the money at the time, I'd have bought a single servo. That would have eliminated the weight of the additional servo AND the aluminum tray.

I did this mostly as an experiment. I've never used ganged servos before and the plane was on the edge of being too big for just one servo. It's right in the middle of needing 2 servos or just one big one. I am using a Matchbox. So, there's some additional weight. But, mostly, this was an experiment to see if I could build a lightweight servo tray and do this with 2 servos. Obviously, it's not as light as a single servo. That wasn't the point here. The idea was to see how light I could build the structure using a combination of traditional materials and composites. I am not sure if I could have built this with balsa and CF. I don't have much experience with composites. I know that balsa would have been significantly lighter than spruce, but I'm just not sure if it would snap during a hard rudder maneuver when there was maximum load on the structure. Don't want to sacrifice the plane to find out.

I'm satisfied with the result, but haven't flown the plane yet. If it holds up, I'll be able to do this same thing again on a bigger plane. Maybe in a couple years.

I know someone is going to knock me for using the dual servos and the aluminum tray. I KNOW it's not the lightest setup in the world. It is an experiment.

I've completely re-designed that battery and RX tray you see lying under the rudder servos. That was only a mock up to check my balance and see if I liked the layout inside the plane. Maintenance and accessability is an issue and I wanted to see if I could actually install that battery tray under the rudder servos and still get to it all for maintenance and adjustments.

That battery tray is now a piece of 1/8 balsa sandwiched in between 2 layers of very thin CF cloth. I glued the whole thing up with epoxy and clamped it down very tightly. I cured it in my oven at about 150F for 6hrs. My wife was NOT happy.[sm=lol.gif] All I have right now is a sandwich about 12" square. I haven't cut any holes in it or trimmed it to fit inside the plane yet. It's very light and stiff as a piece of pine. A lot lighter and stronger than that piece of lite ply I had originally. Camera ain't working right now. Wish I could post a pic of it. I'm so proud of my composite sandwich.

evan-RCU

First, you are going to secure all those wires..... right?

Second, I didn't vote because of a yes and no opinion. I think the manufacturers have a really good handle on 90% of their design work. Many airplanes (and helos) have one or two little areas that they have made too light. Most of these are the landing gear areas, some are the firewall or motor box, but almost all have an area that needs "attention". Sometimes this needed attention is due to our own faults, like flying off poor runways or bad landing skills.
That said I would rather have a nice light airframe that needs some modification than a heavy airplane that flys heavy. The bad to that is the person that accepts what they get and doesn't know enough to stregnthen the weak areas and only gets one flight out of their new airplane.

Rcpilot

My Feedback: (78)

I guess you just looked at the picture and didn't read my post.

It's just a mock-up right now. Thats nowhere NEAR a finished product.

evan-RCU

I did read it but.... you're going to secure those wires, right?

Rcpilot

My Feedback: (78)

Yes, I'm going to secure those wires.
I'll send ya a pic when it's all done.

T. Bob

My Feedback: (9)

There is no question here.
Either you build it right or you build it wrong.
I have seen a lot of heavy planes built like crap and a lot of light ones built like crap (Planes Plus).
The weight is irrelevant build it right and everything will be fine.