Author Topic: Slider Fix (Read 5866 times)

Randy Powell · « **on:** August 28, 2011, 08:56:34 PM »

Well, I had two problems with my plane at the last contest. First was a flight issue. You'd think by this time I'd quit doing this. Paul Walker told me a long time ago not to, but I'm kinda hard headed. I build this plane with identical flaps and put tabs on the wings to make up for the difference in wing length. the plane has about 5/8" of asymmetry. Anyway, it flies pretty well, but has some weird quirks in turns and seems to not be able to decide if there is too much tip weight or not enough. Remembering the previous conversation with Paul, I decided to cut the tabs off and build new flaps. The original flaps were a bit torsionally weak and for reasons I will never know, the silkspan was separating from the flap surface. Something was weird, but it doesn't matter since they are now in my trash can.

The other issue was an actual crack in the fuel tank. The tank has a piece of tubing through the middle and is secured by a nylon bolt (ala Ted Fancher). I've done a lot of tanks like this and never had a problem. But I forgot to reinforce the area around the tube on the top (I did it on the bottom). So of course the thing cracked around the tube on the top. Go figure.

Here are a couple of pictures. The flaps are built, but not shaped yet. Right as they sit there, they weigh just a bit under an ounce each. but after shaping, will be around 3/4oz each. That half what the original flaps weighed. And they are pretty stiff, too, without covering. They are also a touch bigger than the original flaps. The plane is a bit, ah, portly and the additional flapage should help.

Allan Perret · « **Reply #1 on:** August 29, 2011, 07:11:57 AM »

Trying to figure out the plumbing on your tank. In the picture is the right side the front, with the 2 tubes ? If so what is the tube in the back corner ?

Randy Powell · « **Reply #2 on:** August 29, 2011, 09:37:17 AM »

HI Allan,

The top right tube is the pickup tube, the one below it (in the picture) is the uniflow and the one on the left is the overflow. The overflow goes into the tank then goes to the top, inside forward corner. It set up that was because of where I put the vents on the outside. The overflow is under the wing in a recessed slot.

Too much 50s hot rod influence, I suppose.

The plate over the center tube would have been a lot cleaner if I would have built it that way originally, but adding it after the fact was a pain and kind of sloppy. I have the creeping feeling that I will end up building another tank in the end. I hope not.

Randy Powell · « **Reply #3 on:** August 29, 2011, 08:40:57 PM »

The inboard flaps is shaped. Still very stiff and all up weight is about 3/4oz. See, there is a use for that brick balsa you have at the bottom of the balsa stack.

wwwarbird · « **Reply #4 on:** August 29, 2011, 08:48:22 PM »

Randy,

How does that tank work without any kind of wedge to it?

Randy Powell · « **Reply #5 on:** August 29, 2011, 11:05:24 PM »

Works great. I haven't built a tank with a wedge in forever. This tank does have a baffle sitting diagonally across the pickup area. It keeps about a half ounce of fuel near the pickup. But I can still do a cutoff loop.

Of course, all that imagines that the thing doesn't have a crack in it. Which it doesn't now. I think I will put a thin foam pad under the tank when I put it back in.

Allan Perret · « **Reply #6 on:** August 30, 2011, 05:53:00 AM »

Have you made any rectangle tanks without the baffle that worked ?

Randy Powell · « **Reply #7 on:** August 30, 2011, 09:39:23 AM »

I have to say I'm a bit surprised by the interest in the tank.

Yes, I've used a square tank without a baffle. The current tank in my RMD is just a box. The pickup tube goes all the way to the center, rear, outside corner of the tank. The uniflow vent goes to the center of the flat outboard surface but only about half way back. And the overflow vent in just the standard deal. It works fine overall, but there is a slight tendency for it to go a lean in the overhead 8s primarily, I think, because it's near the end of the run and the fuel tends to slosh away from the pickup. That's why I now use a baffle placed diagonally across the area of the pickup tube. It keeps the fuel from sloshing too far away and this cured the issue of a slight tendency to lean in the overheads.

I've done probably 10 or 12 tanks like this without issue. The tank pictured above is pretty solid - at least until I got a crack in it. But that is now fixed and I'm anxious to fly the plane again. Hope to have the thing all repaired and ready by the weekend.

Allan Perret · « **Reply #8 on:** August 30, 2011, 11:42:54 AM »

I remember reading some time ago that you made your tanks without the wedge. So on my current build I decided to give it a try. I figured if its working OK for you and you get more capacity by eliminating the wedge, so why not.. But I didnt know about the baffle, so the tank I already made does not have it. I will probably try it like it is, I could add the baffle later if needed.

Randy Powell · « **Reply #9 on:** August 30, 2011, 01:04:54 PM »

Allan,

As I note, the only difference I've seen is that you tend to get a bit more leaning straight overhead at the end of the pattern. With the baffle, that goes away. But other than that, there isn't much difference.

With the baffle, I put it diagonally as I said. This creates a triangle in the outboard corner of the tank. I solder it top and bottom but leave a small gap on the ends and punch a couple of holes in the middle to insure fuel bleeds through.

Allan Perret · « **Reply #10 on:** August 30, 2011, 01:30:42 PM »

I was thinking about making the baffle about 1.5" long and soldering it in at 45° in back corner. That would make the triangle about 1.0" along the rear and outside walls. Is that big enough ? I was also thinking of clipping off each of the 4 corners (about 1/8") of the baffle for fuel passage.

Randy Powell · « **Reply #11 on:** August 30, 2011, 02:35:17 PM »

Allan,

An inch on the side and and inch on the back. That will give a bit over a half ounce (depending on the height of the tank) and that should work. I just left about an 1/8" gap on each end of the baffle, but cutting the corners would work also. I'd also punch a couple of holes in the baffle itself to bleed extra fuel.

wwwarbird · « **Reply #12 on:** August 30, 2011, 06:38:06 PM »

This tank idea is very interesting, especially for when space is an issue. Other than clunk tanks I always just assumed a wedge was necessary for good stunt use as the tank empties. Whenever possible, I would really like to see some photos of the "guts" of your design Randy.

Randy Powell · « **Reply #13 on:** August 30, 2011, 09:31:25 PM »

Wayne,

I'll do up a drawing and post it.

Randy Powell · « **Reply #14 on:** September 01, 2011, 09:00:03 PM »

OK, I haven't drawn up the tank, yet. I'll get to it.

Meanwhile, here's a pic of the shaped flaps. Ready for final sanding and finishing. Wheeeee!!!!

Allan Perret · « **Reply #15 on:** September 02, 2011, 11:15:36 AM »

Quote from: Randy Powell on September 01, 2011, 09:00:03 PM

OK, I haven't drawn up the tank, yet. I'll get to it.

Meanwhile, here's a pic of the shaped flaps. Ready for final sanding and finishing. Wheeeee!!!!

What will you cover with ?

When building up a flap or elevator, do you ever consider just a triangle pattern, without any straight ribs. I have done this and I like the way it looks. I lay out all the ribs at 60° angle. I think it is just as strong as your straight rib and 45° brace pattern, and maybe a little lighter. Sometimes I cheat the angles a little to make the triangle points at the LE coincide with hinge points.

FLOYD CARTER · « **Reply #16 on:** September 02, 2011, 11:41:17 AM »

As I have reported before, all my home-brew tanks are rectangular. They are much easier to form and solder. They take a couple laps of coughing and wheezing for the engine to shut off. This guarantees no suddenly dead engine at the top of the circle. I haven't used a baffle because I want the last few laps to be a warning to me.
Floyd

Randy Powell · « **Reply #17 on:** September 02, 2011, 12:12:33 PM »

Allan,

Well, the reason I built new flaps in the first plane were three-fold. The originals were too flexible, they were heavy and they weren't full span. I felt the tabs at the ends, attached to the wing tip, were causing problems. I wasn't sure if it was the flaps or the tabs that was causing some weirdness in hard corners. And also, the plane is a bit overweight so I figured since I was building new flaps anyway, I would increase the size to both increase wing area and flap area to increase lift. With a 65 in the nose, I wasn't too concerned with the increased drag.

As far as the pattern of the ribs, as I noted, the original flaps had just triangular ribs and 1/20" balsa sheeting. The twisted a lot. A lot more than I counted on when they were covered. These ribs are extremely resistant to twisting without covering (they will be covered with heavy silkspan and painted). The straight ribs were mostly to increase overall vertical area which will increase stiffness when covered and to increase supported area. They will also help some (not much but a little) with decreasing spanwise airflow.

Floyd,

I don't get much of a burp. I will get a slight break directly down wind right at the end of the flight. This is a signal to me that I can probably do a cut off loop.

Randy Powell · « **Reply #18 on:** September 05, 2011, 08:42:14 PM »

Well, the flaps are ready for paint. Man I am tired of the Zen of Sanding.

Chris Wilson · « **Reply #19 on:** September 08, 2011, 05:53:56 PM »

Randy,
I assume that your flaps are made from three ply's of balsa wood?

If that is correct then does the central ply have cut out slots for the hinges done before gluing together?
(I have given thought about doing matching trailing edges that way.)

Cheers.

Randy Powell · « **Reply #20 on:** September 08, 2011, 09:39:55 PM »

Chris,

The center section is hard 1/8" with the notches cut in and slotted for the hinges. It's built from pieces rather than cut for a single sheet. The top and bottom of the leading edge is a 1/4" square piece and the ribs are from some 3/8" x 3/32". If I do it this way again, I'll use two pieces of hard 1/16" with cross grain 1/32" in the middle and leave space for hinges. Probably be a bit more flex resistant, though this worked pretty well.

I painted the flaps, but had some issues (sand throughs and such) so that got repaired tonight and some more filler slopped on. Sand that out tomorrow and touch up the paint and I can shoot clear and glue the things one and GO FLYING!

Chris Wilson · « **Reply #21 on:** September 08, 2011, 10:21:32 PM »

This is creepy, I was sitting down the other day, with no prior knowledge about your way of making wings and arrived at exactly the same construction method!

The only variance is that I was intending to make the central ply out of 1/16" hard balsa because the hinges are quite thin and patch together said scraps of wood into a combined flap and wing outline that is hollow in the centre - so you have a hoop that represents the entire wings shape when viewed from above.

Mark the hinge line on the trailing edge of that hoop, align the hinges along that line, cut the required shape out and then slice away the flaps using a metre long rule.

That way you have the hinge slots lining up perfectly with matched flaps and trailing edges, then you proceed to work through as you have done.

Do you think that this is a workable method mate?

Randy Powell · « **Reply #22 on:** September 09, 2011, 10:49:16 AM »

Could work. Most hinges are 1/32" thick or maybe a touch more so a 1/32" core is where I'd go. As to the rest, just remember that air weighs less than wood so put as much air in as you can. As to the rest, hey, try it and see what you get. I've tried all kinds of construction methods. Partly to find uses for heavy wood that doesn't make the plane a toad and partly to try to come up with ways to use less wood and more air.

Mark Scarborough · « **Reply #23 on:** September 09, 2011, 12:07:41 PM »

""Partly to find uses for heavy wood that doesn't make the plane a toad""

and here I thought the reason you wanted to build light was to make more allowance for paint?

Randy Powell · « **Reply #24 on:** September 09, 2011, 02:23:14 PM »

Seems I end up doing that sometimes. Hey, at least the change in flaps for this plane lost it an ounce. 64oz is better than 65oz.

Steve Helmick · « **Reply #25 on:** September 09, 2011, 02:23:52 PM »

"Simplicate and add lightness" is an interesting saying. I'd like to know who first said it. It's absolutely true, but you also need to add some complexity to ensure stuff is straight, rigid, and stays that way. Adding a bit (of complexity) for EZ to get right isn't a bad tradeoff, either.

Steve

Randy Powell · « **Reply #26 on:** September 10, 2011, 07:11:04 PM »

Had a bit of a setback. Had to cut part of the covering and refinish those areas. the filler coat is drying now.

Sigh...

Randy Powell · « **Reply #27 on:** September 12, 2011, 11:44:10 AM »

Well, if the darned humidity level would just go down (been hovering around 75-80% for a week), the darned paint would dry out and the wrinkle I have would go away and I could shoot the darned clear! Maybe a hair dryer will work.

Sheesh!

wwwarbird · « **Reply #28 on:** September 12, 2011, 07:53:51 PM »

Randy,

I've got one of those cheapo clamp lights with the spun aluminum "bowl" reflector shield. I use a flood lamp bulb in it and it works really well for focusing some mild heat where needed. You can just park the airplane underneath it and leave it sit as long as necessary. It just might work for what you need and you can find them at almost any hardware store.

Howard Rush · « **Reply #29 on:** September 13, 2011, 12:25:36 AM »

Quote from: Randy Powell on September 12, 2011, 11:44:10 AM

Well, if the darned humidity level would just go down (been hovering around 75-80% for a week), the darned paint would dry out and the wrinkle I have would go away and I could shoot the darned clear! Maybe a hair dryer will work.

Sheesh!

Shoot the clear. You have an important contest this weekend. Better yet, bring the Low Rider.

Randy Powell · « **Reply #30 on:** September 13, 2011, 09:46:09 AM »

OK, I got it done. The flaps finally dried out (I put them in the closet with the furnace for a couple hours. That did it). Shot clear last night. I will rub and assemble tonight.

Howard,

I'll be there. No Low Rider though. I have to buy an engine for it. Even then, it will need a lot of trim. That's a project for over the winter.

Randy Powell · « **Reply #31 on:** September 14, 2011, 08:34:48 PM »

Well, the plane has been reflapped and the tank is fixed. Went to put it together and one of the bolt hole stripped out. Yeah, I was happy. So I need to make a new mount. Shouldn't take too long, but it's frustrating. So, I have a day or two to finish that. Sheesh!

Randy Powell · « **Reply #32 on:** September 15, 2011, 09:36:52 AM »

Hi Ty,

I make plenty of mistakes. The trick is to not worry about it and learn how to fix stuff. I built this plane with removable aluminum engine mounts. So it's not a big deal to just unbolt the old mount, machine up a new one and bolt it in. But it takes time and that's the problem. I have to have it done by the contest this weekend.

>>When some one of your caliber and talent has problems building and or "fixin" a model, then I don't feel so pregnant and alone with my models.<<

Sorry to hear you're pregnant and alone.

Randy Powell · « **Reply #33 on:** September 15, 2011, 09:08:16 PM »

OK, it's fixed with a day to spare. Guess we'll see if it works on Saturday.

john e. holliday · « **Reply #34 on:** September 16, 2011, 05:50:53 AM »

Aw, why not wait til your first official flight?

Anyway I hope it works this time.

Randy Powell · « **Reply #35 on:** September 16, 2011, 12:18:46 PM »

Doc,

I have faith (defined as belief in the absence of proof).

Serge_Krauss · « **Reply #36 on:** September 20, 2011, 01:56:01 PM »

Quote from: Steve Helmick on September 09, 2011, 02:23:52 PM

"Simplicate and add lightness" is an interesting saying. I'd like to know who first said it...

Bill Stout of Ford Trimotor fame.

SK