• How are tows wrapped at the tip end and all lie in the same plane; for the quill?
• How are these tows (quills) held in place after being wrapped around the spar?
• Have the quill holder etc. become an integral part of the blade tip.
• If the tow cures at room temperature the winding procedure must take place at cold temperatures.
• How well is the torque tube resisting twisting?

• Function of Torque Tube: To transmit the commanded tip pitch from the tip-pitch horn out to the tip of the blade.
• The tip end of the blade will be rotated by this tapered composite tube, which will be located inside the spar of the blade. This tube will only require torsional rigidity. It will be constructed out of carbon thread, at a wind angle of close to 45º.

• The radial pins at the root end are used to wrap the tow around so that the new tow path will lie adjacent to the previous tow path.
• The number of pins must be evenly divisible into the number of strands of tow; at every layer.
• For a picture of the use of pins see [FWCS ~ Figure 1-6]
• The pins will be probably be cropped after winding and curing. Or, they will be drilled out for other pins to lock the pitch holder in place. See; 1353.html and 1355.html.
• It may be an advantage for the pins to have a slight axial bend away from the tip end, to facilitate the wrapping of the tow around them. Alternatively, they might have nubs on the ends.

• The first layer consists of a single tape of 1 or more tows at a wrap angle probably greater than 45º.
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• The first layer consists of a single tape of 1 or more tows at a wrap angle probably greater than 45º.
• Use quills to assist with the tip end rotation since the strength of the epoxy will probably be enough.
• All following layers consist of a band of tows and the band consists of 2 tapes. One tape creates one quill and the other tape creates a second quill at 180º about the X-axis (rotation axis) from the first. Subsequent layers will each produce additional pairs of quills and each pair will be located approximately 3.5" closer to the root end than the former pair.
• The radius diameter of the torque tube, where the tape leaves the tube to become the quill, is to be the blade thickness less one hoop wrap (around the spar) and two times the skin thickness at this location.
• The quills pass over (or under) the spar, then wrap around the leading (or trailing) surface of the spar, then back toward the torque tube. They are then bound to the spar tip by the single hoop wind, which passes up the full span of the blade.
• Perhaps the clamp that aligns the quills should consist of a separate clamp for each pair of layers. This will allow the clamping to be done soon after the wrapping of that layer. It also sets the clamp up for the attachment of the next layer's clamp.
• This note was for the previous spar tip design. Since the wedges are 2.1478" wide [ref. 0932.html] each layer on the torque tube i.e. each pair of quills) will be approx. 2.1478" shorter than the previous.
• What about attaching the end of each tow at the tip end with fast acting Krazy clue.

• The torque tubes for one craft should consist of an equal number of items with a CW initial winding and with a CCW initial winding. The CW ones will be used on one rotor and the CCW ones will be used on the other rotor. This is so that the positive pitch that is applied to all 6 blades is equally transmitted up the torque tubes, should the torque tubes not have absolute torsional rigidity.
• Consecutive tows must be laid down in the direction of the root. This is necessary because of the wraping of the quill over the quill tip arm. This necessitates a long X-axis travel because at the root end, once the tow has passed over the pin the eyelet must move further to assure that the tow will not slip off the pin when it is wrapped around the pin. It should be noted that the eyelet is already quite a bit ahead of the wrapping point because of the wrap angle and eyelet distance from the torque tube.

• "... it is known that torsional stiffness is maximized when the filament lay angle (wind angle) is relatively large, but in such event, the bending stiffness is relatively low. At relatively small lay angles, the bending stiffness increases, but the torsional stiffness decreases." ~ Patent US 4,863,414 Lord Corporation. It looks like the optimum angle will be approximately 60º, or even slightly greater.
• If I recall correctly, 30 deg off radial is optimum for filament winding. [Wind angle of 60º] ~ from rnd2
• For maximum torsional stiffness +/-45 degrees is best because that is the direction of the torsional loads. A +/-45 degree tube can be used to transmit torque through a 90 degree bend. ~ from Compositepro
• The large wind angle means that there can be only one tow wrap around each pin at the root end.
• For additional comment on Wind Angle see [Tow Wind Angle] below.

• The diameter of the root end has been reduced and this reduces the taper.
• This will cause the wind angle to be closer to 45º at the root end.
• The torque tube taper will be shallower than the ID taper of the spar. This will allow for a varying elastomer thickness, which will probably be proportional to the desired active twist at each blade element.
• The root end can be supported by the post on the pitch horn.
• There may be no need for additional layers beyond those used to provide quills This is because the increasing diameter will provide the additional rotational strength that is transmitted through the elastomer.
• To provide pins to wrap the tow at the tip end of shorter outer layers consider one or more extensions to the tip wrap bar device that rest over the laid plys and is rotated by the tip wrap bar device.

• Have the elastomer, which is located between the torque tube and the spar, transfer a large percentage of the torque to the spar along the full span of the blade, before reaching the tip. This will significantly reduce the amount of torque that must be transferred at the tip. The torque tube is thicker and has a larger diameter toward the root, which is ideal for a progressive transfer of the twist. By having the thickness of the elastomer greater at the root then at the tip, the transfer of torque will be equal along the span, but the actual rotation of the blade will increase linearly along the span. I.e. The thicker wall on the elastomer at the root will accommodated the greater discrepancy between the rotation of the torque-tube and the rotation of the spar at that point on the span.
• Have the OD of the torque tube small enough at the root end so that it can be pushed to the side and the blade's attachment bolts replaced. This means that the only thing between torque tube and the inside wall of the spar will be a few layers of elastomer and shims. Alternatively, stop the torque tube a couple of inches back from the end of the spar.
• Re Multiple Threads; To start the winding, consider bonding or clamping the leading end of all the threads to a portion of the paddle that will be cut off and some point in the manufacturing of the blade.
• Re Single Tow; Wind single thread back and forth along mandrel, loop it over 'bar' at each end.
• The lesser the bias means the more wraps, the fewer strands to be looped at the root ~ Good; the fewer tows in the quills ~ Bad.
• The final layer may not experience the pressure that the inner layers do in compacting the thread/epoxy.
• Tow Wind Angle: Working on now.
• Which is better; > tows & < angle ~or~ < tows & > angle?? I think that more tows will be better since the over-layer will be ~ 90º and so is the first layer
• Design so that the elastomer transmits a LOT of the torque:
• The area between the quills will be used to tie the two halves of the spar together at the tip end.

• The purchased carbon tube over the cable has an OD of 0.170" ID + (2 x 0.025" wall thickness = 0.220"
• If 12K yarn is used then each tow is 1"/42 = 0.0238" wide by 0.0238" thick. The epoxy may add to this dimension. For more information see; OTHER: Composite - General - Tow Or better yet see Access database FORM: Tow where the tow width, c/w epoxy, is currently shown to be 0.02786216"
• The diameter of the centerline of the initial layer of thread is 0.220" + 0.0238" = 0.2438". This has a circumference of (22/7) * 0.2438 = 0.766"
• The root end has 8 pins for wrapping the tow around, therefore the number of tows must be a multiple or a devisable of 8. The FORM: Torque Tube - Layer is used to work this out.

• Not only is the diameter greater at the root but, perhaps, the thickness should also be slightly greater. This additional thickness means that a few of the windings must start at varing distances away from the tip and if they start at a 45º bias they will have a greater angle at the root than the full length wrappings.
• Transferring some of the torque along the length of the blade via an elastomeric 'sleeve' decreases the amount of torque that must be transmitted all the way to the tip.

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• The purchased carbon tube over the cable has an OD of 0.170" ID + (2 x 0.025" wall thickness = 0.220"
• If 12K yarn is used then each tow is 1"/42 = 0.0238" wide by 0.0238" thick. The epoxy may add to this dimension. For more information see; OTHER: Composite - General - Tow Or better yet see Access database FORM: Tow where the tow width, c/w epoxy, is currently shown to be 0.02786216"
• The diameter of the centerline of the initial layer of thread is 0.220" + 0.0238" = 0.2438". This has a circumference of (22/7) * 0.2438 = 0.766"
• If the tow is wound at a bias of 45º at the tip then the band width is sin(45) * 0.766"= 0.542".
• If 12K yarn is used, the number of strands in the initial band width is 0.542" / 0.0238" = 22.8. This means that 11 tow will go to one bar and 11 tow to the other bar.
• If the OD of the torque tube at the tip end is 0.5" and the purchased carbon tube is 0.220" then the wall thickness at this end is (0.5 - 0.22) / 2 = 0.14" The number of wraps is therefore 0.14 / 0.0238 = 5.88. The actual number will probably be 6 since the number of threads in each band is slightly under the requirement. How much area will the epoxy take up?
• Assuming that the skin consists of two layers the 0.5" diameter location of the torque tube (tip end with only quills protruding closer to the tip.) will be located at r = 0.90 approx. See drawing on DESIGN: UniCopter ~ Rotor - Blade - NACA 00xx - Planform & Thrust

• At the root end the diameter of the mandrel is 1.8124".
• At the root end the diameter of the centerline of the initial layer of thread is 1.8124" + 0.0238" = 1.8362". This has a circumference of (22/7) * 1.8362 = 5.7709"
• Band width divided by circumference is 0.542 / 5.7709 = 0.0939, therefore the bias (band angle) angle = 5.388º

• Not only is the diameter greater at the root but the thickness should also be slightly thicker. This additional thickness means that a few of the windings must start at varing distances away from the tip and if they start at a 45º bias they will have a greater angle at the root than the full length wrappings. Transferring some of the torque along the length of the blade also decreases the amount of torque that must be transmitted all the way to the tip.