Continental 65 HP or more, Ok on Model 4 ????

3400 or 3600 depending on which one. Or so the web site says. It is interesting that the reduction gear results in an increase in thrust. 3600 RPM means the prop length is limited to keep the tip speed under limits (fixed pitch, wood). Interesting stuff. Lots to consider in picking an engine and prop combination. The engine MFG says the VW direct drive requires a wood fixed pitch, so if you really want a ground or air adjustable you need to consider other combinations.

Front Drive - Air-Cooled.
Direct drive, driven off the pulley end (Type 1 only) for standard aircraft configuration. The Front Drive engine turns counter clockwise from the cockpit in a tractor configuration. Wooden props ONLY must be used. This is the most popular configuration.

And here: http://www.greatplainsas.com/gpasproducts.html

John,

Please make the boot cowl removable. With the windsheild in place and the boot cowl riveted in place, the only way you can get behind the panel is to either remove it or slither in on your back. Shades of the Lancair IV. When I was helping with that I excused myself from that chore - no real choice. And with the V my buddy is building in my hangar - he insisted on a removable boot cowl - genius. I think I would use nutserts and easy Loctite though, rather than screws and nuts.

Lowell

Quote:

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Originally Posted by jtpitkin06

Hmmm... must have been another Radial.


Yes, I'm doing a boot cowl. I'm slicing the Continental cowling in parts.

JP

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John,
Give me a call.. we now hove a boot cowl that should work fine on the Continental and Lycoming installs:)

While the older instructions call for riveting the boot cowling to the firewall.. we currently use a sealant and c'sink screws for mounting the boot. It works out well.... Accessing behind the panel is much easier without the boot installed so waiting until the last minute to install it can be helpful. Once installed access ins't too bad from under and over the glare shield... and if absolutley needed the boot can still be removed.

It's offical, I got my Aerospace engineer next door !
Now that he is my renter, look for a few changes to the Kitfox-4,
such as turbine power !

I seem to remember an STC for the Continental, that involved a cordless drill motor, a gear mounted on the prop flange, and a control rod to the panel. Something like $1800 for the STC, for about $300 in parts, and good for about 4-6 starts on a charge.

Ya, I too have seen mods to add starters. The guy in the hanger across from me hand props his O-200, and thinks it's no big deal, but for me ..... Well ?????

I guess I am still exploring options. The C-85-12 might be a better choice, and weight about the same after putting a starter on a A65, but then it really would be too much weight I think (or not?). Perhaps I should try hand propping another plane, and see if it's something I could live with, or not. So I guess right now I am still looking at VW'ing it, at least I know that devel, and the install weight with starter is still only about 165 lbs (+ accessories). !!!!

Thanks for the insight guys

Roger

I've been watching this thread to see where it goes. Just a couple of thoughts:

Hand-Propping: I have a good friend with a Champ. C-85 with no electrics. It props nicely and works fine in that plane. Keep in mind, that plane was designed for the (220# +) weight of the Continental.

VW motor: With the rpm range they need, they will not have a large enough propeller (low speed, high thrust) to make this airframe perform anywhere near acceptable. VWs work in a Thatcher or Sonex, but I have never heard of anyone even remotely satisfied with one in a Avid or Kitfox. Not to mention their actual reliability record is at best, spotty.

Continental (C-65 through O-200) in a model IV: IMO generally a bad idea. This motor even without electrics is too heavy. This airframe was designed around the 582 Rotax (~90#). The 912 is a good substitute (~140#). Anything more is too heavy, period. A friend of mine had a Subaru in his IV and once all the ballast that was needed was added to the tail, he had a poorly performing single seat airplane. His install was at about 230 pounds.

Finding a used, reasonably priced 912 is not impossible. Another friend of mine just bought one (80 hp 912UL, 120 hours TT) for $6500.


Innovation is a good thing. But in this case, IMO, you will be very disappointed in what would otherwise be a great little plane.

Quote:

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Originally Posted by Av8r3400

VW motor: With the rpm range they need, they will not have a large enough propeller (low speed, high thrust) to make this airframe perform anywhere near acceptable. .

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More discussion on this point, please. Someone with a VW powered Kitfox or Avid want to rebutt? I saw one with a 76HP Great Planes, that reported climb rate of 1000 (solo) and high cruise of 115MPH (just about 100kts) TAS at 4500 - 5500. Is that not "acceptable" performance for a Kitfox IV?

I bought my first Kitfox Model IV kit in 1993. I have no personal experience with VWs in IVs, but have been involved with foruns such as this one since 1994. (Early forums were email lists where we recieved every post and most of us read every one - 582, Subaru, Rotax, VW, Model I,II,III,IV,V 6,7, and learned a lot, even about stuff we were not particularty interested in.) Kitfox has been around a long time as have VW conversions. If it was a mix made in heaven, I doubt you would have to ask for a rebuttal, as the forums would be full of talk and Model IVs would be full of VWs as an option to the much more pricey Rotax. Av8r3400 is spot on in his comments from a historical perspective. The issue with the Model IV vs. the Sonex has to be with weight and prop length limits if direct drive and the round cowl blanking most of the prop, where the Sonex has a smooth cowl and lets the wind fly. This phonemenon is an issue also with certain prop designs - Powerfin on the Model IV.

I know there are guys that believe that they will be able to manage the issues, but, I am unaware that anyone has. You can be sure that if the combination works and works well, there would be tons of the good news on the internet. I must say here, though, that if there is someone out there who has a VW powered IV and it is a screamer, Don't keep it a secret. Let us all know and we skeptics will stand corrected.

Lowell

Howdy all;

There is a fellow on youtube with, like a dozen VW powered kitfox-4 videos. He is most well known, but other are out there too. Watching his videos, the planes sounds wicked (love that 4-stroke sound). I think the only issue is the rate of climb is not excellent, it's not bad either, just not that great.


I had a 76 HP Great Plains VW in my Zenith 601 HDS. The HDS has the taper wing, and the span is only something like 23 feet, so it has never been known as a great climber. I would take off at 1260 lbs gross in the summer, when it was HOT in Kansas, and still climb out at about 400 fpm. That might sound bad to you, but the Ercoupe I learned in would only manage 250 fpm !!!!!! I would expect the Kitfox-4, with it’s larger wing to climb at 600+ FPM under the same conditions myself, which is fine with me (didn’t the cub start out with a 65 HP engine ????)

VW aero engines are not the same, that’s for sure. I have seen some pretty crappy ones, but Revmaster, Great Plains and Aerovee are really first rate too. This zenith was a Great Plains VW with a good propeller. Your millage may vary, as they say, but a VW with 70-80 HP has plenty of power for something like a Kitfox-4-1200, the key factor is choosing the right prop. Something most people can’t do, or do wrong.

The VW propeller should have a largish diameter, and a somewhat shallow pitch in order to give a good static thrust and high efficiency. But it must have enough pitch to get you up to your projected cruise speed (don’t’ forget the prop slip !!!!), without over pitching the engine. Personally, I have a propeller calculator program that helps me, but most folks call propeller sizing a black art. Over propping he plane is the easiest thing to do (too much pitch or too much diameter). Usually, I order a propeller with the proper pitch (as calculated), but with a bit too much diameter. Then I install and test run it and check the static rpm at full power. Then I run the numbers through the calculator, and it tells me about how much to cut off each tip in order to bring the rpm up to what is needed. (oh ya, I sure wish I had adjustable pitch !!!!) This process typically takes a 2 or 3 attempts , but in the end the prop is dialed in and wholla !!!!! A perfectly sized VW prop !!!!!

As for VW reliability, once again, it depends on the VW. A factory built or a slopped together former airboat engine ???. I mean really, we have to compare apples to apples here, and I don’t’ think it’s been done. The VW engine has been used on airplanes for something like 70 + years now. It’s an extremely well understood engine, both it’s strengths AND weakness, and it’s weakness can be managed safely (it’s just a question of “are they being managed”).

Roger