main gear and safety

[marbleturtle]

Forgetting to lower the gear is not an issue for me... I'll need to lower the nose gear every time I land so what's 2 more?!?!?!

 

Price is the biggest stumbling block for me. But since we are up in the 200mph club, resistance is exponentially higher than say 160mph so a 20+ gain seams reasonable. I wanted a 3rd tank as a sump for an automotive conversion engine with fuel injection, with retracts it can go in the bulkheads normally occupied by fixed gear. The gear down drag of the retracts gives a little extra slowing power on a steep final. The spar is designed for 10+ g force. Impact is cushioned by the rebound in the gear. Most high performance aircraft carry the gear in the same place. Wider track for better stability on the ground or trying to land in difficult conditions.

 

Everthing appears positive, I just don't know if I can get past the price for the hunk of metal parts you get in return. Decisions decisions.

[dust]

Well 20 mph sounds like too much, i just have a hard time believing it, all of the articles i have ever read said 6 mph or knotts? diference between rg and properly faired landing gear at 200 mph/knots (sorry can't remember if the articles stated knotts or mph)

 

So i will believe that the gear is the largest area i can have an affect on, i don't know if it is 20 or 15 or 10, i just plan on:

 

So dis is my plan, bolt on the gear, estimate the cruise additude and refare the gear using klaus s's suggested wartman aileron airfoil shape that doesn't provide lift in eithor direction and has very wide range of angle of attack acceptance. I'LL PROBABLY MAKE THEM REMOVABLE so i will be able to measure the diference.

 

Dat be the plan, so if it works i'll tell youall next year or so

 

enjoy the build

 

mike

[marbleturtle]

There are several different types of aircraft you can look at that have both faired gear and retract options. The difference quoted between the two is usually substantial.

 

I haven't seen any articles yet specifically related to the Cozy, but I don't think its unreasonable to expect a 20 mph increase. Part of the equation is the design of the prop. If someone converted to retracts without changing their prop to take advantage of the lower drag, then they may not see much improvement.

 

It would be like dropping a small block V8 in an old Hyundai without changing the gearing. The darn thing is still only going to do 80mph because the low gearing was designed for the lower hp.

 

Now switching to retracts is not adding power, but it does reduce drag. At the speeds the Cozy can travel, it seems reasonable that we can realize a good increase in speed with retracts and a higher pitched prop that can take advantage of the reduced drag. I guess the $6000 question is... how much?

[chuckthedog]

I don't know nutten about about main gear retracts sept you got less gas in the tanks cause the gear is hid where the gas was.

I do know about flyin Pickle Forks. The first thing ya gotta do to land, is slow it down. Step 1. throttle back. 2. Drop the GEAR. If ya don't, it wont slow down. 3. extend the belly board. 4. Land the plane. Don't let it land you.

How much gas dose a 200HP engine use to push a Cozy Motorhome to 12,000 feet?

How much gas dose it burn to keep it going 200 MPH, knots. whatever? Can you slap the kids in the back seat from the front seat?

Can you put a Tee in the radiator hose on a Mazda powerplant for a shower? When on a X country, Where do you put the gas cans, to carry the Auto gas your going to burn? And they said the only stupid question was the one that was the not asked.

[marbleturtle]

I KNOW I can't slap the kids in back from the front seat... that's why I'm putting an electric shocker (the cattle prod variety) in the back seats with push button activation from the front seats. That'll shut 'em up!!!

[Jim Sower]

There are no flying Cozys with retractable main mounts. There is at least one Long-EZ with Velocity retracts, but I don't have any figures on it. I believe (key word here) that his RG was a retrofit, so there might be some before/after figures available.

 

That said, the data available centers around Velocity which gets something on the order of 20 kts difference between FG and retract models. Of course, the FG Velocitys have all three struts hanging out there, so one would expect Velocity results to be better - to a very undetermined extent. SQ2000 is as comparable to Cozy as you're going to get with another airplane, and my hearsay impression is that they cruise upwards of 200 kts (which is around 20 kts better than Cozy). Another data point (for me) is that [partially] exposed wheels on retractable main mounts (which Velocity, Infinity and E-Racer all seem to have) causes a lot more drag than one would think. Wheels that are completely covered would therefore seem to be an opportunity for significant savings.

 

Soooooo, I figure that if I'm careful and lucky, I will get an extra 20 kts out of a 200+ hp 13B running at 7000 - 7500 rpm using a 2.85:1 redrive if I also completely cover my main wheels. If I buy Infinity instead of plans stuff, it seems I'll be out of pocket an additional $4000 for the MLG portion of the project.

 

For the sake of argument and round numbers, let's say I get an additional 10% airspeed and put myself over 200 kts fast cruise. That saving can be expressed as getting me to my destination 10% sooner than would be the case with FG (at same power setting and therefore the same fuel flow), which can also be expressed as getting me to the same destination for 10% less fuel. At about 10 gph fuel flow in my Mazda, that's one gph saving trip for trip, or $2.50 per hour. At 200 - 300 hrs per year, I save $500 - $750 per year on fuel so I pay for my retract in 5-1/3 to 8 years. Of course that's using avgas. The savings wouldn't be nearly as much with mogas, but the Mazda running mogas would save nearly $.80 - $1/gal over avgas on EVERY gallon which is $8 - $10 per hour which is $1600 - $3000 per year which completely pays for the ENTIRE engine/redrive installation AND retract in 4 - 7 years (half way to 3/4 of the way to TBO if I wass to articulate it that way).

 

Eight year payout on the RG is perhaps a long time, but every time I blow by some quarter million $ spam can that's forty bucks worth of pure joy (only 20 bucks for passing another canard pusher).

 

Please don't get real picky with the math and beat up on me about some pennies. I was painting with a pretty broad brush.

 

But you get my drift .... Jim S.

[Marc Zeitlin]

Originally posted by Jim Sower

There are no flying Cozys with retractable main mounts.

 

There's at least one. Marv Schuh's COZY III had 700 hours on it in 1995, and at some point he retrofitted the Infinity gear. There's a picture of his plane on the Infinity web site. Jim Marshall's MKIV has the Infinity gear as well, but I don't know if that plane has flown yet - I couldn't find an announcement in the newsletters.