RE: Viper assembly tips?
 

The last Seeker I built weighed 3 lbs 6.5 oz all up.... If the limit was 3 3/4 lbs I'd have to add 5.5 oz to my plane.... That's just wrong :) It was bad enough having to put on a heavier set of landing gear.

RE: Viper assembly tips?
 

3 3/4 lbs. ??????
I used to build lots of Q500 planes with STANDARD size servos and never had problems with weight or wings failing...isnt that what the minimum weight that formula 1 used to be,,and they had cowling and wheel pants.

RE: Viper assembly tips?
 

Formula 1's were 5 lbs....

RE: Viper assembly tips?
 

Sorry...My mistake

RE: Viper assembly tips?
 

High planes, I think you hit on some good points, I was surprised when I first learned about compression and tension, A strip under the top skin would only help in negative g forces.... I believe many builders, including the revo's I flew for years, were made from the stated 48" skins, glass in the middle set as a v on top to increase compression area and avoid 90 degree layout of the glass, the only reason there was a small 2.5" piece of glass on the botom was to help keep the wing to fuse area from being too soft...
This helped to save weight and still have a strong wing... I had one Revo that was almost 4oz underweight... I bought it from Mike D, then sold it back to Gino, who decided to test the compression strenght on pole #3 at one of his first Winterfest....
The pvc just about matched compression strength as the wing exploded as well as the pvc pole....
I am torn between keeping the weight the same or allowing the limit to be raised, sure would make it easier on builders, not me, I hate to build anymore.... Wanta fix my wing???

RE: Viper assembly tips?
 

No problem thestorm, I was just clarifying it.
GS

RE: Viper assembly tips?
 

Hmmm ... increase minimum weight by 4 oz., from 3-1/2 lbs. to 3-3/4 lbs., in event 428 and/or 424 ... not a bad idea, not the first time it's been suggested ... next rule cycle begins this Jan. 1 ... any AMA member can propose it ... forms can be downloaded from the AMA Web site. It'd take all of 10 minutes to fill one out and send it in to HQ ... that is, if anyone actually wants to make a change instead of playing coulda/woulda/shoulda as usual.

I know my ShotGun "coulda" used another ounce at the center section. :eek:

RE: Viper assembly tips?
 

SSSHHHHHHH, be very very quiet, what would happen if the word got out????

All the current manufactors would be stuck, wondering where do I add weight to make this thing weigh???

I have been fighting for years to make em light, and now you are saying throw that out the window and make em heavy...

SSSSHHHHHH< Be very quiet.....

RE: Viper assembly tips?
 

Personally I see less reason to change the minimum weight now than two or three years ago. Not too many years ago a lot of the molded Q500 people that seemed to want an increase, as they couldn't get down to 3.5lbs. Most if not all have since figured it out. Also, most wood Q500 builders have learned how to make light but strong airplanes as well. My last wood Q500's needed up to three ounces of lead to get up to 3.5lbs, and I didn't go out of my way with contest grade wood or anything, just carefull building with standard 6-8lb wood. Now, most are right at the minimum with no problems. Overall, I'd be willing to bet that there is a smaller percentage of wing failures now (foam/wood or molded) than 4 or 5 years ago.

With the availability of reasonably priced high quality mini servos, I doubt many people would be saving money on bigger servos, as the bigger ones that are cheaper than the current mini's are less precise and often lower torque and/or slower.

GS

RE: Viper assembly tips?
 

Either would be fine with me, I sure would like the extra 4 oz now that I am playing with composite wings. Until I'm comfortable with the process and results, I don't plan on skimping on materials.

Many of the earlier composites struggled getting down there, but I think most of them are there, or very close if the right gear is used.

RE: Viper assembly tips?
 

Well ladies and gentlemen, I've been checking out my Viper. Don't know if the early versions came like this but the nose has 2 layers of glass around the outside of the firewall. 1st layer goes back to just behind the wing L.E. down to the L.G. block. The entire tank compartment is lined with 'glass too, so I'd say the firewall is sufficiently strong as is.

I am going to do the 1/64th ply on the insides of the aft fuse. and add some tri stock in the wing hold down plate areas and perhaps a little of the 1/64 ply in the rear hatch opening area.

I've looked at and fondled :eek::) the wing to see and feel if it seems O.K. (it does)
I'd say the wing is a pretty stout piece, and shouldn't be any problem. I usually use a split lock washer under the steel bolt head, then a large flat washer for ARF wing hold downs and haven't had any problems in many years (ever, as far as that's concerned) and I'm not that worried about a few bolt heads sticking up.
I was thinking of just using std. size servos, 'cuz that's what I have a ton of, and at 1.2 oz. they aren't all that heavy IMO. HS-81 for throttle though.

There's a lot of very interesting info flying about in this thread...thanks.:D

BTW, what do ya think this thing will be good for straight and level for say, 1/4 mi.? I was thinking/hoping for around 135-140 maybe?

RE: Viper assembly tips?
 

This is dependent entirely on your engine/prop/pipe set up. The arithmetic is simple.

MAX theoretical MPH= rpm x prop pitch x 0.00094.

Ed S

RE: Viper assembly tips?
 

Thanks Ed...If I can get 16,000 out of the Magnum .52 w/ an APC 9x9 that = 135.something...Hmmm

RE: Viper assembly tips?
 

130 mph is definatley possible, we are getting 120+ with the stock O.S. .46 AX.

The Viper is a decent plane, it sounds like you have looked it over well, which is a good thing.

From what I have seen, the viper is pretty stout, and you should be in good shape.

RE: Viper assembly tips?
 

I am not in favor of racing ARFs only but maybe the 3 lb. 12 oz. minimum weight limit would help the Viper pilot compete with the custom built 424s.

My Viper out of the box weighed as follows:

Wing & Ailerons.......................................... 485 g......17.10 oz
Fuselage, V Tail & Hatches...........................262 g.......9.24 oz
Landing Gear, Wheels & Screws......................61 g.......2.15 oz
Servo Trays, Hinges & Hardware.....................90 g.......3.17 oz
Fuel Tank & Engine Mount..............................72 g.......2.53 oz

Hitec Superslim, HS225 (3), HS85, Switch, &
Futaba NR4K 270 mah Battery.......................200 g.......7.05 oz

TT Pro .40 & Muffler....................................465 g.....16.40 oz

APC 9x6 & Aluminum Safety Nut......................45 g.......1.58 oz

Total............................................. ..........1680 g.....59.26 oz......3 lb 11.26 oz

Note: Oz data calculated with conversion factor of 28.34952313 g/oz

Replace the airborne pack with standard receiver & servos:

Futaba FP R148DP, S3001 (4), Switch, & the
the same battery........................................284 g......10.17 oz

With the standard radio you are close to 4 pounds without a drop of glue. Add some reinforcement and switch to a Tetra tank and you are heavier yet.

RE: Viper assembly tips?
 

Durability – currently it looks like the hollow composite wings use either 1/16” balsa or even 1/20” thick. Enough to build a molded skin, able to take most air loads, but not very strong locally. Doesn’t take much of a bump or scrape to score or crease it. Now if the skins were increased to 3/32”, then the local buckling strength would be doubled (the distance of the top of the skin to the bottom of the skin squared). The compressive strength of the skin is now 150% of the original. All of this just by increasing the thickness by 1/32”. Of course, with 6 lb. balsa, you have just added 1 ¾ oz to the wing.

Add a second servo to the wing – I hate radio failure, especially servos – another oz.

Gives you one oz. to move around for balance. Or instrumentation.

RE: Viper assembly tips?
 

I didn't think about servo failure. I've had one servo fail in a pylon racer that I recall in 16 years of racing, and it was the elevator on a Q40. A second aileron servo wouldn't have helped much :) If the weight was increased on Q500, and the wing could handle the additional 1/4lb (which most the current molded ones can-I'm not aware of any Vortex and only one NemeQ ever failing), I'd make the fuse as rigid as possible to help power transfer, the wing wouldn't change at all.

RE: Viper assembly tips?
 

How does a stiffer fuselage transfer power?

I know this has been common practice and the standard approach for many, many years but I don't understand the phyiscs. I can see how a stiffer fuselage can transfer vibration faster. reduce torsional deflections, but I don't get the power transfer. Where does the power go? Wouldn't it be ideal to turn the energy generated by the engine into thrust and therefore speed?

Or does a stiffer fuse dampen vibration more effectively, so less energy is lost there and more energy/power gets to the prop?

I don't get it, please help before my brain explodes...

RE: Viper assembly tips?
 

Okay, one more shot. A stiffer fuse would have a higher resonance frequency. So, the likelihood the fuse would become excited, like the galloping bridge over the Tacoma Narrows, due to the frequency range generated by the engine is reduced. A structure with less relative deflections should not lose as much energy to the vibration. Therefore, it should transfer a greater percentage of the energy to creating thrust…

Am on the right track here??? I don’t think I’ve had enough Millers to figure this out tonight… :D

RE: Viper assembly tips?
 

I see what you are getting at, but It seems like if you isolated all engine vibrations to the mount, you would wouldnt have any transfer of energy anywhere, resulting in no energy loss. Of course this seems like one of those things you could rationalize either way. The "power loss " we are tralking about anyway is probably completely miniscule. Cool subject though.

Joey

RE: Viper assembly tips?
 

I would think any power that is not at the prop directly is lost anyway, balance the crap out of the prop. Sounds good to me.


Joey

RE: Viper assembly tips?
 

I'm no expert, but I'm of the opinion, you want the stiffest, strongest fuse you can get and still keep it light. That is why I like a thick firewall (1/2"), lots of interlocking tabs on all my hard points, and a fiberglassed and painted fuze. The stiffer the fuze, the less the vibration, which causes the least amount of lost power.

In my opinion, a fiberglassed and painted fuze is good for at least 2-3 mph over one that is ultracoated. This is if, you can still keep the fuze weight (with engine) right at 2 1/2 lbs, leaving a pound for the wing.

RE: Viper assembly tips?
 

About power transfer
I don’t pretend to know the dynamics behind this but let me give you an example. At the Nats this year, during practice, my Pole Cat would routinely turn the black prop 23,500. The first heat, with no changes, the thing would only turn 21,500. I brought it back could find nothing wrong so I rechecked the engine, changed batteries in the tach, put on a lighter prop and guess what? Still turned 21,500. Changed engines still 21500. On closer, I mean real close examination I discovered about ¼th of the firewall was loose (at that time Bruce was using ¼ inch ply for firewalls which are a little flexly). Got some 5 min epoxy, thanks Garry Freeman Sr., fixed it and whata you know, a little better than 23500 (due to light prop). Before discovering problem I twisted and tried to flex firewall as did Jimmy A. Seemed OK. We are only talking about 1.5 inches of the firewall being loose. Sooooooo there is definitely something to solid mounting and power.


Barry

RE: Viper assembly tips?
 

That makes sense. There is no question it works, guys a lot smater then me have sworn by it for many years. I just didn't understand how it worked.

Vibration is definitely a energy/power loss. I get it now, thanks guys...

RE: Viper assembly tips?
 

Dave,

I would agree with you to some point with the advantage of a smoother "fiberglassed painted fuze" surface, but not 2-3 mph difference. I feel the speed advantage comes from the overall fuselage design rather than just fiberglassed fuze alone. The wood/ultracote materials have nothing to do with speed, but smoother surfaces does help. I've tested several fuselages design in trying to find more speed and I noticed quite interesting findings. ;)

Other speed advantages beside having good design and smoother surfaces is a strong built fuselage and a stiff wing/tail. Unlike the typical foam/balsa bagged wing, the composites are much stiffer, which give them the added advantage in speed beside the smoother surface. That's why I design/built all my wings using .007x1"x48" carbon fiber stripe on top and botom, added carbon fiber LE (yes, carbon fiber leading edge) and glassed _ _ _ _ _ _ _ _ _ _ _ etc. Also, I glassed carbon fiber inside the nose of the fuselage/firewall area for added stiffness, which relate to power transfer we're all talking about here. Some say I over-built my plane, but I don't think so.

You can't lead the pack if you follow the herd... Just out of the box thinking.