How do I balance this thing?
02-15-2010, 07:47 PM
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How do I balance this thing?
I'm building an SSC plane based on photos I've downloaded.
60" wingspan, my 1st attempt at cutting wings!
24" long aluminum rails holding an OS .15LA
My question is how do I position the wing saddle, fore and aft?
Then where will the CG be?
Lacking any further information I'll be going with the " looks about right " method....
Steve
60" wingspan, my 1st attempt at cutting wings!
24" long aluminum rails holding an OS .15LA
My question is how do I position the wing saddle, fore and aft?
Then where will the CG be?
Lacking any further information I'll be going with the " looks about right " method....
Steve
02-16-2010, 09:52 AM
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RE: How do I balance this thing?
My eye says that the LE of the wingtip will be really far forward, but it's hard to tell from the picture.
What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.
For a starting CG, I'd shoot for something close to 25-30% MAC, which you can easily calculate.
Is this your first SSC plane or just your first own-design? If it's your first SSC plane, get someone to throw it for you, and give it a good shove, and be prepared for the plane to possibly loop over or nose-dive, it doesn't take much of the elevator trim to be way out on a new design.
What's the wing area?
What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.
For a starting CG, I'd shoot for something close to 25-30% MAC, which you can easily calculate.
Is this your first SSC plane or just your first own-design? If it's your first SSC plane, get someone to throw it for you, and give it a good shove, and be prepared for the plane to possibly loop over or nose-dive, it doesn't take much of the elevator trim to be way out on a new design.
What's the wing area?
02-16-2010, 11:51 AM
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RE: How do I balance this thing?
ORIGINAL: Montague
My eye says that the LE of the wingtip will be really far forward, but it's hard to tell from the picture.
What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.
For a starting CG, I'd shoot for something close to 25-30% MAC, which you can easily calculate.
Is this your first SSC plane or just your first own-design? If it's your first SSC plane, get someone to throw it for you, and give it a good shove, and be prepared for the plane to possibly loop over or nose-dive, it doesn't take much of the elevator trim to be way out on a new design.
What's the wing area?
My eye says that the LE of the wingtip will be really far forward, but it's hard to tell from the picture.
What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.
For a starting CG, I'd shoot for something close to 25-30% MAC, which you can easily calculate.
Is this your first SSC plane or just your first own-design? If it's your first SSC plane, get someone to throw it for you, and give it a good shove, and be prepared for the plane to possibly loop over or nose-dive, it doesn't take much of the elevator trim to be way out on a new design.
What's the wing area?
Once in the air it was fun to fly.
I decided coroplast was not the way to go so this is my 1st attempt with cutting foam wings.
I'm trying to copy a SSC Battle Axe from pictures.
My wing is 9" root with 6" tip by 30" long.. NOT including the 1.5" alieron. I think wing area is around 450"
The fuse rails are 24" long with the OS .15 at one end and the tail feathers at the other end.
WHAT I DONT KNOW! is where to mount the wing saddle? 1/2" forward or backward will make a big difference? and I cant be that accurate from the pictures. THEN, WITH THE SADDLE IN POSTION, I can further adjust the CG with the battery position...
The CG calculators look good but will they work with this design?
Anybody out there got a battle axe?
Steve
02-16-2010, 11:55 AM
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RE: How do I balance this thing?
ORIGINAL: Montague
My eye says that the LE of the wingtip will be really far forward, but it's hard to tell from the picture.
What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.
What's the wing area?
My eye says that the LE of the wingtip will be really far forward, but it's hard to tell from the picture.
What you want is also going to depend on the airfoil a little, and don't forget to adjust the aileron reflex during flight testing.
What's the wing area?
I can take a pic at another angle of the plane if that will help?
My attempt is at a CLARK Y airfoil - what do you mean by aileron reflex? ( Aileron position as adjusted by the cleavis? )
I think the wing area is around 450"
Steve
02-16-2010, 12:13 PM
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RE: How do I balance this thing?
I calcualted 540sqin for the wing area, not bad, a bit small in my book but not terrible. When you did the airfoil templates, were they for 9" and 6", or were they for longer, and then cut down so you could add the aileron? Past experience seems to show that the wing often acts like what the chord would have been for a given thickness of the airfoil, even if the aileron stock makes it a bit longer or shorter.
In other words, take a 9" template (LE to sharp TE), cut off the TE, add TE stock and aileron, and you might wind up with a wing chord of 8" or 10". But the plane will fly pretty much like it would with 9". So I do most of my calculations based on the length of the airfoil templates rather than what's actually on the plane after wing building.
But I've digressed.
1/2" forward or back will make a big differnece.
Your design does vary a bit from the Battle Axe, so you should calculate your own CG location rather than using the Axe.
Your wing is a constant taper and sweep.
So, your mean chord is 7.5", or (6+9)/2.
So 27% of that is 2.025", or 2" in the real world.
So, your CG should be 2" from the LE measured at HALF WAY out along the wing.
So, measure 30" from the center on each side, then 2" back from the LE, and connect those lines at the fuse, and there's your CG.
In other words, take a 9" template (LE to sharp TE), cut off the TE, add TE stock and aileron, and you might wind up with a wing chord of 8" or 10". But the plane will fly pretty much like it would with 9". So I do most of my calculations based on the length of the airfoil templates rather than what's actually on the plane after wing building.
But I've digressed.
1/2" forward or back will make a big differnece.
Your design does vary a bit from the Battle Axe, so you should calculate your own CG location rather than using the Axe.
Your wing is a constant taper and sweep.
So, your mean chord is 7.5", or (6+9)/2.
So 27% of that is 2.025", or 2" in the real world.
So, your CG should be 2" from the LE measured at HALF WAY out along the wing.
So, measure 30" from the center on each side, then 2" back from the LE, and connect those lines at the fuse, and there's your CG.
02-16-2010, 12:20 PM
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RE: How do I balance this thing?
Aileron reflex is raising both ailerons. These extremely short coupled combat planes often act half-way between a flying wing and a conventional plane. By raising the ailerons, you change the pitching moment of the airfoil and at the same time change the incidence of the wing compared to the stab and engine.
This has a couple of effects in the air. For one thing, a plane that is "pitchy" and often suddenly pops the nose up or down can often be made to fly more smootly by increasing reflex. Many designs just won't fly right with out some raising of the ailerons. I suspect that was part of what you describe from your first plane.
It also affects the power-off glide, so one way to test reflex is to fly level at full power and then quickly yank back on the throttle, best is to go deadstick. Watch the glide you get with no elevator input. You should transition into a smooth glide at a reasonable descent rate, no sudden darting up or down, and the glide should be stable, not so flat as to lead to a stall, and not into an increasing dive.
(One of these days I'm going to re-do my airfoil design by running the XFoil plots with the ailerons raised and see if that changes things. Lazyness has prevented me from doing it though).
This has a couple of effects in the air. For one thing, a plane that is "pitchy" and often suddenly pops the nose up or down can often be made to fly more smootly by increasing reflex. Many designs just won't fly right with out some raising of the ailerons. I suspect that was part of what you describe from your first plane.
It also affects the power-off glide, so one way to test reflex is to fly level at full power and then quickly yank back on the throttle, best is to go deadstick. Watch the glide you get with no elevator input. You should transition into a smooth glide at a reasonable descent rate, no sudden darting up or down, and the glide should be stable, not so flat as to lead to a stall, and not into an increasing dive.
(One of these days I'm going to re-do my airfoil design by running the XFoil plots with the ailerons raised and see if that changes things. Lazyness has prevented me from doing it though).
02-16-2010, 02:04 PM
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RE: How do I balance this thing?
ORIGINAL: Montague
I calcualted 540sqin for the wing area, not bad, a bit small in my book but not terrible. When you did the airfoil templates, were they for 9'' and 6'', or were they for longer, and then cut down so you could add the aileron? Past experience seems to show that the wing often acts like what the chord would have been for a given thickness of the airfoil, even if the aileron stock makes it a bit longer or shorter.
In other words, take a 9'' template (LE to sharp TE), cut off the TE, add TE stock and aileron, and you might wind up with a wing chord of 8'' or 10''. But the plane will fly pretty much like it would with 9''. So I do most of my calculations based on the length of the airfoil templates rather than what's actually on the plane after wing building.
But I've digressed.
1/2'' forward or back will make a big differnece.
Your design does vary a bit from the Battle Axe, so you should calculate your own CG location rather than using the Axe.
Your wing is a constant taper and sweep.
So, your mean chord is 7.5'', or (6+9)/2.
So 27% of that is 2.025'', or 2'' in the real world.
So, your CG should be 2'' from the LE measured at HALF WAY out along the wing.
So, measure 30'' from the center on each side, then 2'' back from the LE, and connect those lines at the fuse, and there's your CG.
I calcualted 540sqin for the wing area, not bad, a bit small in my book but not terrible. When you did the airfoil templates, were they for 9'' and 6'', or were they for longer, and then cut down so you could add the aileron? Past experience seems to show that the wing often acts like what the chord would have been for a given thickness of the airfoil, even if the aileron stock makes it a bit longer or shorter.
In other words, take a 9'' template (LE to sharp TE), cut off the TE, add TE stock and aileron, and you might wind up with a wing chord of 8'' or 10''. But the plane will fly pretty much like it would with 9''. So I do most of my calculations based on the length of the airfoil templates rather than what's actually on the plane after wing building.
But I've digressed.
1/2'' forward or back will make a big differnece.
Your design does vary a bit from the Battle Axe, so you should calculate your own CG location rather than using the Axe.
Your wing is a constant taper and sweep.
So, your mean chord is 7.5'', or (6+9)/2.
So 27% of that is 2.025'', or 2'' in the real world.
So, your CG should be 2'' from the LE measured at HALF WAY out along the wing.
So, measure 30'' from the center on each side, then 2'' back from the LE, and connect those lines at the fuse, and there's your CG.
OOOO, Just hit me! Clamp the saddle in the position that puts the CG where I want it!!!
Sooo, put the battery and everything else on the plane, position the saddle&wing so the CG is 2' behind the LE, 15" out on the wing.
That sounds like as good a place as any to try???!!!!
Thanks
Steve
02-16-2010, 02:14 PM
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RE: How do I balance this thing?
Yep, that sounds like a plan. If you can, set things with the battery in "the middle", put everything else together, using tape or zipties to hold things in place, and figure out where the box would go to get the CG at the right point, and mark it.
Then assemble everything, double check, use the battery or anything moveable for fine tuning, and more fine tuning during test flights.
Then assemble everything, double check, use the battery or anything moveable for fine tuning, and more fine tuning during test flights.
02-16-2010, 03:12 PM
#10
RE: How do I balance this thing?
My flying wings fly at 15-18% MAC. This gives me the best dead stick glide without being tail heavy.
I would go through one of the CG calculators that are available on line to figure out where the MAC is.......but if your wing has an equal amount of taper, I believe you can treat it like a constant chord wing and base the CG on the root chord dimension. For example, if the root chord is 10 inches, I'd set the CG about 1.75 inches back from the front edge [17.5%] This should at least be flyable.
Are you going to make the wing saddle adjustable at the field?
I would go through one of the CG calculators that are available on line to figure out where the MAC is.......but if your wing has an equal amount of taper, I believe you can treat it like a constant chord wing and base the CG on the root chord dimension. For example, if the root chord is 10 inches, I'd set the CG about 1.75 inches back from the front edge [17.5%] This should at least be flyable.
Are you going to make the wing saddle adjustable at the field?
02-16-2010, 05:52 PM
#12
RE: How do I balance this thing?
Yea, I should have looked at his photo closer. 25-30% will fly this bird with the elevator.
I've been following his progress since he first started inquiring about how to hot wire foam and it's great to see that he has gotten to this point so fast.
Nice work!
I've been following his progress since he first started inquiring about how to hot wire foam and it's great to see that he has gotten to this point so fast.
Nice work!
02-16-2010, 10:13 PM
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RE: How do I balance this thing?
ORIGINAL: combatpigg
My flying wings fly at 15-18% MAC. This gives me the best dead stick glide without being tail heavy.
I would go through one of the CG calculators that are available on line to figure out where the MAC is.......but if your wing has an equal amount of taper, I believe you can treat it like a constant chord wing and base the CG on the root chord dimension. For example, if the root chord is 10 inches, I'd set the CG about 1.75 inches back from the front edge [17.5%] This should at least be flyable.
Are you going to make the wing saddle adjustable at the field?
My flying wings fly at 15-18% MAC. This gives me the best dead stick glide without being tail heavy.
I would go through one of the CG calculators that are available on line to figure out where the MAC is.......but if your wing has an equal amount of taper, I believe you can treat it like a constant chord wing and base the CG on the root chord dimension. For example, if the root chord is 10 inches, I'd set the CG about 1.75 inches back from the front edge [17.5%] This should at least be flyable.
Are you going to make the wing saddle adjustable at the field?
I havent figured out how to mount something for the wing rubber bands..
02-16-2010, 11:01 PM
#14
RE: How do I balance this thing?
A couple of 3/16" birch dowels that pass through the wing saddle to hold the rubberbands......or sew the dowels to the front and back of the saddle.
It looks like the CG will be just in front of the spar and I'm guessing you might have to move the engine back......just guessing from appearances.
Congratulations, you've got a new skill that will be valuable to you as long as you choose to build with foam.
It looks like the CG will be just in front of the spar and I'm guessing you might have to move the engine back......just guessing from appearances.
Congratulations, you've got a new skill that will be valuable to you as long as you choose to build with foam.
02-18-2010, 08:00 PM
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RE: How do I balance this thing?
I try to do something each night to keep things moving... I'm hoping to maiden it this weekend. should be in the 40s, a heat wave!
Here is a shot from above it it tells you anything?
alot of firsts in this build...couldnt do it without all your help.
wing half:
root is 8.5" tip is 5.25" length is 29.5" plus 1.5" ailerons using a clark Y airfoil.
This is a little smaller than I had estimated in earlier posts. Someone had indicated that was a little small for a .15 engine???
Fuselage length:
from the prop to the LE is 8"
wing is 8.5"
From TE to elevator hingeline is 9"
Stll a few loose ends but almost there.
Here is a shot from above it it tells you anything?
alot of firsts in this build...couldnt do it without all your help.
wing half:
root is 8.5" tip is 5.25" length is 29.5" plus 1.5" ailerons using a clark Y airfoil.
This is a little smaller than I had estimated in earlier posts. Someone had indicated that was a little small for a .15 engine???
Fuselage length:
from the prop to the LE is 8"
wing is 8.5"
From TE to elevator hingeline is 9"
Stll a few loose ends but almost there.
02-18-2010, 08:12 PM
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RE: How do I balance this thing?
Notice my right wing LE. It has a curve to it because I came around the LE of the template to fast and didnt let the wire catch up before I went around the LE...
I cut 12 half wings and got 6 usable half wings. trial and error.
This pink one is my "worst" good one.
The other two are bigger as I moved my pivot point out when cutting them
I'm looking at an all foam P51 next. 32" wingspan... Dying to take a crack at that fuse in foam....
Steve
I cut 12 half wings and got 6 usable half wings. trial and error.
This pink one is my "worst" good one.
The other two are bigger as I moved my pivot point out when cutting them
I'm looking at an all foam P51 next. 32" wingspan... Dying to take a crack at that fuse in foam....
Steve
02-18-2010, 09:50 PM
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RE: How do I balance this thing?
For wing rubber band dowels, I've gone to using 1/4" solid fiberglass rods. You can get them at kite supply places like kitebuilder.com or your favorite source for composites. The fiberglass rods won't break for nothing, which helps keep the wing on in hard mid-airs. I used to use 1/4" hardwood, but the dowels broke way too often.
I like the sliding bracket. Is that just for setup, or do you want to fly with it that way? If you fly with it that way, I'd put the wing rods under the metal rails. That does mean you'll be landing on them, but they can take it. Or use a metal hook system like a lot of guys use on that type of fuse. But I'm not sure I'd rely on that metal bracket to hold shape in very high-Gs, and especially not in a mid-air. So I'd make sure that the wing is holding directly to the rails, and the bracket is just there to keep the box from moving.
Also, you might think about a way to keep the box from flying forward on a nose-first arrival. I've seen a number of Axe-style planes punch holes in the fuel tank as the box comes forward, pushing the tank and throttle servo together and into the engine. Often times, the plywood wing saddle box dies in the process as well, but it kind of depends on exactly what hits what. In any event, look at what will happen should the fuse do a lawn dart, and see if you can reduce damage.
about the size of your plane, it's not small over all for a .15, but I think your wing area is a little small for a competitive SSC design based on what I've seen. The problem comes from the SSC rules requirement of a minimum weight of 2.5lbs (40oz). At that weight, and the intentionally limited power, SSC planes need to have a light wing loading to perform well.
Speaking of which, I can't tell from your pictures what your wing saddle looks like. If you have a flat bottom on the airfoil, make sure you aren't setting the flat part of the airfoil down parallel to the metal rails. Doing that gives you a ton of positive incidence, which you probably don't want. You'll probably want a little negative, maybe a degree or two.
The good news is that the Clark Y has fairly nice stall handling.
btw, I meant to ask earlier, you said you used the Clark Y, was that the actual Clark Y template from an airfoil library, or do you just mean a generic flat-bottom airfoil? A lot of folks in RC models seem to call anything with a flat bottom (like on many trainers) "Clark Y", even though it isn't actually the Clark Y airfoil.
I like the sliding bracket. Is that just for setup, or do you want to fly with it that way? If you fly with it that way, I'd put the wing rods under the metal rails. That does mean you'll be landing on them, but they can take it. Or use a metal hook system like a lot of guys use on that type of fuse. But I'm not sure I'd rely on that metal bracket to hold shape in very high-Gs, and especially not in a mid-air. So I'd make sure that the wing is holding directly to the rails, and the bracket is just there to keep the box from moving.
Also, you might think about a way to keep the box from flying forward on a nose-first arrival. I've seen a number of Axe-style planes punch holes in the fuel tank as the box comes forward, pushing the tank and throttle servo together and into the engine. Often times, the plywood wing saddle box dies in the process as well, but it kind of depends on exactly what hits what. In any event, look at what will happen should the fuse do a lawn dart, and see if you can reduce damage.
about the size of your plane, it's not small over all for a .15, but I think your wing area is a little small for a competitive SSC design based on what I've seen. The problem comes from the SSC rules requirement of a minimum weight of 2.5lbs (40oz). At that weight, and the intentionally limited power, SSC planes need to have a light wing loading to perform well.
Speaking of which, I can't tell from your pictures what your wing saddle looks like. If you have a flat bottom on the airfoil, make sure you aren't setting the flat part of the airfoil down parallel to the metal rails. Doing that gives you a ton of positive incidence, which you probably don't want. You'll probably want a little negative, maybe a degree or two.
The good news is that the Clark Y has fairly nice stall handling.
btw, I meant to ask earlier, you said you used the Clark Y, was that the actual Clark Y template from an airfoil library, or do you just mean a generic flat-bottom airfoil? A lot of folks in RC models seem to call anything with a flat bottom (like on many trainers) "Clark Y", even though it isn't actually the Clark Y airfoil.
02-18-2010, 10:19 PM
#18
RE: How do I balance this thing?
Steve, I bought an all foam Jap Zero many years ago for a .15 RC combat. It's blocks of pink foam that you hog out just enough space to cram in the radio gear. The instructions encourage the use of miles of duct tape wrapped all over it. I never built it, thinking that it would end up being a brick.......but the instructions for this plane raved about how much abuse it could take. Depending on how extravagant you want to go with finishing touches, a basic down and dirty foamy build could go pretty quickly. Your spar notching tool would make quick work of that job.
A 32 incher would end up pretty small for anything but .049 to .074 power and would need to be less than 18 ozs to be a good all around flyer. 14 ozs is actually pretty doable for this size plane.
A 32 incher would end up pretty small for anything but .049 to .074 power and would need to be less than 18 ozs to be a good all around flyer. 14 ozs is actually pretty doable for this size plane.
02-19-2010, 09:45 AM
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RE: How do I balance this thing?
ORIGINAL: Montague
I like the sliding bracket. Is that just for setup, or do you want to fly with it that way? If you fly with it that way, I'd put the wing rods under the metal rails. That does mean you'll be landing on them, but they can take it. Or use a metal hook system like a lot of guys use on that type of fuse. But I'm not sure I'd rely on that metal bracket to hold shape in very high-Gs, and especially not in a mid-air. So I'd make sure that the wing is holding directly to the rails, and the bracket is just there to keep the box from moving.
****I have the same concerns. this was setup for first flight adjustments. I'm thinking it will hold for the first few trimming flights. The redesign saddles will screw into the rails?? ****
Also, you might think about a way to keep the box from flying forward on a nose-first arrival. I've seen a number of Axe-style planes punch holes in the fuel tank as the box comes forward, pushing the tank and throttle servo together and into the engine. Often times, the plywood wing saddle box dies in the process as well, but it kind of depends on exactly what hits what. In any event, look at what will happen should the fuse do a lawn dart, and see if you can reduce damage.
**** good point! With my concerns about the CG being right, A lawn dart could happen. Maybe for now I'll pop a couple of screws up through the rail in front of the saddle. I'd rather destroy the saddle than the servo and tank..*****
about the size of your plane, it's not small over all for a .15, but I think your wing area is a little small for a competitive SSC design based on what I've seen. The problem comes from the SSC rules requirement of a minimum weight of 2.5lbs (40oz). At that weight, and the intentionally limited power, SSC planes need to have a light wing loading to perform well.
*****I have 3 good sets of wings to play with. The pinks are my first attempt at finishing. The others are larger. 10" root with 5.25 tip and 32" long each. On one, instead of cutting in a 1/4" x 1/4" spar I cut the whole front of the wing off lengthwise and spliced in a 1/4" piece of pine. This wing is solid as a rock and weighs about the same!
I;m waiting to finish the 3rd wing. I'm not sure how strong I have to make it by adding a spar??
My pink wing has some flex to it but I stopped the spar about 7-8" from the wingtip and think that will be a weak point when the wing flexes.*****
Speaking of which, I can't tell from your pictures what your wing saddle looks like. If you have a flat bottom on the airfoil, make sure you aren't setting the flat part of the airfoil down parallel to the metal rails. Doing that gives you a ton of positive incidence, which you probably don't want. You'll probably want a little negative, maybe a degree or two.
****** I used the same file for the saddle and the clark Y template. I kept the centerline of the airfoil parallel with the fuse rails so I would think its at 0 incedence?? This is what I mean about that 1st toss, so many factors involved.*****
The good news is that the Clark Y has fairly nice stall handling.
btw, I meant to ask earlier, you said you used the Clark Y, was that the actual Clark Y template from an airfoil library, or do you just mean a generic flat-bottom airfoil? A lot of folks in RC models seem to call anything with a flat bottom (like on many trainers) ''Clark Y'', even though it isn't actually the Clark Y airfoil.
******I actually used illustrator to trace a pic I got off the web labeled as a clark Y so I'm not 100% sure.. I now have profili And I'm trying to gather some common profiles and create templates out of them for a friend to laser cut out of formica.******
I like the sliding bracket. Is that just for setup, or do you want to fly with it that way? If you fly with it that way, I'd put the wing rods under the metal rails. That does mean you'll be landing on them, but they can take it. Or use a metal hook system like a lot of guys use on that type of fuse. But I'm not sure I'd rely on that metal bracket to hold shape in very high-Gs, and especially not in a mid-air. So I'd make sure that the wing is holding directly to the rails, and the bracket is just there to keep the box from moving.
****I have the same concerns. this was setup for first flight adjustments. I'm thinking it will hold for the first few trimming flights. The redesign saddles will screw into the rails?? ****
Also, you might think about a way to keep the box from flying forward on a nose-first arrival. I've seen a number of Axe-style planes punch holes in the fuel tank as the box comes forward, pushing the tank and throttle servo together and into the engine. Often times, the plywood wing saddle box dies in the process as well, but it kind of depends on exactly what hits what. In any event, look at what will happen should the fuse do a lawn dart, and see if you can reduce damage.
**** good point! With my concerns about the CG being right, A lawn dart could happen. Maybe for now I'll pop a couple of screws up through the rail in front of the saddle. I'd rather destroy the saddle than the servo and tank..*****
about the size of your plane, it's not small over all for a .15, but I think your wing area is a little small for a competitive SSC design based on what I've seen. The problem comes from the SSC rules requirement of a minimum weight of 2.5lbs (40oz). At that weight, and the intentionally limited power, SSC planes need to have a light wing loading to perform well.
*****I have 3 good sets of wings to play with. The pinks are my first attempt at finishing. The others are larger. 10" root with 5.25 tip and 32" long each. On one, instead of cutting in a 1/4" x 1/4" spar I cut the whole front of the wing off lengthwise and spliced in a 1/4" piece of pine. This wing is solid as a rock and weighs about the same!
I;m waiting to finish the 3rd wing. I'm not sure how strong I have to make it by adding a spar??
My pink wing has some flex to it but I stopped the spar about 7-8" from the wingtip and think that will be a weak point when the wing flexes.*****
Speaking of which, I can't tell from your pictures what your wing saddle looks like. If you have a flat bottom on the airfoil, make sure you aren't setting the flat part of the airfoil down parallel to the metal rails. Doing that gives you a ton of positive incidence, which you probably don't want. You'll probably want a little negative, maybe a degree or two.
****** I used the same file for the saddle and the clark Y template. I kept the centerline of the airfoil parallel with the fuse rails so I would think its at 0 incedence?? This is what I mean about that 1st toss, so many factors involved.*****
The good news is that the Clark Y has fairly nice stall handling.
btw, I meant to ask earlier, you said you used the Clark Y, was that the actual Clark Y template from an airfoil library, or do you just mean a generic flat-bottom airfoil? A lot of folks in RC models seem to call anything with a flat bottom (like on many trainers) ''Clark Y'', even though it isn't actually the Clark Y airfoil.
******I actually used illustrator to trace a pic I got off the web labeled as a clark Y so I'm not 100% sure.. I now have profili And I'm trying to gather some common profiles and create templates out of them for a friend to laser cut out of formica.******
02-19-2010, 09:52 AM
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RE: How do I balance this thing?
ORIGINAL: combatpigg
Steve, I bought an all foam Jap Zero many years ago for a .15 RC combat. It's blocks of pink foam that you hog out just enough space to cram in the radio gear. The instructions encourage the use of miles of duct tape wrapped all over it. I never built it, thinking that it would end up being a brick.......but the instructions for this plane raved about how much abuse it could take. Depending on how extravagant you want to go with finishing touches, a basic down and dirty foamy build could go pretty quickly. Your spar notching tool would make quick work of that job.
A 32 incher would end up pretty small for anything but .049 to .074 power and would need to be less than 18 ozs to be a good all around flyer. 14 ozs is actually pretty doable for this size plane.
Steve, I bought an all foam Jap Zero many years ago for a .15 RC combat. It's blocks of pink foam that you hog out just enough space to cram in the radio gear. The instructions encourage the use of miles of duct tape wrapped all over it. I never built it, thinking that it would end up being a brick.......but the instructions for this plane raved about how much abuse it could take. Depending on how extravagant you want to go with finishing touches, a basic down and dirty foamy build could go pretty quickly. Your spar notching tool would make quick work of that job.
A 32 incher would end up pretty small for anything but .049 to .074 power and would need to be less than 18 ozs to be a good all around flyer. 14 ozs is actually pretty doable for this size plane.
Steve
02-19-2010, 12:18 PM
#21
RE: How do I balance this thing?
That sounds like a doable plan for a 400 sized plane. I've always cheated on projects like this and taken quick looks at as many kits and plans to see how they do this and that.....mainly to get an idea about how lightly the wing can be built and still hold together. Slight errors in judgement as the decisions are made can really stack on unwanted ounces.
02-19-2010, 05:48 PM
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RE: How do I balance this thing?
sounds good, lots to play with this stuff, that's for sure.
I also cut my own wings. Profili is well worth it. Fwiw, I make my templates out of aluminum flashing material, and sand the edges with 600grit sandpaper. That allows me to print the template from Profili, use a spot of 3M-77 spray glue to attach the paper to the metal, and then cut out with scissors, and sand smooth. Makes creating templates fast and easy. I do get some wire cooling right next to the templates, but it's not enough for me to worry about.
I meant to ask earlier, are you cutting top and bottom at once? I use seperate top and bottom templates, and cut first one side then change templates and do the other. I find this makes it easier to keep the wing straight for me, and I don't have to deal with the wire going around the LE all at once.
I also cut my own wings. Profili is well worth it. Fwiw, I make my templates out of aluminum flashing material, and sand the edges with 600grit sandpaper. That allows me to print the template from Profili, use a spot of 3M-77 spray glue to attach the paper to the metal, and then cut out with scissors, and sand smooth. Makes creating templates fast and easy. I do get some wire cooling right next to the templates, but it's not enough for me to worry about.
I meant to ask earlier, are you cutting top and bottom at once? I use seperate top and bottom templates, and cut first one side then change templates and do the other. I find this makes it easier to keep the wing straight for me, and I don't have to deal with the wire going around the LE all at once.
02-19-2010, 07:33 PM
#23
RE: How do I balance this thing?
For airfoils with big, round front ends, I track the entire template in one fell swoop.
I use formica templates that are sheetrock screwed to the ends of the blank.
For skinny speed plane type wings, I do it in 2 passes, [top then bottom or visa versa] but with the same template left undisturbed until I'm completely done.
I use formica templates that are sheetrock screwed to the ends of the blank.
For skinny speed plane type wings, I do it in 2 passes, [top then bottom or visa versa] but with the same template left undisturbed until I'm completely done.
02-20-2010, 06:45 PM
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RE: How do I balance this thing?
I tried both ways. I think I'll go with two part templates. do the bottom then the top..
I'm seeing variations in wing thickness I want to address next cutting..
I couldnt wait and did this today. Start of the P51 mustang.
The wings I cut with the double taper are kinda like a mustang.
I found metalic duct tape that will look good..
I'm seeing variations in wing thickness I want to address next cutting..
I couldnt wait and did this today. Start of the P51 mustang.
The wings I cut with the double taper are kinda like a mustang.
I found metalic duct tape that will look good..
02-20-2010, 08:57 PM
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RE: How do I balance this thing?
Try this it's easy http://www.inlandsloperebels.com/Calc/cgcalc.html