FX3 with 80 or 83 inch prop

[hawgdrvr]

Hello,

Doing research on a FX3 build and looking for opinions on the prop size. 80 vs. 83 inch and then of course 26 vs. 29 tires as the 29 is the min tire for the 83. Flying will mainly be east coast (VA) grass strips, nothing extreme backcountry in the near future.

I've been advised 83 for resale but in researching this forum there is some discussion where 80 may be better for lower altitude environments such as east coast vs. western mountain areas. Western may be in my future, I don't know but currently I live in VA.

Looking forward to your opinions and any real data from those that may have flown both.

Thank you.

[hawgdrvr]

I think for my use the 8.50 x 6 tires and 80 inch prop would probably suffice here in the VA area and save a lot of money. The problem is will I get "two'foot'itis" and wish I had the bigger prop? What if I move to the northwest to enjoy more backcountry flying and wish I had the bigger prop at elevation and larger tires? Of course resale has to be considered as someone moving from 8.50 x 6 tires to 29 or larger and a 83" prop is going to get hit with about a $15-20K price tag.

Has anyone seen or flown a FX3 with stock 8.50 x 6 tires and an 80 inch prop and can share the experience? How was the performance? Obviously the bias of backcountry with bush tires has to be removed here, just looking for honest observations of the default FX3 config (8.50 x 6 and 80" prop).

[Tsquared]

Neal,

I have the 80” prop and 26” bush wheels on my FX3 that I picked up in June. For reference I’ve got 55 hrs in type but only 2 flights (2hrs total) on demo FX3 with the 83” prop and 29” wheels so my experience in both is limited. My previous tailwheel time was in a grossly underpowered Champ 7EC and a Decathlon 8KCAB

I’m told that the 83/29 combo climbs about 200fpm better but I can’t really notice any practical difference. My 80/26 climbs plenty hard on takeoff and outperforms any GA bird I’ve flown.

Like you I debated on the 80' or 83” prop. I had several discussions with Cubcrafter folks prior to the build and decided to stay with the 80” for now. I live in MN and don’t envision doing any hard back country flying or high altitude/high DA until I retire and move to AZ, TX or some other state that doesn’t have snow and subzero temps for 6 months of the year. Since I have the option of landing on lakes without needing floats, the 80” prop also give me the option of putting skis on it in the winter.

For now the benefit are a higher cruise speed or similar cruise to a 83’/29” but burning less gas. Normal relaxed cruise for me is 62% power at 24 squared which gets me IAS 103 burning 7.4gph. TAS was 109mph. Flying the plane home 70% power at 24 squared got me 119 IAS/128 TAS @ 10.5gph. a 25mph tail wind got me a ground speed of 152 for that flight home which was helpful.
A slow evening flight with the door and window open is 44% power at 17.0in/2380rpm which gets me 77mph IAS/82 TAS burning 5.3gph.

I”m told the 8.5” tire will cruise faster, but are “squirrelly” on the ground. Can’t speak to that but 26” bush wheels and ACME Black Op shocks make for a very easy to taxi and land bird.

By the time I’m ready to retire and move west, I’ll be close to overall on the engine/prop. I’ll reexamine my type of flying and will think about trading up to 83/29 then, but for now I have no regrets for going with the 80/26 combo.

Trent

[hawgdrvr]

Excellent info Trent - thank you.

[kiwibob]

Doing research on a FX3 build and looking for opinions on the prop size. 80 vs. 83 inch and then of course 26 vs. 29 tires as the 29 is the min tire for the 83. Flying will mainly be east coast (VA) grass strips, nothing extreme backcountry in the near future.

I had the LSA Carbon Cub prior to the FX-3 and did about 500 hours on it with 8.5s and the fixed pitch Catto. There were definitely places that I was unwilling to land due to soft strip or sand. Interestingly when I sold it the first thing that the new owner did was put it on 29", mostly for the "look".

I bought the FX-3 with 83/29" on the basis that if I ever wanted them then at original purchase would be the cheapest time to get them. A new 83" Hartzell looks like it's going to be $13-15k plus freight and tax and plus fitting and paperwork. You get it now for $530 plus the tyres but you're going to want them - unless your home field is not grass in which case you might not.

As for performance I doubt that I'd notice unless it makes a very significant difference. What I do know is that there's very little time for reflection between pushing the noise lever and leaving the ground. It happens in a rush.

Finally I've done just over 100 hours in the FX-3 and I still just love the look and knowing that the limiting factor is not the airplane but my competance and competence.

As always YMMV.

[hawgdrvr]

Thanks Bob, great insight. I'm not sure about landing on the grass at my home field (KFCI) yet, but I'm also not sure this will remain my home field so a lot of things in play.

I know there is the debate on SS vs. FX3, someone just emailed me about this. I'd love to see a post from people such as yourself having flown both and get your factual opinions on the comparison of the two so people making a purchase decision can listen to the experiences from people like yourself. I'm set on the FX3 but I did have the time where I was being educated on both and that decision is one that needs to be considered. For another topic, but it's good to have people like you that have owned both to share your experiences should you care to share.

[Rick Bosshardt]

Neal,
we can incorporate this topic in our hangar chat when you come to AZ as well! Ive owned two SS's, and am on my second FX3!
Rick

[chipallen]

You really should do the 29’s and the 83” prop for best performance and, as mentioned, MUCH less expensive now rather than later. You and I will talk more this week.

[kiwibob]

Thanks Bob, great insight. I'm not sure about landing on the grass at my home field (KFCI) yet, but I'm also not sure this will remain my home field so a lot of things in play.

I know there is the debate on SS vs. FX3, someone just emailed me about this. I'd love to see a post from people such as yourself having flown both and get your factual opinions on the comparison of the two so people making a purchase decision can listen to the experiences from people like yourself. I'm set on the FX3 but I did have the time where I was being educated on both and that decision is one that needs to be considered. For another topic, but it's good to have people like you that have owned both to share your experiences should you care to share.

You'll get some great info from Rick and Chip. You also might want to watch Flightchops on YouTube who does a back to back SS, EX and Xcub with Randy here.

I've got four points of difference that you would notice.

FX-3 has way more useful load. The SS may have two seats but one is for a child if you want to stay legal. No way can you have two adults, full fuel and gear in the SS unless said adults are pretty small. Otoh the FX-3 will swallow pretty much anything you want to put in it, two (kiwi size) adults, camping gear, full fuel and a gerry can to top up and it's still legal.

The FX-3 is heavier and uses much more fuel. Economy cruise at 23 squared LoP is 7.6ish gph. My SS running at 1800/1900rpm and leaned by the pull until it coughs method was about 4.5 gph. Makes the full tank range about the same as the SS.

If it goes quiet the FX-3 goes full fine and there is enormous drag from the prop. So much so I rarely need to side slip. The down side of this is if the engine quits you're going to land somewhere very close by.

Finally I just loved the build process. I'm never going to build a plane that I'd want to fly in but the builder assist program was a real treat. I learnt a whole lot and although it was pretty tiring it was well worth while in understanding about the aircraft and knowing that the team at CC would not let anything sub standard though.

Either way you're going to have a blast.

[turbopilot]

FX-3 has way more useful load. The SS may have two seats but one is for a child if you want to stay legal. No way can you have two adults, full fuel and gear in the SS unless said adults are pretty small. Otoh the FX-3 will swallow pretty much anything you want to put in it, two (kiwi size) adults, camping gear, full fuel and a gerry can to top up and it's still legal.

The FX-3 is heavier and uses much more fuel. Economy cruise at 23 squared LoP is 7.6ish gph. My SS running at 1800/1900rpm and leaned by the pull until it coughs method was about 4.5 gph. Makes the full tank range about the same as the SS.

If it goes quiet the FX-3 goes full fine and there is enormous drag from the prop. So much so I rarely need to side slip. The down side of this is if the engine quits you're going to land somewhere very close by.

I have 10 years flying the SS ELSA. No years flying either FX model. So let's get a little more analytical about the differences. It would be interesting to see a survey about what percentage of time a typical Carbon Cub owner flys alone. In my case probably 95%. In my 10 years watching Carbon Cub owners fly in and out of airports the vast majority are flying alone. So if your operations are mainly single pilot the weight limits of the SS ELSA are very easy to meet for routine local missions.

So let's tease apart the differences between the SS and FX-3. We can immediately put aside the elephant in the room. The FX will legally carry 680 lbs more than the SS. If you really need to haul around 680 lbs routinely the discussion ends, the FX is the right plane for you.

But in my 10 years of flying Carbon Cubs that is not how they are typically operated. I have never personally had a mission where carrying another 680 lbs was required. Another 200 would be nice but not 680 lbs. Most Carbon Cubs are operated single pilot for a nice 1 or 2 hour flight. Why? Because the Carbon Cub is so much fun to fly light. I would guess 80% of my hours in the SS are single pilot with 12 gallons of fuel at around 1,200 lbs gross. That is the fun mode in an SS or any Carbon Cub. You can't be too light.

My third Carbon Cub is now coming down the line as I write this. It is another SS. I wrestled with the decision for over a year about whether to get an FX3 or another SS. I never considered an XCub. Here is my bottom line comparison:

1. The FX basic weight is approximately 130 lbs more than the SS when adjusted for the differences.
2. Around 40 net pounds goes to the constant speed prop.
3. Around 30 pounds to the two fuel pumps, plumbing to support the fuel injected engine and heavier engine.
4. Additional weight to support the structure needed for higher gross weight and the new aileron system.

So the additional weight added by the new features of an FX basically added the same weight to the airplane as taking my wife along on every trip I made in the SS. Do you really want your wife with you on every trip.

What is gained by those FX features. This was the hard part of the analysis for me. The SS comes with a fixed pitch cruise prop that weighs 14 lbs. I had a hard time getting performance numbers about what the additional weight of the constant speed prop got me. Some have suggested about 100' less in takeoff roll. But my SS will take off in 60' with a cruise prop. So I scratched my head on that one. What does the additional weight, complexity and maintenance cost really get me with a constant speed prop that I did not all ready have with a light SS with a fixed pitch cruise prop. Still searching for that one. 60' takeoff roll is pretty good.

Fuel injection really made it hard for me. I really wanted fuel injection. That old Stroker 340 just cannot get its leaning act together. So fuel injection was the major issue pushing to the FX. But then we trade simplicity for complexity and additional weight. Fuel injection requires 2 fuel pumps, the old Stroker 340 has none. Just two more items to fail. Was a smother, slightly more efficient engine worth the weight, cost and complexity? My conclusion was yes and I wanted it.

The new aileron system was way over due once CubCrafters went to the awful 44 gallon tank design. All that lateral fuel added to an all ready heavy stick in roll. But it is a 44 gallon tank system with 5 gallons unusable. That is 30 lbs of dead weight. Ugh.

So those are the major differences in the two airplanes once you get by that pesky little problem of a totally artificial constraint on the gross weight limits of the SS with the LSA regulation. The SS was designed for 1,850 lb gross weight, we are just waiting for a really stupid regulation to change.

So in the end my year long analysis it came down to a very simple decision. Do I really need to carry around another 680 lbs in my Cub on a routine basis. Once that was answered the analysis got easier.

And now back to the questioned asked in this thread. Does an FX need an 83" prop and 29" tires? Where in the lower 48 do you really need those features if you are not needing to carry 680 more pounds? Add a pound for the heavier prop and 10 pounds for 29" tires over 26", then an FX 130 lbs heavier, and you have an airplane now 141 lbs heavier than an SS on a comparable basis. All that additional weight will more than offset any performance gains added by the additional FX features in take off roll and landing roll. It appears to be a zero sum game.

My solution was to order another SS, this time with a parachute and a belly fuel tank. The SS will have standard 24 gallon tanks with the belly tank available for the rare times I need more fuel. The belly tank weighs 19 lbs and unusable fuel is just de minimus. The tank easily comes off when not needed. We can argue the virtues of the BRS parachute in another thread. Having flown a Cirrus SR22 for 10 years I felt naked without one. It is 41 lbs of life saving dead weight. There may be an occasion when the decision will seem right. Yikes 41 lbs of dead weight, the same as a constant speed prop. Think about it.

My 2 cents in the great SS vs FX debate.