Dual STI build log

[SNOW JW]

Went flying to IBEX lakebed early in the morning. Wind was dead calm. I was flying low across the lakebed in perfectly smooth air and my TAS showed 102MPH. Ground speed showed 112mph. G3X showed 8mph tailwind? I know groundspeed was correct, but I am wondering if my Pitot system has a small leak? I got reading and I guess 1/4 air line press-in connectors often leak. Thinking maybe the press-in connector I used is leaking slightly. Vans forum many say don't use the press convectors because they leak? Avionics guy is coming next week for the Global and I will have to do a pitot static test.

Dustin I would not trust the push connectors at a low PSI. We have hundreds of these on our truck fleet & they often leak at under 40 psi & often leak more with age & vibration they work great at higher psi 100 & above so the lower the psi the more they leak. Sometimes you can stop a leak with a small amount of AGS Sil-Glyde on the hose.

[yocum137]

You should sell airspeed correction kits. You'd make millions!

Great idea trying that.

Well, dozens of dollars, for sure.

[yocum137]

I am going to check AOA if it needs to be re-calibrated, but I suspect the error is only showing up on the faster end. Made a few 3d printed printed "static guards" of different sizes. Going to start with the one that is the same thickness of the washer I used and go from there.

Dustin - do mind attaching the STL files for these nifty washers? Thanks!

[Shadowrider]

Yes I will post. I am changing the design because it seems to have errors still present in flight testing. When I taped the washer on I think the tape protected the static port better. Hoping next week I can get out and fly it. Also working on some 3d printed gap seals that I am excited about!

[Shadowrider]

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.

[alexM]

I love those gap seals.

[Eric Page]

So do I. Did you print them with flexible TPU filament? Would you be willing to post the files somewhere and provide a link? Thanks.

[yocum137]

Oh yeah, gap seals will make a huge difference and they don’t even need to be so fancy (but I like yours A LOT)! Just something to prevent air from leaking from the underside to the top improves authority. I used painters tape to experiment on my Pietenpol and it was a completely different (better!) flying experience. I’m surprised Kitfox doesn’t have a sealed gap option - I’ll bring that up with Brandon next time I go visit them.

Speaking of the static source and old open cockpit aircraft, we’d put a plastic plug with a 1/16” hole drilled in it in the static inlet of the steam gauges. Can’t do that in an enclosed cockpit, but sheltering the static port completely - extend that semi-circle up and farther back - should reduce the prop wash effect better/more.

[Flybyjim]

How is the gap seal attached?

[Shadowrider]

Yes they are printed in TPU. Stuff is pretty cool. Strong and lightweight. They are attached by going between the elevator and horizontal stab. They pivot with the elevator to keep the seal flat and tight. I have tested them down to about 10F and they are working great. Making a second set for Cory's plane and making a couple tweeks. Not sure they would work on planes that don't have a single layer of oratex because the clearances would be off? I will post more info after a couple of test flights.