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lakeflyer
01-13-2012, 12:58 PM
I'm looking to buy a kitfox 4-1200 and put it on floats, is there a Specific prop one should put on a rotax 912ul to make this combination work, Just wondering if I need to budget for a prop?

dholly
01-13-2012, 01:53 PM
Dan-

I had the same question. Here's some copy 'n paste info I have in my files that will help. Not sure which forum I lifted it from, but this reply was written by an experienced Avid/Kitfox float plane owner whose knowledge and judgement I trust.

Doug



If you are only getting 5100 on your takeoff run that is killing your off the water performance. My first prop on my 912ul Kitfox amphib wouldn't pitch flat enough, so I could only get similar rpm. Off the water performance absoultely sucked! Sure, it still worked, but probably only because I am only at 1100 msl around here, and generally cooler temps. Once I got full rpm for takeoff with the new prop I cut my takeoff time in half, or better.

That wood GSC is a pretty prop, but the IVO will make a lot more thrust. Some friends over the years switched out their GSC's and were shocked at how much better their airplanes performed after the change. So I really think you are on the right track.

I'm surprised IVO recommended the medium for the 912ul. The medium blade has a minimum pitch of 30" with a max of 90", whereas the IVO "standard UL blade" has an 18-52" pitch range. That means it is much flatter than the 30" pitch range of the medium, which willl allow the 912ul to spin up quicker, getting the max power of 5800 rpm for takeoff. I am POSITIVE the 30" minimum pitch range of the medium blade will not let your 912ul get to 5800 rpm for takeoff, much like the "Plus" or "Patriot" UL blade that has 35" of minimum pitch, which are the blades that I had before and wouldn't let my 912ul spin up beyond 5100 rpm for takeoff.

Also worth mentioning, at the other end of the pitch spectrum, my 912ul also can't handle more than 52" of pitch. So having a blade that can go to 90" (like the medium does) will be absolutely useless with a 80 hp 912ul.

I really am thinking someone at IVO must have misunderstood and thought you had the 100 hp 912?

Here's the info showing IVO's pitch ranges and blade types;

IVOPROP Electric In-Flight Adjustable Ultralight Model
For engines up to 100 hp
18"-52" pitch range (Standard UL blade) **
or 35"-70" pitch range (Plus or Patriot UL blade)
48"-72" diameter


IVOPROP Electric In-Flight Adjustable Medium Model
For engines in the area of 100 hp or high ratio gear boxes
30"- 90" pitch range
52"-74" diameter

** The prop that works very well on my 912ul amphib is the 18-52" model UL blade. With that prop I can actually get more than 5800 rpm for takeoff, so you need to be aware and make sure not to overspeed your engine (IVO washers can be used to control overspeeding issue).

WWhunter
01-22-2012, 10:54 AM
I don't have a Kitfox although I am still looking at one in particular. I do have another plane, a RANS S7 that I hope to have amphibious floats I will be installing this spring/summer. All the research and info I have found seems to point to the 2-bladed straight tipped Warp Drive with nickle leading edge as the toughest and most cost effective prop for a 912 on a float plane. A longer 2 blade seems to 'pull' better out of the water than a 3 blade but it may be slower. Not enough slower though for most people to worry...usually only a couple mph. This info is what I have found to be true for certified planes also. A good constant speed is probably the best although if you are going to be flying under LSA, not legal. The worst issue is, once a plane has been taken out of LSA catagory it can NEVER legally be converted back (at least this is my understanding).

By the way, I am located near Itasca State Park if you ever get in the are please stop in. I have a 1,000' strip with an additional 700 feet I am working on.
WW

lakeflyer
01-22-2012, 06:33 PM
WWhunter, thanks for prop information I haven't found a kitfox yet that will work for me. I just sold my C-180 and it had a 2 blade seaplane prop on it, I know there was a 3 blade upgrade for it, I wasn't sure if that was true for the kitfox as well. I do know the larger the prop the more water it picks up in spray and it does alot of damage, it's just as bad as sand. By the way I see you live near me, I live on moonlite bay of crosslake and am always looking for an excuse to go flying, when I get some new wings I'll have to come see your runway. dan

WWhunter
01-23-2012, 07:28 PM
Dan,
You are more than welcome to stop in. I may buzz down that way in the Champ when I get back to MN. Always looking for someplace new to go.
I have it on floats but will be putting the S7 on amphibs this spring so I can keep it at my property instead of up at Mobergs. I have the Champ for sale and think I have a buyer. Its LSA and heavily modified so I am really having a hard time selling it. Pretty heavily modified Champ with an O-235, VG's, droop tips, 39 gallons of fuel, etc. Just need to thin out the herd a bit. Probably going to advertise the 172 also.
If you want any info on how to find my place just send me a PM and I'll respond.
Keith

WWhunter
04-20-2012, 08:47 PM
I guess I need to eat my own words previously posted. After months of research and talking to several different Rotax veterans, I decided to try a 3-blade prop. I just ordered a Whirlwind 70" for my plane. The WW prop is light, well built, and best of all.....made right here in the USA!!
I was set on geting a Kiev, but after thinking of future parts issues, I wanted something in the same league but locally made. Granted I hear nothing but good reports about the Kiev, and personally met Ted, the importer. He is a great guy and very knowledgable, I nearly walked out of his place with a new prop......
I'll try to get a report on the WW as soon as I can. There is supposed to be an article in an upcoming Kitplanes magazine soon that compares several props. The WW prop might just be the 'go to' prop after the word gets out. :-)

predmond
06-13-2012, 06:28 PM
The advice quoted by DHOLLY was from AV8RPS to me in another thread. I have an update. I finally got around to selecting and installing an IVO in-flight adjustable, 3 blade, 72" ultralight. In a word "WOW"!

To save you looking up the background, I have a Model III with IV wings, Rotax 912 80 HP, and Full Lotus 1220 floats with retractable gear from Harbor Sport Aviation in Wisconsin.

I previously had the wooden GSC prop. On a water takeoff run, it would max out around 5100 RPM and unless the weather was cool and I had a good breeze and light chop, it had a hard time to get up on the step, if at all.

Now, it starts out that way, then I bump that little toggle switch up and the engine roars up to 6,000 RPM and it gets right up on the step and away we go shortly after that! Once airborne, I toggle down a bit to avoid over-revving. A remarkable improvement.

Thanks to all, especially AV8RPS who posted replies and made good suggestions.

avidflyer
06-13-2012, 07:57 PM
If you are still looking for that Kitfox 4 with a 80 HP 912 on floats, a guy near Cloquet Mn has one for sale (if he didn't sell it allready.) I saw it on craigs list in the Duluth Mn section. Do a search there and you should find it. Take care, Jim Chuk

PS tell him I said Hi!