Shameless update from Dale Kramer

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?

On Friday, March 18, 2016 at 6:03:54 PM UTC-7, DaleKramer wrote:
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?

I have no agenda, what is yours?

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.

On Friday, March 18, 2016 at 6:24:20 PM UTC-7, DaleKramer wrote:
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.

It is high because it IS high. It is 5-6 times higher than an R22.

Seven motors is an even higher probability of failure. I have seen no DESIGN data (vs speculation) that indicates your "design" will function with the failure of any motor.

Let me remind you: you presented yourself initially as "shameless" self promotion. If you don't like criticism go someplace else.

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.

Dale,

I'm no engineer, but have experienced vortex ring effect caused by too fast a descent into one's own downwash with models, both helicopters and quad-rotors.

I'm guessing vortex ring will be the major design obstacle you'll need to overcome. Consider that in a crosswind, and while maintaining position over the ground descending, the prop wash from the front prop and wing tip props will be moving laterally, so even though they are not positioned in line with, their disturbed air can still conflict with the rear props.

With a limited time envelope to descend and land, there may be considerable pressure on the pilot to descend expeditiously if hand flying. Would this be automated in some manner, or with say a green safe to land "descent profile" indication below a given safe altitude and allowable descent rate, etc.. If, for some reason, the pilot has to abort a landing, say due to wind conditions or surface irregularities, would a vertical take off after a partial descent be possible?

You are on the right track testing with a model, as that should show up any issues.