Sizing wing tube
02-28-2015, 06:04 PM
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Sizing wing tube
I'm planning to build a great planes .60 extra 300
i will redesign the fuse and wing to be a 2 pc wing on a tube and a remove able hatch
the weight is around 8lbs
the wing span will be 64" - 66"
I have been told that the wing tube should be 1/3 the length of the wing panel
tge diameter should be as large as possible that will fit in the rib
i think 1" should fit
can someone give any input on this?
i will redesign the fuse and wing to be a 2 pc wing on a tube and a remove able hatch
the weight is around 8lbs
the wing span will be 64" - 66"
I have been told that the wing tube should be 1/3 the length of the wing panel
tge diameter should be as large as possible that will fit in the rib
i think 1" should fit
can someone give any input on this?
03-02-2015, 10:58 AM
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The length of the joiner needs to be considered along with the strength of the spars. Certainly a tube or rod that extends 1/3 of the span into a panel is something I'd consider rather extreme. If the receiver slip tube for the actual joiner tube is correctly joined to the spar caps and things are boxed in and bound nicely then even as little as 1/5 of the span is fine.
Another issue with a tube versus other method such as rods or blades is that a tube has to be quite large in relation to the width of the spar caps. This makes it hard to box in and connect the spar caps to the slip tube. My choice instead of a tube for a big thick wing like this would be for a joiner blade that is as wide as the distance between the caps and incorporate any taper needed to match the shape. That way I can form the receiving box with the spar caps and plywood webbing and bind it all with Kevlar tow to form a good strong box that isn't overly difficult to build or overly heavy. The blade for a model of this size and weight would be made from aluminium with suitable lightening holes drilled in it.
If you want to go with a tube instead of a blade then first off be sure that the tube is aircraft grade aluminium with a T4 or higher temper. This isn't a time to use the hardware store tubing options. Then this should slip into a snug but smooth fitting receiver tube in the wing panels that is made from something which will accept glue readily so it can be properly glued to the spar caps and boxed in with suitable glass fiber or wood or some other method.
Another issue with a tube versus other method such as rods or blades is that a tube has to be quite large in relation to the width of the spar caps. This makes it hard to box in and connect the spar caps to the slip tube. My choice instead of a tube for a big thick wing like this would be for a joiner blade that is as wide as the distance between the caps and incorporate any taper needed to match the shape. That way I can form the receiving box with the spar caps and plywood webbing and bind it all with Kevlar tow to form a good strong box that isn't overly difficult to build or overly heavy. The blade for a model of this size and weight would be made from aluminium with suitable lightening holes drilled in it.
If you want to go with a tube instead of a blade then first off be sure that the tube is aircraft grade aluminium with a T4 or higher temper. This isn't a time to use the hardware store tubing options. Then this should slip into a snug but smooth fitting receiver tube in the wing panels that is made from something which will accept glue readily so it can be properly glued to the spar caps and boxed in with suitable glass fiber or wood or some other method.
03-07-2015, 06:42 PM
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I sell a variety of sizes of Carbon fiber tubes and sleeves . a 7/8" tube is plenty for two meter pattern planes that weigh 11lbs. you'll be fine if it is even 8" into each wing.
a 7/8" x 24" tube and sleeve is $49.95
a 7/8" x 24" tube and sleeve is $49.95
Last edited by frequent flyer; 03-07-2015 at 06:47 PM.
03-23-2015, 10:18 AM
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I found some various pictures that should illustrate the idea.
First is the way the spar caps are webbed front and back to form receiver boxes in the wing panels. Ideally these should extend out for two or three rib bays. So it means cutting the ribs into front and rear parts for this step.
http://static.rcgroups.net/forums/at...iner%20mod.jpg
Then you make up a blade style joiner that is shaped like this one.
http://www.troybuiltmodels.com/ns/im...SKY-71A-46.jpg
But do NOT use plywood on any but the lightest sort of model. The problem with plywood is that half the layers have the grain running the wrong way to provide any strength. Instead if you're going to use wood get some maple and make the joiner blade from that with the grain running horizontal. Otherwise use aircraft aluminium(not the common soft hardware store stuff), spring steel or carbon sheet laminated to form the thickness needed.
Here's an example of blade joiners used on the outer part of a very large scale glider. The box for dual blades is long because the process shown in this picture described how the box is built into the wing and the wing tip is cut away after building to ensure everything lines up 100%. In this case the builder is using two fairly thin steel blades in the two slots shown.
http://image.tech-domain.com/images/...6/6/46_488.jpg
The one problem with steel blades is that to keep the weight down you want to use thin sheet. But thin steel puts a LOT of pressure into a small area of the wood that forms the blade receiver box. To spread out the load I'd suggest that plywood be epoxied to one or both sides to provide more area to spread the load. Or that two thin blades be epoxiedglued to either side of a plywood center layer.
The advantage is that you can get a huge amount of strength from a blade since there is more of what we need with less of what we don't need. And a blade style joiner does not need a slip tube which is massively wider than the spar caps. So it can also tidy up the construction process.
For big and seriously loaded models you can also look at a built up box joiner such as this picture shows.
http://www.letmodel.cz/img/velke1/joiners/03.jpg
Does any of this give you any ideas for alternatives to tube joiners?
First is the way the spar caps are webbed front and back to form receiver boxes in the wing panels. Ideally these should extend out for two or three rib bays. So it means cutting the ribs into front and rear parts for this step.
http://static.rcgroups.net/forums/at...iner%20mod.jpg
Then you make up a blade style joiner that is shaped like this one.
http://www.troybuiltmodels.com/ns/im...SKY-71A-46.jpg
But do NOT use plywood on any but the lightest sort of model. The problem with plywood is that half the layers have the grain running the wrong way to provide any strength. Instead if you're going to use wood get some maple and make the joiner blade from that with the grain running horizontal. Otherwise use aircraft aluminium(not the common soft hardware store stuff), spring steel or carbon sheet laminated to form the thickness needed.
Here's an example of blade joiners used on the outer part of a very large scale glider. The box for dual blades is long because the process shown in this picture described how the box is built into the wing and the wing tip is cut away after building to ensure everything lines up 100%. In this case the builder is using two fairly thin steel blades in the two slots shown.
http://image.tech-domain.com/images/...6/6/46_488.jpg
The one problem with steel blades is that to keep the weight down you want to use thin sheet. But thin steel puts a LOT of pressure into a small area of the wood that forms the blade receiver box. To spread out the load I'd suggest that plywood be epoxied to one or both sides to provide more area to spread the load. Or that two thin blades be epoxiedglued to either side of a plywood center layer.
The advantage is that you can get a huge amount of strength from a blade since there is more of what we need with less of what we don't need. And a blade style joiner does not need a slip tube which is massively wider than the spar caps. So it can also tidy up the construction process.
For big and seriously loaded models you can also look at a built up box joiner such as this picture shows.
http://www.letmodel.cz/img/velke1/joiners/03.jpg
Does any of this give you any ideas for alternatives to tube joiners?
03-23-2015, 11:48 AM
#6
Yes, that helps a lot! Thank you for going to all the trouble of collecting and submitting the pictures. The project is in the planning stages at this point. Likely it will have 2-36 inch panels with 1/4x1/2 spruce spars and a 1&3/8ths gap between them vertically. I thought I could box those in with 1/16th ply to make up the receiver for the spar, with the balsa removed from between the spars, of course. The area I'm still unsure of is the portion of the fuse that houses the blade spar.
