Vixen Flaperon Update and Another Flaperon Question

[tim.green]

31.5 hours, 1 quart of stripper and a bunch of plastic razor blades later, my flaperons are free of the protective plastic!

They're in really good shape but a close inspection leads to another question - on the left flaperon the trailing edge is a tiny bit uneven. The trailing edge of the underside protrudes 3/32" at the root. The difference diminishes towards the tip - at the 2/3rds point (from the root to the tip) the edges line up.

I'm inclined to trim this off and make the trailing edges even along the span- opinions?

Thanks for your help! Pic of one of the stripped flaperons attached.

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[Maverick]

They're in really good shape but a close inspection leads to another question - on the left flaperon the trailing edge is a tiny bit uneven. The trailing edge of the underside protrudes 3/32" at the root. The difference diminishes towards the tip - at the 2/3rds point (from the root to the tip) the edges line up. I'm inclined to trim this off and make the trailing edges even along the span- opinions?

Personally, I'd leave it alone. Minor imperfections in the trailing edge of the flaperon will be inconsequential to the function of it. On the other hand, trimming this with precision could be difficult and might haunt you more than leaving them alone. It depends on how annul you are about having the perfect airplane rather than a good one.

[jiott]

I would trim it just for aesthetics. A belt sander would make quick work of it and keep the edge straight. Just my opinion.

[Maverick]

I would trim it just for aesthetics. A belt sander would make quick work of it and keep the edge straight. Just my opinion.
Hadn't considered something like that. Good idea.

[n85ae]

if you're going to paint it, just use a little filler and sand it smooth., It will disappear under the paint, and no need to worry
about messing up in the process of making it better ... Which I personally have done more than once ... :)

Jeff

[tim.green]

Thanks everyone. Very helpful. I'm going to carefully try the belt sander idea and if it looks like it's going to work (that's more a comment on my abilities than anything else) I'll trim it. Otherwise, I'll fill and paint.

On a related note - is it worth using solid / flush rivets on the trailing edge (as suggested in the instructions) or should I stick with pull rivets?

Thanks!

[n85ae]

looks nicer with solids, and a hand squeezer is a good investment in tools anyway.

Jeff

[jiott]

I definitely think solid rivets look much better on the flaperon trailing edge. A solid rivet squeezer would be nice, but rarely used elsewhere. I just used a pair of vice grips with the jaws ground flat; worked great.

[CoClimber]

I bought the 10" KNIPEX pliers for squeezing rivets. They worked great and now I have this cool tool.

[Maverick]

No more often than you'll need them, ask around to see if you could borrow squeezers. Anyone building an aluminum plane would likely help you out. Or ask your EAA chapter members.

[n85ae]

I have a pair of Tatco hand squeezers, and a nice ATS rivet gun, but would concur with this idea of using modified vice grips.
The principal is the same and for the flaperon trailing edge it would work perfectly.

Jeff



I definitely think solid rivets look much better on the flaperon trailing edge. A solid rivet squeezer would be nice, but rarely used elsewhere. I just used a pair of vice grips with the jaws ground flat; worked great.

[Delta Whisky]

Tim - this input might be too late but since we are all here to help each other spend lots of money I would recommend using a vixen file.

Here's one on a palm block: https://www.yardstore.com/vixen-file-on-palm-block

And, as a full file: https://www.yardstore.com/10-single-cut-vixen-file-with-tang. (I don't recommend the double cut version.)

Once used, you'll wonder how you ever got along without one.

[tim.green]

Thanks for the great input everyone. I have another question: We're talking about flush rivets, right? Doesn't this require countersinking or dimpling to make them flush? If so - how would you dimple with anything but a squeezer with the correct dimple die?

Also - thanks DW! That Vixen file looks cool and I'm building a Vixen!

[jiott]

Very careful use of a countersink bit will do the trick. Getting the rivets totally flush is not really necessary. Of course use a dimpling tool if you have one.

[CoClimber]

I've attached a photo of the top and bottom of my rivets that I set with my knipex pliers. I'm not sure how well dimpling would work on such thin metal, but I'm not an aluminum airplane builder.

[Dave S]

CoClimber - rivet work looks good. I do like what folks have done with the solid rivets - although both types work fine - much nicer than the pop rivets.

Regarding "I'm not sure how well dimpling would work on such thin metal" the answer is not very well....

FWIW - if the concern folks have is about areodynamics/drag - the rivets are such as small contributor to drag on the kitfox flaperons it is totally irrelevant.

[Delta Whisky]

The rule of thumb: dimple if less than 0.030 inches thick; countersink if greater than 0.030. On my flaps, the factory used round head solids as did I when mounting the counterweights. Since the shop head will stand proud, as will the backside of the dimple, and because a 3/32 diameter rivet head is so small, to me it doesn't make much sense to go to the extra effort of countersinking. Just my $0.02.

[CoClimber]

It would be fun to calculate the drag from those rivets but I agree that it is probably irrelevant. I did do some calculations for unstreamlined wing struts. I believe that I calculated that at 100mph, it takes 22HP to push them through the air. Well streamlined, it takes less than 2HP, assuming my formulas are correct. This was based on an article I read in the EAA a while back.

[jrevens]

The rule of thumb: dimple if less than 0.030 inches thick; countersink if greater than 0.030. On my flaps, the factory used round head solids as did I when mounting the counterweights. Since the shop head will stand proud, as will the backside of the dimple, and because a 3/32 diameter rivet head is so small, to me it doesn't make much sense to go to the extra effort of countersinking. Just my $0.02.

I concur with this. Having done a lot of metal aircraft work, I’ve been taught that you don’t countersink material as thin as the flaperon skins, which I believe are 0.016”. That thickness is less than the height of the head of an AN426 3/32” rivet which requires a 100 deg. countersink. Common pulled rivets would be a little bit better since they normally have a 120 deg. head, but still not good. If you dimple in this instance, you’re dimpling a bonded joint and damaging it at that point. Probably not a big deal, but you are. I personally like the look of the standard AN470 rivets for this. Being at the trailing edge of the structure especially, the drag is inconsequential. There is nothing directly behind the tiny amount of disruption to be affected aerodynamically.

[tim.green]

Thanks everyone and thanks for the pictures CoClimber. Thanks also for your patience as I'm new to all of this (never had to rivet any of the RC airplanes I built!). Two more questions:

- Setting an AN470 rivet with Knipex pliers - any special technique? Just squeeze it until the shop head is the correct height / width?

- Streamlined wing struts: I've been considering these but they are expensive. KF sells a streamlining kit but they caution that struts streamlined with the kit are prone to damage b/c it's a common push point. Are the streamlined struts worth the $$$?

Really appreciate the help everyone!

[efwd]

I used dimple dies on my flapperons. I have very small, flush head rivets. Worked perfectly, and at over 250hrs, no problems yet. Countersinking is a different story. You will oversize the hole without a doubt.

[CoClimber]

Regarding the KNIPEX, if I remember correctly, one of the positions allowed me to fully close the pliers and get the correct amount of squeeze. These pliers keep the jaws parallel so they work quite well for this application. They are fairly expensive but are so versatile that it was easy to justify the cost.

For the streamlining, you need to understand that I am really cheap so what I plan to do is to cut out foam with a cnc hotwire foam cutter glue them to the struts, then cover them with dacron. Initial testing looks good. They would probably crush if you pulled on them so I was thinking about taking a short section and wrapping it in thin aluminum to create a grab zone. I already cut out a bunch of sections but I want to get my plane flying first to do before and after tests.
27177

[Maverick]

For the streamlining, you need to understand that I am really cheap so what I plan to do is to cut out foam with a cnc hotwire foam cutter glue them to the struts, then cover them with dacron. Initial testing looks good. They would probably crush if you pulled on them so I was thinking about taking a short section and wrapping it in thin aluminum to create a grab zone. I already cut out a bunch of sections but I want to get my plane flying first to do before and after tests.

Sweet! Have you considered covering them with carbon fiber instead of the aluminum?

[jrevens]

... They would probably crush if you pulled on them so I was thinking about taking a short section and wrapping it in thin aluminum to create a grab zone.

I don't think you want people pushing or pulling on your wing struts anyway. I put "No Push" decals on mine.

[tim.green]

Thanks for all of your help so far. Update: 32 hours of work with stripper and plastic razor blades and all of the protective plastic is gone! Satisfying!

More questions:

- scoped the flaperon spar with a f/o camera and there are mud dauber nests in the spar. I scraped most of the nests away but there is residue left behind. I'd like to get all this material removed - any suggestions?

- also scoped the hinge bays. Two of them have similar nests. No great access to try to remove them - any suggestions? Can I just leave them?

- the skins are in good shape with a couple of dings. Suggestions for repairing? Would filling with Super-Fil and sanding to shape work and last?

Thanks!

Tim

[Dave S]

Tim,

Its mud daubers so , well mud - I would soak and blast them with water - a little dish soap might help. Any remaining dirt can be a source for corrosion to start so I would elect to flush them out as best as possible. A little cleverness with a bottle brush or extended gun cleaning rod might help with the spar - if the outboard end is not capped should be doable. Dragging a rag through the spar on a string might help with dislodging the stuff. Bottle brushes which come in different diameters have a wire twist core which can be bent to work around the corners of the hanger bays.

Others might have a favored method but I'd sure try to get the stuff out.