rv8bldr
4A Scratch Builder
Recently I posted a thread regarding Hstab incidence and elevator trim throws. It was a GREAT thread as there were lots of ideas and input, all of which contributed to me finally being able to get a stabilized, FULL flap, approach at about 50kts in my 4A. I was never able to get it stabilized below 55 kts so couldn't get the last notch of flaps.
Jon Battson said that he had someone weld an extension onto his flap handle to help with that last notch. Well, duh, why didn't I think of that?
I have now made two mods to the flap handle that I thought you might find interesting.
1. During the initial build process, I welded a raised handle onto the top of the flap handle to make it easier to get the first one or two notches of flaps. Being old and, um, "robust", that's a long way down there and this helper handle makes it super easy. The other issue that raised itself was "How do I depress the flap button to completely lower the flaps ?". Well, I made a dead simple pivoted lever that allowed me to depress the button with a squeeze of my fingers.
2. Now that I knew I needed the flap handle extension, I grabbed a piece of 7/8" x .058 4130 and cut it to slide over the existing handle and still provide a 4" extension. I also welded an appropriate length extension onto the flap button, which is even FARTHER away now. I knew my simple lever arrangement just wasn't going to work given the geometry. I was going to need something else.
I futzed around in Fusion 360 and came up with a pivoting trigger and pulley arrangement that is simple, light, and can be 3D printed. I used some 1/16" braided trim cable and and small nicopress fitting. I realized after taking the pics below that I needed a cable keeper around the bottom of the pulley so that is in the final version that has been installed and flight tested. Works great!
There is almost no pressure on the trigger or pulley when activated because I am in the habit of taking the pressure off of the flap before squeezing the trigger. The parts are printed in PLA which is fine for the trigger, but I need something better for the pulley. ABS maybe? It gets used, on average, about once a flight unless I'm doing circuits. I might be able to find a 1" aluminum or fiber/phenolic one. Regardless, in the meantime I'm checking it during my preflight. I have a bunch of pulleys printed up and it takes about 3 minutes to swap it out so I will do that fairly often just on spec.
Jon Battson said that he had someone weld an extension onto his flap handle to help with that last notch. Well, duh, why didn't I think of that?
I have now made two mods to the flap handle that I thought you might find interesting.
1. During the initial build process, I welded a raised handle onto the top of the flap handle to make it easier to get the first one or two notches of flaps. Being old and, um, "robust", that's a long way down there and this helper handle makes it super easy. The other issue that raised itself was "How do I depress the flap button to completely lower the flaps ?". Well, I made a dead simple pivoted lever that allowed me to depress the button with a squeeze of my fingers.
2. Now that I knew I needed the flap handle extension, I grabbed a piece of 7/8" x .058 4130 and cut it to slide over the existing handle and still provide a 4" extension. I also welded an appropriate length extension onto the flap button, which is even FARTHER away now. I knew my simple lever arrangement just wasn't going to work given the geometry. I was going to need something else.
I futzed around in Fusion 360 and came up with a pivoting trigger and pulley arrangement that is simple, light, and can be 3D printed. I used some 1/16" braided trim cable and and small nicopress fitting. I realized after taking the pics below that I needed a cable keeper around the bottom of the pulley so that is in the final version that has been installed and flight tested. Works great!
There is almost no pressure on the trigger or pulley when activated because I am in the habit of taking the pressure off of the flap before squeezing the trigger. The parts are printed in PLA which is fine for the trigger, but I need something better for the pulley. ABS maybe? It gets used, on average, about once a flight unless I'm doing circuits. I might be able to find a 1" aluminum or fiber/phenolic one. Regardless, in the meantime I'm checking it during my preflight. I have a bunch of pulleys printed up and it takes about 3 minutes to swap it out so I will do that fairly often just on spec.