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Home » Learn » Why Lighter Planes Fly Better

Learn - Why Lighter Planes Fly Better

Does your Plane: On This Page:
a) Fly like a brick instead of a feather?
b) Accelerate in the downlines instead of maintain a slow speed?
c) Snap with high elevator instead of flip?
d) Hover at 3/4 throttle instead of at idle?
e) Lumber out of a torque roll instead of rocket up out of sight?
f) Lose speed in the vertical ascents instead of accelerate?
g) Rock back and forth in a Harrier instead of being rock solid?
h) Fall like a rock in a Parachute instead of stopping on a dime?
i) Mush through a wall instead of banging into it?
j) Land like a tank instead of bird?		 Weights To Shoot For

Bad Ways To Save Weight

Sukhoi Example

Extra 330 Example

"Hop Up" Items

Package For a Typical 40%

If you answered yes to any of these questions, then guess what? Your plane is too heavy! Fortunately for you, TBM specializes in making your airplane lighter!! We have collected the best products from around the globe for lightening overweight aircraft.

Sure, putting in a bigger engine will resolve some of the issues, but other aspects will get worse, especially the slow 3D maneuvers. Your plane is too heavy from a variety of reasons. There isn't one component that you can change to magically transform your lead sled into a competitive IMAC competitor or a nimble 3D killer machine, but don't worry, we can help.

The parts which are too heavy on your plane are probably everything but the servo wire, control horns, fuel tank, links and covering. Yes, your fuselage, canopy, tail feathers, wings, tires, wheelpants, cowl, wing tube, stab tube, tailwheel assembly, pilot, landing gear, spinner, instrument panel, batteries and maybe your engine are too heavy. Some things you can change easily, some are more difficult, and some are just not worth the time and expense. You determine the time and money you want to invest to improve your plane's performance.

IMPORTANT NOTE: We just mentioned 16 culprits of an overweight plane. To obtain a light plane, you must lighten many components. If you lightened each component by just one ounce, you would save a pound of weight in your plane. Save 2 ounces per part and you've saved 2 pounds, and 3 ounces is three pounds. Lightening just a few parts won't have a profound effect on your plane's performance, so either do many things, or don't do anything at all.


Pick up a half gallon of milk. It weighs about 4 pounds. Your 1/3 scale plane could be hauling around more weight than that unnecessarily. Think about how much better your plane will fly without that excess weight. Typical 40% planes are 10 pounds heavier than they should be. Most of the excess weight is in the fuselage, hatch area, cowl, and landing gear.

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Some weights to shoot for if you want the ultimate in performance:

72" wingspan (40 cc engine class) - 11 lbs.
80" wingspan (50 cc engine class) - 13 lbs.
96" wingspan (80cc engine class) - 18 lbs.
103" wingspan (100 cc engine class) - 21 lbs.
118" wingspan (150 cc engine class) - 27 lbs.
123" wingspan ( 160 cc engine class) - 31 lbs.

Planes in these classes could weigh in at these weights if they were designed and built with light weight in mind. Careful attention to every detail is necessary to achieve these weights. There are a few aircraft companies which offer aircraft which can be built to the weights listed above. Most of the other manufacturers' aircraft, whether they are kits, ARF's or ARC's, produce sport planes which can be lightened but will never be exceptionally light planes without major changes to the cowl, fuselage, wings and tailfeathers. You can reasonably lighten planes so far before thinking about a new airplane altogether.

Planes of these weights must be carefully designed and tested. Strength is required in areas of high stress, and these areas are often defined through field testing of prototypes. We don't recommend that you take a hole saw to your current airplane unless you know what you are doing because you could weaken it and the results could be disastrous.

The weights of the planes described above are achieved by stripping off all unnecessary components such as pilot, instrument panel, and wheelpants and the use of standard mufflers rather than canister mufflers, wooden propellers, light cowl, CF parts, Li Ion batteries and more. An airplane which is the ultimate in light weight must be designed in at the very beginning, however, trying to do the best you can with the airplane you have can have very positive results.

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BAD WAYS TO SAVE WEIGHT:

1) Don't lighten the wings. It may well be possible to take weight out of the wings, but many planes, especially ARF's, have had a preponderance of wing failures.
2) Don't eliminate your redundant Rx battery pack and switch harness. Though tempting, we recommend the use of two batteries and two switches in Giant Scale aircraft.

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SUKHOI EXAMPLE:

We modified a Hangar 9 1/3 scale Sukhoi ARF for Tom Smith of the Sarasota Florida club. This plane typically weighs 26.5 pounds with a Zenoah GT-80. We were able to save over 5 pounds to bring the weight down to 21 3/4 pounds. This weight includes a redundant battery and switch system (5 ounces) and pilot. The plane could be made 1/2 pound lighter (21 1/4 pounds) by simply removing these two items.

Modification Stock Item Weight saved
AI "foam" H9 Pilot 3 oz
CF 4" spinner Aluminum spinner 4 oz
TBM Li Ion Batteries

 Ni Cad batteries

 8 oz
No wheelpants (per full scale)

H9 wheelpants

 5 oz
TBM CF landing gear

H9 aluminum landing gear

 10 oz
TBM CF Tailwheel

Steel tailwheel

2 oz
ZDZ 80 cc engine

 Zenoah 445 80 cc engine

 20 oz
Lightened hatch area**

Removed floor and such

 6 oz

Lightened fuse**

 Lightened motor box and formers

4 oz
TBM CF wing tube

 Aluminum wing tube

3 oz
Removed Ballast**

Lead ballast in nose to balance

12 oz
Kavan 4" tires

 Sullivan Skylite tires

 4 oz
 

Total weight saved over stock:

81 oz (5 lb 1 oz)


The plane could be even lighter if the wing was built with lighter balsa and less plywood, the fuselage had less plywood and more balsa, the cowl was produced from thinner fiberglass, and the ailerons were stiffer to be able to use only one servo per wing instead of two, the hatch was built with balsa instead of plywood and aluminum, and more. With the redesign and only one Rx battery and switch, no pilot and such the weight would be closer to 18 pounds. None the less, at 21 3/4 pounds the plane flies dramatically better.

**Lightening of the fuselage and using a lighter engine and eliminating ballast was accomplished by moving the wing rearward 2", and using a single servo pull-pull system to move the CG forward.

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EXTRA 330 EXAMPLE

We modified a Hangar 9 1/3 scale Extra 330 ARF for Brian Jantzen of the Sarasota Florida club. This plane originally weighed 27.5 pounds. We were able to save 2 3/4 pounds to bring the weight down to 24 3/4 pounds.

Item

Weight saved
Hatch: Eliminated pilot, instrument panels, hatch floor, added lightening holes

 11 oz
CF 4" spinner replaced Aluminum spinner

2.5 oz
Two 2200 mah TBM Li Ion Batteries replaced two 2700 mah NiMh batteries

 7 oz
Removed wheelpants

6 oz
TBM CF landing gear replaced H9 aluminum landing gear

10 oz
TBM CF tailwheel replaced steel tailwheel for improved performance

 0 oz
Lightened landing gear cover

 1 oz
TBM CF wing tube replaced H9 aluminum wing tube

 3 oz
Kavan 3.5" tires replaced stock tires

 3 oz
 
Total weight saved over stock:

43.5 oz (2 3/4 lb.)


Again, the plane could be even lighter if the wing was built with lighter balsa and less plywood, the fuselage had less plywood and more balsa, the cowl was produced from thinner fiberglass, and the ailerons were stiffer to be able to use only one servo per wing instead of two, the hatch was built with balsa instead of plywood and aluminum, and more. With the redesign and only one Rx battery and switch, no pilot and such the weight would be closer to 18 pounds. To avoid a tail heavy condition which would require moving the wing tube rearward for balancing, we did not lighten the motor box or use a lighter engine or mufflers.

 

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"HOP UP" ITEMS

Following are items which will take weight out of your aircraft. Combining these components with careful lightening of the airframe itself will result in an aircraft which is much more pleasant to fly.

1/3 Scale Package Actual Weight Approximate Weight Savings
AI "foam" pilot 1 oz 2 - 3 oz
CF 4" spinner 3.1 oz 2 - 4 oz
Three TBM Li Ion Batteries (2200 mah) 10.5 oz (3 packs) 8 - 14 oz
TBM CF landing gear 10 oz (varies) 6 - 12 oz
TBM CF Tailwheel (22 lb.) 1.2 oz 0 - 2 oz
TBM CF wing tube (3') 6.9 oz 3 oz
Kavan tires (3 1/2") 3 oz 3 oz
 
Total Savings: about 2 lbs.

Other Items you may need:
MPI Miracle Switches w/ 6V regulator
Li Ion Charger

Other EASY ways to Save More Weight: Possible Savings
Lighten hatch area (very easy to do) 6 - 10 oz
Lighten fuse 4 - 10 oz
Remove pilot 3 - 6 oz
Remove wheelpants 3 - 5 oz


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Package for a typical 40% scale airplane
40% Scale Package

Actual Weight

Approximate Weight Savings
CF 5" spinner 4 oz 3 - 6 oz
Three TBM Li Ion Batteries 17.5 oz (3 packs) 8 - 32 oz
TBM CF landing gear 12 oz (varies) 6 - 16 oz
TBM CF Tailwheel (40 lb.) 2.8 oz 1 - 3 oz
TBM CF wing tube (3') 6.9 oz 3 oz
Kavan tires (3 1/2") 3 oz 3 oz
 
Total Savings: almost 3 lbs.

Other Items you may need:
MPI Miracle Switches w/ 6V regulator
Li Ion Charger

Other ways to Save More Weight: Possible Savings
Lighten hatch area 8 - 14 oz
Lighten fuse 6 - 15 oz
Remove pilot 3 - 6 oz
Remove wheelpants 4 - 7 oz
Use bolt on mufflers vs canister mufflers 18 oz

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WARNING - Gasoline and Turbine powered R/C model aircraft are not manufactured to withstand unlimited G's. Any R/C model aircraft can fail, be it a wing folding up or a fuselage breaking in half under too high of a load. Just as any full size aircraft, model R/C aircraft have a maximum G rating. Because you are not in the plane flying it and experiencing the G's and reading the G-meter, it is more difficult to judge the G's on the aircraft, and it is very easy to exceed the limits of the aircraft. Understand that if you perform a snap roll, parachute, wall, blender, knife edge loop, or pull hard on the elevator at almost any speed, you can be putting in excess of 15 G's, even in excess of 30 G's, and most aircraft can only designed to take 10-12 G's. If you perform any violent maneuver, you can break your plane. When I perform hard maneuvers, especially for the first time on an airframe, I am prepared for a failure and am prepared for it as best I can be. This mainly includes performing the maneuver far enough away from spectators that in event of a failure that I am not endangering others. In addition, be prepared for the manufacturer to not pay for a new airframe which is broken during flight. It is common practice for any manufacturer to not replace an airframe which breaks in the air or upon landing. I have only seen manufacturers replace airframes when they have received many of the same failures and the manufacturer determines that there was a design or manufacturing error. If you break an airframe, and you are the only one to do so, then it is probably not the fault of the manufacturer. Please fly safely, and avoid full throttle operation other than at low airspeeds.

R/C model jets, warbirds, and aerobatic planes to name a few are not a toy! If misused, it can cause serious bodily harm and property damage. Fly only in open areas, and AMA (Academy of Model Aeronautics) approved flying sites. Follow all manufacturer instructions included with your plane, radio, servo's, batteries and engine. Aircraft manufacturers guarantees each kit to be free from defects in both material and workmanship at the date of purchase. This warranty does not cover any component assembled by the customer. All parts of high stress must be inspected and reinforced if necessary by a competent builder. Some parts should be glued again. High stress areas such as firewalls, motor boxes, wing mounts, landing gear mounts, etc., are areas of high concern. Seek help if necessary. In not case shall TBM be liable for the cost of any product it offers which is not manufactured by TBM. The liability to the manufacturer cannot exceed the original cost of the purchased item. Further, TBM reserves the right to change or modify this warranty without notice. In that TBM has no control over the final assembly or materials used for final assembly, no liability shall be assumed nor accepted for any damage resulting from the use by the user of the final user-assembled product. By the act of using the user assembled product, the user accepts all resulting liability. The kit manufacturers have provided you with a top quality, thoroughly tested kit and instructions, but ultimately the quality and fly ability of your finished model depends on how you build it; therefore, we cannot in any way guarantee the performance of your completed model, and no representations are expressed or implied as to the performance or safety of your completed model. It is the user's responsibility to inspect each component for worthiness.