Author Topic: Build threads look fun (Read 60102 times)

Dave_Trible · « **Reply #100 on:** June 14, 2013, 06:20:24 AM »

Up on its legs and on the road back. Had some of that blasted dust from who knows where inside the canopy so I decided to take the opportunity to pull and change it. I'll likely fly this one by mid next week.

Dave_Trible · « **Reply #101 on:** June 17, 2013, 10:02:09 AM »

Des 1 back in service!

MarcusCordeiro · « **Reply #102 on:** June 17, 2013, 07:16:52 PM »

Cool!

Marcus

Dave_Trible · « **Reply #103 on:** June 26, 2013, 08:53:44 AM »

So... What do you do when it's too windy to practice? Build a new fuel tank. I started this a then thought maybe a few hadn't done this before and might like to see it go together. I'm not too worried about how pretty they are, only how they work. My tanks are different (you've come to expect that from me) and run very consistent from start to finish. Making my own also allows me to size and shape it just how I need it to be. For my .61s I use the tanks shown built in the photo. These have been used and removed from other airplanes and will be reused. These are 7 ounces. I am fitting my .76 (John Deere) into my newest plane and need mo gas. I'm building an 8 1/2 ounce tank of the same design.
Externally points to notice are the slant on the front of the tank and the pinch on the back corner rather than a full length wedge along the outboard edge. The slant is to run the tank up under the pipe header to grab a little more capacity. Likewise the pinch at the pick up corner maximizes the tank capacity in a given space. The noses on my planes are about as short as I can manage so space is tight. For Desperado I can only get the 8 1/2 ounce tank in the take apart version where no wing passes through the fuse so it can extend a little further back.

Dave_Trible · « **Reply #104 on:** June 26, 2013, 08:58:09 AM »

You can see I've made a tin blank which will make the top, bottom and inboard side of the tank. I'll bend this and make the side cap. (Then move it out lest I be late for work!)

Dave_Trible · « **Reply #105 on:** June 26, 2013, 09:01:10 PM »

A few more steps tonight. I'm using a couple motor mounts as a bending tool for the tin.

Dave_Trible · « **Reply #106 on:** June 26, 2013, 09:02:51 PM »

Here I've laid out and cut the blank for the outboard side.

Dave_Trible · « **Reply #107 on:** June 26, 2013, 09:04:41 PM »

Here we've cut slits around the curves for bending.

Dave_Trible · « **Reply #108 on:** June 26, 2013, 09:05:53 PM »

All bends are made and the masking tape pulled off.

Dave_Trible · « **Reply #109 on:** June 26, 2013, 09:11:17 PM »

Now clamping it together for soldering. I'll first tack a few spots then continuous solder down the straight joints stopping just short of the curves. I only use fine rosin core solder (electrical) for this. It melts a a little lower temp but most importantly acid core or silver bearing solder leave corrosive flux behind that will eat up your work in short order no matter how you try the clean it. Just don't use them.

Dave_Trible · « **Reply #110 on:** June 27, 2013, 08:45:09 AM »

Once the seams are soldered on the straight sides I turn and solder the inside of these butt joints too. Until I started doing this I've had a couple seam leaks right here where no lapping metal existed.

Dave_Trible · « **Reply #111 on:** June 27, 2013, 08:46:58 AM »

Each side around the curves is pulled in and soldered.

Dave_Trible · « **Reply #112 on:** June 27, 2013, 08:48:09 AM »

Tadaaa!

Dave_Trible · « **Reply #113 on:** June 27, 2013, 08:49:56 AM »

Butting the front down on fresh tin to trace the front cap.

Dave_Trible · « **Reply #114 on:** June 27, 2013, 08:53:52 AM »

Add some around the edge for a flange, cut and nibble the corners.

Dave_Trible · « **Reply #115 on:** June 27, 2013, 08:54:40 AM »

Fit and solder.

Jeff Traxler · « **Reply #116 on:** June 27, 2013, 03:50:00 PM »

Hi Dave,That tank is lookin' real good.Sure is nice to get a custom fit in an off the rack world.I'll be at the Nats in a couple weeks,maybe I can take a look under the hood?See ya there,Trax

MarcusCordeiro · « **Reply #117 on:** June 27, 2013, 04:32:28 PM »

Nice work!!

Marcus

Dave_Trible · « **Reply #118 on:** June 27, 2013, 07:33:54 PM »

Thanks guys but we got a ways to go. Marcus I can always count on you paying attention. Jeff we will sure spend time at the Nats and you can rattle under the hood there.

Dave_Trible · « **Reply #119 on:** June 27, 2013, 08:29:48 PM »

I'm going to do a little plumbing tonight. I've learned the hard way to use ONLY COPPER tubing for fuel tanks. Brass is common but corrodes in our fuel. If you don't trust what I say put a small piece of brass tube in a jar with a little fuel. Leave it set a few days and watch what happens-green slime. I anneal my copper by passing it through the flame on a propane torch very slowly. The copper should just start to glow a little. Use pliers on both ends. Lay the hot tubing on a safe surface and allow to cool slowly. It will be black with scale but sand it clean with 400 grit paper and wipe with acetone or alcohol. This will make the tubing softer and easily bent without kinking.
I put masking tape on the tank where I need to drill holes and marked the locations.

Dave_Trible · « **Reply #120 on:** June 27, 2013, 08:43:38 PM »

Holes drilled.

MarcusCordeiro · « **Reply #121 on:** June 27, 2013, 08:49:30 PM »

Dave

I like building threads I can learn from.
Thanks for posting

Marcus

Dave_Trible · « **Reply #122 on:** June 27, 2013, 09:16:53 PM »

Tools. Here I use a cut off wheel in the Dremel to cut the tubing. Also use a large soldering pencil. Trigger guns are , well, just not serious......

Dave_Trible · « **Reply #123 on:** June 27, 2013, 09:25:14 PM »

I've beveled the end of the pick up tube so it won't somehow become restricted by the back cap or solder. I insert the tube in the front cap and push it about as far back in the tank as I can. This eliminates most of the burping at the end of the run. When we get to it you'll see I place the end of the uniflow tube very near this same spot with little distance from the end of the pick up. This negates most all the lean out at the end of the run. No three laps of scream. Just a few seconds of speed up and a clean cut off . Anyway, I solder the pick up in place inside so it won't move or flop around with vibration.

Dave_Trible · « **Reply #124 on:** June 27, 2013, 09:28:55 PM »

Now the 'secrets' to my tanks. You'll see I've taken what will be the uniflow line and 1. Beveled the edge sharply and 2. Cut or filed a knotch in the very end. It will develop.....

Dave_Trible · « **Reply #125 on:** June 27, 2013, 09:32:38 PM »

I'll close for tonight with one more shot. I've bent the uniflow to its approximate shape and laid it on top the tank in its position when installed in the tank. You can ponder what you are seeing while I get my beauty sleep.

Dave_Trible · « **Reply #126 on:** June 28, 2013, 07:24:47 AM »

At this point I want to touch on my line of thinking about uniflow design and placement. What I'm showing I've used since the ST.46 days with very good results. I get frustrated if the airplane speeds up noticeably through the pattern. There are a few engine issues that could cause that but it's usually tank design. I have seen guys fiddle and fiddle with engines, fuel, props, plugs when the real issue was the tank.
The desired result is to provide a blanket of air pressure to replace depleting fuel and push on the fuel for a more consistent fuel head at the Venturi. What I see as problems are 1. A uniflow line that is placed in a way that centrifugal force pushes fuel back up the uniflow line restricting the easy flow of air down the line. Think of the stopped up kitchen sink. Nothing goes down when stuff is coming up. 2. Placing the end of the uniflow line such that it is no longer submerged in the fuel at some point in the run, letting go the pressure head you've built up in the tank. This drops the head at the Venturi and engines goes leaner. This is the bit about screaming laps at the end of your flight.

Dave_Trible · « **Reply #127 on:** June 28, 2013, 07:32:24 AM »

Given these things my answer is the uniflow line you see. You'll see that centrifugal force will throw fuel OUT of the line helping draw air in. The line arcs up out of the fuel in such a way that the fuel would have to run up hill to come up the line. The end will be soldered directly on top the pick up tube right near its end. The uniflow bevel will be turned away from the pick up opening to block air bubbles from going directly out one and in the other. Instead it bubbles to the air pocket on the inboard side and stays trapped there until the very last few seconds of the run when the end of the uniflow is exposed.

john e. holliday · « **Reply #128 on:** June 28, 2013, 09:13:55 AM »

Dave I have used a sharp pointed punch to make the holes in my tanks. It give a little meat or solder. Sometimes I may even put a washer over the tube for more vibration protection. I like your tank design. It reminds me of Rabe's tanks.

Dave_Trible · « **Reply #129 on:** June 28, 2013, 06:45:46 PM »

Quote from: john e. holliday on June 28, 2013, 09:13:55 AM

Dave I have used a sharp pointed punch to make the holes in my tanks. It give a little meat or solder. Sometimes I may even put a washer over the tube for more vibration protection. I like your tank design. It reminds me of Rabe's tanks.

John I've sure poked many tank holes before but I tend to get heavy handed and gorge out holes way too big. Drills are safer for me.

Dave_Trible · « **Reply #130 on:** June 28, 2013, 07:27:10 PM »

Getting set up to solder in the uniflow. Now you can see why the bevel and knotch in the end of the tube. I'm setting the tube about 1/8" forward of the end of the pick up. You might also notice I ran the uniflow up to the top of the tank then turned down to exit the bottom. This is simply to not allow fuel to gravity drain back out after filling.

Dave_Trible · « **Reply #131 on:** June 28, 2013, 07:31:09 PM »

Soldered in place.

Dave_Trible · « **Reply #132 on:** June 28, 2013, 07:37:11 PM »

Now I've soldered the other end at its exit along with the overflow, which is capped after filling the tank.

Dave_Trible · « **Reply #133 on:** June 28, 2013, 07:41:18 PM »

One last look inside. You can see the overflow way in there running up to the top front corner to get max fill with the airplane sitting normally on the ground.

Dave_Trible · « **Reply #134 on:** June 28, 2013, 07:44:17 PM »

Now I'm going to pour in a couple ounces of acetone and shake it around a minute to loosen the rosin flux and dust. Then just pour it out and let dry while I fashion the rear cap.

Dave_Trible · « **Reply #135 on:** June 28, 2013, 08:31:49 PM »

All soldered up but one more step....

Dave_Trible · « **Reply #136 on:** June 28, 2013, 08:42:48 PM »

In the tank submersion test vessel- bread pan full of water. Blow test looking for bubbles/leaks.
This job is done. Ready to install. Making tanks isn't tough and you should try. They might look crude but you get better with practice.

Dave_Trible · « **Reply #137 on:** June 29, 2013, 08:42:58 AM »

Ouuuuu... Dat tight!

john e. holliday · « **Reply #138 on:** June 29, 2013, 09:34:12 AM »

Tank looks great Dave. The punch I use is out of the old school compass we used to use to make circles and arcs.

Bill Little · « **Reply #139 on:** June 29, 2013, 10:55:20 AM »

Quote from: Dave_Trible on June 17, 2013, 10:02:09 AM

Des 1 back in service!

Hi Dave,

A truly "professional" repair you did there! When you cannot tell where the damage was, it's truly well done.

BIG Bear
RNMM/AMM

Dave_Trible · « **Reply #140 on:** June 29, 2013, 12:07:56 PM »

Thank You Bill! Just glad to have the bird back. I think it's the Nats ship as of right now.

Bill Little · « **Reply #141 on:** June 29, 2013, 01:02:12 PM »

Quote from: Dave_Trible on June 29, 2013, 12:07:56 PM

Thank You Bill! Just glad to have the bird back. I think it's the Nats ship as of right now.

Best of Luck at the NATS, Dave. I can only "wish" I could be there this year...........

BIG Bear
RNMM/AMM

MarcusCordeiro · « **Reply #142 on:** June 30, 2013, 05:55:43 AM »

That's as custom-fit as one can get...
Looks great too!

Marcus

Avaiojet · « **Reply #143 on:** June 30, 2013, 06:20:58 PM »

Outstanding!! Kudos!!

Great workmanship and the photos are excellent also.

A Grand Slam!

Charles

Dave_Trible · « **Reply #144 on:** June 30, 2013, 08:54:24 PM »

Thank you guys for your kind comments. Getting this one ready for the second half, the team trials. I'll test fly it as soon as I get back from Nats. I'm already wondering how that .76 will feel in a 650 sq in airplane. May have to tie myself to a stake in the ground, but I should cut this d#&$ Kansas wind.

Dave_Trible · « **Reply #145 on:** July 07, 2013, 08:34:29 AM »

I have a little time between practice sessions so maybe can do a little on the original project of this thread. I'm digging a few hardware parts out of a hangar queen to reuse and save time. I had made a point early on about cutting lightening holes in soft balsa ribs to a fault. When I cut away some covering on the queen (Desperado #2 which was subject to too many design developments) I found exactly what I was talking about earlier. If you look closely you'll see how just the tightening silk span crushed the ribs and altered the airfoil shape. This is why I'm leaving the ribs solid with the minimum lead out clearance.

Dave_Trible · « **Reply #146 on:** July 07, 2013, 09:31:33 AM »

Back on the building board I sheeted and cap stripped the wing and left to dry overnight. This morning I lifted the wing. I removed the first cap I tack-glued on the leading edge and squared off the wing and tips to receive the 3/16 final cap. I left it wide and will trim it later.

Dave_Trible · « **Reply #147 on:** July 07, 2013, 09:32:40 AM »

Cap being applied.

Dave_Trible · « **Reply #148 on:** July 07, 2013, 09:34:57 AM »

Out of the queen I got the tip weight box which I mounted in the new wing. It's made of pieces of motor stock to hold screws and 1/16" plywood.

Dave_Trible · « **Reply #149 on:** July 07, 2013, 10:24:37 AM »

Here the bellcrank has been installed. It is suspended between the two plywood platforms. The pushrod is retained with a wheel collar-not soldered. Now I will JB Weld anything in here that could work loose. Over the years I've had two cases where the nuts screwed down tight on the bellcrank and bushing causing heart surgery in the airplane. That's what taught me to JB the works. Never a problem since.