[Graeme Smith]

Hi, 
just wondering re extending the RW shaft, I remember that over the years a few have gone down that path, and I also remember that some had issues with flying i.e. porpoising, at the time it was thought that the cowling of the turbine was the issue.

I simply am looking for results issues and benefits as I have a tentative plan to fit a gearbox with a tail rotor drive (not the RW one) along with a new tail rotor hub and I am thinking a good time to lift the rotor head another 6" or so., Also a new swash plate with a far greater range, (The swash plate in the attached is for a 3 bladed design, and the shown bell cranks were for a full set of push pull rods.)






I also wonder if raising the rotor head without raising the tail rotor might also have something to do with it.

Just thinking out loud, maybe someone with some first hand experience could offer their thoughts??

[Jared Hartzell]

I believe I saw that @Daniel Misner (family) had accomplished this, maybe he can chime in on it.

With having a semi-rigid rotor system, it's better to have a raised mast in order to improve CG limits. We could also improve cyclic authority this way as there's less of a concern about blades striking the tail boom; but that would also require a different or modified swashplate and flight control design. The lower excess of blades straps would have to be cut back as well to allow for greater teeter angles. If you look at the Robinson helicopters, there is a lot of space between the blades and the tailboom due to the tall mast with much better CG limits (most certified helicopters have at least double the CG limits that rotorways do, which is why many do not need ballast weights). However, they also incorporate a tri-hinge design to allow the blades to cone in order to reduce loads at the blade root and maintain balance... There is a greater risk of mast bumping with this design, however.

Another solution is switching to a three-bladed design which may not require a taller mast but it would need to be beefier to handle the loads. That would also greatly improve CG and eliminate the risk of mast bumping... But at an increased cost, added weight and space. A better powerplant would be desirable if going that route.

All of these would be major modifications and it'd be best to get an experienced aerospace engineer to assist. But it's definitely something I'd like to see, particularly a fully articulated 3-bladed design with a Lycoming, similar to the Cabri G2!

[Graeme Smith]

I believe I saw that @Daniel Misner (family) had accomplished this, maybe he can chime in on it.

With having a semi-rigid rotor system, it's better to have a raised mast in order to improve CG limits. We could also improve cyclic authority this way as there's less of a concern about blades striking the tail boom; but that would also require a different or modified swashplate (Yes that is something we have already designed and it would suit the new shaft coming from the gearbox) and flight control design. The lower excess of blades straps would have to be cut back as well to allow for greater teeter angles. If you look at the Robinson helicopters, there is a lot of space between the blades and the tailboom due to the tall mast with much better CG limits (most certified helicopters have at least double the CG limits that rotorways do, which is why many do not need ballast weights). However, they also incorporate a tri-hinge design to allow the blades to cone in order to reduce loads at the blade root and maintain balance... There is a greater risk of mast bumping with this design, however.

Another solution is switching to a three-bladed design ( yes I have pondered that and would like to pursue the strap pack rotor head with composite blades) which may not require a taller mast but it would need to be beefier to handle the loads. That would also greatly improve CG and eliminate the risk of mast bumping... But at an increased cost, added weight and space. A better powerplant would be desirable if going that route. ( I think the 3 blades and strap pack head would be weight neutral)

All of these would be major modifications and it'd be best to get an experienced aerospace engineer to assist, (yes I already a CAR35 available .) But it's definitely something I'd like to see, particularly a fully articulated 3-bladed design with a Lycoming, similar to the Cabri G2! I am not a fan of the Lycoming, not saying they are bad, just we have moved ahead with engines so another engine preferable diesel and or JetA is my thinking, higher RPM but that is manageable with the gearbox)

The big question would be, IF I did prove a new design that would fit within the standard RW layout, albeit with some changes, would people want to upgrade their RWs?

My plan atm is to keep the stock RW boom but cut the skin back to the last bulkhead then fit an aluminium mount that would bolt to the bulkhead and on top of that mount to fit the tail rotor gearbox, this would then allow the tail rotor drive shaft to be mounted to the top of the boom different tail rotor set up entirely a lot like the Robbie style.

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[Jared Hartzell]

@Graeme Smith Are you saying a turboshaft or a reciprocating powerplant with diesel or Jet-A? For reciprocating engines, that will pose a lot of challenges—especially with power to weight ratio. But, I think you have something in mind there already. I wouldn't want a turbine powerplant, the operational cost goes way too high and I'd feel more comfortable flying a certified reciprocating helicopter than an experimental running on an APU at that price point.

Now, would I want to upgrade my rotorway with all of this? Yes, absolutely. But, the question is—at what cost? If it's going to price up to a used Enstrom 280 or a Robinson R22, well.. That makes the decision a little difficult. The major benefit if it did would be the low cost of operation in comparison.

If these modifications are successful (new tunnel-cover TR driveshaft system, gearboxes, reliable powerplant, 3-bladed rotor design, standard CG limits/better cyclic authority), you will essentially have what everyone wishes Rotorways were. Looks great, keep up the great work Graeme!! You should create a thread in the Rotorway Builders forum section "Documentation/Blog" so you can share your progress on this amazing build!