B Model Flap Question

[pappas]

(I have the old servo motor as well but rigged a DIY electronic solution for my flap position indicator and sensor that cost 25 bucks or less. Can be viewed in the Sonex group in Facebook.)

Gregg, I am not on Facebook, can you post the details of your DIY position indicator here?

Never mind, I found it. You electronics guys have all the fun. I have no clue how to make that thing!

[Spaceman]

What size fuse or breaker are you guys using on your flap motor circuit?

I initially had a 5a fuse installed (I don't really remember how I chose that), and before I installed the wings and flaps I could run the motor up and down until it stopped moving (or slips its internal clutch or whatever it does at the end of its travel). Anyway, once I started rigging the flaps I found that it would pop the 5a fuse right as I hit the upper end of the flaps' travel, and that was before I had really started setting them to the neutral position as called out in the plans. Nothing was binding , but maybe it was just hitting a little bit of friction right at the top. I switched to a 7.5a fuse, and then I could run the motor to the upper stop again without popping it.

Then I started actually setting the pushrods up, and I found that if I set the flap at that specified neutral measurement (74mm or whatever it is in english...), it would still sometimes pop the fuse right at the top when I raised the flaps. Again I can't feel any binding if I move them by hand so it must just be a tiny bit of friction right at the top.

I lengthened both pushrods one turn from there and now it works great, I'm just not quite at the specified measurement. From what I can tell with my digital level they're about 0.5 degrees down from where the plans want them. Should I try a 10a fuse or just stop worrying about it?! It's wired with 18 gauge wires and it's not a very long run...

Also, just for another data point, my pushrods were also way too long with 3" threaded rod. I cut them to 2" and now they're good but both ends are screwed pretty much all the way in. 1-7/8" probably would have been perfect for me.

From full up to all the way down my flaps appear to move 27 degrees too. That's probably good enough and I don't know what I could reasonably do to get more travel anyway so I'm not too worried about that!

[Spaceman]

Here's what my travel looks like by the way!

[T41pilot]

I have a 5 amp breaker for my flaps with no issues so far. They were run several times during the rigging process. I don't linger on the switch at all when it gets to the end of travel in either direction. Under normal circumstances I would have chosen the value by looking at the model of actuator and looking up max current draw under load and then went above that by 1.5 or 2 times the value. I can't remember if I actually did that or not. 10 amps is a lot of current and I wouldn't expect the actuator to be using that much. If you can, find the actuator model and manufacturer and look up the specs. It's been too long since I installed it to remember. My plane is closed up now, so I can't easily find that for you without removing my seat back. Let us know what you find in case I need to change my breaker too.

[pappas]

I have a Vertical Power VPX Sport handling all of my electrical systems fusing and power routing tasks. It is adjustable and I can set any amperage I want for the components. I set my flap fuse limit at 7.5.

I set flap presets at 10, 20, and 30 (actually 27 degrees, I don't think anyone gets the full 30 with the actuators we have). I touch the stick-mounted switch once for each next downward stop and the actuator will go directly to the selected stop. One touch upward, and the flaps go all the way up to zero.

The VPX allows me to limit travel, (an adjustable setting), to a final up and a final down stop. However, I can control my flaps without presets from my EFIS, similar to a panel-mounted switch. I noticed that if I hold the manual switch for too long at the top or bottom of travel, the fuse will pop. I think that is what is happening to you. In an effort to make sure that the flaps are all the way up or all the way down, you may be holding the switch a little too long which overloads the circuit and blows the fuse.

I also noticed in your video that if your initial digital reading is 2 degrees and your final reading is 27 deg, you may only have 25 degrees of down flap. I used the same digital level to set mine up. As long as the dirty stall turns out to be in the 44-46 mph range you are probably ok.

I also noticed that the plans called for a 3-inch pushrod. No, way too long! I think the plans are wrong. Mine is almost the same as yours.

Remember that if you have more than 2 and 29/32 inches distance above the leading edge as a flaps neutral starting point, that will mean that your flaps trailing edge is actually hanging down a bit into the airstream. Like flying with 2, or so, degrees of down flaps all the time. It took me a while to get that right but it made a big difference for me in the air. Less than 2 29/32's and you will have reflexed flaps). I tried reflexing the flaps for better cruise. It gave me next to nothing in speed and made the stall speed higher.

[Spaceman]

Gotcha, thanks for the info gents. Yeah I try not to excessively run the motor once it hits its stop, but when I was popping fuses it would pop instantaneously... so like the only way to not pop it was to stop short, which I don't think would be practical for flight haha! Now that I have the 7.5a fuse in it seems to be working fine; I think I will stick with that. Yeah 10a seemed like a bit much to me, and if I was just brute forcing the flaps to the top of their travel anyway that didn't really seem like the right answer.

The vertical power setup sounds awesome. Mine isn't anything as fancy as that, but I put a position sensor on the actuator so I can see on my G3X screen where the flaps are at least. I still have to manually control the switch.

Lou, the 2 on the level at the start of the video is 0.2 degrees... I zeroed it on the flap but it went from 0.0 to 0.2 when I sat in the seat. So I guess I have 26.9 degrees of travel really!

I did some more messing around today and also rigged the left flap. Oddly the left flap only travels about 25 degrees even though everything is the same between the two of them as far as I can tell. I'm not sure if 2 degrees difference with full flaps will be noticeable in flight. I guess I'll find out! In the C-130 if the flaps break and go asymmetric we don't get any notice until they hit 7 degrees difference, and that's not too dramatic. Probably not a valid comparison though haha

Anyway, I investigated more why I can't get my flaps in exactly the right 'up' position. As far as I can tell they're each about 0.3 degrees down from where they're supposed to be. I might try filing a tiny bit off the upper trailing edge of the wing to make some clearance, but I think I'll save it for later. I also found it pretty tricky and inconsistent to measure anyway, so I might just be measuring it poorly.

For reference, on the ground my upper longerons are at 8.4 degrees, and the top of the flaps are at 20.0 degrees when all the way up. So relative to the plane, the top surface of the flaps slope downward at 11.6 degrees. Maybe they should be 12? That's a heck of a lot easier to measure in my opinion!!

[pappas]

Oh yeah, 0.2 makes more sense. My flaps are not exactly the same either. However, I don't feel any effect unless I am going too fast for the flap angle I have deployed. Full flaps at 60 mph or less and I don't feel any adverse effect. Full flaps at 100 and I get a distinct heavy left wing.

[Spaceman]

Makes sense!

[pfhoeycfi]

Turns out that I mounted the flap hinges onto the lower wing skin too far forward. I had shoved them against the spar to guaranty that they were straight. However, that had the effect of restricting the top leading edge of the flap from coming forward all the way and causing the trailing edge to be too low.

Moving the hinges aft a bit from the rear spar changes the geometry enough to allow the flap to reside in the full-up position, reducing my 3 1/4 inch rigging measurement to the 2 29/32 inch neutral dimension required. So, it looks like I gained the additional down flap by raising the neutral point.

All my fault......Again! Thanks, Kerry for the confirmation.

Same happened to me...I have 3 1/4 inch and my hinges were located as per the plans. I'll have to drill out all the rivets and move the hinges slightly aft. Do you recall how much you actually moved your hinges? I suspect it will be trial and error. I should have delayed riveting the wing side of the flap hinge until after rigging ...

[pappas]

Peter,
I don't remember the distance that I moved the flap hinge aft of the lower rear wing spar. I do remember that the spec is in the plans and I set it to the plan measurement. It made all the difference.