[aparchment]

Dan:

Just saw your April 3rd posting on your site where it looks like you were working on your trim tab. Having recently completed mine and agonized over various aspects, I was just curious what you were doing on April 3?

Mine came out reasonably well, but I am considering doing it over due to the following:

- amount of hinge revealed is not consistent from root to outboard edge. It's only off by at most 1/16th but it is noticeable. The trailing edge alignment from elevator to trim tab is perfect though and the range of motion and smoothness are not affected.

- the height of the trim tab bottom skin is perfectly aligned with the height of the elevator bottom skin at the root but about 1/8th lower than the elevator skin at the outboard edge. I am at a loss to explain how/why that happened.

- I didn't bend the ends of the trim tab skin because it was a huge pain, instead I opted to make riblets. They came out well, but it will require some filling to make everything look perfect. Fortunately I plan on painting this section of the plane.

Antony

 

[TShort]

Ha! I guess I'm not the only one that sneaks around the site looking at pages that aren't fully updated yet!

Thomas
-8 wings

 

[dan]

Antony,

My opinion is not to sweat the small stuff. If the trim tab is functional, then that's all that matters imho. If you opt to fix cosmetic items, then, well, that's your call to make.

I haven't updated my site in a while. I built a new trim tab as one of many "paint prep" items that I'm punching through. My original trim tab had a little crimp in the trailing edge, and it had developed a bit of play at the clevis attachment. Could have fixed those with filler and new horns or a bigger clevis, but I wanted to build a new trim tab anyway. Trim tabs are cheap, and I wanted a perfect one.

This time around I put my half-baked composites skills to use, chopped the end tabs off, and made flush composite ends. It was more an exercise in playing around rather than resolving any major issue. I didn't have any problem with the V-block bends the first time around, but I wanted to see how it would come out with composite ends. I'm happy with it.

 

[mike newall]

"paint prep"..........................

Now that's a scary phrase Mr Checkoway, sounds like a scheme is in mind and the paint may be on order ?

 

[aparchment]

Thanks Dan

Thanks Dan:

Actually I am curious about how you did the composite caps for your trim tab. I would like to do the same and perhaps also cap the ends of the HS and other control surfaces. I am experimenting with filling the trim tab riblets with expanding foam and glassing over it, but I am concerned that the layup will delaminate where it meets the metal skin at a 90 degree angle. If this happens, at best there will be a crack visible in the paint, at worst the filler will come apart. Any suggestions?

Mark Manda filled the tips on the ends of his empennage so that they were flush, but unfortunately I didn't get a detailed answer from him on how he did it.

Antony

 

[szicree]

I don't mean to question anybody's workmanship so please don't take it that way, but before you go filling ends of ribs and such with foam and glass go look at some examples REAL close. Most of the planes I've seen with filled stuff show signs of cracking, splitting, etc. I'm not saying that it can't be done, but the vibration and temperature extremes make it tough to get glass and metal to get along together. I still haven't decided whether I'll go that route or not, but at this point I've got a hundred more pressing items to finish. Lastly, by the time your plane looks like a plane, the little crap will be barely noticable. I mean that having a complete airplane sitting in your garage is kind of mind-boggling (in a REALLY cool way) and whether or not it has perfectly pretty little faired in elevator tips matters not. I think Bare-Metal Dan knows just what I mean.

 

[dan]

Actually I am curious about how you did the composite caps for your trim tab.

First let me say that I don't recommend this method...ok, that said...

I epoxied 1/4" foam riblets in place about 1/8" recessed into the ends of the trim tab (the aluminum inside was roughed up along the epoxy line to promote adhesion). I then mixed up a thick West System epoxy + flocked cotton (flox) paste and filled the ends with it. I did one end at a time, letting the trim tab stand up on the end, with the end resting on clear plastic wrap. When cured, the ends were nearly done already -- square and smooth. I then did some minor filling with Rage Gold.

There are better methods, but that's the method I used.

 

[aparchment]

nice!

Nice technique! Thanks Dan. I was mulling over how to have the foam not go flush with the top of the riblet so that I could built it up with some sort of reinforced epoxy. Your riblet idea should work really well and hopefully stand up to vibration and resist cracking! The trim tab is the perfect test.

By the way, for others, the first attempt of the expanding foam did not work well on my test piece.

Antony