Twin-Air 45 build thread
12-22-2003, 11:36 PM
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RE: Twin-Air 45 build thread
ORIGINAL: Wingman357
... This will also be real nice option for the 60/120 size Twin-Air.
... This will also be real nice option for the 60/120 size Twin-Air.
The TW60 has a built up airfoiled tail, so hiding the cables in the stab will be far easier. we could even hide the control horns... But that's going to be another thread.
12-23-2003, 08:04 AM
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RE: Twin-Air 45 build thread
Crashnfix just posted a thread on a twin-rudder Duelist that has a link with lots of specs and excellent pics. John, be sure to take a look!
[link=http://www.rcuniverse.com/forum/Twin_Rudders_on_the_Duellist%3F%3F%3F/m_1371550/tm.htm]http://www.rcuniverse.com/forum/Twin_Rudders_on_the_Duellist%3F%3F%3F/m_1371550/tm.htm[/link]
Rudders are mounted on the ends of the stab, a bellcrank system is used to drive pushrods that appear to be buried in the stab, and custom hardwood control horns are used for hookups.
After putting even more thought to all this I think that we need to keep simplicity a high priority. The Twin-Air is currently a pretty straightforward kit. Giving it a tail section that requires a whole lot of craftsmanship would probably not be the right thing to do. I am sure John can burn any shapes and keyways that are required so that is not a problem. But I don't think we don't want a whole bunch of custom-fitting required to make it work.
OK, so enough philosophy. Let's keep on generating ideas.
Walt
[link=http://www.rcuniverse.com/forum/Twin_Rudders_on_the_Duellist%3F%3F%3F/m_1371550/tm.htm]http://www.rcuniverse.com/forum/Twin_Rudders_on_the_Duellist%3F%3F%3F/m_1371550/tm.htm[/link]
Rudders are mounted on the ends of the stab, a bellcrank system is used to drive pushrods that appear to be buried in the stab, and custom hardwood control horns are used for hookups.
After putting even more thought to all this I think that we need to keep simplicity a high priority. The Twin-Air is currently a pretty straightforward kit. Giving it a tail section that requires a whole lot of craftsmanship would probably not be the right thing to do. I am sure John can burn any shapes and keyways that are required so that is not a problem. But I don't think we don't want a whole bunch of custom-fitting required to make it work.
OK, so enough philosophy. Let's keep on generating ideas.
Walt
12-23-2003, 09:34 AM
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RE: Twin-Air 45 build thread
Walt,
So were back to the original Twin-Air .25 design with the linkage underneath the stab and the fin/rudders on the ends of the stab like this:
So were back to the original Twin-Air .25 design with the linkage underneath the stab and the fin/rudders on the ends of the stab like this:
12-23-2003, 10:21 AM
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RE: Twin-Air 45 build thread
After playing around with my sketch some more for a while I am pretty well convinced that keeping the rudders outboard on the stab (or close to it) really simplifies things. The rudder can extend below the stab without interfering with the elevator and the linkage can be hooked up either under the stab or through the stab with a minimum of complications.
So yes, basicly I am favoring the original .25 concept for the rudders right now. I'd like to take a look at what it would take to imbed the control rods in the stab though. I need to expand my drawing so I can play around with belcrank locations, etc.
Walt
So yes, basicly I am favoring the original .25 concept for the rudders right now. I'd like to take a look at what it would take to imbed the control rods in the stab though. I need to expand my drawing so I can play around with belcrank locations, etc.
Walt
12-27-2003, 07:07 PM
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RE: Twin-Air 45 build thread
Hope everyone had a great Christmas! 
Now that the holiday is over I am back to working on the Twin-Air again. The wing assemblies are finished and I just epoxied the wing halves together. I'm gonna clean up the bench and begin on the fuselage tomorrow. Once I have the fuse framed up I will begin looking more closely at how to handle twin rudders and linkage. And I still need to build the nacelles...
Here are some pics showing my progress:
Pic 1- wing tip bracing is formed from scrap
Pic 2- servo mounts are complete. I deviated from the plans (I think) and recessed them into the wing.
Pic 3- wing bottom showing completed servo and landing gear mounts
Pic 4- final checks before joining the wing halves
Walt
Now that the holiday is over I am back to working on the Twin-Air again. The wing assemblies are finished and I just epoxied the wing halves together. I'm gonna clean up the bench and begin on the fuselage tomorrow. Once I have the fuse framed up I will begin looking more closely at how to handle twin rudders and linkage. And I still need to build the nacelles...
Here are some pics showing my progress:
Pic 1- wing tip bracing is formed from scrap
Pic 2- servo mounts are complete. I deviated from the plans (I think) and recessed them into the wing.
Pic 3- wing bottom showing completed servo and landing gear mounts
Pic 4- final checks before joining the wing halves
Walt
12-29-2003, 01:55 PM
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RE: Twin-Air 45 build thread
ORIGINAL: William Robison
The ony bad point I see is lack of positive rudder location in the neutral position, good hinge sealing will be needed to prevent flutter. Perhaps even rig the rudders with a slight outward angle with the servo at neutral.
Bill.
The ony bad point I see is lack of positive rudder location in the neutral position, good hinge sealing will be needed to prevent flutter. Perhaps even rig the rudders with a slight outward angle with the servo at neutral.
Bill.
I hope you don't mind me putting my 2 cents in here.
But If I understand this right? then the rudders would have (looking from the top) toe in. or tail out. I think this would be good with both engines running, and would decrease yaw with one engine out, as the loss of airflow over that rudder would allow the other rudder to (take precedence) and help keep the plane straight.Just a thought. but I like it as a cheap added stability issue.
Thanks.
John.
I'm keeping a close eye on this plane, and will order it with the twin rudder set-up, once decided on.
Great thread. Thanks all.
Rick.
12-29-2003, 02:15 PM
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RE: Twin-Air 45 build thread
Smoky:
You are welcome to stick your two cents in. Or even three cents if you wish.
And yes, you got my idea on the rudder rigging correct.
Bill.
You are welcome to stick your two cents in. Or even three cents if you wish.
And yes, you got my idea on the rudder rigging correct.
Bill.
12-30-2003, 09:07 PM
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RE: Twin-Air 45 build thread
I just finished the first wing half of my TwinAir. I had to modify it to accommodate a set of RomAir retracts. I used the existing gear block as the forward rail then cut and fitted a 1/2 x 3/8 hardwood block for the rear rail. I notched the ribs the same as the other block. Using the existing rail moved the gear mount reward about 1 1/4 inch. I also moved the gear outward one bay. This puts the retract gear wheel in about the same location as the bent wire wheel of the original gear. This kit quality is excellent!!!, everything fits perfect and goes together like a puzzle. I'm planning on attempting the twin rudders. I'll make as much as possible off the plane before making the final commitment. I've got two TT .46 pros all broke in and waiting. Thinking about a three blade 10-7 prop. Has anyone tried that combination? Keep the rudder info and thoughts coming.
12-30-2003, 09:34 PM
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RE: Twin-Air 45 build thread
Daw:
With twin 46 engines I like MAS 10x6 three blade props best. They will fly with 10x8 3b props, for me the best combination of speed and climb comes with the 10x6 3b mounted.
Bill.
With twin 46 engines I like MAS 10x6 three blade props best. They will fly with 10x8 3b props, for me the best combination of speed and climb comes with the 10x6 3b mounted.
Bill.
12-30-2003, 11:06 PM
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RE: Twin-Air 45 build thread
David,
Glad to hear you are working on your plane too. I got slowed down on mine the last couple of days. I took some time out to replace the tailfeathers on my Nobler- had a minor midair with a huge Extra a few weeks ago and the big prop ate through most of the rudder and one side of the stab.
Second that on the kit quality. Everything fits absolutely perfect. No retracts for me though. I want this plane to be a regular flyer and our runway is grass- not "retract freindly". I will be running 46 FX motors in mine and also plan on going with 3-blade props.
I'm just now getting started on the fuse. And I'm beginning to put more thought on the twin rudder design again.
Walt
Glad to hear you are working on your plane too. I got slowed down on mine the last couple of days. I took some time out to replace the tailfeathers on my Nobler- had a minor midair with a huge Extra a few weeks ago and the big prop ate through most of the rudder and one side of the stab.
Second that on the kit quality. Everything fits absolutely perfect. No retracts for me though. I want this plane to be a regular flyer and our runway is grass- not "retract freindly". I will be running 46 FX motors in mine and also plan on going with 3-blade props.
I'm just now getting started on the fuse. And I'm beginning to put more thought on the twin rudder design again.
Walt
01-01-2004, 01:10 PM
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RE: Twin-Air 45 build thread
HAPPY NEW YEAR!
I spent my new years eve detailing options for the twin rudder linkage. I attached sketches of the three options that I believe are most do-able. The rudders are located at the outboard ends of the stab on all three options because I am sure that this will reduce complexity of the linkage hookeup. All of the sketches are to scale and I assumed use of Du-bro connectors and Golden-rod. The connectors are also drawn to scale. With things this tight I didn't want to make any "fit" assumptions!
I haven't detailed the fin/rudder yet but design will be very similar for all three options.
Option 1- linkage below the stab. Essentially the same as the .25 prototype except for the Dubro dual take off ball link connector at the control horn. It uses exposed hard-wire pushrods and a single support guide at the center of each wire to reduce flex. I assumed ball link connectors at the rudders- the kind that you can screw a threaded rod into. The rod extends into the rudder and is glued in-place.
pros- stab construction is essentially unchanged, linkage to rudders relatively simple, "fit" of linkage is not all that critical.
cons- mounting bellcrank adds some complexity, linkage is all exposed.
Option 2- linkage embedded in stab. Similar arrangement to option 1 except the bellcrank is positioned so that the ball link extends into the stab. A groove is desined into the stab for Golden-rod to be glued in and both the top and bottom of the stab are sheeting with 1/16 sheet. Rudder connections are the same as for option 1 except that the ball links are positioned so that they can ride "inside" the stab.
pros- no exposed control wire
cons- fit and dimensions are critical since everything is extremely tight. All or part of stab must be built up with sheeting. Open "gaps" are required within the stab at the bellcrank and rudder connections to allow for lateral movement of the control rods as the bellcrank and ball links rotate. Structural integrity of the elevator connection is a bit of a concern. The bellcrank will be exposed (can't sheet the bottom of the stab at the bellcrank area)
Option 3- embed curved golden rod within stab. This concept was thrown into the mix earlier but I was concerned about using braided cable. However I grabbed a length of blue/yellow golden rod and discovered you can actually bend this stuff to a radius of 3" with absolutely no binding. All we would need to make this work is a 5" radius. The stab would be cut into 3 sections and the sections glued down onto 1/16 sheeting leaving a 1/4" channel. Glue the golden rod into the channel and then cover the top with 1/16 sheeting. The control rods are connected to both ends of the servo horn and the rudder linkage setup is the same as for option 2.
pros- all linkage is hidden except for connections at the rudders. No bellcrank to mount. Structural integrity of elevator connections should not be a problem.
cons- linkage hookup at rudders is still somewhat complex since ball links must ride "within" the stab. May need to beef up stab where it is glued to the fuse because much of this area will be hollow. Bent rod tubing may tend to introduce warp in finished stab.
Right now I am favoring option 3 and I will pconstruct a concept prototype today. If we can agree on the linkage than we can get started on design of the rudders and detail of the linkage connections!
I am putting construction of my fuse on hold until the tailfeather design is complete. Please provide your opinions/feedback!!! [8D]
Walt
I spent my new years eve detailing options for the twin rudder linkage. I attached sketches of the three options that I believe are most do-able. The rudders are located at the outboard ends of the stab on all three options because I am sure that this will reduce complexity of the linkage hookeup. All of the sketches are to scale and I assumed use of Du-bro connectors and Golden-rod. The connectors are also drawn to scale. With things this tight I didn't want to make any "fit" assumptions!
I haven't detailed the fin/rudder yet but design will be very similar for all three options.
Option 1- linkage below the stab. Essentially the same as the .25 prototype except for the Dubro dual take off ball link connector at the control horn. It uses exposed hard-wire pushrods and a single support guide at the center of each wire to reduce flex. I assumed ball link connectors at the rudders- the kind that you can screw a threaded rod into. The rod extends into the rudder and is glued in-place.
pros- stab construction is essentially unchanged, linkage to rudders relatively simple, "fit" of linkage is not all that critical.
cons- mounting bellcrank adds some complexity, linkage is all exposed.
Option 2- linkage embedded in stab. Similar arrangement to option 1 except the bellcrank is positioned so that the ball link extends into the stab. A groove is desined into the stab for Golden-rod to be glued in and both the top and bottom of the stab are sheeting with 1/16 sheet. Rudder connections are the same as for option 1 except that the ball links are positioned so that they can ride "inside" the stab.
pros- no exposed control wire
cons- fit and dimensions are critical since everything is extremely tight. All or part of stab must be built up with sheeting. Open "gaps" are required within the stab at the bellcrank and rudder connections to allow for lateral movement of the control rods as the bellcrank and ball links rotate. Structural integrity of the elevator connection is a bit of a concern. The bellcrank will be exposed (can't sheet the bottom of the stab at the bellcrank area)
Option 3- embed curved golden rod within stab. This concept was thrown into the mix earlier but I was concerned about using braided cable. However I grabbed a length of blue/yellow golden rod and discovered you can actually bend this stuff to a radius of 3" with absolutely no binding. All we would need to make this work is a 5" radius. The stab would be cut into 3 sections and the sections glued down onto 1/16 sheeting leaving a 1/4" channel. Glue the golden rod into the channel and then cover the top with 1/16 sheeting. The control rods are connected to both ends of the servo horn and the rudder linkage setup is the same as for option 2.
pros- all linkage is hidden except for connections at the rudders. No bellcrank to mount. Structural integrity of elevator connections should not be a problem.
cons- linkage hookup at rudders is still somewhat complex since ball links must ride "within" the stab. May need to beef up stab where it is glued to the fuse because much of this area will be hollow. Bent rod tubing may tend to introduce warp in finished stab.
Right now I am favoring option 3 and I will pconstruct a concept prototype today. If we can agree on the linkage than we can get started on design of the rudders and detail of the linkage connections!
I am putting construction of my fuse on hold until the tailfeather design is complete. Please provide your opinions/feedback!!! [8D]
Walt
01-01-2004, 02:16 PM
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RE: Twin-Air 45 build thread
Walt,
I am in learning mode here, so I am watching and listening to you all you guys from the sideline. I for one appreciate your efforts on this.
Thanks
I am in learning mode here, so I am watching and listening to you all you guys from the sideline. I for one appreciate your efforts on this.
Thanks
01-01-2004, 04:47 PM
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RE: Twin-Air 45 build thread
Happy New Year All!
Sorry for being out of it for a bit, but I've been fighting a stubborn Christmas Cold. [:'(]
Anyway,
Taking all of the great ideas put forth so far and putting them all together, I think this design simplifies the linkage a little bit at the expense of having a little of the linkage exposed.
The LEFT rudder connects to the RIGHT side of the rudder servo and the RIGHT rudder connects to the LEFT side of the rudder servo. No need for a belcrank and both rudders are easily adjusted. Differential rudder throw (for Bill) can be added by using offset rudder horns on the rudder servo.
Sorry for being out of it for a bit, but I've been fighting a stubborn Christmas Cold. [:'(]
Anyway,
Taking all of the great ideas put forth so far and putting them all together, I think this design simplifies the linkage a little bit at the expense of having a little of the linkage exposed.
The LEFT rudder connects to the RIGHT side of the rudder servo and the RIGHT rudder connects to the LEFT side of the rudder servo. No need for a belcrank and both rudders are easily adjusted. Differential rudder throw (for Bill
) can be added by using offset rudder horns on the rudder servo.
01-01-2004, 05:14 PM
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RE: Twin-Air 45 build thread
Hi John!
Glad to see you haven't given up on this. I think we are getting very close now!
I like your use of regular control horns for the rudder connections. I am already half-way through the "test prototype" build on my option 3 and burying the golden-rod with the 5" radius looks very do-able! I think the key to burying the rods will be to get smooth, accurate cuts in the stab. Could you program your laser cutter to take care of the compound curves in your design? Making those cuts with a knife would be very tough.
I also think that using regular control horns for the rudder connections per your latest is the way to go as long as the golden-rod can handle the two 4" curves. We also need to make sure that there are no interference problems where the two rods must cross shortly after they enter the fuse. Looks like another "prototype" may be needed to check.
I'll post some pics of my prototype build and let everyone know how it goes. By the way it looks like the diameter of the golden rod is small enough to fit into a 3/16" sheet. I'm not sure its worth going to this, but it would reduce the overall thickness of the stab after sheeting to 5/16".
Walt
Glad to see you haven't given up on this. I think we are getting very close now!
I like your use of regular control horns for the rudder connections. I am already half-way through the "test prototype" build on my option 3 and burying the golden-rod with the 5" radius looks very do-able! I think the key to burying the rods will be to get smooth, accurate cuts in the stab. Could you program your laser cutter to take care of the compound curves in your design? Making those cuts with a knife would be very tough.
I also think that using regular control horns for the rudder connections per your latest is the way to go as long as the golden-rod can handle the two 4" curves. We also need to make sure that there are no interference problems where the two rods must cross shortly after they enter the fuse. Looks like another "prototype" may be needed to check.
I'll post some pics of my prototype build and let everyone know how it goes. By the way it looks like the diameter of the golden rod is small enough to fit into a 3/16" sheet. I'm not sure its worth going to this, but it would reduce the overall thickness of the stab after sheeting to 5/16".
Walt
01-01-2004, 06:27 PM
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RE: Twin-Air 45 build thread
My prototype is a success!
I used short lengths of goldenrod tube to make sure that the stab parts were properly positioned on the sheeting while the glue dried, then glued the tubing into the channel and sheeted the top.
I keyed the "fin" onto the "stab" and attached the ball connector into the "rudder" hardwood block. I attached the "rudder" using two CA hinges, and hooked up the socket to the goldenrod and connected it to the ball. Everything works perfectly!
I still prefer John's latest proposal. I can see that any errors made in the channel near the rudder will create problems with the ball link, and will be very hard to fix after everything is glued together. Also the ball link is very visible from the side of the rudder. The control horns would actually be better hidden.
But the goldenrod takes the 5" radius bend with no problems and the assembly technique is very simple. Now we just need to verify that it will take the two 4" radius bends.
Here are pics- don't laugh, this was only a trial!
Walt
I used short lengths of goldenrod tube to make sure that the stab parts were properly positioned on the sheeting while the glue dried, then glued the tubing into the channel and sheeted the top.
I keyed the "fin" onto the "stab" and attached the ball connector into the "rudder" hardwood block. I attached the "rudder" using two CA hinges, and hooked up the socket to the goldenrod and connected it to the ball. Everything works perfectly!
I still prefer John's latest proposal. I can see that any errors made in the channel near the rudder will create problems with the ball link, and will be very hard to fix after everything is glued together. Also the ball link is very visible from the side of the rudder. The control horns would actually be better hidden.
But the goldenrod takes the 5" radius bend with no problems and the assembly technique is very simple. Now we just need to verify that it will take the two 4" radius bends.
Here are pics- don't laugh, this was only a trial!
Walt
01-01-2004, 06:31 PM
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RE: Twin-Air 45 build thread
Walt,
I just tried overlaying a 5" radius set of curves on my drawing and we can handle that curve fine.
As for the laser cutting compound curves? That's not a problem. If we can draw it, the laser can cut it.
If we drop the Horizontal Stab thickness down to 3/16" I'd prefer to switch the top and bottom layers from 1/16" balsa to 1/32" ply for strength. This would also get us back to our original 1/4" thickness. Now all of this is going to add weight to the tail. As long as we use just enough epoxy to glue the ply to the stab and use an epoxy/micro ballon slurry to fill the cable channel I think we are going to be fine. We can also think about "lightening" holes in the horizontal stab . . .
The model has a larger CG range than what is shown on the plans. The wing can carry the extra weight -- at 6.5lbs the wing loading is 18.4 oz/sq ft and at 7.5 lbs the wing loading is 21.3 oz/sq ft. in general however, extra weight decreases performance.
I just tried overlaying a 5" radius set of curves on my drawing and we can handle that curve fine.
As for the laser cutting compound curves? That's not a problem. If we can draw it, the laser can cut it.
If we drop the Horizontal Stab thickness down to 3/16" I'd prefer to switch the top and bottom layers from 1/16" balsa to 1/32" ply for strength. This would also get us back to our original 1/4" thickness. Now all of this is going to add weight to the tail. As long as we use just enough epoxy to glue the ply to the stab and use an epoxy/micro ballon slurry to fill the cable channel I think we are going to be fine. We can also think about "lightening" holes in the horizontal stab . . .
The model has a larger CG range than what is shown on the plans. The wing can carry the extra weight -- at 6.5lbs the wing loading is 18.4 oz/sq ft and at 7.5 lbs the wing loading is 21.3 oz/sq ft. in general however, extra weight decreases performance.
01-01-2004, 07:13 PM
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RE: Twin-Air 45 build thread
John
I already have some 3/16" cut and ready to verify that the tubing will fit (it appears to be 3/16 OD). Based on my prototype I don't think that it is necessary to fill the channel- even with the 1/4" there was very little channel left to "fill" and by gluing the tubing in it actually becomes part of the structural support.
Using ply with the 3/16 makes sense to me and lightening holes would help the weight. Unless you tell me otherwise I will leave the final design to you. Now that we have most of it worked out I think you are in the best position to move forward with it. (Let me know if you disagree).
This has been fun!
Walt
I already have some 3/16" cut and ready to verify that the tubing will fit (it appears to be 3/16 OD). Based on my prototype I don't think that it is necessary to fill the channel- even with the 1/4" there was very little channel left to "fill" and by gluing the tubing in it actually becomes part of the structural support.
Using ply with the 3/16 makes sense to me and lightening holes would help the weight. Unless you tell me otherwise I will leave the final design to you. Now that we have most of it worked out I think you are in the best position to move forward with it. (Let me know if you disagree).
This has been fun!
Walt
01-01-2004, 09:24 PM
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RE: Twin-Air 45 build thread
Ok folks we need consensus from the group. Below are the finalized two pictures of the twin tail option for the Twin-Air .45.
The first picture shows the golden-rods in place going to a single (or double if you like) rudder servo. I couldn't get the 5" radius when I actually layed it out, but we're close. Also if we use the Red outer and yellow inner nyrods (flexible type) we can get a tighter radius. But I think we're ok here.
This picture also shows the updated horizontal stabilizer with some lightening holes because we are using a 1/32" ply skin top and bottom for strength. Also shown are (2) per side 1/4" SQ balsa keys for the Fin. This will make alignment a snap and will add strength to the joint.
There is an inset on the upper left which shows that the joint is reinforced with a 2" ribbon of 0.5 oz/yrd glass cloth sandwiched between the Fin/Stab and a 1/2" Triangle stock piece top and bottom.
This should prove sufficiently strong for "abusive" flying styles (though I'm not certain it will hold up to three successive snap rolls on a vertical downline
The second picture shows the fin and rudder configuration.
Note there are a few minor details omitted, but I think the idea comes across.
Ok folks, weigh in with your opinions.
The first picture shows the golden-rods in place going to a single (or double if you like) rudder servo. I couldn't get the 5" radius when I actually layed it out, but we're close. Also if we use the Red outer and yellow inner nyrods (flexible type) we can get a tighter radius. But I think we're ok here.
This picture also shows the updated horizontal stabilizer with some lightening holes because we are using a 1/32" ply skin top and bottom for strength. Also shown are (2) per side 1/4" SQ balsa keys for the Fin. This will make alignment a snap and will add strength to the joint.
There is an inset on the upper left which shows that the joint is reinforced with a 2" ribbon of 0.5 oz/yrd glass cloth sandwiched between the Fin/Stab and a 1/2" Triangle stock piece top and bottom.
This should prove sufficiently strong for "abusive" flying styles (though I'm not certain it will hold up to three successive snap rolls on a vertical downline
The second picture shows the fin and rudder configuration.
Note there are a few minor details omitted, but I think the idea comes across.
Ok folks, weigh in with your opinions.
01-01-2004, 09:54 PM
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RE: Twin-Air 45 build thread
On thought. Look at the similar tail of the P-38. There is a kind of bumper at the bottom in the case of an aggressive take off, it is to contact the runway. Might consider some type of reinforcement in this area. This plane has a very long fuse........which is good, do not misunderstand my meaning, but it also means that the under side of these rudders is more exposed to a runway contact. Do not change the design. I like the large rudders.
Good Luck,
Twinman
Good Luck,
Twinman
01-01-2004, 10:31 PM
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RE: Twin-Air 45 build thread
Twinman,
Yes, a tail wheel under the fuse would handle the occassional "unlimited" take offs.
Of course, then we could make the Twin-Air a tail dragger . . . .
Yes, a tail wheel under the fuse would handle the occassional "unlimited" take offs.
Of course, then we could make the Twin-Air a tail dragger . . . .
01-01-2004, 11:19 PM
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RE: Twin-Air 45 build thread
Looks great, John!
I will give it a closer look in the morning. Also the glue on my 3/16" test will be dry and ready to evaluate by then.
I have been assuming the red outer and yellow inner rods. They are very flexible and small diameter, which is exactly what we need.
This version looks like it should look good and work well, and it should be pretty easy to build.
And yes, we will need a tailskid. A little late for me (and others) to make it a tail-dragger though.
Walt
I will give it a closer look in the morning. Also the glue on my 3/16" test will be dry and ready to evaluate by then.
I have been assuming the red outer and yellow inner rods. They are very flexible and small diameter, which is exactly what we need.
This version looks like it should look good and work well, and it should be pretty easy to build.
And yes, we will need a tailskid. A little late for me (and others) to make it a tail-dragger though.
Walt
01-02-2004, 08:13 AM
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RE: Twin-Air 45 build thread
Tail Dragger
Guys, I would not worry about this as a tail dragger. Twin engine tail draggers are a real pain and you have enough to worry about. The problem is that the engines usually come up at different rates and this causes more trouble, on take off, than you want or need for a fun to fly plane.
I was only worried about possible damage to the rudder bottom. Consider to make at least the lower part of the rudder stronger to be able to stand abuse......my two cents.
Twinman
Guys, I would not worry about this as a tail dragger. Twin engine tail draggers are a real pain and you have enough to worry about. The problem is that the engines usually come up at different rates and this causes more trouble, on take off, than you want or need for a fun to fly plane.
I was only worried about possible damage to the rudder bottom. Consider to make at least the lower part of the rudder stronger to be able to stand abuse......my two cents.
Twinman
01-02-2004, 11:19 AM
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RE: Twin-Air 45 build thread
I tested the 3/16" sandwich with a 5" radius bend this morning and it works fine. Since the tubing is the same diameter as the balsa thickness, I glued the top sheeting on at the same time that I glued the tubing in to make sure that none of the tubing rode above the surface of the balsa. This worked well. I wish I had waited before putting this together because I would have tried a tighter bend. Now I am about out of spare balsa to make prototypes with!
John, here are some things to think about when finalizing things-
I haven't tried pulling the tubing out of the groove near the end as will be needed to attach it to the control horns. But a straight run before making this bend would probably make it a lot easier. So we have a trade-off between the radius of the embedded bend and getting the tubing straight where it exits the sandwich...
We will need a clearance slot in the bottom hardwood sheeting for the tubing to extend through. It may take some trial and error to get the length and location of this slot right. We will need to work out a good construction technique too since pulling the tubing up out of the groove near the end will tend to want to make the rest of the tubing spring out of the groove.
We definitely will need keys and tri-stock to secure the rudders. What type of glue do you prefer on the fiberglass? My thoughts are to use epoxy, position the cloth and then add the tri-stock over it in a single step.
You will have to work out the location of the "keys" on the 3/16 lumber so that you can make the cutouts for the control tubing in a logical manner. These are going to be some wierd looking parts!
Have you considered where the tubes cross in the fuse yet? This still looks very tight to me. You will need to provide clearance for the higher tube to ride over the lower tube. This means that the top of the fuse will have to be higher, or the end of the fuse cut down a little and the stab lowered a bit so that there is clearance where the tubes enter the fuselage. Even with adequate clearance the bends could be tight here. Hopefully not too tight!
During the build we will not be able to secure the tubes in the fuse until after the elevator is glued into position. So we need to be able to mount the elevator before gluing the top deck on the fuse so that we can work the tubes into position and secure them. Do you see any problem with this?
As drawn the fins/rudders exend a good bit below the stab. Do they need to go down this far? Looks good, but we will need a sizable skid plate. Do you have an idea has to how the lowered rudders will affect flight performance- its quite a change from having all the rudder above the stab.
I really think that this proposal can work well and it is still my #1 preference. But there are still quite a few details that must be resolved in order to make it a "relatively easy" build. In retrospect it seems to be quite a bit more complex than the "single tubing bend with ball-link rudder connection" design that I proposed earlier.
I can't wait to see your next update!
Walt
John, here are some things to think about when finalizing things-
I haven't tried pulling the tubing out of the groove near the end as will be needed to attach it to the control horns. But a straight run before making this bend would probably make it a lot easier. So we have a trade-off between the radius of the embedded bend and getting the tubing straight where it exits the sandwich...
We will need a clearance slot in the bottom hardwood sheeting for the tubing to extend through. It may take some trial and error to get the length and location of this slot right. We will need to work out a good construction technique too since pulling the tubing up out of the groove near the end will tend to want to make the rest of the tubing spring out of the groove.
We definitely will need keys and tri-stock to secure the rudders. What type of glue do you prefer on the fiberglass? My thoughts are to use epoxy, position the cloth and then add the tri-stock over it in a single step.
You will have to work out the location of the "keys" on the 3/16 lumber so that you can make the cutouts for the control tubing in a logical manner. These are going to be some wierd looking parts!
Have you considered where the tubes cross in the fuse yet? This still looks very tight to me. You will need to provide clearance for the higher tube to ride over the lower tube. This means that the top of the fuse will have to be higher, or the end of the fuse cut down a little and the stab lowered a bit so that there is clearance where the tubes enter the fuselage. Even with adequate clearance the bends could be tight here. Hopefully not too tight!
During the build we will not be able to secure the tubes in the fuse until after the elevator is glued into position. So we need to be able to mount the elevator before gluing the top deck on the fuse so that we can work the tubes into position and secure them. Do you see any problem with this?
As drawn the fins/rudders exend a good bit below the stab. Do they need to go down this far? Looks good, but we will need a sizable skid plate. Do you have an idea has to how the lowered rudders will affect flight performance- its quite a change from having all the rudder above the stab.
I really think that this proposal can work well and it is still my #1 preference. But there are still quite a few details that must be resolved in order to make it a "relatively easy" build. In retrospect it seems to be quite a bit more complex than the "single tubing bend with ball-link rudder connection" design that I proposed earlier.
I can't wait to see your next update!
Walt
01-04-2004, 09:17 AM
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RE: Twin-Air 45 build thread
All-
This thread got quiet all of the sudden! Hopefully everyone is still building planes and thinking about the twin rudder design!
Here are some pics updating my build progress.
Pic 1- fuselage. Further work on the fuse is on hold until the tailfeather design is ready. The fuse instructions are very detailed and the build looks pretty straightforward.
Pic 2- nacelles. Man this part is going to be tight. I am using Dave Brown motor mounts sized for my OS 46 motors- the ones with the round mounting surfaces. I had to sand down the top and bottom of the mounts a little to get them to fit. And getting them in position and mounted after the nacelles are complete could be fun. The nacelle build is rather interesting. I need to take a step back and sort out the rest of my lumber so that I am sure which pieces go where. The next step is to glue in the front panels (shown in pic). After that the instructions say to glue in 1/8 by 5/8 balsa fillers on the top and bottom of the front panels. I haven't located any 1/8 by 5/8 pieces and the drawing seems to show them as 3/16" thick instead of 1/8". I also haven't decided what glue to use for this assembly. I like white glue because it sands best, but CA would be a lot easier to deal with, and epoxy would probably be stronger... any recommendations out there?
Pic 3- fuse and nacelles positioned on wing. Everything fits perfectly! And I'm starting to be able to see just what this plane will look like!
Walt
This thread got quiet all of the sudden! Hopefully everyone is still building planes and thinking about the twin rudder design!
Here are some pics updating my build progress.
Pic 1- fuselage. Further work on the fuse is on hold until the tailfeather design is ready. The fuse instructions are very detailed and the build looks pretty straightforward.
Pic 2- nacelles. Man this part is going to be tight. I am using Dave Brown motor mounts sized for my OS 46 motors- the ones with the round mounting surfaces. I had to sand down the top and bottom of the mounts a little to get them to fit. And getting them in position and mounted after the nacelles are complete could be fun. The nacelle build is rather interesting. I need to take a step back and sort out the rest of my lumber so that I am sure which pieces go where. The next step is to glue in the front panels (shown in pic). After that the instructions say to glue in 1/8 by 5/8 balsa fillers on the top and bottom of the front panels. I haven't located any 1/8 by 5/8 pieces and the drawing seems to show them as 3/16" thick instead of 1/8". I also haven't decided what glue to use for this assembly. I like white glue because it sands best, but CA would be a lot easier to deal with, and epoxy would probably be stronger... any recommendations out there?
Pic 3- fuse and nacelles positioned on wing. Everything fits perfectly! And I'm starting to be able to see just what this plane will look like!
Walt