New tandem tractor design and build

DennisFetters

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Hi Dennis,
I do like the look of Option-B as well. I wish it weighed a little less.

Can you elaborate a little about why you feel that Option-B will fly better? Do you mean that the reduced drag will make a noticeable positive performance difference even at the higher weight?
As always, I appreciate the input.
Michael

I like the wheel-pants and engine cowling, and the tail looks good too. Yes, if you could make the winglets move would be great. The few extra pounds are well worth the looks and better stability. Everything about an aircraft can't just be funtionable.
 
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ILikeJetsToo

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I like the wheel-pants and engine cowling, and the tail looks good too. Yes, if you could make the winglets move would be great. The few extra pounds are well worth the looks and better stability. Everything about an aircraft can't just be funtionable.

Hey Dennis,
This is one of the multi-rudder tail layouts I have been playing with. It actually has a little more vertical volume than the other options that I showed before, and it has three rudders.

If I shift the plates mid span and aft a little like this, I can line up the rudder hinge-lines and get three reasonable sized rudders. Right now I just have them as 1/2 inch thick blades.

The horizontal stab has a foam core, so I’m still working on some linkage concepts. I modeled a few exposed linkages to interconnect the rudders, but they seemed vulnerable to damage and looked pretty bad.

The plates positioned at mid span look a bit like the ones on the Pitcairn PA-18 that Kermit Weeks has.

Michael
 

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DennisFetters

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If it were me, I would leave them of the ends of the horizontal stabilizer. They will be easier to mount. Also, the further they are out from center the better they will catch the propwash when it deflects.

If you "V" the ends of the HS and mount the VS on the ends, then you can run two push-rods inside the trailing edge of the VS. I attached some pictures of something I have designed and still working on to give you an idea of what I'm talking about. The one picture of the model don't have the lines drawn where the rudders are. On the drawing, I showed it see-through where you can see the position of the HS. This goes on a pusher, and in my configuration I didn't need a rudder on the center VS.

You are going to have a really nice gyroplane!
 

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ILikeJetsToo

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You are going to have a really nice gyroplane!

Thanks for the encouragement Dennis. I really appreciate it.

Thanks for the rudder images, too. I see what you are saying. I'll spend some time looking at concepts with the plates moved further out. The trick will just be fitting the rudder linkage inside the horizontal. I'll play with it for a bit and post some more options. I'd like to take the time now to get this right, so it's a nice flying aircraft later. Thanks for giving me your thoughts on this.

I'm starting to think maybe I should just make a new horizontal stab. If I did, I could incorporate the rudder linkage and also add twist to the horizontal for engine torque compensation. What do you think of adding twist (different incidences on each side) to the horizontal?

Michael
 

ILikeJetsToo

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In addition to doing design work lately, I've also been making good progress on the fuselage internal structure. I finished the two carbon fiber landing gear ribs. Because I needed to make two identical main gear ribs, I invested the time into making a nice fiberglass mold. I formed the mold over a band-saw cut medium-density fibreboard plug.

The ribs have unidirectional carbon fiber upper and lower caps to support landing gear bending loads, and they have 1/4 inch thick solid laminate sheer webs to accommodate bolting the gear assembly between the ribs.

I'm really pleased with how they turned out and how well they fit on the inside of the fuselage skin.

Michael
 

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DennisFetters

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Thanks for the encouragement Dennis. I really appreciate it.

Thanks for the rudder images, too. I see what you are saying. I'll spend some time looking at concepts with the plates moved further out. The trick will just be fitting the rudder linkage inside the horizontal. I'll play with it for a bit and post some more options. I'd like to take the time now to get this right, so it's a nice flying aircraft later. Thanks for giving me your thoughts on this.

I'm starting to think maybe I should just make a new horizontal stab. If I did, I could incorporate the rudder linkage and also add twist to the horizontal for engine torque compensation. What do you think of adding twist (different incidences on each side) to the horizontal?

Michael

Happy to help with ideas. I always show my monkeys here my ideas while I'm designing, and try to get them engaged into the design. The conversations always spur a different view for me.

I think twisting the HS would be a lot of trouble and the results probably wouldn't be worth it, and would probably get you a bruised elbow at the airshows.

If you want to counteract prop torque, you may be better offsetting your rotorhead to the side a little so that the torque will force it to hang straight. Or tilt your rotor disk to the side, but then you have to counteract with rudder and always fly a little cocked.
 

DennisFetters

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In addition to doing design work lately, I've also been making good progress on the fuselage internal structure. I finished the two carbon fiber landing gear ribs. Because I needed to make two identical main gear ribs, I invested the time into making a nice fiberglass mold. I formed the mold over a band-saw cut medium-density fibreboard plug.

The ribs have unidirectional carbon fiber upper and lower caps to support landing gear bending loads, and they have 1/4 inch thick solid laminate sheer webs to accommodate bolting the gear assembly between the ribs.

I'm really pleased with how they turned out and how well they fit on the inside of the fuselage skin.

Michael

How about you stop playing around and come and work with me here in China!!?? I really need your skills.
 

ILikeJetsToo

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Hi Michael,

Option B looks better, but I've heard some pilots complain that wheel pants limits them to hard surface runways. They tend to mud up on soft field landings. Quite a few pilots end up tearing them off. Thanks for the great posts! - Matt

Hi Matt.
I agree with your assessment on that. Other than the obvious drag benefits of wheel pants, I think they can be a bit of a pain to deal with sometimes. I've always thought it would be fun to build a bush plane some day, so I have a soft sport in my heart for large exposed tires.

After thinking a lot about it over the last few weeks, I'm leaning toward the basic Option B with an improved tail.

Thanks for the input,
Michael
 

Murray Barker

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I'm starting to think maybe I should just make a new horizontal stab. If I did, I could incorporate the rudder linkage and also add twist to the horizontal for engine torque compensation. What do you think of adding twist (different incidences on each side) to the horizontal?

Michael[/QUOTE]

Yes,best to do it the Cierva way. This is how I did it on my LittleWing.

Also I don't think the winglets need to have rudders attached,I have plenty of rudder authority even at low speed. I have the same engine as you are using.
 

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ILikeJetsToo

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Yes,best to do it the Cierva way. This is how I did it on my LittleWing.

Also I don't think the winglets need to have rudders attached,I have plenty of rudder authority even at low speed. I have the same engine as you are using.

Hi Murray,
Thanks for the photo. Can you tell me a little more about how the tab on your LittleWing works? How big is the surface and how much is it deflected? Is it only on one side?

How do you like your engine? What prop are you running on it? I have a Culver 76"x57" wood prop that Rotec recommends, but I'm a little concerned that the pitch is too coarse for my gyro.

Thanks for your time,
Michael
 

Murray Barker

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Michael, The trim tab is pivoted either end and is ground adjustable by screwing the shaft between the rod ends in or out. I have one on either side and they span the full width of the HS.

They only have to be deflected a small amount to keep the gyro straight under all power settings.

I will have to check the size of my prop but mine is slightly over pitched, I only get 3200 engine rpm wide open, 3500 would be better.

My prop is the one recommended by Rotec but I think they were thinking fixed wing not gyro.

No problems with engine so far.
 

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ILikeJetsToo

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Michael, The trim tab is pivoted either end and is ground adjustable by screwing the shaft between the rod ends in or out. I have one on either side and they span the full width of the HS.

They only have to be deflected a small amount to keep the gyro straight under all power settings.

I will have to check the size of my prop but mine is slightly over pitched, I only get 3200 engine rpm wide open, 3500 would be better.

My prop is the one recommended by Rotec but I think they were thinking fixed wing not gyro.

No problems with engine so far.

Thanks for the info Murray,

I'm glad your Rotec is working well for you.

If you could check your prop size and pitch, that would be really helpful.

Thanks,
Michael
 

mccarthyinv

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What a beautiful machine!

I have been around gyro's since 1981 and time and time again, the tractor gyro configuration makes so much sense from a stability standpoint.

With that said, I would add an option for a fully inclosed cockpit.

All the sporty gyro video's out there show guys flying in beautiful warm weather.
In reality, to avoid the wind, many of use get up on cold mornings and and take off when its 50 degrees F outside or colder, its hard to enjoy the ride when your freezing your ass off, or we inadvertently flying into rain.

A totally inclosed cockpits would add a nice degree of comfort.

I was seriously looking at the Pitt Bull gyro but can't find any info about it and the company has since vanished. The next option was the LittleWing gyro, which I bought plans for, but I'm not really fond of welding. Though its a proven design.

So your design looks like the ticket! But will you have an ultralight version? Some of us don't have a prayer of getting all the training and the medical certificate to fly anything else.
 

Jean Claude

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If you want to counteract prop torque, you may be better offsetting your rotorhead to the side a little so that the torque will force it to hang straight.
In my opinion, offsetting the rotor head gives a vertical mast when engine is full throttle, but gives a tilted mast in the opposite direction when the engine out.



Or tilt your rotor disk to the side, but then you have to counteract with rudder and always fly a little cocked.

Keep horizontal the rotor with the stick is the natural reflex of the pilot for to fly right at full throttle. In this case the rotor is tilted on the side relative to mast, by hand.
Shorten a link rod only changes the stick position in flight.
 
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ILikeJetsToo

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What a beautiful machine!

A totally inclosed cockpits would add a nice degree of comfort.

I was seriously looking at the Pitt Bull gyro but can't find any info about it and the company has since vanished. The next option was the LittleWing gyro, which I bought plans for, but I'm not really fond of welding. Though its a proven design.

So your design looks like the ticket! But will you have an ultralight version? Some of us don't have a prayer of getting all the training and the medical certificate to fly anything else.

Hi Dan,
Thanks for the comments. I think tractor gyros have some nice benefits, too.

I did consider designing an optional enclosure for it, but I really enjoy open flying, so I decided to go with full open for now. It could be pretty windy though, so we will see how it is and I'll modify accordingly.

This design could fall under the experimental light sport category, so you would not need a medical to fly it. Training for a light sport ticket would be required, but light sport training is pretty minimal.

Thanks,
Michael
 

ILikeJetsToo

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In my opinion, offsetting the rotor head gives a vertical mast when engine is full throttle, but gives a tilted mast in the opposite direction when the engine out.

Keep horizontal the rotor with the stick is the natural reflex of the pilot for to fly right at full throttle. In this case the rotor is tilted on the side relative to mast, by hand.
Shorten a link rod only changes the stick position in flight.

Hi Jean Claude,
Thanks for the input. If this was your design, and you were building it, what method would you use for engine torque compensation?

Have a good evening,
Michael
 

Jean Claude

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Engine torque compensation can only come from the detwisting of the flow. In my opinion, a wide horizontal tail passing through the prop wash can reduce, even with no asymmetry.
JC
 
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DennisFetters

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There are a few good ways to compensate for normal prop torque, all of which work and are safe.

A gyroplane is going to stay in a narrow airspeed range. It's never going to be a good high-speed vehicle, so in fact it best shines at low and slow speeds over other aircraft. Thinking that way, probably the best way is the oldest way, and just adjust the pushrods to lean the rotordisk to compensate. After all, that way it's hand adjustable in flight! ;-)

In helicopters we offset the rotorhead by leaning the mast to take care of essentially the same problem, except it's tailrotor thrust.

Twisting the horizontal makes me think of problems after a high speed throttle chop... But again, what is high speed for a gyro and I've never done it!!
 
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