Recent content by RPM314

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  1. RPM314

    Engine options for my Lazair

    Hey, that's my neck of the woods. IDK if you're still considering electric but I wanted to chip in the options I was aware of. The rotomax is the most economical in this power range but it's a bit heavier than necessary. In case you haven't come across them already, Hacker motors has offerings...
  2. RPM314

    Testing a method for making spar caps inside a sandwich panel

    I think I see what you mean Billski, the cross loads in the resin will eat into its ability to take shear loads between the fibers, for example. Thanks for pointing me towards the correct reading about this. It's my bad for being ambiguous, but I originally meant that the higher section modulus...
  3. RPM314

    Testing a method for making moldless-ish D tube skins

    Possibly. The break even point in weight between that (outer skin only) and sandwich skin will be in the neighborhood of 10mm foam thickness, which might be a ground handling issue if the inside surface is unsupported.
  4. RPM314

    Testing a method for making spar caps inside a sandwich panel

    The point about reduced strength might be valid. For a 0.3 mm plate curved to the ~600mm radius of the top of my airfoil, the plate surface is placed under 0.025% strain, compared to 3.5% (140x) breaking strain of a typical West system epoxy (I know that pultrusions are made with bis F but...
  5. RPM314

    Testing a method for making moldless-ish D tube skins

    Yeah, the back of my napkin says that 1mm would be enough for everything other than a snap roll. But I also just ran a check for stiffness, and while both carbon and birch check out for torsional frequency, 1mm birch skin has a critical speed for roll reversal around 90 knots compared to over...
  6. RPM314

    Testing a method for making spar caps inside a sandwich panel

    Apologies for the ambiguity. The carbon is a replacement for the foam, it is butt jointed to it instead of laid on top. If the foam and carbon were different thicknesses, you would need to bevel the foam one way or another to make the transition.
  7. RPM314

    Testing a method for making moldless-ish D tube skins

    For sure, that's historically the most common way to do it. But for the design I'm considering, the carbon fiber sandwich panel skin is limited by the minimum gauge of available materials to (nominally) about 4kg. A +/-45deg birch plywood skin for the same D tube would be limited by strength to...
  8. RPM314

    Testing a method for making moldless-ish D tube skins

    Is this the wing in question? Makes sense to me, making a rounded spar at the LE before bagging the skin would surely reduce the sag close to zero. I don't think plywood skins are viable for ultralight gliders though, I would probably stick with fabric.
  9. RPM314

    Testing a method for making spar caps inside a sandwich panel

    I mean that the radius of curvature I got out of the carbon was close to that of the upper airfoil surface, though admittedly I didn't try to quantify it. The foam in question is divinycell, which is a PVC foam. All PVC foams are known for having good compressive strength. I'm not quite sure...
  10. RPM314

    Testing a method for making spar caps inside a sandwich panel

    Hi everybody, After learning that it's possible to purchase carbon pultruded strips from China in 0.3 mm thickness, I wanted to test if it were possible to form a spar cap out of these strips to match the curvature of an airfoil, so that the maximum possible depth of a spar could be achieved. It...
  11. RPM314

    Testing a method for making moldless-ish D tube skins

    Hi everybody, After being inspired by the work of Rol Klingberg on YouTube building his new ultralight glider, I decided to test out and idea that I had for making the D tube skin using the shear web and ribs as a male mold instead of hot wiring a dedicated male mold. This is of course a trade...
  12. RPM314

    A proper UAV

    The Tiger turrets are a good start but if you want to get it moving at a good clip you should face the flak battery aft as well. Every gram of thrust helps.
  13. RPM314

    has anyone used fiberglass laminates for gusset material

    As with everything you should be able to make it strong enough by throwing a sufficient amount of material at it, just do your own testing. Others have suggested buying hobby plywood to keep the shipping low, just to add one more source for you to compare I usually get birch ply for my models...
  14. RPM314

    Attention Tailless Nerds!

    There's probably more mass and moment arm to play with in the central pod/fuselage, so I'd imagine the effect to be relatively weak.
  15. RPM314

    Attention Tailless Nerds!

    Yeah, me neither. I don't see how to do that without strong yaw control, or flat spins for that matter either. Knife edge is of course out of the question. But many key staples of an aerobatic routine can be done with just bank, yank, and a lotta power. Loops, immelmans, rifle rolls, etc...
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