Weight considerations with O-320

[Renegade007]

don't forget about the Lycoming 233 and or the AEIO 233 engines... a good mid range choice of 120 hp and lighter than the 235 engines.

Doc

[Lowrider]

Paul,

Forgive me for coming late to the party, but why didn't you folks use the full 1320 lbs for the LSA Panther design...seems that would increase flexibility a bit? I guess a longer wing would decrease roll rate but also increase stability but it is a very cool plane as is.

[psalter]

One thing that Dan and I would like to clarify, if we do increase the maximum gross weight, it will NOT apply to aircraft that is being used in the LSA category. To meet LSA criteria for stall speed, the gross weight of the Panther CANNOT exceed 1115 lbs with the long wing. This has nothing to do with the actual gross weight capacity of the structure.

As you will probably remember from ground school, stall speed is a function of weight, wing area, and lift of the wing. With our wing area and lift available, we had to lower the gross weight slightly during testing to meet the stall speed requirements. In the US, we are not allowed to use flaps in order to meet the stall speed requirements for LSA. An LSA aircraft stall speed is based on the clean configuration.

The moral of the story is keep it light, especially if you intend to use it in the LSA category.

I am not an expert in fuels by any means, but in studies that I read about on the effects of ethanol, here are some of the important problems.
1. Ethanol can damage some rubbers, plastics and sealants.
2. Ethanol absorbs water, and from what I read, that mix can form an acid, and cause corrosion of some types of aluminum and other types of materials.
3. Ethanol based fuels do not have a very long shelf life before they start breaking down. It is in the order of a couple of weeks, AVGAS can last a lot longer, more like months due to its formulation and additives.

There are other reasons as well, but these are the easiest to understand.

So, why can cars run it? They are designed with materials to withstand the detrimental effects of ethanol, not just in the engine, but the entire fuel system from tank to pumps to the injection system. And most people will use up a tank of gas in a car in a couple of weeks, so it doesn't it doesn't go bad in that time, and doesn't absorb as much moisture.

Most planes end up with gas sitting in them for long periods of time without being used (unless it is on a cross country trip). So they have more chance to go bad and collect moisture.

Basically, the longer you leave ethanol based fuels sit, the more problems you will have. Use it quick no matter what vehicle or equipment you use it in.

[Lowrider]

I think Ly Con says they can get 4 hp per cyl. with their "head smoothing". Add in some gains from electronic ignition, throttle body and a good Vetterman exhaust a 160 hp 0-320 might see an easy 180 or more with 9:1 pistons. Bump up to 10:1 pistons and 200 hp isn't out of the question...maybe.

Hi test mogas without corn is best but I think it's the potential problems with seals, hose and the like with the dreaded alcohol. Maybe someone smarter than I can confirm or comment on that.

[at7000ft]

I had an O-320 powered 1975 Grumman Traveler that I upgraded to High-Compression pistons (via STC). The STC artificially reduced the max RPM from 2700 to 2650 (2650 RPM was nominally 157.5 HP, which met the FAA "within 5% of rated power" rule to avoid having to run a full test flight regime. But realistically, it picked up a bunch of power and torque at every power setting. That "10 HP" increase made an amazing difference in ROC (from 650 FPM to over 1000 FPM in identical conditions). It didn't really change cruise speed much, except at higher altitudes, when the extra power made a bigger difference. At 8500-9500 feet, I could turn 150 more RPM with the HC engine, which translated into an additional 5+ KIAS of cruise.

But the biggest change that I noted was that fuel consumption reduced by almost exactly 1 GPH with the HC engine. It got to altitude a LOT faster, which meant less time at full throttle (and full rich mixture until above 5000 ft). I keep detailed information about fuel burn, so was able to determine the averages over a full-year period before and after the HC upgrade. Over a full year for each case, my average fuel consumption went from 8.3 GPH (before) to 7.4 GPH (after). And that's with me flying pretty much "max cruise" all the time, except when doing pattern work. (What's the point of owning a fast airplane, if you're going to fly slow?)

A high-compression O-320 is an amazingly efficient engine. The only drawback is that it can be a LOT harder to find an STC for auto-gas in certified aircraft. But that won't impact the Panther...

That's interesting Jim, there is little if any difference in price between a used 150 hp vs. 160 hp 320s, and fairly simple to upgrade a 150 hp.
Being able to use premium auto gas would be nice but the Lycoming people (unlike the Jab/Rotax people) say no alcohol can be used, but that may be what they have to say for the certified market. Very hard finding no-alcohol premium in CO.

Rick H

[Lowrider]

Rick, I'm with you!

The LSA I'm building is a high wing designed for an 0-200 but I've beefed up the front end and wings to take the 0-320 because of DA around here. We (Idaho) looses at least a couple planes per year to low powered planes at high density altitude and I choose not to be one of them.

The Panther/Cougar design is really beginning to make sense to me and if/when I move forward it will be with an 0-320 also.

[JimParker256]

I had an O-320 powered 1975 Grumman Traveler that I upgraded to High-Compression pistons (via STC). The STC artificially reduced the max RPM from 2700 to 2650 (2650 RPM was nominally 157.5 HP, which met the FAA "within 5% of rated power" rule to avoid having to run a full test flight regime. But realistically, it picked up a bunch of power and torque at every power setting. That "10 HP" increase made an amazing difference in ROC (from 650 FPM to over 1000 FPM in identical conditions). It didn't really change cruise speed much, except at higher altitudes, when the extra power made a bigger difference. At 8500-9500 feet, I could turn 150 more RPM with the HC engine, which translated into an additional 5+ KIAS of cruise.

But the biggest change that I noted was that fuel consumption reduced by almost exactly 1 GPH with the HC engine. It got to altitude a LOT faster, which meant less time at full throttle (and full rich mixture until above 5000 ft). I keep detailed information about fuel burn, so was able to determine the averages over a full-year period before and after the HC upgrade. Over a full year for each case, my average fuel consumption went from 8.3 GPH (before) to 7.4 GPH (after). And that's with me flying pretty much "max cruise" all the time, except when doing pattern work. (What's the point of owning a fast airplane, if you're going to fly slow?)

A high-compression O-320 is an amazingly efficient engine. The only drawback is that it can be a LOT harder to find an STC for auto-gas in certified aircraft. But that won't impact the Panther...

[jackinkeywest]

Rick,

I am by no means an 'expert' but I can confirm a properly built 0-320 will cruise nicely on 7 GPH at altitude. I flew my RV-7A (N174JL) w/0-320 and Hartzell C/S prop cross-country for approx. 90% of the hours I put on her (250ish) so I can speak with some authority on the fuel burn. That was a great airplane and the right engine setup flying cross country from Ventura, CA to Las Cruces, NM over a LOT of mountains.

If I take the plunge on building a Panther, I will probably go with the Corvair since I will be living in the 'flat-lands' of North Florida and spending more time at 3500' rather than at 10,500'. In your case, flying around CO in high DA, I vote for the 0-320 for the same reasons you mentioned.

Good luck,
Jack in Key West/Suwannee River near Bell, FL

[at7000ft]

I am building a long wing Panther and am planning on going with a used 320. Here is how I justify the 320, please let me know if I am missing something (maybe I will change my mind). And no I am not a Lycoming snob like most RVers, I fly behind a Corvair Pietenpol currently.

Used mid-time O-320s are cheaper than the smaller used Lycomings and Continentals or Jab 3300s or Rotaxes, and close to the cost of building a new Corvair.

Several RVers and LongEZ drivers at my airport with 320s claim to be able to get down to 7 gph at cruise, I use around 5.5 gph with my Corvair now (which is putting out probably 70 HP and my DA).

My airport (KFLY in CO) summer density altitude is between 9 and 10,000 ft. and I really would like more than 100-120 HP (which at 10,000 DA comes out to more like 70-84 HP).

The Lycoming cowling Dan designed on Bob Woolley's Panther looks fantastic (and it ain't even painted yet).

Yes it's heavy but as others have discussed with conical mount, wood prop, skytec starter, light generator, and me going on a diet (i'm 200 lbs now), acceptable, especially since Dan designed the Panther for light 320s (and Bob Woolley is proving that, and his is not all that light).

The 320 has been around since the 50s and there isn't an A&P at most any airport in the world that does't know how to work on one and find parts for one (I know it's prehistoric technology but try to find an A&P at a small airport that can diagnose a software problem in the ECU of your ULPower 260i that just stopped running).

Extreme reliability.

Anyone have a good used conical 320 they want to get rid of?

Rick H

[newamiga]

Tony.. I am really looking forward to seeing what your weight and balance comes in at. As a "svelte guy", I would love to try the 320 in the LSA compliant model, but the Jab may be a nice compromise in weight in power.

Carl