proptop

My Feedback: (8)

Guys, I just got a NIB Viper (for $85 bucks, so I didn't want to pass it up) and I'd like to know if there are any things I should look out for? You know, maybe a better way of setting it up or structural deficiencies? I'm not worried about it being class legal or anything, I just want something quick to assemble and that'll be (sorta) fast...
I was thinking of using my Magnum .52XLS w/ Macs pre tuned pipe? Or perhaps an MVVS .49 that I have set-up as rear exh. and mt. the eng. upright to run the pipe straight back over the wing. Also was thinking of an APC 9x9 to start with?
The servos I was thinking about are Expert SL451's w/a Hitec 555 Rx. and a AAA NiMh rx. pack. Is the stock tank gonna be o.k or will I need a bubbless type? I'm just going to be "sport" flying with it, so I don't plan on racing, unless one of my buddies sees how much fun I'm having and gets one too... Thanks, Tom.

daven

My Feedback: (1)

Prop Top,

Looks like your on the right path. Your receiver, servos, and battery will all be fine. The stock tank will be fine also, you will just need to set the needle slightly richer than if you went with a bladder set up.

I believe there were some viper tips on here earlier, but I believe the jist of the issues were the following:

The wheels are bad, and will pop off the axles. Replace them (www.darrolcady.com)
Replace the metal wing hold down bolts with nylon
Verify the incidence of the tail (I may be confusing with the predator)

I would suggest adding some 2 oz glass inside the nose area and firewall.

proptop

My Feedback: (8)

Thanks Dave...I dug a little deeper into a search and found out about reinforcing the rear fuse. and checking the tail incidence too.

Ed Smith

Proptop,

I have never owned a Viper Kit. In the interests of safety however I would consider the following. The Viper is an ARF designed and built for a .40 size engine. ARFs being what they are it is very likely it is not "Overbuilt". You intend to power it with a tuned pipe .52 size engine.

As Dave says, reinforce the nose area, or the firewall may head out leaving the rest of the airplane behind. It would be wise to check the incidences of all three components, Engine, Wing and tail. If these are in conflict you could have a real tiger by the tail on it's first flight. Take a close look at how the control surface hinges are affixed, some have been known to pull out. Are the control linkages tight with no play? if there is play you will get flutter and anything can happen

Any reinforcing and repairs that you do will add weight. This will put greater stress on the wing during flight. Is the wing structure adequate to hold up under the stresses you willl be imposing on it? Does the wing have a credible spar? Not just a piece of carbon laying flat under the skin, that is useless.

The foregoing is offered purely to help you keep the airplane in one flyable piece. Remember, I you do have an accident, you have exceeded the power recommendations of the manufacturer. You will be on your own in the insurance department!

Ed S

proptop

My Feedback: (8)

Thanks Ed, I really appreciate the advice. Will definately do the incidence and thrust line alignment checks, and a little C F in the aft fuse. area and firewall. I built a Patriot a couple of years ago, and sold it when I got a real good offer for it. I want to try something quicker, with a lot less work and investment involved. Been building and flying since '74, so I know about keeping it light and tight, and we don't have any pylons to bank and yank around, so I plan on taking it fairly easy with the G's. I'm looking for something that'll be a step up (speed wise) from my Dago Red that I can just have fun with and not worry about too much.

daven

My Feedback: (1)

Ed,

I run Carbon Fiber under the skin on all of my quickees, with no spar and very little fiberglass (1 layer of 2 oz, 8" at TE and 15" at LE on the bottom only).

Far from useless if done properly.

Never had a wing fold yet, and have had ready to fly wings at 15 oz.

And yes, these have all been 428 powered planes. You may be overbuilding your wings Ed. Especially if you are completely fiberglassing and painting your wings.

The .52 you plan on using, even if piped, will not be as fast as a Nelson powered Viper. I've seen quite a few handle the nelson, so if you look it over good, you should be in good shape.

Ed Smith

Dave,

There have been more posts than I care to read about the dubious quality of Chinese built ARFs. My post was a caution about exceeding the recommended power source for one of these, that is all.

Your advice seems to be "do not worry about it, just look it over" I am sure the AMA will be comforted knowing that a V.P. for the racing S.I.G has that attitude towards safety.

Ed S

daven

My Feedback: (1)

Ed, from what I have seen, the Viper wing is of much better quality and strength than the Lanier wings (albeit at a significant weight gain). If he had been talking about the Lanier wing, I would have given different advice (as in not using a Nelson or Jett). I see no reason why the stock viper wing can't handle 428 engines, or a Piped Magnum .52 for that matter. We've had quite a few of them flown locally with no folds that I am aware of.

I have been one of the minority locally who has asked that stock Predator wings not be flown in 428, but I have seen no reason why the stock viper wing can't hold up. I would change the wing bolts to nylon as I stated above, not for shear, but because I've seen too many metal bolts loosen in flight under vibration.

As to being V.P. of district #5k, as far as I know the election is not over, or have I been appointed to this position.

garys

The Vipers I've seen have all had very strong wings, unlike the Preditors. I wouldn't worry about a wing failure on a Viper. I think Dave pretty much hit the Viper weak points (wheels, firewall, wing/tail bolts, incidences). If this thread was referring to a Preditor, I would definately say to reinforce the wing for anything more than a 424 level engine.
GS

NitroWoman

My Viper had a few problems. The original wing out of the box did not have the fiberglass over the wing joint properly epoxied. Had to send it back to Tower for replacemant, no problem there. Replacment wing OK. Used a Jett tank and had to move the aileron servo back 1" to clear. Flew with a Rossi Q-500 .40, not as fast as a Nelson but still fun. On my last landing I hit the weeds on the end of our field (these things don't want to slow down). It wasn't going very fast and it hit fairly gently and flipped over on it's back. I didn't think there would be any damage. I was wrong. Fuse broke in half just behind the radio hatch and the firewall was loose, just being held on by the glass, I couldn't detect any pins. I have landed my Predator much harder than this with no damage. Sure glad the Rossi didn't come loose when I was standing in front of it. The machine screw wing hold downs were no problem and never came loose. The plane is easily fixable but there is going to be a weight penalty. Reinforce the rear fuse and the firewall during construction and save yourself some grief.

Ed Smith

Dave,

I hope you read the previous post. Imagine a tuned pipe .52 on that one! I rest my case.

Ed S

Stand

There have been several posts here on mods for the Viper and Predator. I found one by Paul Herman:
http://www.rcuniverse.com/forum/m_12...tm.htm#1213413

There is also a write up at Darrol Cady's web site:
http://www.darrolcady.com/./Racing_I...cing_info.html

Check the "Predator/Viper ARF modifications"
Stan

John Z Williams Jr

Ed states,

"A piece of carbon fibre that lays under the skin, that is useless"????
Hmmm, I know many of the Revlutions had just that, the only spar in the wing was the strip of carbon fibre, there have been many many, many revlutions out there that hold up just great with the useless carbon strip....
I would make sure I know what I am talking about when I make such a definitive statement...

PS There are other custom quickees that I know the builders have taken this strip of uselesss carbon and lay it up under the skins, they too have held up to the forces of 428 for over 5 years now!!!!

I think Dave is correct, you probably have you're wing way over-built....

Just my opinion, well sort of...
JZW

John Z Williams Jr

Ed, you rest you're case because a plane flipped over on landing and broke the fuse???
You rest you're case because the wing did not have glass on the center section???
As stated by Dave and others, you do have to look these arf planes over well before you fly them, geeze, I have had professional kits need more work than the stated bad arfs... There is no substitute for a good "Overview" this includes everything... That means all the suspect areas of wing hold blocks, firewall, pinned? not pinned? what is it.. after all the known problem areas of any plane, then look at everything else to make sure the plane is in the best possible condition to withstand the forces of flight and landing...
Just me thoughts,
JZW

Ed Smith

I probably lack your vast building experience. However When you have done as much composite work as I have the you will understand basic principles.

A little lesson. Take a strip of .015 x 3/4 wide x 36" long unicarbon. It is easy to bend it in a loop. Now try and bend the same piece edgways. Which is the stiffest?

In a foam wing, one strip like that, vertically in a slot is all that is needed for a spar. Hardly overbuilt.

Ed S

HighPlains

My Feedback: (1)

I have to agree with Ed (omygod). We are dealing with lethal forces with pylon racing. Over the years, I have seen so many airplanes show up to races that are total pieces of crap and unsafe allowed into local contests. Radios that had problems, due to previous crashes. Poor radio installations. Pilots that are over their heads for the speeds involved. We have been very lucky with the rule book events. Not so lucky in less restrictive warbird event.

Even the best radio can fail, the best pilot make a mistake, the latest airplane design have a fatal design flaw. Our only defense is to remain aware, and question anything that doesn’t look right.

John Z Williams Jr

Highplanes, you basically said things that enforce what my second post said, there is no substitute for a thourough "Overview"
that means everything... I always find areas that need attention in arfs and I always find areas that need attention in the kits that are not arfs but are professional kits designed for pylon... You should know the areas to re-inforce and you should know the technics to do this, if not, find someone that does... Call the designer, manufactor or just someone that knows how to make a plane strong, reliable and so forth... I am not sure what you where disagreeing with me about, but if its the carbon fibre spar, then I only know what I have experienced over the last 7 years of pylon racing... I have been building since I was 9 years old, so that would be about 29 years, give or take... What I have seen is if the wing is built and supported or re-inforced in the right areas, using a carbon fibre strip that runs under the skins the length of the wing, will hold up to the speeds and g forces of pylon racing. I gave an expample of one of the most popular and most used pylon planes in the country in its day... This plane did use a carbon strip under the skin for years and if I am not mistaken, Mike D. had told me years ago that he was not aware of hardly any folds, I think he said there was one by Richard Oliver back in 98, I think this was the year Richard Verano won all 3 events and the Revlution was the plane he flew in q-500 that year...
Anyway, all I wanted to point out was to say a carbon fibre spar that lays under the skin is useless is far from true in my opinion...
That does not mean that a wing could fail with this set-up... It just means I have seen this method used many, many, many times with little to no problems... I have never seen a Revo wing fail, ever....
Just my thoughts,
JZW

daven

My Feedback: (1)

Bill Vargas and I have been using that worthless piece of CF under the skin on every Racer II and Seeker built without a spar, or anything running verticle (Except for 1 test wing). As far as I know, there was one failure, but that was on a special "very light" wing that we were testing. I believe there were only about 5-10 of those made, and the others all held up fine.

I just don't think a vertical spar is necessary, although it definately would yeild a stronger wing.

I guess I build them to fly, not to survive a crash.

willflyforfood

This Dominator kit doesnt have anything that runs completely through the center, the carbon strips are spliced / butted in the middle. Only the fiberglass on top and bottom keeps the center together. Thought it was kind of weak but people tell me different.



Joey

daven

My Feedback: (1)

I built my dominator wing per the instructions, and it lasted 4 years with many Nelson flights before it finally midaired this summer. An old guy dug it out of the trash, repaired it, and is now flying it in our NCPL class.

diggs_74

Is that wing going to retire with Al, or is it going to get passed down to someone else

daven

My Feedback: (1)

I don't know, but Al sure seems to like it.

It was so old, it wasn't even green

DHG

My Feedback: (7)

What matters is not just what materials you use, but how they are attached together and how they support each other. A vertical strip of CF that's not epoxied firmly to the top skin will break loose and do an S-bend under the skin, pushing the foam out of its way fore & aft as the wing buckles. An all-CF skin on a foam core with no vertical shear web to hold the top & bottom together will also fail quite spectacularly if there's a "stress riser" or dent that allows it to split loose from the core in one spot.

Or you can have two perfectly good panels joined in the middle without enough carry-through. That's the easiest to fix once you find all the pieces.

HighPlains

My Feedback: (1)

I don't personally think that carbon fiber is all that good for compression. In other words, I don't put any under the top wing skin. I use carbon in tension, where is unsurpassed by anything that's not dangerous or very expensive. The compressive loads (on a foam/balsa wing) are withstood by the balsa top skin. So I use a minimum of 3/32 on the top skin of 6-8 lb. weight. The bottom skin is strong enough with 1/16" and the .007 x 1/2" carbon strip. Since I glass the center section it doesn't matter that it is butt-joint at the center. If I were worried by weight, then I might consider one piece skins (48") with carbon for at least 24" thru the center and slightly less glass cloth on the center. Glass is important there just to keep the balsa from compressing which can cause failure due to localize buckling of the skin where it contacts the fuselage.

The structure of the composite (hollow) wings is different. There an "I-beam" built with carbon caps seem popular and pretty damn strong. The weakness of the hollow wing would appear to be minimal balsa in the upper skin that can buckle rather easily. Quickies need about 4 more oz. to the weight of the model so that the molded airplanes can be built stronger with slightly less money.

daven

My Feedback: (1)

I wouldn't mind the minimum weight rasised to 3 3/4 lbs. This would help build a stronger and safer plane. It would also allow people to use heavier and stronger servos in place of the minis we are using now.