Looking for some real world numbers on a 100 hp STI

[Kitfox Pilot]

I ordered a STI kit back in aug so I have lot of decisions to make. Like everyone did I'm wondering what engine to use. I would love to have 130 to 150 hp but do I really need the much greater cost and complexity.
I went out to Kitfox a couple weeks ago to finalize some options I wasn't sure about and I wanted to fly a kitfox which I did with stick and rudder. We flew in a 7ss with a 914 and constant speed prop. It was a very nice ride for sure.
I live in the fairly flat lands of southern Illinois, most hills are lower than 1000 ft so a turbo isn't needed for crossing mountains.
Could anyone tell me what they are seeing for takeoff roll on grass with a 100hp STI with a 200 lb pilot? And ground roll with 400 lb on board?
Not your best take off distance, just your ave. I do want to get out of some short places, 500ft or so.
Thanks for any help on my HP decisions .

[Shadowrider]

Only a handful of STI's flying. All the ones I know of are running more HP than 100. Only one that I know of running a 100hp rotax is John Moriarty, who just sent his engine off to get boosted! He should have some good numbers for you as he flew his with the 100hp rotax for a bit before. Down at sea level 100hp should perform well. From what I gathered I think the STI wing is about 40lbs heavier than the 7ss.

[Kitfox Pilot]

Thanks Dustin, I guess I didn't realize there weren't more of them flying than that, I haven't followed kitfox for that long but all you read seems or be STI. The 914 seems like a lot of extra items for just 15 more hp. I understand if you fly in the mts this is a big plus. The edge engine like yours looks like the next option if the 912s not enough. All the original stats for the Sti are put out while using the 912 according to kitfox website. 150ft takeoff and landing is really impressive and is a really good pilot I'm sure. I'm most concerned with hauling a passenger in the summer out of my home field.

[rv9ralph]

if I remember correctly, Trent's Freedom Fox, a Model 5 airframe had 100 hp. He upgraded to the STi wing a year or more before his engine failed and he upgraded again to the 915is a year ago. You could look at some of his older videos to see his performance. He has a video from 2 years ago or so evaluating the STi wing on his Kitfox.

Ralph

[Kitfox Pilot]

Thanks will do.

[Kitfox Pilot]

if I remember correctly, Trent's Freedom Fox, a Model 5 airframe had 100 hp. He upgraded to the STi wing a year or more before his engine failed and he upgraded again to the 915is a year ago. You could look at some of his older videos to see his performance. He has a video from 2 years ago or so evaluating the STi wing on his Kitfox.

Ralph

It says he had the big bore kit, 120 hp. That would be a nice hp without a turbo but you have to machine the heads and the case.

[Shadowrider]

Nikk took me for a ride in his 7SS with 100hp out of kpvu 4500’ on a day temps where around 75-80. Close to 400lbs of passengers and I bet we where off the ground in 3-400’ climbed up to 7500’. It was not a hotrod but did just fine. So if you have a STI all things stay the same it will take off quicker and climb better. How much not exactly sure. John used to have a 7SS wing and then he switched to STI. I asked him if he could tell a difference and which wing he likes better. He said he doesn’t miss the speed, lost 15mph, and likes the better climb rate of the STI and added saftey especially at high DA.

[3 tracks]

The takeoff numbers you are trying to achieve are probably doable with the 100hp at those altitudes. I had the bigbore and a different cam also a 75" airmaster. It performed well, my airstrip is at 3,000 ft. Takeoff with me full fuel and survival bag is approximatly 400lbs. I would be off the ground in about 250' on a warm day. Like Dustin said i don't know anyone with the stock 912uls in a STI. McBean had one in the factory STI when it was in the testing stage , you could ask him.

[Av8r3400]

Keep in mind, weight is the key to performance. Trent's plane has an empty weight of over 950 pounds. At sea level I have little doubt a 100 hp plane at 700 pounds or less will perform very well, indeed.

[Kitfox Pilot]

Keep in mind, weight is the key to performance. Trent's plane has an empty weight of over 950 pounds. At sea level I have little doubt a 100 hp plane at 700 pounds or less will perform very well, indeed.

Larry, I have watched your videos in the past and your landings at your home in the Gospel lake video with trees on both ends look very impressive. Do you fly out of that strip with 2 people aboard? Harlan

[Av8r3400]

Larry, I have watched your videos in the past and your landings at your home in the Gospel lake video with trees on both ends look very impressive. Do you fly out of that strip with 2 people aboard? Harlan


Yes, I have.