Shameless update from Dale Kramer

Paul,

None of the rotors are directly in the propwash cone of the others, so I do not see any direct interaction between them causing a blanketing effect that reduces AOA of other other rotors.

Thanks for the comments, all welcome.

Dale

You might be assuming zero wind. Stationary hovering with no wind fits what you've said. However, when you add in wind, the downwash from the upper rotors will not be perfectly vertical and will be influenced by the wind direction and speed. It's easy to envision the downwash moving downward at an angle that would cause it to intersect with one of the lower rotors. Adding or subtracting a few knots or a few degrees could correct or exacerbate the effect. Exactly what wind speed would cause a loss of lower rotor effectiveness would be an interesting vector to work out. Perhaps that would be a design limitation that could be demonstrated and placarded.

I envision it like doing a 360 hovering turn with a good wind in a conventional helicopter. As some point, you hit a spot where the tail rotor loses effectiveness as the wind affects its angle of attack. Mentally flip it 90 degrees and imagine the wind being the downwash from an upper rotor and you'll get what I'm thinking about.

Good luck!

Paul A.

I've spent a lot of time today reading up on VRS and AsymVR in the case of the V-22. What I can conclude so far is that my my vLazair design departs radically from any VRS states that have been analyzed for both helicopters and VTOLS.

So that leaves extensive testing of the 1/4 scale model of the vLazair as my best course of action (good thing that is what I had planned . It looks like dreaming up all these possible conditions where VRS may cause an issue and then testing those conditions with the model. That will be fun to do.

Thanks again, Dale

If you used tilting ducted fans, instead of a tilting seat, it would not be as innovative. The ducts would also add drag in horizontal flight compared to folding props. But, if I understand correctly, ducted fans are much less prone to the vortex ring problem.

On Thursday, March 17, 2016 at 6:31:51 PM UTC-4, bumper wrote:
If you used tilting ducted fans, instead of a tilting seat, it would not be as innovative. The ducts would also add drag in horizontal flight compared to folding props. But, if I understand correctly, ducted fans are much less prone to the vortex ring problem.

For this transitional design I think ducted fans would weigh too much, reduce my top speed too much and cause too many structural problems. Tilting fans is what I am trying to avoid ... synchronization issues, tilt mechanism weights, complexity ... I am trying to have a design that people can relate to as 'somewhat' of a conventional airplane shape during cruise.

On Thursday, March 17, 2016 at 4:19:30 PM UTC-7, DaleKramer wrote:
On Thursday, March 17, 2016 at 6:31:51 PM UTC-4, bumper wrote:
If you used tilting ducted fans, instead of a tilting seat, it would not be as innovative. The ducts would also add drag in horizontal flight compared to folding props. But, if I understand correctly, ducted fans are much less prone to the vortex ring problem.

For this transitional design I think ducted fans would weigh too much, reduce my top speed too much and cause too many structural problems. Tilting fans is what I am trying to avoid ... synchronization issues, tilt mechanism weights, complexity ... I am trying to have a design that people can relate to as 'somewhat' of a conventional airplane shape during cruise.

Your "design" looks to have a very high disk loading. What CAD analysis (if any) have you done of this design, and what CAD tools did you use?

Tom

On Thursday, March 17, 2016 at 10:36:06 PM UTC-4, 2G wrote:
Your "design" looks to have a very high disk loading. What CAD analysis (if any) have you done of this design, and what CAD tools did you use?

Tom

I assume you are asking about rotor disk loading in hover mode which is about 18 lbs.ft^2

And my hover lift efficiency is about 5 hp/lb

I don't see either of those being 'high' unless you start comparing the design out of category. I believe the nearest category for hovering should be multirotor. In the multirotor category I would expect it to 'above normal' because I use the same props/rotors to achieve static thrust for hover and for traction thrust at high airspeeds during cruise, so compromises are made for both flight conditions.

I am a little confused in that I traditionally think of CAD programs as simply the program used to draw a design on a computer. From the question I think you might mean CAE or CFD or simply analysis tools like XFLR5.

In any case I used XFLR5 for aerodynamics analysis, Javaprop for prop analysis and I have not done any CFD yet.

On Friday, March 18, 2016 at 5:27:44 AM UTC-7, DaleKramer wrote:
On Thursday, March 17, 2016 at 10:36:06 PM UTC-4, 2G wrote:
Your "design" looks to have a very high disk loading. What CAD analysis (if any) have you done of this design, and what CAD tools did you use?

Tom

I assume you are asking about rotor disk loading in hover mode which is about 18 lbs.ft^2

And my hover lift efficiency is about 5 hp/lb

I don't see either of those being 'high' unless you start comparing the design out of category. I believe the nearest category for hovering should be multirotor. In the multirotor category I would expect it to 'above normal' because I use the same props/rotors to achieve static thrust for hover and for traction thrust at high airspeeds during cruise, so compromises are made for both flight conditions.

I am a little confused in that I traditionally think of CAD programs as simply the program used to draw a design on a computer. From the question I think you might mean CAE or CFD or simply analysis tools like XFLR5.

In any case I used XFLR5 for aerodynamics analysis, Javaprop for prop analysis and I have not done any CFD yet.

CAD, or computer-aided design, covers the gamut of software tools, not just basic drafting. I was thinking of aeronautical engineering tools, however. You obviously have available drafting tools.

Your disk loading is quite high, between a Super Stallion and an Osprey. This precludes an autorotate capability. Having 5 motors operating to sustain a hover represents a corresponding high failure probability with no recovery.

How would you land conventionally with propellers on the wing tips? Would they fold back?

I think it is incumbent upon you to disclose to potential investors that you are not an engineer (unless you have an aeronautical engineer on your team, of course).

1. Nowhere have I indicated that there was an auto-rotate capability.
2. I said that I traditionally think of CAD as drawing programs, I believe that is backed up by the current Wikipedia definition of CAD.
3. The answer to your folding props question is clearly stated on the link I provided. I choose let you go read it there.
4. I have also disclosed an extensive biography on the link provided and encouraged people to read it, as should you.
What is your agenda?

5. You choose to define my rotor disk loading as 'high' with examples of air vehicles of two different categories, why?
6. There are 7 motors used during hover on the vLazair and your assumption appears to be that a failure of any single one, would have no recovery. That is incorrect. Multirotors can operate with one or more rotors disabled, depending on design.