Page 3 of 5 FirstFirst 12345 LastLast
Results 21 to 30 of 42

Thread: FX3 Wing Fuel Tank Recommendation?

  1. #21
    Senior Member
    Join Date
    Jul 2015
    Location
    Broken Arrow, OK
    Posts
    841

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Bob,

    I had asked other builders to please repeat this test and report and I haven't found anyone yet that has. I've even asked several builders I've helped and they didn't do it either. I guess everyone is not as curious as I am but I wish someone would so we can get repeatability.

    I did not separate the fuel tanks as they come from the factory already assembled and ready to install. The 12.0 lbs was both fuels tanks with hoses and all hardware attached to them as they would drop into the bay. The other thing that would add weight to that would be the straps that hold them in and then the larger fuel cover that goes over both fuel bays with extended fuel.

    Obviously there is no way I could come up with a generic statement on unusable fuel since my last 2 airplanes have varied by quite a bit. That is why I do each airplane so I know what THAT AIRPLANE will do. Since I'm not going to go re-create the flight configuration needed to make the most fuel unusable, I'll just have to rely on what CC says and that is 39 gallons usable (5 gallons unusable) which is 1 gallon less than the same tanks in an EX2. Why the difference? I'm not sure. The rear spar is different on the EX3 and possibly the power difference in the CC363i will make a difference????? I have no other ideas.

    What I do know, and the importance to me is that I KNOW if I'm low on fuel for whatever reason.....i will fly it level as best I can do until touchdown with the fuel selector on BOTH and I know how much fuel I need for it to continue to flow.

    If you read on down in the post you will see my March, 2020 update on the last airplane I did which different. There was only about 3/4 of 1 gallon in each wing unusable (when fuel selector on BOTH) and I was actually able to account for the tanks and lines holding right at 44 gallons. So, essentially......I would ASSUME then that I can fly this airplane down to only 42.5 gallons before it runs out instead of only 39 listed.....AS LONG AS I'M FLYING STRAIGHT AND LEVEL AND HAVE FUEL SELECTOR ON BOTH.

    Anyway, that's just what I've found.


    Quote Originally Posted by turbopilot View Post
    Dave, excellent well documented information. Sure wish we could get this from CubCrafters. So is the quote below from post 131 of thread your current bottom line for the 44 gallon tank option. Given the variability you have seen in your airplanes do you have "fail safe" bottom line the would account for the variability seen in all FX's? Two issues now emerging. What are the "dead" weight issues associated with the 44 gallon versus 24 gallon systems and how much fuel is really available for both tanking systems.

    Did you ever weigh the 10 gallon tank and hardware alone? CubCrafters did tell me they think it is 17 lbs or 8.5 lbs per tank but based on your weights for both tanks I wonder.


    THE FULL FUEL CAPACITY THEN IS 42.5 WITH ADVERTISED 5 GALLONS UNUSABLE IN ALL CONFIGURATIONS THAT MAKES 37.5 GALLONS USEABLE AND NOT 39 AS ADVERTISED.
    I do know from my test though that actually there was only 2.5 gallons unusable in the static, level configuration for 40.0 useable.
    Last edited by Daveembry; 09-04-2020 at 10:44 AM.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  2. #22
    Senior Member turbopilot's Avatar
    Join Date
    Feb 2010
    Location
    La Quinta, CA
    Posts
    536

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Quote Originally Posted by Andy View Post
    You make arguments that may well apply to an SS but the OP was asking about an FX-3.

    Weight simply isn't an issue for me.
    It is for me. Old habit I cannot break.

    So the arguments apply to both SS and FX if your goal is to have an airplane with lowest possible empty weight for your missions. We had this discussion over in the 80 vs 83 inch prop thread. Weight is weight whether it is payload weight or empty airplane weight.

    I have been flying the Carbon Cub since it was introduced. Those of us from the early days have become weight obsessed, for sure. That was the primary goal for the first Carbon Cubs. Every part was evaluated down to the once in those days. So hard habits are hard to break. My approach to this airplane is to pull every once of "fat" out and have an airplane with no compromises for the mission it will fly. That is very hard to do as these new enhancements and options come along.

    So I plead guilty to being weight obsessed but only for weight that does nothing to serve the mission.
    Bob Anderson, CC11-00435, N94RA

  3. #23
    Senior Member Andy's Avatar
    Join Date
    Dec 2019
    Location
    Glendale, AZ
    Posts
    714

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Quote Originally Posted by Daveembry View Post

    Also to be clear, as I stated....it was in a "level flight attitude" as prescribed by CC and not "fuselage level".
    The CubCrafters leveling procedure for weighing is by reference the front and rear spar carry throughs. I also witnessed the repair center avionics guys using the door frame as a level reference for ADAHRS alignment.

    Both procedures use a level reference that is only approximately related to the aircraft attitude in level flight. The attitude for level flight is a variable that depends on factors including weight, airspeed, thrust, flap setting, CG position etc.

    The starting point for the weighing procedure is "obtain an approximate flight level attitude". The only part of that which I understand is "approximate".

    My only reason for commenting on this is that the level flight condition at which you approach fuel exhaustion is not likely to be the same as the "level" condition in which you made the test.
    Last edited by Andy; 09-04-2020 at 11:05 AM.

  4. #24
    Senior Member
    Join Date
    Jul 2015
    Location
    Broken Arrow, OK
    Posts
    841

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Well OK then....

    In any case, in an "approximate flight level attitude"....I'm confident that the fuel is gonna go into the fuel lines exiting the tanks. The main different to be noted is that this attitude is much different than in a 3 point condition if people are testing. For the purposes of this discussion, I think that is irrelevant. But again......just my thoughts and I'm not going to micro-analyze it.

    Quote Originally Posted by Andy View Post
    The CubCrafters leveling procedure for weighing is by reference the front and rear spar carry throughs. I also witnessed the repair center avionics guys using the door frame as a level reference for ADAHRS alignment.

    Both procedures use a level reference that is only approximately related to the aircraft attitude in level flight. The attitude for level flight is a variable that depends on factors including weight, airspeed, thrust, flap setting, CG position etc.

    The starting point for the weighing procedure is "obtain an approximate flight level attitude". The only part of that which I understand is "approximate".

    My only reason for commenting on this is that the level flight condition at which you approach fuel exhaustion is not likely to be the same as the "level" condition in which you made the test.
    Dave Embry
    "You only live once.......but if you do it right.........once is enough."..

  5. #25
    Senior Member
    Join Date
    Jul 2020
    Location
    FL001
    Posts
    282

    Default Re: FX3 Wing Fuel Tank Recommendation?

    The moral of the story and question is would any FX3 owner remove the extended range tanks with presumed impact on resale value? Are FX3 owners obsessed with weight like the initial breed of SS owners? We have a bigger engine, bigger prop, higher fuel consumption, higher lift capacity due to engine/prop. We have the ability to carry more cargo via a cargo pod for camping trips, travel, and those like ME that simply cannot pack light.

    It comes down to WHY? Why would you do that? To me I would not and will not. I am not obsessed with weight, quite the contrary. I'm adding BRS, I'm adding a cargo pod (Carbon Concepts at some point) and I'm going 100% urethane paint and zero polytone, and I just ate ice cream!

    I figured I'd raise this question as it needs wider discussion than the small group that has been discussing it and see what other opinions are mainly from FX3 owners in regards to the extended range tanks.

  6. #26
    Member
    Join Date
    Oct 2015
    Location
    Atlanta, GA
    Posts
    62

    Default Re: FX3 Wing Fuel Tank Recommendation?

    I would love to hear others opine.

    What is the altitude above which the BRS is effective? Is it like the Cirrus? At 500’.


    Sent from my iPad using Tapatalk

  7. #27
    Senior Member
    Join Date
    Jul 2020
    Location
    FL001
    Posts
    282

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Quote Originally Posted by Schwbo View Post
    I would love to hear others opine.

    What is the altitude above which the BRS is effective? Is it like the Cirrus? At 500’.
    The ROT I hear is if you need it pull it and don't worry about altitude or airspeed, you are a passenger at this point. The other number I've heard is 100ft but you know of all the factors that weigh in (speed, etc.).
    Last edited by hawgdrvr; 09-04-2020 at 11:41 AM.

  8. #28
    Senior Member chipallen's Avatar
    Join Date
    Jan 2010
    Location
    Marietta, GA
    Posts
    802

    Default Re: FX3 Wing Fuel Tank Recommendation?

    We have a FX-3 owner who had an accident a couple of years ago. He is a "Cirrus guy" and he told me that the BRS would not have done anything to help in his situation (low and slow). Although it might take 500 ft. for the chute to fully deploy, below that it could still slow you down and make a deadly accident a survivable one. I'm personally not a big fan of the BRS,(and giving up control of the airplane when you pull the red handle), but I'm glad we have that option for those that are.

    As to standard vs. long range fuel tanks, I don't really want to be the sales guy tasked with selling an FX-3 with standard tanks; that's not what the market demands and after selling over 100 CubCrafters airplanes over the past 12 years, I am very sensitive to building airplanes that I know will have good resale value.

    Chip Allen

    SWT Aviation, Inc.
    Cubcrafters Southeast Sales Center
    Marietta, GA

  9. #29
    Senior Member turbopilot's Avatar
    Join Date
    Feb 2010
    Location
    La Quinta, CA
    Posts
    536

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Quote Originally Posted by chipallen View Post

    As to standard vs. long range fuel tanks, I don't really want to be the sales guy tasked with selling an FX-3 with standard tanks; that's not what the market demands and after selling over 100 CubCrafters airplanes over the past 12 years, I am very sensitive to building airplanes that I know will have good resale value.
    Chip, two used FX's sitting on your lot identical in every respect. One holds 44 gallons in the wings the other holds 54 gallons (24 the wings and 30 in the belly) with a $6,000 belly pod option that can go on and off at will. Yet the empty weight of the second FX is less than the first. I submit the airplane with the belly tank is the one with "long range fuel".

    I know which one I would buy. Just not buying this resale issue because of a difference of where more the fuel is stored.

    As to BRS. Given the low airspeeds of the CC you pull it any time you think you are going to hit something faster than 25 feet per second (17 mph), the descend rate of the CC under the chute. After flying SR22's for 10 years I feel naked without it.
    Last edited by turbopilot; 09-04-2020 at 12:05 PM.
    Bob Anderson, CC11-00435, N94RA

  10. #30
    Senior Member turbopilot's Avatar
    Join Date
    Feb 2010
    Location
    La Quinta, CA
    Posts
    536

    Default Re: FX3 Wing Fuel Tank Recommendation?

    Quote Originally Posted by hawgdrvr View Post
    Are FX3 owners obsessed with weight like the initial breed of SS owners? We have a bigger engine, bigger prop, higher fuel consumption, higher lift capacity due to engine/prop.
    .
    As we have covered elsewhere, the gross weight adjusted Vo (maneuvering speed) of the SS and FX are the same. The approved maneuvering speed increases in the FX with more weight over the SS but then you pay the price in performance as the weight increases in the FX above the limited 1,320 lbs in the SS. For reasons I don't understand the FX maneuvering speed is limited to 106 mph at 2,000 lbs while the SS is limed to 97 mph at 1320 lbs. Seems like FX should have a higher Vo at 2,000 lbs. But then XCub has Vo of 99 mph at 2,300 lbs. So go figure.
    Last edited by turbopilot; 09-04-2020 at 09:52 PM.
    Bob Anderson, CC11-00435, N94RA

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •