Konrad
Very Strong User
I should know better!
With the Redshift Mk I there is design flaw in that the tail control horns are too short. With my Redshift Mk I I found that flipping the V-tails effectively makes them bottom hinges control surfaces. This was very productive. Moving the hinge line gives one an added 4mm of vertical space to lengthen the control horns. With this new V-tail configuration on my Redshift Mk I I was able to double the length of the control horn from an effective 5.5mm to 11mm length. This modification and the use of threaded servo arms (thanks Jonathan Wells) results in much needed servo resolution. So far so good!
Now I made my mistake in that I was so happy with the performance of the Redshift’s V-tail, I offered to do the modification to a Redshift I had seen flying around these parts. Heck, I had flown this other Redshift and notice the same complaint the owner had. That is with the stock control horns the Redshift did not hold trim (the V-tail double centered).
As both V-tail halves use the same alignment pin spacing the mod should have been to simply drill new holes for the main V-tail joiner (mount), bend the stock 1.9mm wire horns 180°. Oh, and drill a tap the servo arms.
I thought this would take an hour or so of work and a night or two to allow for the epoxy curing steps. Well, I’m sure those of you that know about metal rework see the problem. Yep, that 180° bend on wire that already had been stressed trying to get some servo resolution. Yep, as I bent the wire it broke!
This forced me to replace the wire. It is doable but not all that easy. I then failed the already stressed kevlar hinge. (All the bending earlier had stressed the hinge). So I now had a re-horn and re-hinge job for the V-tail. I did the classic kevlar repair where I could. But for the hinge line adjacent to the control wire I had to use 3M 5200 compound (again thanks Jonathan Wells).
Since I was doing so much rework I had the bright idea of gaining maybe another 0.5mm of horn length by moving down from a 5mm to a 4mm spherical joint. Well, JPJet does not have 4mm spherical joint that will pass 2mm wire. So I had to drill out the brass ball from 1.6mm to 2mm, that a trick all by itself. I had made the assumption that the wire horns were 2mm. Wrong the stock OEM horns are 1.9mm in diameter. So I had to drill another set of brass balls.
When I first started this I was hoping to have extended the horn from 5.5mm to 8mm maybe 9mm. Well, two week later I was pleasantly surprised to find that with this “customer’s” Redshift I now had an effective control horn length of 10mm!
When I took on this work I though that the RedShift still had the OEM control snakes. I was pleasantly surprised to find that the builder/ assembler had replace the snakes with carbon push rods. And here is where I found what might have been a contributing factor with the double centering. The left over sheath for the snakes had been left in the fuselage. (It would have been very difficult to remove the glassed in sheaths). One of the V-tail push rods had gotten wedged between one of these sheaths and the fuselage causing a lot of drag.
And now that I knew the controls to the back were push rods and not the OEM snakes I saw that the push rods were dragging on the wing joiner. I don’t know why the builder had placed the servo tray as high as he did in the fuselage. But this meant that to clear the wing joiner I’d have to kink the push rod. (I hate doing this) But I was able to remove some other push rod kinks. So it was a wash as far as control rod stiffness. I should point out that with the threaded servo control arm that the push rod would have been offset at least another 3mm towards the wing joiner. You might be able to see that in my servo tray installation I’ve set the tray 4mm further down in the fuselage to clear the wing joiner.
There was one more gotcha waiting for me. The servo end of the push rod was a wire of 2.3mm diameter. I would have to turn this down to 2mm to allow me to thread the wire for the 2mm x 0.4 thread I had cut into the servo arm.
And with the ever expanding work scope creep, this Redshift had little or no lateral support in the area of the ballast window. So, I added as much epoxy, glass and kevlar as I dared and still have room for pushrod clearance. I go into details on how to correct this issue here.
forum.alofthobbies.com
Now I have to wait for the fires and smoke to clear to test if in fact I have solved this Redshift’s double centering issues. I know I now have much better servo resolution and power. The original set up had a servo arm of 7mm and a surface control horn of 5.5mm. The new ratio with the flipped tail is servo arm 4.5mm and the control horn being 10mm. That’s 0.78:1 for the OEM set up verse 2.2:1 for the flipped V-tail!
All the best,
Konrad
With the Redshift Mk I there is design flaw in that the tail control horns are too short. With my Redshift Mk I I found that flipping the V-tails effectively makes them bottom hinges control surfaces. This was very productive. Moving the hinge line gives one an added 4mm of vertical space to lengthen the control horns. With this new V-tail configuration on my Redshift Mk I I was able to double the length of the control horn from an effective 5.5mm to 11mm length. This modification and the use of threaded servo arms (thanks Jonathan Wells) results in much needed servo resolution. So far so good!
Now I made my mistake in that I was so happy with the performance of the Redshift’s V-tail, I offered to do the modification to a Redshift I had seen flying around these parts. Heck, I had flown this other Redshift and notice the same complaint the owner had. That is with the stock control horns the Redshift did not hold trim (the V-tail double centered).
As both V-tail halves use the same alignment pin spacing the mod should have been to simply drill new holes for the main V-tail joiner (mount), bend the stock 1.9mm wire horns 180°. Oh, and drill a tap the servo arms.
I thought this would take an hour or so of work and a night or two to allow for the epoxy curing steps. Well, I’m sure those of you that know about metal rework see the problem. Yep, that 180° bend on wire that already had been stressed trying to get some servo resolution. Yep, as I bent the wire it broke!
This forced me to replace the wire. It is doable but not all that easy. I then failed the already stressed kevlar hinge. (All the bending earlier had stressed the hinge). So I now had a re-horn and re-hinge job for the V-tail. I did the classic kevlar repair where I could. But for the hinge line adjacent to the control wire I had to use 3M 5200 compound (again thanks Jonathan Wells).
Since I was doing so much rework I had the bright idea of gaining maybe another 0.5mm of horn length by moving down from a 5mm to a 4mm spherical joint. Well, JPJet does not have 4mm spherical joint that will pass 2mm wire. So I had to drill out the brass ball from 1.6mm to 2mm, that a trick all by itself. I had made the assumption that the wire horns were 2mm. Wrong the stock OEM horns are 1.9mm in diameter. So I had to drill another set of brass balls.
When I first started this I was hoping to have extended the horn from 5.5mm to 8mm maybe 9mm. Well, two week later I was pleasantly surprised to find that with this “customer’s” Redshift I now had an effective control horn length of 10mm!
When I took on this work I though that the RedShift still had the OEM control snakes. I was pleasantly surprised to find that the builder/ assembler had replace the snakes with carbon push rods. And here is where I found what might have been a contributing factor with the double centering. The left over sheath for the snakes had been left in the fuselage. (It would have been very difficult to remove the glassed in sheaths). One of the V-tail push rods had gotten wedged between one of these sheaths and the fuselage causing a lot of drag.
And now that I knew the controls to the back were push rods and not the OEM snakes I saw that the push rods were dragging on the wing joiner. I don’t know why the builder had placed the servo tray as high as he did in the fuselage. But this meant that to clear the wing joiner I’d have to kink the push rod. (I hate doing this) But I was able to remove some other push rod kinks. So it was a wash as far as control rod stiffness. I should point out that with the threaded servo control arm that the push rod would have been offset at least another 3mm towards the wing joiner. You might be able to see that in my servo tray installation I’ve set the tray 4mm further down in the fuselage to clear the wing joiner.
There was one more gotcha waiting for me. The servo end of the push rod was a wire of 2.3mm diameter. I would have to turn this down to 2mm to allow me to thread the wire for the 2mm x 0.4 thread I had cut into the servo arm.
And with the ever expanding work scope creep, this Redshift had little or no lateral support in the area of the ballast window. So, I added as much epoxy, glass and kevlar as I dared and still have room for pushrod clearance. I go into details on how to correct this issue here.
Redshift Mk I (New Purchase)
I often judge a man’s true opinion about a product by wether he spends his own resources on a replacement. Well, I was so impressed at the potential that my first Redshift (a used purchase) demonstrated in only its first dozen or so flight that I purchased a second Redshift. My first Redshift...
forum.alofthobbies.com
Now I have to wait for the fires and smoke to clear to test if in fact I have solved this Redshift’s double centering issues. I know I now have much better servo resolution and power. The original set up had a servo arm of 7mm and a surface control horn of 5.5mm. The new ratio with the flipped tail is servo arm 4.5mm and the control horn being 10mm. That’s 0.78:1 for the OEM set up verse 2.2:1 for the flipped V-tail!
All the best,
Konrad
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