Building a scale 1/4 scale Super Cub from Balsa J3 kit
02-10-2015, 09:13 PM
#826
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Leroy
02-10-2015, 09:31 PM
#827
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John M it sounds like you have done more of this than me, that's where the input from others comes in handy, you can put it in your pot and mix it up with yours and when you need something that pot really comes in handy. I have a pretty big pot and there is always room for more and I'm using a lot of it on this plane so keep it coming.
Leroy
Leroy
Seems to be the simplist solution so far................As I see it.
bird.
02-11-2015, 07:21 AM
#829
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Mike, I looked through my photos and couldn't find a close up of it. I put most of my pictures in 'Dropbox' and they have disappeared! Very unhappy about that. I had nearly every aspect of the build chronicled.
I was thinking about another way that I made that jury strut work also. I had some 1/16th aluminum sheet that I cut some strips from on the band saw that were just wide enough and just long enough to go completely thru the strut. It basically was the strut with a nice airfoil covering. I pinched the ends and drilled them. Very stout. I then used the same aluminum to make 'L' brackets to attach them.
One place you might find a source of aluminum scrap is at your local airport. We have a small 'uncontrolled' airport here and I know the FBO personally. I get what I need. There are even repair shops at controlled airports or home built projects going on that might be able to lend a hand in that area. Find a fab shop somewhere in your area. If they don't have what you need, ask them if they know of someone else.
bird.
I was thinking about another way that I made that jury strut work also. I had some 1/16th aluminum sheet that I cut some strips from on the band saw that were just wide enough and just long enough to go completely thru the strut. It basically was the strut with a nice airfoil covering. I pinched the ends and drilled them. Very stout. I then used the same aluminum to make 'L' brackets to attach them.
One place you might find a source of aluminum scrap is at your local airport. We have a small 'uncontrolled' airport here and I know the FBO personally. I get what I need. There are even repair shops at controlled airports or home built projects going on that might be able to lend a hand in that area. Find a fab shop somewhere in your area. If they don't have what you need, ask them if they know of someone else.
bird.
02-11-2015, 11:10 AM
#831
One thing I have done with the aluminum strut material to make a strong end termination, is to take a threaded rod, 2-56 or 4-40, and glue it in the end with JB weld. You can shove some cotton down the end a little ways into the strut to create a dam, preventing the JB weld from running all down the inside of the tube. After this cures, you can take your cut off wheel and grind the end to a nice shape. Now with the threaded end sticking out of the strut, you can use a clevis, with one side broken off and use this as your mounting hardware. It also allows some adjustment with the threads. If the K&S tubing is not strong enough for you, you can JB weld a long threaded rod through the entire length of the airfoil tubing.
It is too bad that Glenn Torrence models does not carry his strut material anymore. It had thick walls. He had several shapes and sizes. I am sure he got it from somewhere, so I would bet it could be had from another source. If these struts are not taking a ton of load, I bet the K&S Aluminum could be made to be strong enough though. So long as you are happy with the shape and sizes they offer for the application.
It is too bad that Glenn Torrence models does not carry his strut material anymore. It had thick walls. He had several shapes and sizes. I am sure he got it from somewhere, so I would bet it could be had from another source. If these struts are not taking a ton of load, I bet the K&S Aluminum could be made to be strong enough though. So long as you are happy with the shape and sizes they offer for the application.
02-11-2015, 12:07 PM
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It is my opinion the K&S is more than strong enough, but, if one wants stronger http://www.toni-clark.com/ carries stainless steel.
02-11-2015, 12:10 PM
#833
But why go through all the hassle with re-enforcing the annealed K&S tubing... reforming the 3/8" tempered brass tubing works nicely, and its strong enough on its own to do the job.
I've seen birds work, and he could turn a paper clip into something no one would ever dream of, so no disrespect to you my friend... but that 3/8" inch K&S tubing is "sooo" tender, you could not use it in a situation like folding struts where its assembled and dis-assembled many times... it would work as a covering over something more substantial, but there is only enough room to pass a 1/8" inch re-enforcement rod or tube down the middle.. then you have to find a way to fit the jury spreader tube (spade ends) in there to fit in with the whole shebang, not to mention the attachment brackets on the wings... it becomes so tight of a fit, making everything as thin and small as possible to fit together, you jeopardize the structural integrity you need to do the job... that's why 1/3 third scale has the advantage over 1/4 scale, everything is that much larger to work with.
John M,
I've seen birds work, and he could turn a paper clip into something no one would ever dream of, so no disrespect to you my friend... but that 3/8" inch K&S tubing is "sooo" tender, you could not use it in a situation like folding struts where its assembled and dis-assembled many times... it would work as a covering over something more substantial, but there is only enough room to pass a 1/8" inch re-enforcement rod or tube down the middle.. then you have to find a way to fit the jury spreader tube (spade ends) in there to fit in with the whole shebang, not to mention the attachment brackets on the wings... it becomes so tight of a fit, making everything as thin and small as possible to fit together, you jeopardize the structural integrity you need to do the job... that's why 1/3 third scale has the advantage over 1/4 scale, everything is that much larger to work with.
John M,
Last edited by John_M_; 02-11-2015 at 12:18 PM.
02-11-2015, 12:40 PM
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Thank you John M. for your kind words. I'll get to work on that paper clip idea right away!
AMR carries wooden strut material. Talk to Dany. Tell him bigbird send you, seriously! They have router bits that they cut them with. The rear and front main struts are two different sizes on their third scale cub. I used the rear size for my Pawnee. They are very easy to true up on a belt sander, it will take a lot to get the router marks out but makes a very nice strut. As far as acquiring thick aluminum strut material, The fella that produced the nice fiberglass float kits and went out of business made his own to sell. He sold out and I don't know who got the die. It is a simple process in that you have several stages of rollers graduating down to the shape desired with a hand crank to feed it. Perhaps motorized. I have a friend that could help me design and build one and I might try to. Also, a lot of wood shops that do reproduction trim and decorative moldings have a lot of 'shaper' blades made from the original profiles of recovered wood. You might ask them where to have one made and get an airfoil shaped bit for your router and make some. Might be worth the cost. If you can't find nice clear spruce, use poplar found in home depot or any lumber yard. Very nice wood. It is considered hard wood although it is in the softer end of hard and very strong.
Just a thought from the bird brain!
bird.
AMR carries wooden strut material. Talk to Dany. Tell him bigbird send you, seriously! They have router bits that they cut them with. The rear and front main struts are two different sizes on their third scale cub. I used the rear size for my Pawnee. They are very easy to true up on a belt sander, it will take a lot to get the router marks out but makes a very nice strut. As far as acquiring thick aluminum strut material, The fella that produced the nice fiberglass float kits and went out of business made his own to sell. He sold out and I don't know who got the die. It is a simple process in that you have several stages of rollers graduating down to the shape desired with a hand crank to feed it. Perhaps motorized. I have a friend that could help me design and build one and I might try to. Also, a lot of wood shops that do reproduction trim and decorative moldings have a lot of 'shaper' blades made from the original profiles of recovered wood. You might ask them where to have one made and get an airfoil shaped bit for your router and make some. Might be worth the cost. If you can't find nice clear spruce, use poplar found in home depot or any lumber yard. Very nice wood. It is considered hard wood although it is in the softer end of hard and very strong.
Just a thought from the bird brain!
bird.
02-11-2015, 01:52 PM
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It is my opinion the K&S is more than strong enough, but, if one wants stronger http://www.toni-clark.com/ carries stainless steel.
bird.
02-11-2015, 02:09 PM
#836
Leroy, the full size door latch uses metal rods connected to a bell crank that's attached to the door handle shaft.... the shaft goes through the entire door and the inner door handle connects to that same shaft.
There's a "U" channel on the bottom of the window frame that interlocks with the top of the door frame when the window and door are closed, so there is no latch on the window frame, just the "U" channel holds the window frame closed.
JB Weld is your best friend when it comes to joining some of these small parts together... this is what I've done so far with my door handle... that long brass tube will be cut to length once I get the thrust wash in place just behind the outside door handle... I'll JB a bell crank to the shaft once I get the shaft through the door (after its covered and painted), and then connect two 1/32" music wire rods to the bell crank as the latch pins at each end of the door... the 1/32" rods will have to be bent so they track laterally as the bell crank turns with the handle... the 1/32" music wire rods will stick out about 3/16" of an inch (or less) and protrude into some holes in the outer door frame, I'll use some 1/16" brass tubing to reenforce the holes in the door frame... once that's all completed, the inside door handle will push into the outer door handle shaft, I'll press a piece of plastic inner nyrod inside the shaft tube and then drill it out for a press fit on the inside door handle shaft... I've done some tests and it works rather well... the inner door handle will never see any operation so a press fit to hold the handle in place is good enough.
John M,
There's a "U" channel on the bottom of the window frame that interlocks with the top of the door frame when the window and door are closed, so there is no latch on the window frame, just the "U" channel holds the window frame closed.
JB Weld is your best friend when it comes to joining some of these small parts together... this is what I've done so far with my door handle... that long brass tube will be cut to length once I get the thrust wash in place just behind the outside door handle... I'll JB a bell crank to the shaft once I get the shaft through the door (after its covered and painted), and then connect two 1/32" music wire rods to the bell crank as the latch pins at each end of the door... the 1/32" rods will have to be bent so they track laterally as the bell crank turns with the handle... the 1/32" music wire rods will stick out about 3/16" of an inch (or less) and protrude into some holes in the outer door frame, I'll use some 1/16" brass tubing to reenforce the holes in the door frame... once that's all completed, the inside door handle will push into the outer door handle shaft, I'll press a piece of plastic inner nyrod inside the shaft tube and then drill it out for a press fit on the inside door handle shaft... I've done some tests and it works rather well... the inner door handle will never see any operation so a press fit to hold the handle in place is good enough.
John M,
Last edited by John_M_; 02-11-2015 at 02:27 PM.
02-11-2015, 02:22 PM
#837
, I was just trying to express that you could make it no matter what you had in hand, it was meant as a blatant expression, not a wise crack... it takes a special skill to take something and make it do something else it was never intended to do... those craftsmen skills are getting rarer and rarer.***EDIT***
BTW, Paolo Severin has the same tubing Toni Clark has... it's like 26 bucks per meter length, a little less for the smaller sizes... then you have shipping an import taxes... its worth it for the right project.
John M,
Last edited by John_M_; 02-11-2015 at 02:48 PM.
02-11-2015, 03:22 PM
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Bird, send me a PM with your email and I'll send you his catalog. I have bought a lot of stuff from him and the freight is not much different than from here in the states.
02-11-2015, 03:27 PM
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And by the way, think about this, the mfg's put wood in the kit to make the struts with but yet some don't think aluminum would do the job. There is not that much load on the struts and the load that is there is a compression or extension type. It would take a great deal of force to damage the wood or aluminum and the jury struts stop any flex that may have existed with either product.
02-11-2015, 03:47 PM
#841
And by the way, think about this, the mfg's put wood in the kit to make the struts with but yet some don't think aluminum would do the job. There is not that much load on the struts and the load that is there is a compression or extension type. It would take a great deal of force to damage the wood or aluminum and the jury struts stop any flex that may have existed with either product.
That's right, the K&S streamline aluminum tubing, 5/8" to 1" wide has the strength, and the ends can be attaches easily... my understanding was regarding using the 3/8" streamline aluminum tubing for the jury struts, which has an very thin wall, as the sized get smaller, the wall thickness gets thinner... after shaping the ends the remaining tabs are very fragile, like that "flight metal", it bends easily.
John M,
02-11-2015, 04:40 PM
#843
Trying to recreate this setup to look scale is hard to do with the 3/8" wide K&S streamline tubing.. its the ends tabs the bolt goes through that just don't have any substance to it.
John M,
02-11-2015, 07:54 PM
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[QUOTE=John_M_;11981347]I wasn't being facetious bird , I was just trying to express that you could make it no matter what you had in hand, it was meant as a blatant expression, not a wise crack... it takes a special skill to take something and make it do something else it was never intended to do... those craftsmen skills are getting rarer and rarer.
I know John M. and I thank you as I said for your kind words. You are right, craftsmen are rare these days and I really hope to be one one day! When I grow up! Come to think of it, I don't want to grow up! Just grow old! When I tip over I hope to have super glue on my fingers, a piece of balsa in my left hand and a super glue bottle in my right hand sitting at my building table!
bird.
, I was just trying to express that you could make it no matter what you had in hand, it was meant as a blatant expression, not a wise crack... it takes a special skill to take something and make it do something else it was never intended to do... those craftsmen skills are getting rarer and rarer.I know John M. and I thank you as I said for your kind words. You are right, craftsmen are rare these days and I really hope to be one one day! When I grow up! Come to think of it, I don't want to grow up! Just grow old! When I tip over I hope to have super glue on my fingers, a piece of balsa in my left hand and a super glue bottle in my right hand sitting at my building table!
bird.
02-11-2015, 08:02 PM
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thanks.
bird.
02-12-2015, 02:51 AM
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Well there is a lot of info. on the subject of the jury struts and I'm going to be using the brass tubes made oval. 3/8" looks to be big enough and it's easy to jump a size. Also the door handle is doable with an idea I have mixed with some others I have seen, I will post what I come up with.
On with the fun stuff, hinging the ailerons & flaps. First of all a good guide and layout is critical to a good job, I made the drilling jig out of a 2X2 cut on my band saw which cuts very nice and square, once its drilled for the guide it's hardened with thin CA, only other things needed is a 1/4" wide file and a 1/4" brad point bit which cuts cleaner than a standard bit in soft balsa.
With the guide clamped on (center is found looking into guide hole) drill it, file the 4 sides and test fit a hinge butt then move to the next one and repeat.
Fit is perfect and I mean perfect, hope to do as well on the others, movement is very smooth and there is plenty of travel on the flap. I really wanted to see it on the plane, I'm very happy the way it's coming out.
On with the fun stuff, hinging the ailerons & flaps. First of all a good guide and layout is critical to a good job, I made the drilling jig out of a 2X2 cut on my band saw which cuts very nice and square, once its drilled for the guide it's hardened with thin CA, only other things needed is a 1/4" wide file and a 1/4" brad point bit which cuts cleaner than a standard bit in soft balsa.
Looks really good.
bird.
