Speed Mods

[hydroguy2]

I'm planning a few modifications this winter in the hopes of picking up 3-5kts on the top end. This thread will be where I track these changes. I'm waiting for a smooth day to go out and get good baseline data. I want to ensure I'm making improvements not going backwards.
In the meantime, I started Mod #1, the tailwheel fairing. Here's what 20 minutes of breathing fiberglass dust looks like.

[cjensen]

Cool Brian! That's a good mod for racing. I'd be a little leery about landing on grass or unimproved strips with it on, but it sure looks cool!

[Spike]

If that gets to be your thing I would think you can spend tons of time doing really cool stuff to an RV for speed.

Spike

[hydroguy2]

it's becoming "my thing" for sure. Wish I had more money and time to travel to more races.

I'm planning many of my mods to be easily swapped out. This way I can visit the strips I want and also be a little faster for racing. The tailwheel fairing takes about 5 minutes to change. The wingtips I'm building will take another 5 minutes or less to swap thanks to the hinge method of attachment.

today we had a beautiful day out there, cold but nice......except it was a little rough at 8000'msl, 6000'DA. So I tried to get some good baseline numbers.
OAT -12*C
DA 6000'
MP 25.1
RPM 2470
FF 10.5
KTAS 178 and increasing Then BAM! a little clear air turb....pull the throttle, and nose up to 140kts. I was just getting set up for the runs when it was getting too rough for high speed for me. I still had to get RPM up to 2580 adjust for 100*ROP. Oh well guess I'll have to go again. I need to take someone as a recorder. It's difficult to do the flying and logging data and look out the window and keep my shorts clean.

[Bob Barrett]

I look forward to seeing your modifications It will be really interesting to see how much you gain. I find it hard to believe that you will be able to gain much with the wing tips but it won't be the first time I have been wrong

[hydroguy2]

As I understand it, smaller tips work best down low less drag so speed goes up. whereas at higher Altitude the plane likes the more lift from the bigger tips. The tips I have planned will reduce my wing span roughly 14" and will be quick changable. Others who have gone before me have seen gains of ~3kts....oh stall speed goes up about the same.

[hydroguy2]

Got off work today and had time before the Superbowl chili was ready. I took Aurora up for a little buzz arounf the vallley. I found smooth air and tried another speed run. I'll take this as my baseline data for any modifications I make.
7000'msl, 6650'DA, WOT, 25"mp, 2600rpm, 173kts IAS, 190kts TAS(I have ~2kt error at this speed). So I call it 188KTAS.



Return run pic showed 188kts. I'll take it. Now I need to finish my tailwheel fairing and work on my wing tips

[hydroguy2]

Plans chenged. I haven't got around to building new wing tips, but tore the plane down for internal lower cowl mods.

here is a outlet. I used Al sheet to build a baffle to help striaghten the turbulent flow. the transition area firewall to outlet benefits from smoothing it out.....so I've been told. I also redid the clunky exhaust hangars


Next up, shaping an temporary outlet. this will be to blend the slower cowl air to the free stream. this is another area that suffers at high speed and has vortices at the cowl/belly interface.


My 4 pipe system points down a little(one side more so) I wanted to try to reduce drag in this area also so here is a before pic.

and after slicing a wedge off the pipes.....looks slicker anyway


AL .032 cowl fairing installed with 3 screws into cowl lip and speed taped to the fuse.


now if I can get the weather conditions I need for "Approach to Vne" flight testing. this pic was a yesterday, today it's howling (possible gusts to 55mph)


the goal is drop CHT's 15-20* and 3 kts speed gain. CHT rise or slow down=fail

[Spike]

I can't way to say "I knew you when."

Bohannon jr?

Spike

[hydroguy2]

well I don't know about that. gonna need sponsors before I can go much further.

With Kris only finding part time work since finishing her Master degree, money has been tight this winter. Mods are cheaper than gas. I even (god forbid) mentioned to Kris I might have to sell Aurora as we have been eating into our savings. Or trade her(aurora not kris) for a nice RV-3 and some cash. I figure she doesn't like to fly anyway.

"NO" was the response, "that plane is you"

then yesterday she found out she got her full time gig/promotion. her pay will more than double next week....Hooray Aurora has been spared from the chopping block. WHEW.

[captain_john]

"NO" was the response, "that plane is you".

She is an honorable woman!!!

Glad you guys are getting some traction now! Congrats to her and more cha-CHING!!!

Planes DON'T run on AVGas, they run on MONEY!!!

You can almost see the dollar bills in the slipstream on takeoff!

CJ

[hydroguy2]

Work-weather schedule allowed a little test run tonight. I had all the mods installed but figured that was not the proper way to test, SO:

Tonights run was to test the plenum seal work and the internal lower cowl outlet baffle and exhaust area cleanup. I tried to get the same conditions. But couldn't get OAT 02*C and 6650' DA. Also I didn't realize I also had an extra 0.5" MP tonight than during my baseline run. I did a little cleanup on the RamAir inlet too.

What does this mean?....I have no idea. I will say that that CHT's were the about the same(335-348)even though OAT was 15*C warmer. And I showed 189-192kts TAS. Baseline was 188-190.

I call it draw. It appears faster, the numbers look slightly better, but it could all be in the scatter. Next nice day, I'll install the cowl outlet extension and run again.