Super Sport empty weight

[davedeford]

Greetings,

I am a new member on this forum, considering two Super Sports for purchase. Both have 912S engines and simple glass panels, and both appear to be well built, fairly close to factory standards. One is a tri gear (no wheel pants) with Warp Drive prop, and the other has 850x6/Alaska Bushwheels tail wheel setup. Advertised weight of the tri gear is 745 lbs., while the tail dragger is 837 lbs. I really like light weight, but I also know that lots of variations creep into the measurements. I am wondering what a reasonable range of empty weights would be for these configurations, and what variables to watch for that might affect the actual weight.

Thanks!

Dave

[Paul Z]

You could trim a few pounds off of the tail Dragger by going with the new Smoothies John put on my plane. I'd have to go check the weight and balance but mine is just a little over 800 lbs as a Tri gear it was about 780. I plan on going to the airport tomorrow I could get the exact weights for both my plane as a TriGear, and as a Tail Dragger. However the weights sound in line.

[Dick B in KY]

My SS7 with 912ULS taildragger weighed in at 808 lbs.

Dick B

[jtpitkin06]

A reasonable weight range for the airplanes in either configuration depends on your intended use. If LSA is important to you then an empty weight of around 800 pounds is a good target. With a gross weight of 1320 the 800 pound empty weight gives you the ability to load it with 400 pounds of people and bags and still have room for 120 pounds (20 gals) of fuel. That’s 3 1/2 hours plus reserves.

So when looking at empty weights look at the limitation on gross weight. If you have an LSA airplane with an empty weight of 800 loaded to 1320 pounds with 27 gals of fuel it has the same performance as one with an empty weight of 850 loaded to 1320 pounds with 19 gals of fuel.

Remember that LSA is a paper limitation not a structural limitation. If the airplane you select is Experimental – Amateur Built, you can load a Kitfox up to 1550 pounds with the proper landing gear. If that is the case then I’d say you could have an empty weight
pushing 850 or more. Fifty pounds is a 3% of the loaded weight. I doubt you will see difference in performance. between 1500 and 1550.

It should be noted from Paul Z’s numbers that you can replace a nose wheel and strut with a small tail wheel and a couple of tundra tires resulting in a heavier airplane. Those big bouncy tires weigh a lot more than your standard 6.00 – 6 tires. They also have a lot more drag.

Depending on how much paint is on the airplanes, what equipment is installed, etc. I’d day that your empty weight numbers on the airplanes in question are within range. Your only difference is the fully loaded endurance, and that might be affected more by bladder duration than the fuel in the tanks.

John
Greenville, TX

[ken nougaret]

I must say, 745lbs sure sounds light for an s7!

[Dave S]

Davedeford,

I initially wondered what was meant by "advertised weigh of 745#"....I'd want to check to see if that is the actual empty weight - possibly a terminology deal??? Agreeing with Ken, while it is entirely possible to get a kitfox down to an empty weight of 745#.....most are not that light. I think examples provided by both the old and new factory gave target/example/ideal empty weights of 750#...again...probably most early and recent S7's are not that light as we build them.....

But it really isn't a problem anyway...John Pitkin's examples of real world stuff is right on. These are experimentals, and we don't make the planes identical in the first place....the empty weight does depend on the equipment & paint. Not all of the early S7s had the airfoiled tail or used the false bottom ribs - or the lift strut fairings either. Although most do now, there will be a little difference in weight with & without. Currently the factory uses intercostal ribs for the Speedster tail (airfoiled tail) which incorporate lightening holes so the whole setup weighs less than it once did. The Kitfox continues to get better as we go along:)

Our S7, which is an early model 7 with the manual trim, comes in at a tich over 850# for empty weight.....and it is a nose gear - 912 & warp drive. Some would call that obese, however, the useful load in a "kitfox heavy" is waaaay better than the 2 place normally certified airrcraft I once flew.....this one has a complete dual electrical system including two batteries and the optional alternator which accounts for most of the extra weight. Even with the empty weight on the high end of the bell shaped curve....we can load up myself, my wife, full fuel and 140# of baggage and be just at 1550#.

I am reasonably certain that when I gain too much chronological superiority, need to sell the Kitfox, and retire to the res to teach a class on how to catch and clean grouse that the next owner of the plane will probably do away with the dual electrical system and the high draw electrical stuff on board - like the standard anticollision lights which suck up a whole lot of electrons.

800 +/- 50# ...... all well within where a kitfox S7 can up on empty weight.

I guess I wouldn't worry about a higher weight because the plane has a great useful load in any case...performance??????......probably affected more by our piloting technique than by an extra 50 - 60 #.

As a sidebar....I often ponder how many experimental aircraft are weighed with bathroom scales, which are notoriously variable - rather than certified scales......but that's another page in the book......;)

Sincerely,

Dave S
Kitfox 7 Trigear
912ULS Warp Drive
St Paul, MN

[Paul Z]

My plane as a SLSA Tri-Gear weight 789 lbs, as a tail Dragger 806 lbs.

She did put on a little weight, 27 lbs heavier. According to John's comment, it's because of my Tundra Tires. I opted to buy 8.5 X 6 4 Ply Dresser Smooth Tundra Tires 10 lbs each, 20 lbs for the pair, approximately $400 Pair Kitfox Aircraft. I guess I sacrificed 6.2 Lbs (Smoothies compared to the standard 6.0 X 6 tires) for function, performance, looks, and I like the $$. I personally think the Dresser Smoothies look good, perform well, and for the price difference I opted to go with them over the 6.0 X 6 or 8.5 x 6 standard aircraft tires. I love their advertisement ""Pillow Soft" 22 x 8.50-6 4 Ply stands 22 inches tall and weighs in "featherlight" at under 10 lbs. Compare that to a standard 850-6 6 Ply." They do mark for a smooth landings.

20 lbs - 13.8 lbs = 6.2 lbs increase for the Smoothies

See below link
http://www.desser.com/store/products/850%252d6-4-PLY-AERO-CLASSIC-SMOOTH-TUNDRA.html

6.0 X 6 6 Ply Aero Classic 6.9 lbs each, 13.8 lbs for the pair, $416.95 Pair Aircraft Spruce, lighter but cost more than the Dressers.

Standard 8.50 X 6 6 Ply which average 15 lbs. each, or 30 lbs for the pair.

26 X 21 X 6 Airstreak Alaskan Bush Wheels 31 lbs $2200 pair Kitfox Aircraft, ouch on the weight, and OUCH on the Cost $$.

When the factory did my weight & balance they had left 1.5 gallons in the header tank & probably 1/2 gallon in each wing tank. Judd couldn't syphon any more out. So 2 to 2.5 gallons of fuel at 6 lbs per gallon, I guess there was about 12 to 18 lbs of fuel on board. So with the Smoothies 6 lbs and the fuel 15 lbs, that accounts for 21 lbs of the 29 lb weight gain. I left a few items in the plane so it gained some weight because of the fuel, my junk and my Zion (definately junk). I plan on weighing her when we do our annual, I'll make sure & drain all of the fuel and clean out all of the junk including the Zaon.

The tail spring and tail wheel assembly, the tube nose wheel assembly I was surprised how heavy it is, but I would guess the tail wheel assembly weighs more than the nose wheel assembly.

[av8rps]

I have to somewhat agree that even though some of our Kitfoxes get a bit on the piggish side, they still can haul more, and are generally less impacted by the load we put in them than comparable GA aircraft, or some other homebuilts are.

Best proof of that I can give is my model 4 on amphibious floats. On only 80 hp, but yet at an empty weight approaching 800 lbs, it flies just great. Even with two grown human beings and hours of fuel, its a great flying and performing aircraft. Especially compared to other seaplanes. So an 800 lb Kitfox on wheels with 25% more power, and more built-in airframe strength and load carrying capacity should be a piece of cake to own and operate effectively. Not to mention fun ;)

I prefer to fly seaplanes because of where I live (I'm surrounded by water). And because adding a 250 to 300 lb set of floats can wreak all kinds of havoc on performance of any aircraft, I would still prefer a lighter airplane. But a newer Kitfox in the 800 lb range will still perform well, even on a set of amphib floats. Ironically, there are many 100 hp airplanes that won't even get off the water on a set of amphibs. Typically in the seaplane world, you need 150 to 180 hp before things start working well. So the Kitfox truly is a lot more capable than most other aircraft, and is also much more capable than most realize.

This design is just exceptional, so it is also a lot more forgiving when you just can't make it as light as you'd like to.

My two cents...

Davedeford,

I initially wondered what was meant by "advertised weigh of 745#"....I'd want to check to see if that is the actual empty weight - possibly a terminology deal??? Agreeing with Ken, while it is entirely possible to get a kitfox down to an empty weight of 745#.....most are not that light.....=

[GuppyWN]

My plane as a SLSA Tri-Gear weight 789 lbs, as a tail Dragger 806 lbs.

She did put on a little weight, 27 lbs heavier.

I'm going to break a cardinal rule and do math in public. I think you're only looking at 17lbs there Paul. Take out that 1 1/2 gallons of fuel and your baby probably only put on about 8lbs, not 27.

[Paul Z]

You are correct but it is in the weight and balance as part of the dry weight. I do believe the fuel is the biggest part of her weight gain! She seems to have a little extra junk in the trunk. I believe the header holds about 1.5 gallons, and I have tried siphoning the wing tanks I really think each had about .5 to .75 gallons in each tank.

[neville]

On the subject of weight; for those who might be considering the 912iS
engine, my super sport with 912iS has an empty weight of 820.4 lb.
It has GLASS PANEL, 1 COM, XPNDR, ADS-B, INTERCOM, ELT, 2 GPS, and
a extra Aero-volts 12 cell battery used as a dedicated engine computer
back-up. It is my understanding that the 912iS weighs about 40 lb more
than the carb equipped 912. I am using a tricycle gear at present.

[t j]

You are correct but it is in the weight and balance as part of the dry weight. I do believe the fuel is the biggest part of her weight gain! She seems to have a little extra junk in the trunk. I believe the header holds about 1.5 gallons, and I have tried siphoning the wing tanks I really think each had about .5 to .75 gallons in each tank.

The weight and balance term is "Empty weight" and should include only the unusable fuel.

[neville]

I stand corrected, basic empty weight is 820.4.

[colospace]

Neville,
Your 40 lbs more weight comment sure caught my attention :eek: as I plan to use the iS engine also. Checking the Rotax site, they list 124.5 lbs for the ULS and 140.2 lbs for the injected iS engine. A 15.7 lb difference, which is more palatable to me.

[Danzer1]

From what I've researched, the 15.7 Lb is base engine weight difference and does not include the external component changes/weights: Different air intake, different engine mount, different dual electric fuel pumps or the ECU.

From what I've been able to gather, the total weight change should be in the 20 to 22 Lb. range. All in all, still not very significant when you consider the fuel burn advantage, no carb icing and simpler control - other than the price of course!

The 40 Lb difference mentioned might be closer when comparing to an 80hp 912UL.

Greg

[neville]

My 40lb statement was based on a casual conversation back when the 912Is was introduced. I agree that 20lb more is a lot closer. I do know
that the figure does not include muffler or fuel system components
not supplied with engine. However, I am very pleased with the engine
performance even without the Sport upgrade (on order). Because of
the computer control it is a joy to start at any temperature and restarting
when engine is warm. One down side is the cost of a BUD's adaptor
to check engine performance/faults ( $900.00).