karlik

Gotta ask before I get too far into this.

I’m (hopefully) scratch building an S-58 / H-34 fuse for my Falcon 40 FP, and a little concerned about the tail rotor.

Should I expect any major changes going from the rotor mounted on a simple boom to having part of the airflow blocked by a large tailfin? I have switched from that cheap gear driven system to a GWS direct drive motor, and I’m hoping the end result will have the motor/rotor/tailfin looking pretty close to scale.

Factory setup is 12.5 inches from the main shaft to the tail rotor. With the new fuse it will be 14 inches (don’t expect much change in flight characteristics there). It will also be moved about 2.6 inches higher than it’s current position, will that have any effect?

dknovick

Since you haven't received any answers, I assume that:
a) No one knows
b) You haven't hit your target audience

So, as a first test, why not add some blockage to your F40, and see what happens. Slowly increase it 'til is similar to your final fuse.

-Dave

karlik

I've asked a few questions in the scale forum here in the past but I get the impression they don't take to newcomers. Thought maybe a more generic forum would get some response.

I've registered at a site that is only scale and I'll ask the question there. I'm sure as I progress I'll have several more questions and it'd help to find a forum that responds.

I suspect it has little or no effect but a friend who is a real plane pilot asked and made a good case that blocking a percentage of airflow will have an effect.

noobflyer01

I think the major reason you're not getting many responses is:
1.  you would need an audience that owns the falcon 40
2. the said owners would have to modded their ship to a scale ship.

I'm going to be honest, the falcon 40 isnt worth modding to a scale bird. its a cheap trainer.

try modding a 450 size ship like the trex 450 and you'll get many more responses.

Rafael23cc

My Feedback: (6)

I have zero experience with the Falcon, and zero experience with scale birds. But your question can be answered with Physics and helicopter flight theory.


By increasing the length between the main shaft and the tail rotor, you are making the tail rotor more efficient in regards of holding power. Check out twisting forces and moment arms in your physics book for a better explanation.

Then you will be putting a large object (the scale tail fin) in front of the tail rotor. I imagine that it will cancel any efficiency that you might have gained by increasing the distance between the tail rotor and main shaft. There is only one way to find out, and dknovick seems to be a good approach to the problem.

Rafael

karlik

I don't think the fact it's a cheap trainer has that much to do with the answer. A generic answer from someone who has modded a trex with any scale fuse that obstructs the tail rotor would have given me some indication. The difference would be I don't have as many options to overcome any problems it might create as someone with a trex would. I'm not employed so a trex ain't in the plans right now.

I have lots of scrap balsa from some of my past "plank" projects and this will be a low cost learning experience that will keep me occupied while I'm sitting here on my butt, so I figure the falcon is worth modding.

Thx Rafael and Dave - I'm trying to figure out a way to stick something behind it as a temporary test. I think I'll kill 2 birds with 1 stone and make a version of only the tail fin and experiment with different ideas of how to mount the motor on top at the same time. If I can come up with a way to mount the tail fin to the motor, it should work to mount the motor to the tail fin later.

noobflyer01

Karlik I apologize if I sounded likea snob and did not contribute to your thread. People gotta pull me out of the clouds sometimes. I am very fortunate to have a job. Hope you can find work soon.

about your scale modding. consider getting a better motor as the scale would put more weight load on the heli. I believe the stock falcon 40 comes with a brushed motor. putting that extra weight will require a brushless motor or that brushed stock motor will not last long.

I do have a brushless motor or two laying around that I'm not using and willing to donate to someone who needs it. Just send me a PM

Rafael23cc

My Feedback: (6)

Anything that is roughly the same surface area as the fin you intend to mount should be enough. Key word there was surface area. A flat piece of wood, plastic, anything. that is the same as the final fin, should be able to give you an indication of what to expect. I suggest to place it on the UNMODIFIED falcon and test it that way. Then you can extend the boom and move the tail rotor. Remember to do just one modification at a time and test fly it. If you do more than one mod at a time you will not know which one could be the cause of trouble.

Rafael