Kitfox model 2 weight and balance

[dalords]

Almost complete with my project (rebuild) Kitfox model 2. The plane never came with any weight and balance data, so I have to go off and recreate it. I was wondering what is the CG limits of this model? Is the datum the wing root leading edge like it is on a model 4? is anyone will to email me their weight and balance data sheet so that I can get an idea of what it should be? If so send it to dalords@cablone.net. I will be weighing the plane this weekend.

[dalords]

Or anyone who would have a model 2 or 3 construction manual section that went through how to do the center of gravity calculation

[jiott]

The W&B spreadsheets on the Kitfox website (Technical FAQ) should work fine for you. You just have to enter your own data for your specific aircraft, and use the fore and aft CG limits for your specific model. You should be able to get these limits from the factory. The worksheet methods and procedure will work for any airplane.

[dalords]

That's the problem I am having. Kitfox doesn't have this info. They don't deal with the older models. Yes they have some parts but as for anything else you are pretty much on your own. That's why I would like the info from another model 2 owner

[KFfan]

My offering from the build manual of S/N 359

[dalords]

that helped out a lot Lou thanks. It did however bring up some new questions, my plane is tricycle not tail wheel, so how do the guys with nose wheel figure out the most fwd and most aft CG. what's the process for figuring it

[KFfan]

I must admit I am new to flying as well as Kitfox. I am not aware the model 2 was ever offered as a tri-gear. I don't know how the difference in the gear would effect the W&B calculations. My fledgling mind reasons the overall calculations would be the same as long as you have the model 2 wings. Again, I am just learning aeronautics. I am confident someone more knowledgeable (http://www.merriam-webster.com/dictionary/knowledgeable) will chime in on this and set me straight.

[dalords]

It wasn't offered in tricycle gear. We also run a rotax 912 engine and have the tail the same size as a model 4. EXPERMENTAL. We have done a lot of modifications. Part of the fun of owning one. what I found interesting is the manual you sent me identifies the MAC and empty weight for a model 1. listing the max gross as 950 rather than 850. We are going back into phase 1 testing and plan on increasing our gross weight to 1000

[KFfan]

I noticed that as well. I'm thinking the kit manufacturer used the manual for the model 1 and made appropriate changes for the model 2 without correcting other references. Saved doing a complete rewrite.

[jiott]

The most fwd and most aft CG depends only on the wing MAC which is given in the manual pages KFfan posted. So it is the same for both nose or tail dragger. So go ahead and use the calculation procedure in those pages.

[KFfan]

Jim
Thank you for confirming my intuition and stating it more elegantly.

[KFfan]

Doug
FAA-H-8083-1A, the weight & balance handbook, is available on the FAA web site in PDF format for reference.

[cgruby]

Almost complete with my project (rebuild) Kitfox model 2. The plane never came with any weight and balance data, so I have to go off and recreate it. I was wondering what is the CG limits of this model? Is the datum the wing root leading edge like it is on a model 4? is anyone will to email me their weight and balance data sheet so that I can get an idea of what it should be? If so send it to dalords@cablone.net. I will be weighing the plane this weekend.

I have a spreadsheet for calculating w&b for a type III, which I imagine is close. If you'll send me some data, I'll be happy to calculate it for you.

You will need:
Empty weight
Gross Wt
Location of main gear axle centerline from the leading edge of the wing
Location of nose gear axle centerline from the leading edge of the wing
Max allowable forward CG
Max allowable aft CG

When you measure the location fo the axle centerlines, the aircraft has to be level (it may already be sitting on a tricycle gear).

Cheers,

[jiott]

The W&B spreadsheets on the Kitfox website (Technical FAQ) should work fine for you. You just have to enter your own data for your specific aircraft, and use the fore and aft CG limits for your specific model. You should be able to get these limits from the factory. The worksheet methods and procedure will work for any airplane.

As I posted above, I strongly recommend using the above spreadsheets on the Kitfox website; they are very easy to use once you have the data from going thru the procedure posted by KFfan. It doesn't matter which spreadsheet you use (model 4, 5, 6 or 7) as long as you use the fore & aft CG limits for your particular airplane. The spreadsheet doesn't calculate the limits, it only calculates the actual CG for a particular loading. You then take this actual CG number and compare it to the fore & aft limit range to see if you fall within it.

[jiott]

One more thing: make sure you plug in the "arm" distances for pilot/passenger, fuel, baggage for your actual airplane (given in the last page of KFfan's post) in the appropriate places in the spreadsheet. Then with that spreadsheet you can quickly explore what happens to the CG with various combinations of fuel, baggage, and pilot/passenger weights. The calculation formulas are built into the spreadsheet so you don't have to do any math.

[KFfan]

Doug

Here are the original W&B pages for S/N359. Happy calculating!

[dalords]

Thanks everyone for the replies. Jim and Lou here is where I run into the problem, its not figuring out the weight and balance, its the wording in the manual that Lou sent. For the most aft CG it tell you to add a gal of fuel to the fuselage tank and then add bodies or weight in the seat basically till you reach your gross weight, then for the most Fwd CG it tells you to fill the fuselage tank all the way and add a single roughly 120lbs person. My problem, I don't have a fuselage tank, just wing tanks, so then do I omit that part of the procedure? for aft max CG add weight to my gross weight and take a scale reading, same for the Fwd CG, just add 120lbs in the seat and take the scale reading?

[t j]

The old kitfox manual weight and balance instructions had you weigh the plane with couple different fuel loads and a couple big boys to sit in it to determine where the CG would be located with those weights. You then knew if those loads produced a CG that was outside the limits. That is a very confusing way of doing it.

The conventional method is to include only the things in the plane that would be in it for every flight except fuel and pilot. The only fuel in the plane should be the "Unusable" fuel. That will give you the Empty CG. All other loading possibilities can then be easily calculated.

Hope that doesn't confuse you more.

[KFfan]

Doug

Your last post caused my brain to flash back to, I think, seeing some pages that describe the process step by step. I have gone through quite a few pages of the documents I have. Tomorrow I'll see if I can rediscover them. When I do, I'll scan and post them.

Tom
You were posting as I was. What you relate vaguely strikes a bell.

[dalords]

That's kind of what I was thinking Tom. So with the basic empty weight add total fuel plus max passenger weight to get to total gross weight and then do the math to find max aft CG? Same with max fwd, except with only one small guy? I noticed on the spread sheet for weight and balance for model 4 on the kitfox website it already list max fwd CG at 10.2 and max aft at 16. shouldn't I fall somewhere close to that?

[t j]

Max aft and max forward are the limits that the CG must Stay between when the plane is flown.

For the model 1 through model 3 these limits are:
Max aft limit is 28% of the wing cord (51"). .28 X 51 = 14.28"
Max forward limit is 20% of the wing cord. .20 X 51 = 10.2"

Most adverse forward and most adverse aft are actual CG locations with loads you expect to fly the plane with.

There is an EAA "Hints for home builders" video that explains it in an easy to understand format. I'll see if I can find it and post a link.

[t j]

Okay here's the link to the video on how to calculate the empty CG. You will notice he used the nose of the airplane as the datum. That was so he didn't have to deal with negative numbers.

You should use the wing leading edge as your datum so it will be the same as all other kitfoxes and you can also use the spread sheets for nose wheel planes on the kitfox factory page.

You can easily modify the Model 4 spread sheet and enter your CG limits and headings and such. Those don't affect the calculations if you want to go ahead and play with it. Just remember your aft limit is 14.28" not 16".

Remember to put a negative (-) sign in front of the nose wheel arm. Also, if you later want to do some "What if calculations" for altering anything forward of the wing leading edge. Such as installing a different prop or engine.

Start with this video then scroll down under it and you will find the rest of em.

http://www.eaavideo.org/video.aspx?v=2895768031001

[dalords]

Way to drop the knowledge Tom. That is what I was looking for. All of you have been great. Again thanks Lou for the copies, and everyone who commented.

[t j]

Here's the video on how to get the measurements of arms.
http://www.eaavideo.org/video.aspx?v=2874081572001

[KFfan]

Thanks for the education Tom!

[rv9ralph]

Great information posted. To the original question on weight and balance on the rebuild... If the aircraft was previously registered, the FAA has a file with all the documents submitted at the time the original air worthiness certificate was issued. If you contact Oklahoma City or your local FSDO you may be able to get a copy. I was lucky when I acquired my Kitfox, the Operating Limitations had been misplaced. A representative from the local FSDO was at our monthly EAA meeting, after talking to him, I sent him an email the next day as he recommended and he emailed back within a few days the entire file in .pdf format. The original W&B was included.
Ralph