Strega ARC surfaces travel problem

[Miguel Marzan]

Hello guys! This is my first post in this forum, so let me introduce to you. I am Miguel Marzán from Spain, and I am putting together a Brodak's Strega ARC.

I have build many scratch planes, and this is my first ARC, I am very happy with it because it comes everything straight, well glued and pretty well sanded. I have reinforced the flap horn boxes with fiberglass and also rounded off the leading edge. I also have done a mechanism to take apart the wing and some weight lightening. I have covered the wing and stabilizer with mylar.

And now, I am stuck with the control linkage, and need your expert advice. I am using the standard horns, but in my box came a strange (for me) flap control horn which is not the typical 90º degree between the line formed with the holes and the part which goes inside the flap. I mounted it and glued it as usually. I trimmed the neutral with the bellcrank, flaps and stabilizer aligned in neutral position and everything OK, but when  testing up/down travels I noticed that the flaps have the same up/down travel (about 40º, that I think is OK), but the elevator has more down than up travel and less movement than the flaps (less than 30º). I have the carbon fiber rod attached to the lower hole on the flap horn and the middle hole on the elevator horn. Is this normal? I think this travel difference is caused by the flap horn. What do you think about it? Any advice of how can I set up this to have a symmetrical movement with this type of horn?

Thank you in advance and have good flights this weekend!

[Peter Ferguson]

Miguel, welcome to the forum.
I have read through your question and pulled out a set of Strega horns to see what your issue is. On the flap horn the first hole out from the pivot is perpendicular to the flaps. That is where the elevator pushrod connects. The second flap hole, which connects to the belcrank pushrod, is not perpendicular with the flaps but is forward of the flap hinge line. This is to accommodate the angle of the pushrod to the belcrank so there is a right 90 degree angle between the rod and the horn.
Your elevator pushrod should be connected to the elevator horn using the hole that is the same distance from the elevator pivot as the first flap hole for 1:1 movement. My Strega set has only one hole in the elevator horn so it is simple and 1:1. It sounds like your elevator horn has multiple holes, in that case use the hole that is the same distance from the pivot as the flap horn. You may be using a hole that is farther out than the flap hole which would give the elevators less angular movement. Correct this and recheck.

If you still have less up than down on the elevator look for a bind with one of the horns or the belcrank, disconnect the pushrods and move the flaps and elevators to make sure they are free. Move the belcrank to make sure it is not binding or hitting a stop.
If they are free its probably your belcrank, It may not have been centered when you set the pushrod length. Look in the wing to see if it is set to neutral with the flaps at neutral, if not , you can either live with it or you will have to replace the flap pushrod end. I would do this by making a longer rod end for the flaps, cutting the carbon tube and resetting the flaps and belcrank at neutral with the new rod end installed. Good luck , let us know what you find.

[Dennis Adamisin]

Miguel
WELCOME to Stunt Hanger!

Peter Fergusons instruction is exactly what you need to check.  THe only thing I would add was I was hoping that you could also post some pictures of your set up - perhaps take a picture of your flap horn and the elevator horn.  That would make it easier to determine if you should try to make any changes.

[Miguel Marzan]

Thanks Peter, my problem was that the elevator hole did not have the same distance from the pivot than the flap one, so I have drilled another hole in the flap horn with the same distance as on the elevator to achieve the 1:1 movement.

If only the manual just had said anything about the 1:1 movement it would be an instant fix, but I was doubting because it was the first time I saw such a movement relation. I am used to 1:1 or even more movement on the elevator than on the flaps, so it was a good point to question the experts!

Another question, I am going to power it with a brand new Saito 62 (I am also novice with 4s in CL), and I am not sure about the CG position; I have read different positions in the forum, and the manual. Someone with a Strega could recommend me a good starting point for the first flights? I need to know that in order to decide the engine position.

This weekend I have finished the adjustment of the control linkage and the tail take apart mechanism, I hope to finish the fuselage and install engine and tank this week. The target weight is about 63 oz ready to fly. So far is 60 oz with only the fuselage covering an finishing left, I hope I reach it (I prefer lighter planes).

Dennis, I will post some pictures as soon as I learn how to do it.

Thank you for your answers, this is a very good CL forum!

[Dennis Adamisin]

Miguel
I think a 63 oz Strega with a Saito 62 will be a good performer!  Good luck with the completion

To post pictures here, go to the "Additional Options" button to the left of and below the message writing space.  Click on that and it will direct you to how to upload your pictures.

[Peter Ferguson]

I think a 62 oz Strega ARC will be a miracle. If you get there I would like to know what you did to lighten it up. I have had 4 and only one under under 68 oz but they all flew fly fine.

My CG is set at 7 1/4" forward from the flap hinge line.   20 -25% MAC is 7 3/4 - 7" forward from the hinge line. Others have told me to move it forward  but it flew nose heavy for me forward of 20% and resulted in embarrassing upside down power on landings and such.

Miguel what did you do, if anything, to correct the unequal elevator throw (more down than up) ?

[Miguel Marzan]

Hello guys. Sorry for not having replied before, but I have been very busy.

Peter, I solved the unequal throw by cutting a bit of a central rib that was on the bellcarnk's way, now I have both equal up/down throw and also 1:1 flap/elevator movement.

I also post some photos of the transmission linkage after and before the new holes that I did to achieve the 1:1 movement.

You can also see how is my work up to date and the lightning.

To lighten it I made a lot of holes, removed one of each two ribs on the wing, and some sheeting on the wing and stabilizer, I also removed most of the front plywood and the ventilation tunnels. It all counted to make it a bit lighter, but the most significant work was done on the wings. I attach a word file where you can see it (the weights are in grams).

Now I only have left to run-in the engine and build a tank for it any suggestions for the tank? Remember, a Saito 62.

[Peter Ferguson]

Miguel , thanks for the photos and chart . I'll have to try some of your ideas. Let us know how the finished weight comes out and how it flies.

[Dennis Adamisin]

Miguel:
I really like how you lightened up your Strega.  I am also amazed at how much weight you were able to save.  Your lightened Strega WIll be a very good flyer with the Saito in it too!

I have no direct experience with the Saito so I do not have any advice to offer on your set-up.  However the people running the 4-strokes report them to be pretty easy to run.  THe ones I have seen run very well.

[Peter Ferguson]

Miguel, I just noticed you made your Strega into a take apart. I would like to see how you joined the wing LE to the fuse and would appreciate a photo of that area. I was reinforcing my fuse to LE wing joint with carbon cloth and epoxy to prevent the nose from coming off. Did you reinforce that joint?

[Miguel Marzan]

Hello Peter,

The wing is joined to the fuselage with 4 M3 screws, 2 on the front and another 2 on the rear. I epoxied two beech wood strips with their nuts on the fuselage. On the wing, I reinforced the bottom of the fuselage with 3mm Finnish plywood. This bottom fuselage is glued to the wing and has the holes for the screws.

I have not reinforced anything. The only thing I did in the fuse to LE zone was closing the hole made to insert the tank with balsa to isolate the engine/tank compartment from the wing. I also re-glued with epoxy the zone because  the original glue is rubbish, I think it would come off with the time and vibrations.

¡An important advice! If you use my take apart system on your Strega, be sure to make a neat joint between wing and fuse. This is very important. Mine had a couple of mm hole between them, and when I put it together I discovered that this allowed some lateral movement of the nose. That would destroy the model in a few flights with the vibrations of the Saito, so I adjusted the joint and now it does not move at all.

I have not tested the model in flight yet, but I think it does not need more reinforcements.

I hope this indications help you a bit, I also accept any suggestions. I will make some photos for you tomorrow and post them as soon as possible.

[Miguel Marzan]

Here you have some photos of the take apart system, I hope it helps.

[Allan Perret]

Hello guys. Sorry for not having replied before, but I have been very busy.

Peter, I solved the unequal throw by cutting a bit of a central rib that was on the bellcarnk's way, now I have both equal up/down throw and also 1:1 flap/elevator movement.

I also post some photos of the transmission linkage after and before the new holes that I did to achieve the 1:1 movement.

You can also see how is my work up to date and the lightning.

To lighten it I made a lot of holes, removed one of each two ribs on the wing, and some sheeting on the wing and stabilizer, I also removed most of the front plywood and the ventilation tunnels. It all counted to make it a bit lighter, but the most significant work was done on the wings. I attach a word file where you can see it (the weights are in grams).

Now I only have left to run-in the engine and build a tank for it any suggestions for the tank? Remember, a Saito 62.

The bend in the pushrod (elevator end) is not good.  It looks like you did that to get enough travel because it would hit the surface.  It would be much better to move out to the last hole available on both ends and keep the rod straight.  This should maintain the 1:1 ratio.

[Miguel Marzan]

Hi Allan,

You are right on the bend in the pushrod (elevator end), is does not look good. As you said, I did that to get enough travel because it would hit the surface. I know the best thing would be to keep the rod straight, but I want to keep the chance of regulation, so I have no choice. Thank you for the advice, I will straighten the rod once I have fly tested the model if I do not need to make changes in the mevement ratio.

[Miguel Marzan]

edited

[Miguel Marzan]

Well, the Strega is finished at last.

It flies very well. I have also noticed how hard the Saito pulls, I think I will have to move forward the leadout cable guides because after a 7 min. flight my arm is tired.

I have to trim it and get used to it (I have only done 4 flights with it), but I think this plane/engine combination will give me lots of satisfaction.

I post a couple of pictures of the finished plane and the first flights, I hope you like it!

[Peter Ferguson]

Miguel, it even looks light! How close  to your target weight did it come out? . Be sure to check on those take apart screws once in awhile. Good to see that its flying. regards.

[Miguel Marzan]

I am glad that you like my model.

Well, I did not reach the target by far. The final weight is 65,82 oz. I do not know where that 2 oz came from, well yes, I suppose decoration and glue excess. But I am not worried about it because the Saito pulls hard and the Strega is also a big plane, so I do not have power or sustentation problems.

The target of 63 oz. remains for the next one, I still think that it is an achievable target.