Author Topic: Control surface fit and interesting issues (Read 3505 times)

Randy Powell · « **on:** May 14, 2007, 09:43:07 PM »

OK, so the last plane I built, a classic, had an issue when I went to put it together after the clearcoats. I got a little too clever with the rather good fit of the control surfaces. I didn't leave enough room for paint and the things were a very, very tight fit. As in they didn't move. So I sanded the end of the flaps (between the flap and fairing) down and had to do the same with the elevators. Still a nice fit, but it was just before a contest.

Now comes the really fun part. It rained at the contest. I dried the plane off pretty well, but today when I took it out of the rack, the control surfaces again wouldn't move. Seems some water had crept into the area I sanded and swelled the wood. Great, so more sand paper and I got them moving freely again.

The surfaces are glued on (the hinges, that is). Any ideas on how to dribble some sort of sealer in there so this doesn't happen every time the plane gets damp? I do live in the Northwest, so the chances of them getting damp again are pretty good.

What sort of sealer? Just dope? Maybe something else?

John Miller · « **Reply #1 on:** May 14, 2007, 10:02:41 PM »

Wow Randy, I've never had this problem. Probably because, by trade, I'm a sheetrocker. (close is good enough, the finisher will fix it.....

)

Seriously, How big of a clearance gap have you managed to sand in? I would consider at least 1/16", then use epoxy to seal from future downpours.

John

Howard Rush · « **Reply #2 on:** May 14, 2007, 10:10:29 PM »

Do unto finishers as you would have framers do unto you.

Larry Wong · « **Reply #3 on:** May 14, 2007, 10:13:18 PM »

Well Randy I thought I was the only on that did things like that, what I did was sanded it with a nail file to about 1/16" then put some thin C/A carefull not to let it drip on the finish, the C/A will seal it so that you can sand it with fine paper , it's like plastic.hope this helps

frank carlisle · « **Reply #4 on:** May 15, 2007, 05:19:17 AM »

Dang Randy.........this is a problem for sure.
If I'd have done it I would first mope around the house wondering how all my great ideas can go so wrong (I do this all the time).
It looks like maybe 3 choices---
#1--deflect the control surfaces as far as you can and use a little brush to get in there and seal 'em with dope or something.
#2--cut the surfaces off and reset the hinges.
#3--keep it dry. Get a tarp or plastic drop cloth to cover the plane when it rains.

Oh and by the way--my latest flub was creating a snug fit side to side for the fuel tanks on my LA Heat. Now that it's finished the dope has drawn the opening in some and now I have to pry the engine compartment sides apart to get the tanks in there.
Ain't it grand?

frank carlisle · « **Reply #5 on:** May 15, 2007, 06:26:12 AM »

Guess what Randy??

I did the same thing you did. Yesterday I glued the hinges in for the elevators. Today I checked them and they are snugged right up against the trailing edge of the stabilizer and the movement is restricted. Dang.

Ward Van Duzer · « **Reply #6 on:** May 15, 2007, 10:51:29 AM »

Hey Guys,

I am presuming that you're talking about Making the notch in the flap too small for the hinge to move freely.

Try this. I got the idea from Hunt years ago and it works like a charm for me. We're going to make a little tool for SANDING a perfect notch in the flaps/elevator every time. Check the pictures. The object is to make the tool create a notch abt. 1/32" too deep, and abt. 1/16" too wide for the brand of hinge you are using. Cut and shape various sizes of plywood to sandwich together what you need. I have several of these all identified for the different hinges I use.

Cut the slot using whatever you do for that process. Then use this little tool to file/sand the hinge notch. Making the tool to create a notch a little oversize for your brand of hinge will give you a perfect notch every time.

Bill Little · « **Reply #7 on:** May 15, 2007, 11:21:20 AM »

HI Ward,

I'm pretty sure they are talking about the side to side clearance of the moving surface and the fillets on the fuselage.

Randy,

I use heavy sandpaper folded over itself a few times and stuck between the flap, or elevator, and the fillet. As you move the control surface against the sandpaper, fold it over again and sand some more. Thin CA and the little Teflon tube seals it back up and a very little touch of the correct shade of dope will make it all go away and seal it from moisture.

Randy Powell · « **Reply #8 on:** May 15, 2007, 11:49:02 AM »

Thanks for all the input. I used a piece of sandpaper glued to a piece of 1/64" plywood (making it about 1/25 of an inch). Got it sanded in and have a slight amount of clearance. It moves well with no rub now. I'll probably try the dribble in some CA idea. Just a touch.

Frank,

You wouldn't believe the number of flubs I've had to fix. I suppose that's the problem when I go to a contest. Others see a pretty plane. All I see are the number of things I had to fix. Sigh... Such is life.

frank carlisle · « **Reply #9 on:** May 15, 2007, 03:15:53 PM »

My flub has to do with getting the leading and trailing edges of the stab and elevators so close that they don't have all the travel they did before I glued the hinges.

Thanks for the tips guys.

Randy,
I've seen the lists of fliers you fly contests with. You're flying with some high ranking guys. The pressure is terrific trying to keep up with them.
I know what you mean about you see ugly and they see pretty. I'm suffering exactly that as I assemble the Heat. I almost wish I hadn't blabbed so much about it now.

minnesotamodeler · « **Reply #10 on:** May 15, 2007, 04:37:04 PM »

Well, good advice given all around; only thing I can add is that when I need a little more clearance between the flap/elevator and fairing, I take material off the fairing, not the movable surface...at least then it's easy to get to for sealing/doping, etc., being it's facing out rather than toward the fuselage.

Frank, I've lost count of the number of times you've described something I thought I was the only who did: This time it's "...mope around the house wondering how all my great ideas can go so wrong..." Somehow comforting to know I have company.

--Ray

Randy Powell · « **Reply #11 on:** May 15, 2007, 04:45:58 PM »

Frank,

The flubs I find most frustrating are, like the control surfaces here, are areas that I got too "cute". I don't know how many times I've come up with some idea, executed it, then found out that I fogot to consider something. Oh well, it's flies pretty well.

frank carlisle · « **Reply #12 on:** May 15, 2007, 06:21:36 PM »

Randy,
The plane flying good is the most important. And I've seen your planes. They're colorful and well done.
I usually flub the worste in sanding everything off. The planes are lite but they do tend to get wiffles when I cover and dope 'em...........note to self-don't sand it all away.

Great minds Ray........think alike. Sometimes instead of moping I sulk.

Randy Powell · « **Reply #13 on:** May 20, 2007, 01:38:33 PM »

Well, I gound the ends of the flaps off. Cleaned it up and hit it with some CA. Sanded again and it looks to be sealed. I managed (of course) to get some on the top of the flap. Sigh... Took a long time to clean that up.

captcurt · « **Reply #14 on:** May 20, 2007, 01:56:36 PM »

Hi Randy:

I'de have done it with epoxy--thinned a little with alcohol. Let it set for a bit to soak in, then slide a pc of cotton fabric into the gap and wipe off the excess. Less wicking danger than CA>

Hope it stays good for you. We had some real issues with control surface swelling during the last two Nats events.

Curt

frank carlisle · « **Reply #15 on:** May 23, 2007, 03:02:41 PM »

Is everything working good with the controls now Randy?

Randy Powell · « **Reply #16 on:** May 23, 2007, 03:45:48 PM »

Frank,

Well, they were operating pretty freely until I taped the hinge line. Sigh... Still work OK, but are stiffer than I'd like. Should be fine. I'll find out this weekend at the Northwest Regionals, I guess.

frank carlisle · « **Reply #17 on:** May 23, 2007, 04:22:57 PM »

I've been wondering if taping the hingeline really increases the planes proficiency significantly or if it's one of those things we do because other people say it should be so.

What's your take Randy? Did you fly the plane without tape? And then with tape?

peabody · « **Reply #18 on:** May 24, 2007, 03:58:25 AM »

Frank...I'm not Randy, nor do I fly worth a crap, but Brett Buck says to tape hingelines.....BEFORE even the first flight.
Brett may be abrasive and may hold PAMPA in too high esteem, but he can flat fly an aeroplane and he knows what he is talking about...

minnesotamodeler · « **Reply #19 on:** May 24, 2007, 08:48:33 AM »

Well, I'm glad that's settled...

frank carlisle · « **Reply #20 on:** May 24, 2007, 08:56:50 AM »

Quote from: peabody on May 24, 2007, 03:58:25 AM

Frank...I'm not Randy, nor do I fly worth a crap, but Brett Buck says to tape hingelines.....BEFORE even the first flight.
Brett may be abrasive and may hold PAMPA in too high esteem, but he can flat fly an aeroplane and he knows what he is talking about...

Just idle curiosity on my part Peabody........I haven't ever taped hingelines but I do have a plane I've been flying for several years. I think I'll tape it and see if I can tell if it makes a difference.
The difference should be measurable or at least noticeable Right?

peabody · « **Reply #21 on:** May 24, 2007, 11:59:45 AM »

Frank...yo should feel it, yup.

frank carlisle · « **Reply #22 on:** May 24, 2007, 03:21:04 PM »

Quote from: peabody on May 24, 2007, 11:59:45 AM

Frank...yo should feel it, yup.

I'll give it a whirl Peabody..........

Randy Powell · « **Reply #23 on:** May 24, 2007, 04:38:49 PM »

Hi Frank,

Taping hinge lines is a trim tool like any other. By far, I've had more planes that have benefited from this than not. The current PA plane I'm flying, it's a toss up. With the hinge line taped, it tracks a bit better and the very slight hunt I get goes away. But it doesn't turn as well. Probably too much lift from the wing. I have it taped and just have to work the handle a bit more.

I've had other planes that did not behave as well with the hinge line taped. They developed some weird habits. This also could be attributed to possible misalignment or possibly too high a lift to payload ratio. This was more common with the high aspect ratio planes I was building for awhile. They just flew better without the tape. I built a couple of those with inset, pocketed control surfaces in an effort to avoid taping and get a good hinge seal. That worked pretty well.

I've also used hinge line taping for other trim issues. The USA-1 I build was exactly according to Warren Tiahrt's plans. It had a much bigger inboard than outboard flap. As a result, the plane rolled away from me pretty hard on inside or outside control. Nice for line tension, but didn't look all that hot. I put a tab on the outboard flap, but it wasn't enough. I ended up taping the hingeline on just the outboard flap and the plane came around a flew very well.

I've also taped just partial hinge lines to get certain effects. It's just another trim tool. When taped, you don't get air leakage between the top and bottom of the wing (or tailplane). This gets rid of some issues of weird tracking (where air is indiscriminately moving between the top and bottom surfaces) and it also makes the wing more efficient so you create additional lift (and drag). Can be a good thing if the plane is a bit porky. Gives a little extra payload carrying capability. There are a lot of uses, depending on what you're trying to accomplish.

Oops, forgot to address the question ::blush::

The Novi has a slight tracking problem in level flight. It seems fine in maneuvers, but in level flight it displays a very slight hunt. Hopefully, taping the hinge line will cure that. I'm guessing that this has at least something to do with the outboard flap having a very slightly wider hinge gap that the inboard. I couldn't tell by looking, but a caliper says it's true. This, along with too much elevator made it interesting to fly at the last contest. Now that I have the elevator control adjustment issue resloved (had to re-work the hatch to I could get to the stupid thing - another Doh!

) I hope that with taping the hinge line, all the minor issues will be resolved and I can just fly the thing.

frank carlisle · « **Reply #24 on:** May 24, 2007, 05:19:17 PM »

Well............................that was a well put together explanation of taping hingelines Randy. And I have a better idea of it's uses.
I gather that like any other trim solution taping has it's place.

Randy Powell · « **Reply #25 on:** May 25, 2007, 12:20:37 AM »

Frank,

Most planes (almost all) will benefit from taping the hinge line. I've had a few special cases that it either didn't help or made the problem worse, but that's pretty unusual. For the most part, it just works.

frank carlisle · « **Reply #26 on:** May 25, 2007, 09:32:14 PM »

I've got a Pathfinder that I'll tape up. Then I can see for myself. I'll try to get it out this weekend.

Bill Little · « **Reply #27 on:** May 26, 2007, 01:45:25 PM »

HI Frank,

I haven't responded, until now.......... Brett, Ted, Bob W., and most all of the guys from the West, plus Windy (he ain't from the "West"!), all seem to tape the hingelines right off the bat now. Those guys seem to finish pretty high up on the NATS food chain!

Me, I just use full span cloth hinges........I think I got that from that guy up near Berea, OH..........actually I know I did.