Dual STI build log

[Shadowrider]

I am 879 Lbs. Turbo engines are not for everyone but I have loved my engine. If I where to build again I would use the same engine. Don't get me wrong the 915 is a great engine, I just like the weight and power advantage of the EP912STI. At the power setting I am running I am around 160-165hp... according to Thomas's dyno. But....that comes with some risk. The advantages of the 915 is its turn key engine. It also has many redundancies built into it, but with that comes the weight penalty. If you want a turn key engine the 915 is a great option. There is some tuning and setting boost settings you have to initially setup, but I enjoy the ability to adjust the engine. I think I need 200hp now though

[yocum137]

Dustin - I've got some time to kill waiting to buy my engine (Rotax stopped taking orders for the 915 until Jan 1, 2023 :cringe so I'm printing gap seals.

How many of each do I need to print?

11hrs for the long one!

Thanks!
Dan


[QUOTE=Shadowrider;103790]Gap seals are done! Test flew it yesterday and they made a huge difference. Feels like the elevator is much larger. Tail comes up quicker, and less prop wash buffeting on steep climb-out. I now have significantly more tail authority, which means I can stall slower (power off because I don't run out of tail) but with that the stall breaks a lot harder. Nose drops hard. Will have to get used to that. My landing was a little wonky because I couldn't figure out why I was teetering and realized my tail was on the ground but my mains where still in the air. Usually if I land tail first is when I am trying to get really short and I pull hard at the last second and the tail will touch first. Its noticeably faster also! I changed too many things at once to be ably to give accurate numbers. Modified the static guard. My theory is at high power settings, high cruise I am getting prop wash pressurizing the static port, so a little guard seems to be giving more accurate indicated airspeed readings. Low end speeds are accurate before, but topend speeds seem to be off. It was way to ruff yesterday to check the numbers but I will shortly.
[/QUOTE

[Shadowrider]

They take forever to print but worth it!

You need 2 of the ones with the hole. Two of the short ones and 6 of the long ones. Takes about a week to print them all.

How many of each do I need to print?

11hrs for the long one!

Thanks!
Dan

Gap seals are done! Test flew it yesterday and they made a huge difference. Feels like the elevator is much larger. Tail comes up quicker, and less prop wash buffeting on steep climb-out. I now have significantly more tail authority, which means I can stall slower (power off because I don't run out of tail) but with that the stall breaks a lot harder. Nose drops hard. Will have to get used to that. My landing was a little wonky because I couldn't figure out why I was teetering and realized my tail was on the ground but my mains where still in the air. Usually if I land tail first is when I am trying to get really short and I pull hard at the last second and the tail will touch first. Its noticeably faster also! I changed too many things at once to be ably to give accurate numbers. Modified the static guard. My theory is at high power settings, high cruise I am getting prop wash pressurizing the static port, so a little guard seems to be giving more accurate indicated airspeed readings. Low end speeds are accurate before, but topend speeds seem to be off. It was way to ruff yesterday to check the numbers but I will shortly.
[/QUOTE

[Shadowrider]

Speed mods update:

Shock monster fairings, Cabane gear fairings, horizontal strut fairlings, brake fairings, 6-7mph. Flying next two Cory who has not put these on yet with identical power settings and rpms I am seeing 6-7 mph TAS faster.

[Kitfox Pilot]

[QUOTE=Shadowrider;106531]Speed mods update:

Shock monster fairings, Cabane gear fairings, horizontal strut fairlings, brake fairings, 6-7mph. Flying next two Cory who has not put these on yet with identical power settings and rpms I am seeing 6-7 mph TAS faster.

QUOTE]

Speed and they look great too!

[FoxbuilderWill]

I've heard that drag reduction also helps with climb performance.
Have you noticed that side by side with Cory?

[Shadowrider]

That would make sense. I weigh less than Cory so I usually have him on the climb. I would assume the increase in climb would be very minimal and probably not able to accurately measure?

My latest thing I have been working on is when you climb really steep like 55 IAS or slower we get lots of feedback from the stick. Prop wash is hitting the tail and causing it to shake. This shaking wears out or damages the plastic sliding block in the horizontal stab. As the tail shakes it impacts the slider and dents it causing more gap. I have gotten quite a bit of play in my tail, so I took the block out, and replaced it. Only lasted a couple flights before play shows back up. If you look closely at the picture you can seen how damaged the end is. I think with more HP the more it gets damaged. I decided to try 3d printing a slider block out of TPU after seeing how strong the stuff is. I have about 10 hours and 20 takeoff and landings with it and it has zero play. TPU has flex so when the propwash is hitting it hard, it has some give, instead of denting it. I will keep testing and report back if I see anything of concern, but so far its been great. Reduced the stick shake on WOT steep climbs. I put it on thingiverse for anyone that wants to print it.

https://www.thingiverse.com/thing:5662547

[Shadowrider]

Flying pictures!

Little Sahara sand dunes.................... feels like your on another planet.

[Kitfox Pilot]

[QUOTE=Shadowrider;106552]That would make sense. I weigh less than Cory so I usually have him on the climb. I would assume the increase in climb would be very minimal and probably not able to accurately measure?

My latest thing I have been working on is when you climb really steep like 55 IAS or slower we get lots of feedback from the stick. Prop wash is hitting the tail and causing it to shake. This shaking wears out or damages the plastic sliding block in the horizontal stab. As the tail shakes it impacts the slider and dents it causing more gap. I have gotten quite a bit of play in my tail, so I took the block out, and replaced it. Only lasted a couple flights before play shows back up. If you look closely at the picture you can seen how damaged the end is. I think with more HP the more it gets damaged. I decided to try 3d printing a slider block out of TPU after seeing how strong the stuff is. I have about 10 hours and 20 takeoff and landings with it and it has zero play. TPU has flex so when the propwash is hitting it hard, it has some give, instead of denting it. I will keep testing and report back if I see anything of concern, but so far its been great. Reduced the stick shake on WOT steep climbs. I put it on thingiverse for anyone that wants to print it.

https://www.thingiverse.com/thing:566254

I'm glad you posted this because I have been thinking Mine was the only one that did the shake thing on a hard slower climb. I was blaming mine on the prop but if yours does it too it's just a thing I guess.

[Eric Page]

The horizontal stab slider in this airplane is a pretty primitive, low cost design. Its function is very much dependent on the fit-up achieved by the builder when installing the Delrin blocks, and it's apparently subject to rapid deterioration if the plane is flown at the edges of the performance envelope.

A better design would rigidly mount the stab to a small linear bearing running on a precision-ground chromed rod. It would weight a little bit more, but it would constrain the stab against hammering in turbulent airflow. It's probably not a difficult retrofit for someone with some fabrication and welding skills (not me, in other words!).