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Old 05-19-2019, 12:55 PM
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I'm guessing Suds that the carbon rod was twisting which created the flutter , ouch.!!


So from the video I saw of this plane yesterday, it didn't do any high speed passes only alot of 3D flying and Spencer wasn't on the control in the video .
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Old 05-19-2019, 01:08 PM
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I don’t know how much CARF has access to analysis tools (ANSYS, NASTRAN, etc) but I do and would be happy to help. I’m guessing that there might me some resonance(s) that are causing the flutter.
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Old 05-19-2019, 01:56 PM
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The stock ball linkages were busted and had major slop. They are basically being held my supporting washer's on each side. Metal on metal ball linkages require lubrication which was not done by various pilots. The production ball linkages will have traditionally plastic on metal m4/m5 ball linkages.

I use the same metal on metal ball linkages on my carf turbines jets near the thrust tube but have to lubricate them. Traditional plastic on metal is not an option when we are dealing with residual turbine heat.

I ordered the kit once I confirmed weight to be 38lbs dry with the ZDZ 195 on cans, heavy tank, heavy batteries, heavy smoke tank, etc.

I plan to fly mine with the GP178 on stock mufflers, kuza tank, small batteries. Hoping to get mine to be 36.5lbs.
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Old 05-19-2019, 02:28 PM
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Quote:
Originally Posted by suds View Post
I saw this flying on the 3D line at Nall this past week. Really looked good from both an aesthetic and performance standpoint. Very impressive performance.

Until the Thursday noon demo with Spencer on the sticks.
During the first high speed pass/manouver, the main wings developed significant flutter...everyone around me saw it as well. I'm sure Spencer saw it as the remainder of the demo flight was all low n slow...so kudos to him for backing it down and still putting on a good show.
I don't know if the flutter was related to the servos not being able to keep up or inherent flex in the carbon rod setup.
Is this the video, Rob?

https://youtu.be/WXpXvyFjFDM?t=1076
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Old 05-19-2019, 05:24 PM
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Originally Posted by Aeroplayin View Post
Is this the video, Rob?

https://youtu.be/WXpXvyFjFDM?t=1076
Yes, difficult to see in the dark background in the video.
Happened 18:39-18:42 range of this video.
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Old 05-20-2019, 05:09 AM
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Mainly a RCU member - 1st time here on FG. RCU members hardly ever reply nowadays.

Wanted to see if anyone had any insights into the new CARF Extra that was displayed at Joe Nal 2019:

https://carf-models.com/en/products/extra330lx3m

I saw this at the demo's a few times and was shocked to see such performance from a composite. The engineering is something I have not seen before. I also watched someone grab a xicoy scale and weight it at 38lbs which seems to be incredibly light. My lightest balsa/plywood/carbon laminate ARF is about 42lbs so this was a surprise.

Any insights on the engineering? Never seen this before.
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Old 05-20-2019, 08:10 AM
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Originally Posted by Pilot3DFG View Post
Mainly a RCU member - 1st time here on FG. RCU members hardly ever reply nowadays.

Wanted to see if anyone had any insights into the new CARF Extra that was displayed at Joe Nal 2019:

https://carf-models.com/en/products/extra330lx3m

I saw this at the demo's a few times and was shocked to see such performance from a composite. The engineering is something I have not seen before. I also watched someone grab a xicoy scale and weight it at 38lbs which seems to be incredibly light. My lightest balsa/plywood/carbon laminate ARF is about 42lbs so this was a surprise.

Any insights on the engineering? Never seen this before.
Although I'm certainly not a CARF insider, I do have a few opinions.

First, the lightest balsa 40% I've seen was 38 lbs dry with a DA-150L. This was a kit built plane from one of the big three manufacturers twelve years ago. It could be built to 41 pounds if the builder was not conscious of weigh during the assembly and weight can easily get away from you if you build it like a furniture maker as opposed to an aeronautical engineer. The two perspectives are very different.

Second, composites have come a long way since I first saw them up close and personal for the first time in 2011. But the bigger the plane, the lighter the cube loading potential (oz/cu ft), which is a density value and relative to scale, unlike wing loading. This is true because there is a lot more empty space in a bigger plane.

Third, one of the main concerns with designers is the wing weight. With big planes, balsa designers use sheeted foam because it is easier to build strength and rigidity (Young's Modulus) with these materials than trying to reinforce the D-box and against wing twist with hard wood, carbon rods, or light ply.

The perfect combination, IMO, is a composite fuse with a sheeted foam wing. But sheeted foam also needs care and attention to keep the weight down with the strength up. Anyone who bought the Dalton ML ARF that was assembled in China knows that the sheeted foam wings were a disaster, coming in at over 5 pounds per wing.

My opinion has always been that when CARF or Krill finally got the engineering to the point where they could make the wings light without them folding up in flight, they would at least have a winning formula on their hands from a materials perspective.

They say on their website that the seven flat hinged wing weights 1500g or 3.5 pounds for their 3 meter plane. In comparison, my 2.6m plane has eleven flat hinges and each sheeted foam wing covered with Ultracote weighs 2.16 lbs. So this weight, IMO, is excellent. I'm 185 lbs and can stand of the wing's MAC of my plane, so I'm not worried about strength.

If I were marketing their plane, I'd show a lot more videos and have someone stand on the suspended wing panel just to eliminate any question about strength and rigidity.

They would certainly still need an understanding as to what makes a good scale replica fly well, so that's another reason why I'd like to see more videos.

Another thing I do with all my planes is put the main wing tube through the fuse and lock it down in an assembly frame or have a friend hold it down in the frame, then twist the fuse by the stab tube. The idea is to also have a rigid fuse too.

A light plane with a strong wing, with a rigid fuse that has a clean form and great paint job that only a composite can offer, makes the extra cost well worth it -- all just MO. But there are only those final concerns that most guys will have, and I think there are easy ways for them to eliminate those concerns with a few illustrations.
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Old 05-21-2019, 12:21 AM
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Quote:
Originally Posted by Pilot3DFG View Post
Mainly a RCU member - 1st time here on FG. RCU members hardly ever reply nowadays.

Wanted to see if anyone had any insights into the new CARF Extra that was displayed at Joe Nal 2019:

https://carf-models.com/en/products/extra330lx3m

I saw this at the demo's a few times and was shocked to see such performance from a composite. The engineering is something I have not seen before. I also watched someone grab a xicoy scale and weight it at 38lbs which seems to be incredibly light. My lightest balsa/plywood/carbon laminate ARF is about 42lbs so this was a surprise.

Any insights on the engineering? Never seen this before.

One of my friends has a TUNY built Carden that weighs 39.5 pounds, I weighed it myself with the XIcoy scale. I was shocked. It has a DA 200 with canisters. 40% aircraft. Anyways, not trying to sound argumentative, but people are definitely learning where to cut out weight and still maintain strength.
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Old 05-21-2019, 04:19 AM
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Originally Posted by Aeroplayin View Post
Although I'm certainly not a CARF insider, I do have a few opinions.

First, the lightest balsa 40% I've seen was 38 lbs dry with a DA-150L. This was a kit built plane from one of the big three manufacturers twelve years ago. It could be built to 41 pounds if the builder was not conscious of weigh during the assembly and weight can easily get away from you if you build it like a furniture maker as opposed to an aeronautical engineer. The two perspectives are very different.

Second, composites have come a long way since I first saw them up close and personal for the first time in 2011. But the bigger the plane, the lighter the cube loading potential (oz/cu ft), which is a density value and relative to scale, unlike wing loading. This is true because there is a lot more empty space in a bigger plane.

Third, one of the main concerns with designers is the wing weight. With big planes, balsa designers use sheeted foam because it is easier to build strength and rigidity (Young's Modulus) with these materials than trying to reinforce the D-box and against wing twist with hard wood, carbon rods, or light ply.

The perfect combination, IMO, is a composite fuse with a sheeted foam wing. But sheeted foam also needs care and attention to keep the weight down with the strength up. Anyone who bought the Dalton ML ARF that was assembled in China knows that the sheeted foam wings were a disaster, coming in at over 5 pounds per wing.

My opinion has always been that when CARF or Krill finally got the engineering to the point where they could make the wings light without them folding up in flight, they would at least have a winning formula on their hands from a materials perspective.

They say on their website that the seven flat hinged wing weights 1500g or 3.5 pounds for their 3 meter plane. In comparison, my 2.6m plane has eleven flat hinges and each sheeted foam wing covered with Ultracote weighs 2.16 lbs. So this weight, IMO, is excellent. I'm 185 lbs and can stand of the wing's MAC of my plane, so I'm not worried about strength.

If I were marketing their plane, I'd show a lot more videos and have someone stand on the suspended wing panel just to eliminate any question about strength and rigidity.

They would certainly still need an understanding as to what makes a good scale replica fly well, so that's another reason why I'd like to see more videos.

Another thing I do with all my planes is put the main wing tube through the fuse and lock it down in an assembly frame or have a friend hold it down in the frame, then twist the fuse by the stab tube. The idea is to also have a rigid fuse too.

A light plane with a strong wing, with a rigid fuse that has a clean form and great paint job that only a composite can offer, makes the extra cost well worth it -- all just MO. But there are only those final concerns that most guys will have, and I think there are easy ways for them to eliminate those concerns with a few illustrations.
Thx. I know the 2.6M Model Power Slicks in EU (Gernot's TAC freestyle winning composite arf) are even lighter at 35/36lbs but they are a little smaller at 114/115". I have seen high speed blenders on those with ZDZ 180's on them and they handle it well. I can only assume that the CARF is just as stout.

This CARF is 120"X120". I have seen other CARF jets pull hard G's so I not not as concerned about the airframe itself not being able to handle high energy XA type flying.

My major question is about the engineering inside the fuselage itself. Can anyone comment on it - has anyone come across such design/engineering in other model aircrafts?
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Old 05-21-2019, 06:07 AM
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The CARF control system is a redesign of an old idea. Torque tubes were fairly common practice years ago when radios were very limited by channel count. I've seen toque tubes used for ailerons, elevators, flaps, etc. CARFs take on the system is very innovative. I'm hoping that it works as well as they claim. It should go a long way to minimizing the wing weight.

I would worry about the wear and longevity of the system. Flutter seems like a real problem, but if they get it right it'll be amazing.
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Old 05-21-2019, 12:00 PM
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Thx. I know the 2.6M Model Power Slicks in EU (Gernot's TAC freestyle winning composite arf) are even lighter at 35/36lbs but they are a little smaller at 114/115". I have seen high speed blenders on those with ZDZ 180's on them and they handle it well. I can only assume that the CARF is just as stout.

This CARF is 120"X120". I have seen other CARF jets pull hard G's so I not not as concerned about the airframe itself not being able to handle high energy XA type flying.

My major question is about the engineering inside the fuselage itself. Can anyone comment on it - has anyone come across such design/engineering in other model aircrafts?
Hmmmm.... when I said this....

Quote:
Originally Posted by Aeroplayin View Post
They say on their website that the seven flat hinged wing weights 1500g or 3.5 pounds for their 3 meter plane. In comparison, my 2.6m plane has eleven flat hinges and each sheeted foam wing covered with Ultracote weighs 2.16 lbs. So this weight, IMO, is excellent. I'm 185 lbs and can stand of the wing's MAC of my plane, so I'm not worried about strength.
By "my plane", I meant the 2.6m balsa, ply, and sheeted foam plane I scratch-built. Not the smaller CARF models. The wing panel I tested from my plane was originally 1080g, so I lightened it a little more, then tested the second version by standing on it. So the stress was 185 lbs and the stain was 5/8th inch at the MAC.

I'm not sure if CARF does and stress and strain tests for Young's Modulus but it would remove cognitive dissonance in their marketing message by showing this type of strength and rigidity.
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Old 05-22-2019, 05:33 AM
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The CARF control system is a redesign of an old idea. Torque tubes were fairly common practice years ago when radios were very limited by channel count. I've seen toque tubes used for ailerons, elevators, flaps, etc. CARFs take on the system is very innovative. I'm hoping that it works as well as they claim. It should go a long way to minimizing the wing weight.

I would worry about the wear and longevity of the system. Flutter seems like a real problem, but if they get it right it'll be amazing.
Thx for sharing this. So the concept is not entirely new - which helps and possibly confirms that this has more or less has been tried in the past successfully.

Flutter seems like a real problem, but if they get it right it'll be amazing. Agreed.

I am going to place an order. The model power is what I wanted but is a little small and the delivery time is about 1 year. CARF is a much more reasonable 2-3 months.
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Old 05-24-2019, 12:32 PM
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Hmmmm.... when I said this....




I'm not sure if CARF does and stress and strain tests for Young's Modulus but it would remove cognitive dissonance in their marketing message by showing this type of strength and rigidity.
call them up and let them know your available for crush testing
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Old 05-24-2019, 12:41 PM
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LOL... I'd be happy to test the whole plane for them.
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Old 05-24-2019, 02:38 PM
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Jim if you’ll test it on electric, I’ll test it on gas!
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