Wood Vs Metal turtledeck

Discussion in 'Pitts Fuselage & Empennage' started by Russ, Nov 20, 2017.

Help Support Biplane Forum by donating using the link above.
  1. Nov 20, 2017 #1

    Russ

    Russ

    Russ

    Member

    Joined:
    Sep 29, 2017
    Messages:
    9
    Likes Received:
    1
    Hey guys,

    Looking to start the build of the turtledeck, and after looking around the forum I am still trying to find which is lighter, wood or metal. Further to that where in the turtle deck can you reduce the former and skin thickness to maintain rigidity and structure, but throw a bit of weight out. Would like carbon, but will just stick with metal or wood on this one. Still looking to have a door and baggage area, thin as possible. Would aluminium formers with a bonded ply skin work? Does anyone have any idea of the finished weight?

    Cheers.
     
  2. Nov 20, 2017 #2

    Neil

    Neil

    Neil

    Well-Known Member Lifetime Supporter

    Joined:
    Nov 10, 2006
    Messages:
    6,060
    Likes Received:
    865
    Gender:
    Male
    Location:
    Monroe, Louisiana
    Mine is wood. I have a better picture somewhere. I'll see if I can find it. later.

    IMG_5728.JPG
     
  3. Nov 20, 2017 #3

    TFF1

    TFF1

    TFF1

    Well-Known Member

    Joined:
    Apr 30, 2010
    Messages:
    3,167
    Likes Received:
    576
    If it's only about weight, go aluminum. Weight wise it's going to be a wash. The aluminum will be less trouble over time. If you want to play racket ball on it, go wood.
     
  4. Nov 20, 2017 #4

    bf92

    bf92

    bf92

    Well-Known Member Lifetime Supporter

    Joined:
    Jan 1, 2008
    Messages:
    1,603
    Likes Received:
    379
    I made the turtledeck on the BF9-2 out of aluminum originally, but wasn't satisfied with it, so made the one I used out of wood. Gained 2.25lbs, but it was much stiffer, which was more important to me than weight. It's a working airplane, so I wanted it to be able to withstand lots of x-c with baggage, and "leaning" from spectators.

    Danny
     
  5. Nov 20, 2017 #5

    will moffitt

    will moffitt

    will moffitt

    Will moffitt Supporting Member

    Joined:
    Jul 23, 2012
    Messages:
    1,411
    Likes Received:
    342
    Gender:
    Male
    Location:
    Anacortes,wa
    Mine is fibreglass. Pretty girls and kids are offered the opportunity to sit in it, which they love. They always sit on the td matter how I tell them not to. Strength is important in this case.

    Will
     
  6. Nov 20, 2017 #6

    Knight Twister

    Knight Twister

    Knight Twister

    Member

    Joined:
    Jan 24, 2008
    Messages:
    2,680
    Likes Received:
    1,081
    I used aluminum on my S1, mainly because I had a set of factory bulkheads fall in my lap. If I ever build another Pitts I will use wood. Personal preference.
     
  7. Nov 20, 2017 #7

    PittsDriver68

    PittsDriver68

    PittsDriver68

    Well-Known Member

    Joined:
    Jan 9, 2013
    Messages:
    4,080
    Likes Received:
    1,120
    If you want light and strong, make it out of Divinycell core with one layer of carbon on each side. You can shape the core, carefully using a heat gun over some formers. Aircraft Spruce has the materials.

    Best of luck,

    Wes
     
  8. Nov 20, 2017 #8

    cwilliamrose

    cwilliamrose

    cwilliamrose

    Well-Known Member Lifetime Supporter

    Joined:
    Nov 10, 2009
    Messages:
    7,636
    Likes Received:
    1,648
    Location:
    SW Florida (94FL)
    I'm going with metal, personal preference for me as well plus the fact that I've never built one that way in the past. I'm not sure about the weight, my hunch is that aluminum is lighter.
     
  9. Nov 20, 2017 #9

    race38

    race38

    race38

    Member Lifetime Supporter

    Joined:
    Apr 20, 2012
    Messages:
    1,337
    Likes Received:
    277
    Years back, I saw a Laser with a side opening Turtledeck.
    Bulkhead at the seat and 1 forward of the vert stab, with dzus fasteners along the top longeron.
    Made access really nice.
    Was aluminum but could be carbon sheet. Might try that for mine WHEN ever I get there.
     
  10. Nov 20, 2017 #10

    PittsDriver68

    PittsDriver68

    PittsDriver68

    Well-Known Member

    Joined:
    Jan 9, 2013
    Messages:
    4,080
    Likes Received:
    1,120
    This time of year, when I have to take all of the seat parts out of my Pitts, climb into the airplane facing the tail, scrunch down as much as I can, and try to squeeze my upper body and a can of lube into the opening between the bottom of the turtleneck and the top of the battery, reach out as far as I can, and put a little lube on the elevator pushrod idler arm pivot and rod ends, I envy the Extra owners who just take off the top of the airplane and can easily access everything in the tail.

    Best of luck,

    Wes
     
    EAABipe40FF and dylanxpeters like this.
  11. Nov 20, 2017 #11

    cwilliamrose

    cwilliamrose

    cwilliamrose

    Well-Known Member Lifetime Supporter

    Joined:
    Nov 10, 2009
    Messages:
    7,636
    Likes Received:
    1,648
    Location:
    SW Florida (94FL)
    It's spots like that where you wish they had put an inspection ring.
     
  12. Nov 20, 2017 #12

    Jean-luc

    Jean-luc

    Jean-luc

    Well-Known Member Lifetime Supporter

    Joined:
    Jul 18, 2007
    Messages:
    676
    Likes Received:
    37
    The 1/16 " plywood is lighter than the .025" aluminum;only the 1/4" plywood bulkheads are heavier.Why not build the bulkheads with some balsa core between two layers of plywood !!!!
     
    smizo likes this.
  13. Nov 20, 2017 #13

    crankyklingon

    crankyklingon

    crankyklingon

    Well-Known Member

    Joined:
    Mar 25, 2010
    Messages:
    1,673
    Likes Received:
    697
    Here's my thoughts on the subject.
    Made mine from wood, 1/16 with 1/4 ply bulkheads with one layer of 4oz cloth over the outside. Still came out very light and the fwd door and bulkhead assembly is strong enough to be used as a guide to keep the belts up even with the shoulders for correct geometry.
    Also the whole floor is removable. This gives great access for servicing the battery and voltage regulator which are behind the seat. Also great for lubing the elevator push rods.
     
    Jean-luc likes this.
  14. Nov 21, 2017 #14

    chubb.rc

    chubb.rc

    chubb.rc

    Registered Users

    Joined:
    May 15, 2011
    Messages:
    132
    Likes Received:
    5
    What about doing stringers with cloth over it
     
  15. Nov 21, 2017 #15

    chubb.rc

    chubb.rc

    chubb.rc

    Registered Users

    Joined:
    May 15, 2011
    Messages:
    132
    Likes Received:
    5
    Like you do on the side of your plane
     
  16. Nov 21, 2017 #16

    cwilliamrose

    cwilliamrose

    cwilliamrose

    Well-Known Member Lifetime Supporter

    Joined:
    Nov 10, 2009
    Messages:
    7,636
    Likes Received:
    1,648
    Location:
    SW Florida (94FL)
    Stringers & fabric can be easily damaged by stuff inside the turtledeck. If the T-deck is wood or metal you can rest a bit easier about what you put in there and how tightly you pack it.
     
  17. Nov 21, 2017 #17

    chubb.rc

    chubb.rc

    chubb.rc

    Registered Users

    Joined:
    May 15, 2011
    Messages:
    132
    Likes Received:
    5
    That is true but if your looking for it to be light wouldn't that be a lighter choice. If your looking for light your pry not putting heavy stuff in there sport flying.
     
  18. Nov 21, 2017 #18

    cwilliamrose

    cwilliamrose

    cwilliamrose

    Well-Known Member Lifetime Supporter

    Joined:
    Nov 10, 2009
    Messages:
    7,636
    Likes Received:
    1,648
    Location:
    SW Florida (94FL)
    Even airplanes used for competition need to have a practical side. If you're going to spend a week at the Nationals you better figure out how to take a week's worth of stuff with you. You have to be creative in your use of the available space and you have to be able to do some stuffing to get it all in there.

    I'm not sure multiple stringers are any lighter than the skins they replace but they are not nearly as bullet-proof.
     
  19. Nov 21, 2017 #19

    wzm

    wzm

    wzm

    Well-Known Member

    Joined:
    Sep 26, 2016
    Messages:
    172
    Likes Received:
    121
    The difficulty of construction is worth mentioning. In the optional aluminum turtledeck plans, the third bulkhead has a really tight radius corner, and a 5" flanged hole in the middle of it. A 5" flaring die is not a cheap one time use tool (http://www.trick-tools.com/5_inch_Mittler_Bros_Aircraft_Punch_Flare_Tool_1300_044AC35_2216), and it's easy to get folds when bending a flange in the 1" radius corner at the top of the bulkhead. Press forming the third bulkhead might work better, but the front two bulkheads are too large to press form at home.

    I halfway suspect the difficulty of forming nice bulkheads is why so many turtledecks are wood.

    On the weight front, it's important to remember that the turtledeck is one of the furthest aft places you can save weight. A few pounds at the turtledeck will do more for moving the CG forward then dropping a few pounds in instruments.
     
  20. Nov 21, 2017 #20

    Knight Twister

    Knight Twister

    Knight Twister

    Member

    Joined:
    Jan 24, 2008
    Messages:
    2,680
    Likes Received:
    1,081
    You can fly cut that 5 inch hole and flange with a bob stick. Homebuilding legend Bob Barrows used to flange every lightening hole with a simple stick.
     

Share This Page