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1kitfoxflyer
03-06-2011, 09:13 PM
Anyone know what's the largest engine that will fit in the mod IV 1050 xl?

Av8r3400
03-07-2011, 06:33 AM
I don't know what you mean with the "XL" but the IV-1050's were designed to have a 582 two stroke.

The 912 Rotax works well (this is what mine is). You may be able to find a few out there with VW or Jabaru motors on them. The Subarus, Corvairs, Continentals and Lycomings are going to be just plain too heavy for the mount designs and are probably not the best fit. Considerable tail balast will be needed to keep them trimmed and this will chew away quickly at the limited weight capacities.

I have a friend who used to have a 1050-IV with a Subaru (scrapped now). It was basically a single seat airplane with that amount of engine weight and ballast needed in the tail.

There are some Rotec, Continental and Lycoming powered IV-1200s. However, these are still going to be very nose heavy.

t j
03-07-2011, 08:01 AM
Here's the information I have on the XL. In 1994 I saw a write up in an aviation magazine about the XL. The cost of a complete kit including 503 Rotax was $14,995. I traveled to the Skystar factory to look at an XL because I wanted one. When I got there they had discontinued the XL and had started making the Model 4 again naming it the Classic 4. They told me the Classic 4 was the same thing as the XL and they would sell me a Classic 4 with a 503 for the same price.

A few years later when I mentioned that on the kitfox list a guy called BS. He said he had built an XL. He said the factory had a few left over model 3 fuselages and were selling them with model 4 wings etc. and calling it the XL.

My Classic 4 builders manual has quite a few pages from the XL manual. The engine section is all XL. The wings if built by the XL manual will have only 2 top false ribs in each bay instead of three and no bottom false ribs. If the fuselage is truly a model 3 the vertical fin and rudder will be smaller than the classic 4.

Anyhow, using logic I would say that being as the model 3 can use a 912, so can an XL.

avidflyer
03-07-2011, 08:31 AM
Hey Tom, last week I measured my Kitfox 4 Classic 1200 and the top of the verticle stabilizer was just over 67" off of the floor. Easy to check what you have with a tape. http://www.teamkitfox.com/Forums/images/icons/icon7.gif Take care, Jim Chuk

PS just to take the tailspring out of the equasion, cause some might be bent more or less than others, I ran out to the garage and measured again. I have 34" from top of vert. stab. to top of horizontal stabilizer.

rogerh12
03-09-2011, 10:36 AM
Hey don't forget about the VW !!! Great Plains VW has a complete FIREWALL forward kit for the model 3 & 4. Gives you 65-80 HP to work with, depending on size and options. Light weight aluminum cylinders are now available, dropping the engine weight about 10 lbs. Engine can be rebuilt for only about $500 in parts (vs $8000 for the 912).

Lion8
03-09-2011, 02:58 PM
I have the model IV as well. Currently installing a Jabiru 80hp on it. The engine weight is 130#. I believe the VW's are around 160 to 165#'s. The Subaru is over 200#'s. 912 Rotax 80 hp.weighs in just over 130#'s. Then there's the cost of each. Make a chart for all the possible engines with the cost and weight then make your choice. Hope this helps a little, Tom, N.J.

dholly
03-10-2011, 08:20 AM
Just an FYI... the 2011 Engine Buyer's' Guide was just published in the April 2011 issue of Kitplanes Magazine.

jtpitkin06
03-15-2011, 10:58 AM
When this thread started a week ago I thought of several quick retorts but decided to wait a bit.

I wasn't sure if the question was, "What is the heaviest motor you can install?; or, "What is the maximum horsepower you can hang on the front of a 1050?"; or, "What is the largest physical size motor that will fit on the front or under the cowling?

First the heaviest

With a weight limit of 1050 lbs your choices are a bit restricted. Practically, you would like to stick with the lighter engine choices to keep your payload up. With a lighter gross weight you don't need as much horsepower to get sprightly performance. Compare your 1050 with say an 80 hp motor on it to a Model 7 1550 pound aircraft with 120 horsepower. They have the same power to weight ratio and would climb about the same. The bigger aircraft may cruise a bit faster, but not much.

Now for horsepower.

If you don't care about payload, you can probably put an engine on the front as large as a PT6. It would go like a scalded dog to the far end of the runway where it will have consumed all the available fuel and ripped the wings off in the process. The airframe is pretty draggy and excess hp doesn't really help that much. So consider 120 hp about the maximum.

And now for Physical size.

With a new cowling, you could mount an engine as large as the Continental O-200, but, once again, you will be limited in payload.

There's a reason the early Kitfox aircraft had small, lightweight engines. They were a good match. Sure, the TBO on some of them was short, but they didn't cost much at the time to rebuild. Lots of owners happily flew around with a small two stoke, rebuilt the engine every year, and had a great time. Now, it seems many pilots shun the two stokes and want a heavier four stroke with more power.

So to answer you question(s): In the case of a 1050 Kitfox, I would think a 912 and all the cooling, muffler, and accessories is pushing the weight, size, and hp limits.

John Pitkin
Greenville, TX