STC needed for c-65 to c-85 engine upgrade

[N95645]

Re: STC needed for c-65 to c-85 engine upgrade

Greetings all,

My first post here since joining a year ago. I'd be interested in the STC info for the upgrade too. My ride, a ' Apr '46 BC12D, already has the two wing tanks with the A-65-8 but was wondering about the other structural changes. Also, change of subject: any benefit to putting on wheel fairings, specifically any gain in airspeed at cruise? Thx!

GEO6

[pftcraft]

Re: STC needed for c-65 to c-85 engine upgrade

What are the changes and where do I get written or drawings... for fuel system changes, revised wing fitting, and minor structural changes..? I already have the two wing tanks.

I also have a Harer STC but I don't want to use it because I'm not interested in converting to F 19 with 1500gross. Are the drawings included with the Harer STC the same ones the factory had for doing the mods...?

[Pearson]

Re: STC needed for c-65 to c-85 engine upgrade

There are mountains of information concerning changing to a larger engine OR increasing the gross weight of your Taylorcraft. Sign in and use the search feature.

A few points of interest; a BC12D-85 and a Model 19 are pretty much the same airplane. The Harer STC gives you THREE different levels of modification. You get to choose WHICH level of modification you want to do.

In my opinion, the Harer STC is the simplest way to EITHER install a C-85 engine, add an electrical system, or increase your gross weight to 1500 lbs. The ONLY way you can increase the gross weight or add the electrical system, is to use a longer engine mount (Univair) that moves the engine 4" forward. That means you have to modify the cowl or find a used F-19 cowl.

OK so now what is involved with doing the Harer STC? Search feature will give more detailed info. But briefly, depending which level you choose, it involves; level #1-bolting on a C-85 engine (1280 lb gross wt.), level #2-bolting on a C-85 engine with a longer engine mount, installing larger bushings in the wing spar attach point (1500 lb gross wt.), level #3-same as level #2, but with an electrical system.

The fuel system changes involve larger fuel lines and a different vent system to the tanks. The minor structural changes involve taking out the baggage sling and installing a piece of plywood across the lower longerons, also adding side windows.

Wheel fairings make the plane look great and take away a few pounds of useful load. They also help keep mud from slinging up onto the bottom of your wings. If you are looking for a speed increase, I suggest you invest your time on tweaking the rigging of your plane.

If you want the drawings, I suggest you buy the Harer STC. I think Forrest has the info on that. But you really don't need the drawings to do the wing mods. It is just bigger bushings and weld a tiny little plate between the two attach fittings on each side.

If you use the search feature for; wing bushings, Harer STC, gross weight increase, you will find many many posts asking and describing what needs to be done and how to do it.

I hope this helps.

[akndrifter]

Re: STC needed for c-65 to c-85 engine upgrade

I did a little searching around, but couldn't find if the O-200 was aloud with the Harer STC. Maybe Im just missed it somewhere....

[Pearson]

Re: STC needed for c-65 to c-85 engine upgrade

The Harer STC is for a C-85 ONLY. You can do the Harer STC and THEN get a 337 for up to, I believe, 10 more horsepower, or maybe it is only 10% more horsepower. But even that will not get you up to a 100 HP O-200. People that are doing that are getting one time STCs or something else. Quite a few people are doing the Harer STC and then using a C-85 that has the STC to install the internal parts of an O-200. That is TWO separate STCs. As far as just taking an actual O-200 and using it with the Harer STC, you can't do that without additional paperwork.

[astjp2]

Re: STC needed for c-65 to c-85 engine upgrade

Its 10%, not 10 horsepower. Tim

[akndrifter]

Re: STC needed for c-65 to c-85 engine upgrade

Seems like C-90 would fit the bill well. I read up some, and saw Dano had one. Seems like a real performer. How hard would it be to get one approved these days?

[N95645]

Re: STC needed for c-65 to c-85 engine upgrade

ALCON or just happen to be interested,

What will the C-85 do for performance over the A-65? I expect you can get off the ground a lot quicker and climb should go up to too. What about cruise? Also I see that it will plus up the aircraft gross and useful load by 80 pounds.
Require a different prop too (metal vice wooden)?
I was thinking about doing the same thing but only if the performance is good enough. I didn't think that going to a A/C 75 would be worth it. Any thoughts from thems that knows?

GEO6
BC12D N95645

[N95645]

Re: STC needed for c-65 to c-85 engine upgrade

Richard,

Thanx and pardon my temporary case of the dumba$$ as i scanned but didn't read as closely as I should have. As for cruise, I am getting about 82mph right now at 2150 and a 3.5 gal per hour burn. My real interest is the 80 additional pounds of ACL as I resemble Baby Huey getting in and out of the cockpit. I'd like to be able to take someone else up legally upon occasion.

GEO6

[VictorBravo]

Re: STC needed for c-65 to c-85 engine upgrade

Richard,

Thanx and pardon my temporary case of the dumba$$ as i scanned but didn't read as closely as I should have. As for cruise, I am getting about 82mph right now at 2150 and a 3.5 gal per hour burn. My real interest is the 80 additional pounds of ACL as I resemble Baby Huey getting in and out of the cockpit. I'd like to be able to take someone else up legally upon occasion.

GEO6

The 85HP upgrade will give you a VERY significant benefit in takeoff and climb.

The Taylorcraft's big and efficient wing will make a lot of lift when you ask it to, but the increase in drag immediately "maxes out" a 65HP engine's ability to pull it through the air. That 20 extra HP (the torque really) overcomes that drag, allowing you to make full use of the wing's lifting ability.

The increase in cruise speed is minimal if you do not change propellers. I went from maybe 95 to 99 indicated using the same metal prop at easy cruise power. With a different metal cruise prop the speed went way up but the climb was only a little better than the 65HP engine. Metal prop upgrade alone will make a noticeable difference on either engine.

If someone could STC a modern composite two-position prop, the T-craft would be able to make VERY good use of it.

[astjp2]

Re: STC needed for c-65 to c-85 engine upgrade

Wasnt there an adjustable prop for the taper shaft 85 that was adjusted by turning a crank on the dash? Something like a beech Ryobi????

[Pearson]

Re: STC needed for c-65 to c-85 engine upgrade

about 82mph right now at 2150 and a 3.5 gal per hour burn

GEO6,

The numbers you quoted in your last post don't add up. If you are truly turning 2150 rpm, you should be getting another 10 mph and burning another half to 3/4 gallons per hour. I suggest you have your tach checked out.

As a comparison, I weigh 200lbs. With just me and only 12 gals of fuel onboard, I will indicate 91 to 93 mph, depending on density altitude. That is while turning 1950 rpm with a 45 pitch prop on a stock A-65. I usually burn between 4 and 4.25 gals/hour. At 2150 rpm I would be indicating around 95-96 mph.

Obviously rigging, air density, prop pitch, and other factors will affect your speed. But it really sounds to me like your tach is indicating higher than it should. I would be curious about what rpm you would indicate at full throttle in level flight. Also what prop pitch do you have?

[Pearson]

Re: STC needed for c-65 to c-85 engine upgrade

After reviewing the Harer STC I need to clarify what I posted on this thread earlier. In order to increase the gross wt to 1280 lbs you still have to install the larger bushings in the wings and weld the small plate between the two attach fittings. I guess the weight only goes to 1280 lbs because you don't move the engine forward with the longer engine mount.

There is nothing in the STC about "just bolting on a C-85" and getting the gross wt increase to 1280 lbs. There is also nothing about bolting on a C-85 and keeping the original 1200 lb gross wt. It only covers using the C-85 with the wing mods that give you the 1280 lb gross.

[Larry Lyons]

Re: STC needed for c-65 to c-85 engine upgrade

Richard, what size are the larger bushings called out in the Harer STC; I.D. & O.D.? And does the STC call for them out board too? Right now everything I have seen is at the root only.

[N95645]

Re: STC needed for c-65 to c-85 engine upgrade

Richard,

I wish I were getting your numbers. Tach was checked with the strobe thingy and 2150 actual reads 2238 on the gauge so that is what I usually cruise at. The gent I bought it from told me he was getting about 82 to 85 mph and he was also an A&P. I have the standard Sensenich wood 72CK42 prop on it. As for how it is rigged etc, I wouldn't have a clue as to how to address that. The finish was done with what I was told was that Blue River Process back in '99 when it was recovered. Not sure if that increased parasite drag or what. The engine was majored back in 2003 and the comp checks were all good at the last annual in June.

All I know is if I want it to get over 90 mph indicated I have to point the nose at the dirt. As for gas burn- it really has been very good. I am 6'2" and 245.

Bill, I had time last night to follow the threads after using the search engine. Don't think I will pursue the engine upgrade/gross increase while she flys just fine (but slow).

Tim