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  1. #1

    Question Building a 108" C-130. Needing some outside input

    I am building a 108" C-130 from scratch. This bird will have retracts, brakes, fowler flaps, functioning ramp/door, cargo rails, and will be used to airdrop pallets, Jeeps, ect. I am quite a ways into the build and have several questions.
    1. This aircraft will have a modified flat bottom airfoil, a wingspan of 108", a chord of 12.5" and about 2.5" of camber. I don't want to overbuild this thing but am worried about the overall strength as I have never done a complete scratch build. It goes without saying but i have no intentions of pulling high g`s in this bird.

    My initial thought is to make a 1 piece detachable wing using 2 parallel boxed spars, one 3" aft and one 9" aft. This is very similar to the actual aircraft except it uses I-beam spars and the outer wings detach outboard of the #2 and 3 engines. I would love to set up mine to detach the same way but don`t want to create a weak point or add the excess weigh of aluminum tubes or carbon rods. I was planning to use 3/8x1/4 or 1/2x1/4 hardwood for the upper and lower parts of the spar and 1/8 balsa for sheer web. I am hoping that someone with a little more experience could give me some insight, i would estimate that the fuselage will weigh between 8 and 10 lbs. fully sheeted with radio and servos. all of the fuel/batteries will be in the wing aft of each engine or in the aft nacelle, this should help with wing flex a bit. This brings me to my second question

    2. Power plant: First of all i need to decide how much thrust i will need, I planed to use 4x .25 or .35 glow motors, however i am terrified of syncing and keeping 4 glow motors running. I also thought of using 4 electrics for reliability but have ZERO experience with them. Thoughts?

    I took a picture this morning while cleaning the garage to show where i am at. Click image for larger version. 

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  2. #2
    thailazer's Avatar
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    Good luck with this project. If it helps, my 12.5 lb 100 inch span Twin Otters had 1/8 inch by 3/8 inch spruce spars top and bottom with a balsa sheer web that made up a strong D tube up front. Had two 20 inch long ply (3/32 inch) dihederal shaped carry throughs on the wing center, one on the main spar and another one a bit back to carry the high moments at the wing center. You are right in being careful to not overbuild it as weight will build up in a hurry. My wing was stiff as a board when it was done and very light. For engines, the OS25 AXs should be plenty of power. For syncing, just make sure you have clevises that can adjust the mechanical carb rotation to make them all exact. Exact RPM syncing is not as important as getting things close and keeping all the engines running. (i.e. RPM can be quite different but thrust will be pretty close.) You might consider running all the glo plugs to a central connector to simplify start up. Also... I would add some horizontal ribs on your vertical stab. It looks a bit under-built with just those long vertical ribs there.
    Tiger Flyer #49

  3. #3
    Thanks for the input. After looking at several different threads i decided using 1/4X1/2 hardwood to build fore and aft boxed spars, there will be two in the wing which should make it extreemely strong for little weight. I am most likely going to go electric even though i dont have any experience with them, I will feel a lot safer in knowing about the only way to loose a motor is to fry it or drain the battery. As for the vertical stab, it will be fully sheeted just as the horizontal stab is and as the fulilage and wing will be.

  4. #4


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