0675
MAKE: SynchroLite ~
Rotor - Blade - Composite - VR-7b - Spar
Outside Helicopter
CalVert (University of Maryland Proposal)
The spar is a 'D' shape. The center of the 'D' is hollow and the wall of the 'D' consists of layers of unidirectional fiberglass located between 45 degree plies of carbon on both sides, i.e. inside and out
SynchroLite
Drawing:
Notes:
Give serious consideration to producing the blade by pultruded construction using prepreg carbon and/or glass thread, to reduce the weight slightly. Evaluate the method and cooler tray proposed for the UniCopter blade manufacturing.
___________________
Manufacturing Steps:
Machine Honeycomb:
Shaped by passing a rotating drum of abrasive material along the top then bottom surfaces. The drum is located by means of a template at each end of a table etc. See item 0668
Cover honeycomb:
Use thin fabric ply to cap top and bottom of honeycomb or a sheet of unpolymerized epoxy adhesive.
Produce Spar:
Shorter plies are to have a chevron cut.
Top and bottom plies are to run full length.
Pull unidirectional carbon tight from tip end.
Use a caul plate on the top and bottom of the spar when curing so that the 'ledges' of the chevron plies will not come through.
General Notes:
If the uni-directional carbon, used to makeup the spar flanges, runs inboard on one flange and then back along the other, then the lower flange should have fewer layers running the full span of the blade since it is the to flange that will be in compression. NOT SO IF CONE IS SET FOR AVERAGE LOAD.
Both flanges must be the same.Strength Calculations:
For aircraft wing
|
Weight of helicopter |
50 lb. |
|
Load factor |
10 G |
|
Span (pin to tip) |
96" |
|
Thickness |
1" |
|
Half weight at 70% of 104" (disk radius) |
72.8" |
|
which is (72.8 / 96) |
75.8% of blade |
|
Moment = ((96/12) x 550 x 10G x .758)/( 4 blades) |
8338 ft-lb |
|
Distance centroid of flange to flange |
0.75" (approx.) |
|
Flange load 8338 / 0.75 |
11117 lbs |
Based on carbon and vacuum bag:
65,000 psi in compression
70,000 psi in tension
|
Top flange (cap) |
11117/65000 |
0.1710 sq-in. |
|
Bottom flange (cap) |
11117/70000 |
0.1588 sq-in. |
|
Thickness of top flange |
0.1710/2 |
0.0855" |
|
Thickness of bottom flange |
0.1588/2 |
0.0794" |
Ideas:
Leave pulled carbon at tip end and use it to attach tip weights and/or tip cap?
Fill-in open segments at trailing edge of honeycomb with vertical carbon chopping. This will give surface area for bladder to push against and also close the 'C' spar into a 'D' spar. ??
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Last Revised: October 4, 2002