Author Topic: Jetco Shark assembly, volume 2. (Read 2972 times)

Paul Smith · « **on:** January 22, 2010, 11:01:31 AM »

The thread was getting a bit too long, so I started a new one.

It took a lot of thought to decide how I wanted to align the fuselage. It has a built-in 5/16" banana to the right to help the rudder offset. Plus, the front end had to be widened a bit fit the ST G51.

The kit formers are heavy (but not all that big) and the grain runs vertically so there isn't any effective left/right crush resistance.

I layed out the taper with strips on masking tape on my glasstop dining room table. After plotting a centerline, I transferred the offset side lines to the tape with a ball point pen. I cut ten new 90 degree blocks off a 2x4 with my Sears cutoff saw.

The fuselage was beefed up with some 1/8" x 1/2" balsa verticals to resist splitting of the sides.

The gage blocks were glued to the table with hot melt. The formers were replaced with short bits of balsa oriented crosscar for crush resistance.

All this needs to dry by 4:00 PM so I can knock off the blocks and scrap the glue off the table before my wife comes home.

With the full size raw blocks taped in place it weighs 9.8 ounces. Now, how much can I whittle off?

john e. holliday · « **Reply #1 on:** January 26, 2010, 10:51:03 AM »

Hope the glue cured in time. Still looking good. Amazing what a person will go thru for perfection.

Paul Smith · « **Reply #2 on:** January 26, 2010, 11:59:39 AM »

Here we have the major top & bottom blocks taped and spot-glued in place. Each block is held by 3 or 4 tiny drops of glue so it can bee removed for hollowing.

The whole assembly weighs 9.8 ounces now. The challenge is to take off all I can. One good thing about heavy wood - you can show good progress as you whittle it away.

I was building four planes at once. In addition to the Shark, also a Magnum, Clown, and Super Clown. The goal is to concentrate on wood working while the house is sealed for the winter. Some time in mid-March, I'll put away the saws and clamps and clean the basement for painting.

As of yesterday, I put the Magnum on the back burner in favor of better progress on the other three.

That gouge is a Swiss steel tool that cost me $40. Kind of spendy for a hand tool, but it works well for hollowing blocks and makes shavings instead of fine sawdust.

Paul Smith · « **Reply #3 on:** January 27, 2010, 08:53:04 AM »

As I settle in to some relaxing sanding and gouging while watching 24 and Burn Notice, I can contemplate some of the upcoming engineering challenges:

Fuel tank access: The classic way, as shown in the plans, is to permanently build in a certain Veco tank that Lew has known to work well with the (unmuffled) K&B 45. Of course, I'm using a different engine and I don't have a clue about what tank to use or how high to mount it. So I need to design a tank hatch that doesn't weaken the front end too much or add too much weight.

Engine Cowl: The huge ST 51 is going to need some major redesign vis a vis the old K&B 45. Also, the conjunction of the cowl and tank hatch needs some thought. The nose gear pretty well cuts the front end in half.

Dorsal Fin, cockpit, & canopy: There's a need for some substantial mass reduction here. The kit canopy is too thin to work and it's broken. So it's vacuum form a new one or go to a painted balsa canopy.

Control System: I have good assortment of Morris, Sig, Brodak, and Jetco control parts on hand. I can't go much farther until I temporarily install a flap horn and fit a bellcrank that lines up with it properly. My current front runner is a Morris 3.5" bellcrank.

Final Assembly; I reject the kit procedure of building the wing, then constructing the body around it. This would make me sand the blocks while trying to miss the wing & tail. NO WAY! I'm keeping the modules apart as long as possible. Getting things hooked up inside will be a challenge.

Paul Smith · « **Reply #4 on:** January 31, 2010, 04:12:06 PM »

I kinda fell behind on the progress, completing a couple of smaller builds that I really need for this season.

Also, I added a new tool to my chop, a Red Chinese drill press from a low cost importer. Only $80, which is less than a lot of handheld power drills. After a half-century of doing it the old way, this is a big breakthrough. I was mostly concerned with space, not cost. But as it turns out, this tool doesn't need to be bolted down, so I can stow it under the table when I'm in a painting phase.

The tank hatch was resolved in a basic way. Just fore-and-aft 4/40 blind nuts in the plane and the hatch secured with flat head bolts. The holes being nicely aligned with the new drill press.

Also, some routine sub-assembly work on the flippers. As a contribution to mass control, the very heavy 1/16' cheating was replaced with some lighter 1/20".

john e. holliday · « **Reply #5 on:** February 01, 2010, 09:22:49 AM »

Looks very similar to the Harbor Freight drill press I got some time ago. Has been very handy and stores under the desk when not needed. Those flaps look awesome.

Paul Smith · « **Reply #6 on:** February 01, 2010, 04:26:25 PM »

Continuing the process,,,

Dropping a bigga moda into your ride is never an easy job. The basic K&B 45 (unmuffled) weighs 9.6 ounces. My new ST G51 with a 1.5 ounces MACS muffler will be 13.5 ounces, almost a 4-ounce beating. Maybe I can recoup a few tenths with a thinner cowl. The engine is bulked up with tape in preparation for cowl building.

My efforts to lighten the ship have resulted in a tail feather assembly that weighs only 3.3 at this point. Maybe that effort will be nullified if I have to add tail weight.

The wheel weaves as the wheel wills and none can see the pattern until it is done.

Dennis Adamisin · « **Reply #7 on:** February 01, 2010, 06:02:30 PM »

If its nose heavy just use the greenhead

OK forget I said that. A really extreme plan might be to try to machine all the ugly of the 51; turn the sylinder round, remove 50% of the mounting lugs, do some dental work on those front webs. It will never match the greenhead but there is probably 1.5-2.0 oz of extraneaous aluminum there...

OK forget I said that too...

BTW the Shark is going together great. Hang in there!

Paul Smith · « **Reply #8 on:** February 02, 2010, 06:26:10 AM »

Lightening the engine?

Trouble is : We tried stuff like that with combat engines and found that grinding the aluminum didn't get us much, the real weight is in the steel and we don't dare mess wid it. This whole size plane is a learning exercise, so maybe it will balance just right. There's always tail weight and another thing I'm familiar with: moving the engine back one bolt space.

Not to panic. Maybe the old kit Sharks came in tail heavy and needed nose weight. This still has an even chance of coming out right.

Dennis Adamisin · « **Reply #9 on:** February 02, 2010, 10:40:26 AM »

Quote from: Paul Smith on February 02, 2010, 06:26:10 AM

Not to panic. Maybe the old kit Sharks came in tail heavy and needed nose weight. This still has an even chance of coming out right.

Good point. My Dad & Leroy Gunther built their's (1964 or so) with the then new ST 46's & no mufflers. My Dad's was somehting like 64 oz and needed a 2 oz nose weight. Gunny's first Shark was 81 oz (!!!) and used special 1-pc bronze spinner backplate/thrust washer that weighed something like 4 oz. You powre system would have come in handy back then.

The flip side is that yours is bound to be lighter than their's were and you have done a great job in pulling weight off the tail. Keep the spinner as light as possible, use a tongue muffler - & put a weight box in the rearmost fuse!

Keep charging. I can almost hear the cello music as that Shark gets ready to attack...

Paul Smith · « **Reply #10 on:** February 06, 2010, 01:54:17 PM »

I'm slowly grinding along here. Finally stepped up to my big hurdle, the flight controls.

Once it's built in, we really crossed the Rubicon. As the photo shows, I replaced the big plywood bellcrank mounts with smaller trapezoids, beefed up with extra plywood bearings where the axle sits. In addition, the pivot has been moved inboard to put the output on the centerline.

I made bushings for control horn by wrapping it with copper wire, then covering the wire with heat shrink tubing. When glued to the TE and lubricated, this should last long enough.

With the flap horn firmly taped in place, I slide the BC mount fore & aft little find true center of the flap movement. Since all this will be trapped inside, there's no need make anything adjustable. That adds weight and failure points.

I used a Tom Morris 3.5" bellcrank. Tom says the fibre material works forever with a piano wire axle and just a little one time lubrication. So I made the 3/32" output rod the same way. The would thing was assembled with 4/40 bolts for the test fitting. The permanent rod goes in at the last possible moment.

Paul Smith · « **Reply #11 on:** February 06, 2010, 04:09:47 PM »

The MACS muffler showed up. Only 1.5 ounces and it clears everything OK. Can't say much more prior to bench & flight testing.

James Mills · « **Reply #12 on:** February 06, 2010, 04:28:57 PM »

Quote from: Paul Smith on February 06, 2010, 04:09:47 PM

The MACS muffler showed up. Only 1.5 ounces and it clears everything OK. Can't say much more prior to bench & flight testing.

Paul,

I run my Shark 45 with a ST 51 and the weight of the engine for the power you get was never an issue (I think new my Shark weighed about 64 ounces). You can cut some nose weight if needed by going to a tongue muffler (about 3/4 oz.). I've used both a tongue and an Adamisin tube muffler with good results.

James

Paul Smith · « **Reply #13 on:** February 07, 2010, 11:51:56 AM »

If I finish it and hit the CG within 3/4 ounce I'll be happy. The CG of the MACS muffler is a lot farther aft than a tongue, so the extra fraction of an ounce won't be quite as damaging. The big issue is if the engine runs happy with it. Another minor issue is whether the tongue or the MACS actually reduces noise. I don't want to give the electricuters any more ammo than I have to.

Alan Hahn · « **Reply #14 on:** February 07, 2010, 06:20:16 PM »

Quote from: Paul Smith on February 07, 2010, 11:51:56 AM

<snip>... Another minor issue is whether the tongue or the MACS actually reduces noise. I don't want to give the electricuters any more ammo than I have to.

Hey Paul,
The silence isn't all it's cracked up to be. Who wants to hear the judges comments during the flight?

Kinda makes you want to stop the motor right there!

EddyR · « **Reply #15 on:** February 10, 2010, 07:04:39 AM »

Paul that flap horn and clevis should not be in that plane. Those horns with the nylon center are a death wish and the clevis is a Ted Fancher death wish. Ask him about the metal clevis. Get a Tom Morris horn and ball links.

Just friendly advice. I had a Shark in 1974 and the K&B.45 pulled it OK but it was light at 54 ounces. I have pictures of and seen Lou fly his Shark several times with a ST/46 in it and it must weigh at least 60+ ounces.
Ed

Paul Smith · « **Reply #16 on:** February 10, 2010, 04:05:29 PM »

Thanks for the advice. I take it seriously.

As for clevises: The threaded type are a definite failure point. No doubt about, they all fail in the threaded area. But I've used the soldered clevis a lot with 100% success.

I studied several Morris horns. No doubt they are bullet proof, heavy duty, and they'll last like furniture. But planes that last like furniture fly like furniture and the object of this exercise is assembling a kit Shark to a reasonable weight. The Morris horn, complete with ball links, would have cost me .8 to .9 ounces.

It tested both my Sig/clevis rig and a Veco welded horn with a ball link and both a 3.5 pound (54 ounce) loads test.

I might regret it, but I've decided to stay the course and try for light weight.

john e. holliday · « **Reply #17 on:** February 11, 2010, 09:23:07 AM »

Paul, the heart of any plane is the control system. I would never sacrifice dependability for weight savings. Especially the horns with the nylon arms. They are good for sport flying, but would never use them on a plane I spent a lot of time on.

Larry Fulwider · « **Reply #18 on:** February 11, 2010, 12:36:18 PM »

Quote from: Paul Smith on February 10, 2010, 04:05:29 PM

. . .
As for clevises: The threaded type are a definite failure point. No doubt about, they all fail in the threaded area. But I've used the soldered clevis a lot with 100% success.
. . .

It tested both my Sig/clevis rig and a Veco welded horn with a ball link and both a 3.5 pound (54 ounce) loads test.
. . .

The clevis pin is only 1/16" diameter and is simply spot welded to one of the side arms. That is where they break, not where they attach to the pushrod (mssing pin on left clevis in pic).
The bulkier DuBro (center) doesn't have that issue, and there is a safety clip on the other side of the clevis. The Ultrahobby clevis (right) is bulletproof, and was purposely made for demanding CL apps. It has a screw-in 3/32 pin. Steve Moon, who makes these, says on .35 or smaller planes, the DuBro is OK. If you use a clevis, don't use the spot welded ones.

No one has any real data on clevis pin breakage. Failure rates might be as low 1% in 50 hours of use -- which means you will find many people with 100% success rates. And a lot of Ty's, Ed's, and Larry's! Keep using them, and you get to join our "club" of "victims".

Static tests don't tell you much about survival of parts in the air. Vibration, line jerks, are the killers. Your test, if set up on a vibrating table, and allowed to run for some number of hours would possibly be meaningful.

The danger of the nylon horn is less breaking than shifting position due to stress and vibration. You may find, in the middle of a flight, full up just became slightly down.

Larry Fulwider

Edit: Clarify missing pin in clevis

Larry Fulwider · « **Reply #19 on:** February 11, 2010, 12:46:31 PM »

Quote from: Paul Smith on February 07, 2010, 11:51:56 AM

. . . The CG of the MACS muffler is a lot farther aft than a tongue, so the extra fraction of an ounce won't be quite as damaging. The big issue is if the engine runs happy with it.

Good thinking on the CG of the MACS. Please do a follow up here or a new thread on how the MACS works out. Very interesting product.

The Shark is looking great!

Larry Fulwider

Randy Powell · « **Reply #20 on:** February 11, 2010, 12:57:06 PM »

>>The wheel weaves as the wheel wills and none can see the pattern until it is done.<<

Great, quoting Robert Jordan. I love it.

And tell me you're not going to use unsecured clevises? That's just asking for it.

Paul Smith · « **Reply #21 on:** February 11, 2010, 03:48:10 PM »

I don't use the threaded clevis at all. When I used the soldered clevis I either cover it with heat shrink or Dacron line with Hot Stuff.

The engine has been mailed off to be inspected and blessed.

This is end of building for a while I have to take a couple weeks off to attack the slopes at Purgatory, Crested Butte, and Telluride and the trails at Molas Peak, Splains Gulch, and Silverton. I'll think about control linkages a lot on the chair lift.

RandySmith · « **Reply #22 on:** February 11, 2010, 06:27:45 PM »

Quote from: Paul Smith on February 06, 2010, 01:54:17 PM

I'm slowly grinding along here. Finally stepped up to my big hurdle, the flight controls.

Once it's built in, we really crossed the Rubicon. As the photo shows, I replaced the big plywood bellcrank mounts with smaller trapezoids, beefed up with extra plywood bearings where the axle sits. In addition, the pivot has been moved inboard to put the output on the centerline.

I made bushings for control horn by wrapping it with copper wire, then covering the wire with heat shrink tubing. When glued to the TE and lubricated, this should last long enough.

With the flap horn firmly taped in place, I slide the BC mount fore & aft little find true center of the flap movement. Since all this will be trapped inside, there's no need make anything adjustable. That adds weight and failure points.

I used a Tom Morris 3.5" bellcrank. Tom says the fibre material works forever with a piano wire axle and just a little one time lubrication. So I made the 3/32" output rod the same way. The would thing was assembled with 4/40 bolts for the test fitting. The permanent rod goes in at the last possible moment.
[/quote

Paul

You will not be happy if you use the nylon flap horn, I have personally seen many of them make good stunt ships into unflyable ships...The nylon will NOT stay tight and you WILL get play in the horn, it will be able to rock back n forth and your Shark will hunt.

You cannot have a ship that tracks really well with slop in the flap horn or bellcrank....the elevator can have slop but not the flap horn.

Many times you can tell this holding it in your hand..however even if it is tight now it will get loose and sloppy when it is flown

Regards

Randy

Author Topic: Jetco Shark assembly, volume 2. (Read 2972 times)

Alan Hahn