I Have a question about wooden blades
02-10-2004, 07:42 PM
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I Have a question about wooden blades
I would like to know what is the cheapest type of wood to use for making the main blades for a Hirobo Shuttle Sceadu-50 RTF, and also whats the best size to use?
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02-10-2004, 10:32 PM
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RE: I Have a question about wooden blades
Do you mean actually MAKE a set of blades from scratch?
Its nt a task for a beginner at working on models, but I've done it for a GMP Cricket. (rather simple blades...)
You need straight grained birch or maple for the forward 40% of the blade If the grain has a knot... you don't want it in your blade no matter how small or tight it is. A knot is where the blade will shatter when you get the rotor up to speed.
The rest of the blade can be Balsa for training to just hover. For anything beyond SLOW moving around you need to use all hardwood. Slow mving around was close to the Cricket's limit of capability... but the smaller rotor diameter allowed it to get away with 60% of the blade being balsa and doing normal forward flight. (maybe 25 mph top forward speed... Loops were WAY out of its capabilities.)
The best home made blade wll be laminated 1/4 inch square sticks to make the blade chord. the laminated wood is stronger and stiffer than a single cut piece the same width. You need a pair of GOOD straight edge bars to use when doing the clamping. Ues 2 hour or 24 hour epoxy to glue it up.
The hard part is cutting the airfoil evenly down the entire blade. The factories have specially made table-router bits or planer blade sets to do this. (that's why the wood blades cost so much... those custom ground bits or blades are EXPENSIVE.) You would have to build a jig to guide a belt sander to do each section of the airfoil, the feed the blade blank through. (very carefully)
The Cricket blade shape is convenient to duplicate... 1 1/8 X 1/4 inch taper trailing edge stock is the right shape for the rear 60% of the blade.
the forward 40% has a simple rounded lower part to the leading edge, and a fairly simple curve to the upper part of the airfoil. (not an aerobatic blade... more appropriate to an autogyro) with just a few minutes thought and preparation... I had an appropriate jig made to do the leading edges very quickly.
***
Blade making is not rocket science... but it is tedious and requires a perfectionists eye for detail.
Its nt a task for a beginner at working on models, but I've done it for a GMP Cricket. (rather simple blades...)
You need straight grained birch or maple for the forward 40% of the blade If the grain has a knot... you don't want it in your blade no matter how small or tight it is. A knot is where the blade will shatter when you get the rotor up to speed.
The rest of the blade can be Balsa for training to just hover. For anything beyond SLOW moving around you need to use all hardwood. Slow mving around was close to the Cricket's limit of capability... but the smaller rotor diameter allowed it to get away with 60% of the blade being balsa and doing normal forward flight. (maybe 25 mph top forward speed... Loops were WAY out of its capabilities.)
The best home made blade wll be laminated 1/4 inch square sticks to make the blade chord. the laminated wood is stronger and stiffer than a single cut piece the same width. You need a pair of GOOD straight edge bars to use when doing the clamping. Ues 2 hour or 24 hour epoxy to glue it up.
The hard part is cutting the airfoil evenly down the entire blade. The factories have specially made table-router bits or planer blade sets to do this. (that's why the wood blades cost so much... those custom ground bits or blades are EXPENSIVE.) You would have to build a jig to guide a belt sander to do each section of the airfoil, the feed the blade blank through. (very carefully)
The Cricket blade shape is convenient to duplicate... 1 1/8 X 1/4 inch taper trailing edge stock is the right shape for the rear 60% of the blade.
the forward 40% has a simple rounded lower part to the leading edge, and a fairly simple curve to the upper part of the airfoil. (not an aerobatic blade... more appropriate to an autogyro) with just a few minutes thought and preparation... I had an appropriate jig made to do the leading edges very quickly. ***
Blade making is not rocket science... but it is tedious and requires a perfectionists eye for detail.
