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Old Aug 02, 2009, 11:17 PM
Lee
PERFECT LANDING !!!
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USA, UT, Orem
Joined Jul 2004
9,078 Posts
Quote:
Originally Posted by AC5FF
Hey Lee
Great sloping vid there! Would be hard pressed to tell it was an RC bird over the real one most of the time... (at least when you weren't doing loops n rolls! LOL)
I have had some fun with the hawks and falcons in the area with the high climb rate and the aerobatics.
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Old Aug 11, 2009, 04:02 PM
If it wasn't for the foam
PA
Joined Dec 2004
522 Posts
what size to build?

Darn! I reached the end of the thread! I was soooo enjoying that!

I'm ready to replace my backyard flyer, so I plan to move the guts from my Blu-Beagle to an FFF Eagle, but I'm not sure what size to build. Here's the specs on my Beagle and its innards:

-- 36" span X 6.5" chord
-- AUW 8 oz.
-- LensRc 20mm 8 turn 2660 KV motor
-- GWS 4.5x3 DD prop
-- 2S 830 mah lipos
-- 7 oz thrust @ 7 amps, 45mph pitch speed

The motor/battery worked great on my Beagle, although it was ridiculously over-powered. It had a near-vertical climb and could fly for 30+ min. on a battery.

I think I'd like to shoot for a 10-12 oz. AUW eagle. Is that a good weight given my power system? Can the 42" be built that light, or should I scale down smaller? (I build light, and have light gear.)

I'll be building the wing as per plan, including dihedral. And I thought I'd try RET for simplicity and light weight. Is there a size below which I don't need a spar, given the 3 layers of FFF?

BTW, great thread everyone!
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Old Aug 12, 2009, 04:43 PM
If it wasn't for the foam
PA
Joined Dec 2004
522 Posts
I decided on the 42", based on others' AUW's in that size. Now I can't decide between RET (V-tail) or AET (v-tail or flat + clear plastic fin). I plan to use only 2 servos, and I'm striving for simplicity. Are my assumptions correct:

RET w/ v-tail mixing: will need at least 4 deg. dihedral; won't roll well if at all; good for docile, realistic flying. May need to cut ailerons anyway to set required reflex. (Not sure why some built-in AOI wouldn't simplify all of this - but how much?)

AET - will work w/ flat wing or minimal dihedral; will need v-tail or clear plastic fin; will be more maneuverable but less realistic in flight; will require more hands-on piloting; reflex will be easier to adjust.

I'm leaning toward AET w/ the V-tail. Has anyone operated the v-tail in elevator-only fashion by using two pushrods from opposite sides of a servo horn, with one control horn on top and one on the bottom?

Do the bent up tips help with anything besides looks (assuming I have enough regular dihedral)? Since the bend line isn't parallel with the fuse, don't those act as air brakes? I'm thinking of leaving the tips flat to reduce drag. (but they do look really cool!)

Got my plans printed today, and I'm getting ready to start cutting!!!
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Old Aug 12, 2009, 05:43 PM
Dance the skies...
Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
17,568 Posts
Good decision on the smaller one for your power sytem.

I have both ailerons and full V-tail R/E mixing, but I can tell you that rudder- only turns will be a slow rolling/diving action, not a nice skid turn. I ONLY use rudder when I want to turn very sharp, which is not very often. I turn normally with just ailerons (with a little elevator only when necessary)... very nice, flat, realistic turns.

But my ailerons use dual servos, though. I also left the tip end of the ailerons fixed (I cut and hinged, but did not cut the very tip end free... left it fixed to the wing. The aileron then twists as it deflects, giving some natural reflex to the aileron action, very much like a real bird. I call them "warperons" for this reason. The long thin foam doesn't offer excessive resistance to movement when deflected.

With one servo for ailerons, I'd cut them free as you normally would. The angled pushrods, though, will give you differential movement. If you put the control horns on the bottom of the wings, you'll get more down than up (opposite of what might normally be done) and that will affect how the plane will bank and turn.

I also modified the tips... used a hair dryer to gentle curve them upwards, with the bend line parallel to the flight direction... looks/works great.

My build post in this thread shows these mods (plus a few others).
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Old Aug 13, 2009, 03:54 PM
If it wasn't for the foam
PA
Joined Dec 2004
522 Posts
Tom, thanks for the input. AET it is. I like a lot of your ideas and will attempt to incorporate some.

The warperons and curved wing tips are a nice touch. Maybe I'll spend a few extra grams and use an HS-55 servo for a little more torque, and still do the warperons with a single servo. And maybe a little extra sanding near the outboard TE will ease the torque requirement.

A few tweaks to the shape will make it more realistic. Hopefully I won't change the optimal CG location, as I'm not looking for a trial and error project on this one.

I've done single servo ailerons before and used two adjacent arms of an X-shaped servo horn. Does this help to alleviate the differential aileron throws you mentioned?

I like how you mounted your tail. Now I just have to work out the angles to get a 0 deg AOI.

Have you painted yours yet? I'd love to see more pics.

Tom
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Old Aug 13, 2009, 05:28 PM
Dance the skies...
Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
17,568 Posts
Quote:
Originally Posted by tduro
Tom, thanks for the input. AET it is. I like a lot of your ideas and will attempt to incorporate some.

The warperons and curved wing tips are a nice touch. Maybe I'll spend a few extra grams and use an HS-55 servo for a little more torque, and still do the warperons with a single servo. And maybe a little extra sanding near the outboard TE will ease the torque requirement.

A few tweaks to the shape will make it more realistic. Hopefully I won't change the optimal CG location, as I'm not looking for a trial and error project on this one.

I've done single servo ailerons before and used two adjacent arms of an X-shaped servo horn. Does this help to alleviate the differential aileron throws you mentioned?

I like how you mounted your tail. Now I just have to work out the angles to get a 0 deg AOI.

Have you painted yours yet? I'd love to see more pics.

Tom
My aileron servos can produce about 10-15% more torque than HS-55s. I used one of the on-line servo torque calculators and that predicted that I'll only be drawing about 1/3 of the servos rated torque at full deflection and WOT. So I think one HS-55 is capable of powering the warperons... yours will be smaller since I built the larger version. But my hinge resistance is also almost nil... I used "Z" hinges with as you may have seen in my build post. You can minimise the aileron differential effect with two adjacent arms on an "X" horn, or with different hole in a circular one, but getting similar up and down movement with one servo will be a crap shoot. Maybe you'll get lucky! Oh yeah, my ailerons are made from Elmer's paper-covered foam board with paper removed. It is very flexible... much more so than Depron.

I changed the wing profile slightly to look a little more realistic... moved the "thumb" bump on the LE inward slightly and cut the tip feather notches deeper.

To get the right tail angle I installed the wing on the body and levelled it. Then I aligned the tail on the fuse and raised the back with a small level resting in the V-tail until it also read level, then measure how hig off the body the aft edge of the tail was. That got me pretty close to how far down into the body the front of the tail had to go. But cut less than that on the first cut... the body is tapered and the compound angle is not the same when viewed from the side. Also you'll not I changed the profile of the tail slightly. I wanted the LE to be much straighter like the real bird, so I widened the front to match the body width, and drew a nearly straight line back to the outer tail feather aft point (if that makes any sense)

FWIW, the Vtail does serve one other function on my eagle I didn't mention. Mine climbs to the left more and more as throttle increases. I'm not sure if this is due to slight offset in my V-tail or just the nature of the bird. But I did correct this by adding two P-mixes to my tail servos linked with my throttle stick.

Also FWIW, there's several videos of my eagle (and another) on this web site:
http://exposureroom.com/members/tomfrank.aspx/assets/

Yes, mine is painted now... here's a few of pics:
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Last edited by Tom Frank; Aug 13, 2009 at 05:36 PM.
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Old Aug 13, 2009, 07:51 PM
If it wasn't for the foam
PA
Joined Dec 2004
522 Posts
Nice job Tom! She really slows down, which is what I'm looking for - I'll be flying out of a tight spot. Great paint job too!

I'll be building the body and tail out of 1/4" white foam board (w/ the paper peeled), and the wings out of blue FFF. I could do the ailerons out of the white foam and glue/tape them back to the wing if it seems they'll be more flexible that way. I'll have to see how it goes.

I noted your tail and wing mods, and I was thinking the same thing. I've looked at hundreds of eagle pics, and want to make mine realistic (at least from a distance)

I'm not too concerned about the aileron differential w/ a single servo. I've done this on pylon racers and jet-like models with fast roll rates. Worked great, although not always the most axial rolls. If it worked OK there, it should be fine on a slowflyer like the eagle. (I think)

I don't have a programmable TX, so I'll need to trim her out another way.

Thanks for sharing!

Tom
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Old Aug 13, 2009, 08:16 PM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
18,240 Posts
Wow, nice detail on your Eagle Tom. That looks really nice. Care to share how you did it?
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Old Aug 13, 2009, 10:26 PM
Dance the skies...
Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
17,568 Posts
Quote:
Originally Posted by tduro
Nice job Tom! She really slows down, which is what I'm looking for - I'll be flying out of a tight spot. Great paint job too!

I'll be building the body and tail out of 1/4" white foam board (w/ the paper peeled), and the wings out of blue FFF. I could do the ailerons out of the white foam and glue/tape them back to the wing if it seems they'll be more flexible that way. I'll have to see how it goes.
...
Tom
The most amazing thing I've found with the eagle is how well it handles wind! I've flown mine in winds up to about 15mph, to the point where the ground speed was nil, and it is still very stable for such a light, low wingloading.

One other thing you could do with your wing is make the full profile wing base piece out of the white foam board (with warperons intact), and just use the blue foam for the two partial profile layers on top. Out of curiosity, why the preference for the blue foam for the wings? I've never used that foam (not available here), so don't know it's properties.
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Old Aug 13, 2009, 10:43 PM
Dance the skies...
Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
17,568 Posts
Quote:
Originally Posted by Vantasstic
Wow, nice detail on your Eagle Tom. That looks really nice. Care to share how you did it?
THANKS! I probably spent as much time painting the bird as I did building it!

I used acrylic paint from Michaels, three shades of brown and some black for feather highlights. I D/L probably a dozen eagle pics off the net to see what the real deal looks like up close, and they vary depending on the age of the bird. Younger ones are mostly shades of mottled lighter brown. They don't even get the white head and tail plumage until about 5 years old, and by then the feathers also darken to dark brown/black.

I wanted the thicker wing section (i.e. the "arms" of the bird) to look darker in the air since thats they way they look when I see them flying here. The thicker foam there does just that even though the light brown in the pics don't look that way. I brushed on the based colors for the three layers (tok 2-3 thin coats to get uniform color), then with a very stiff bristle brush, dabbed on the mottled look with a different shades of brown or black to get the look I wanted. I did it rather haphazardly and randomly... I didn't want to definite shaped pattern to show. Ditto for the body.

The feathers at the TE took the most time. I used thinned black for the feather "veins", brushing outward on each side of the feather center, again with a stiff bristle brush. Then, when finished with that, I just dragged the brush the length of each feather to make the shaft while the pint was still wet to them off.

The head and feet detail is just freehand lines with a large black Sharpie pen, adding the eye, beak, and feet color with a small brush afterwards.

It looks really nice in the air. I was flying it at a local park earlier this summer, and people walking by all looked up, pointing and amazed at an eagle flying only about 200 feet up! They didn't see me off to the side with my TX, and I had throttle down to the point where you could not hear or even see the prop. They were completely fooled!
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Old Aug 14, 2009, 07:46 AM
If it wasn't for the foam
PA
Joined Dec 2004
522 Posts
Quote:
Originally Posted by Tom Frank
Out of curiosity, why the preference for the blue foam for the wings? I've never used that foam (not available here), so don't know it's properties.
I used to use the white foam more when we were buying cases of 4' x 8' sheets at work for mounting maps and stuff. Peeling the paper got old after awhile, although I liked the material. I left that department and now work in a different building, so it's not as easy to get their scraps.

I bought a bundle of the blue foam at Lowe's after reading about it on RCGroups. 25 2'x4' sheets for $33 seemed like a steal. So now I'm rationing the white foam I have left, and trying to use the blue for big pieces. Someone more experienced than I might find some differences between the two materials, but they're nearly identical as far as I can tell.

Here's some pics of my typical build M.O. - blue wings and white for other parts. This is my 8oz. beagle that I fly in my backyard. I've got 4 wings of varying designs for different purposes and conditions. I even made a vulture wing for it that flew well, but it never got its own body and tail. That's why I'm so excited about the eagle project.

I'm glad to hear you brushed on your paint. I hate spraying. Do you have any idea how much weight your paint added?
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Old Aug 14, 2009, 10:30 AM
Dance the skies...
Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
17,568 Posts
Quote:
Originally Posted by tduro
...
I bought a bundle of the blue foam at Lowe's after reading about it on RCGroups. 25 2'x4' sheets for $33 seemed like a steal.
...
I'm glad to hear you brushed on your paint. I hate spraying. Do you have any idea how much weight your paint added?
The Lowes stores here don't typically carry the blue foam bulk packs for some reason. I did see some at a more distant Lowes once, but it was all warped from sitting stacked on the rack.

I didn't take before/after weight checks on the paint. I flew the plane quite a few times before I painted it, and with such a low wing loading, I wasn't concerned about the final weight. Several flights were with a 2.4 oz. camera on board, and I could not really tell any difference in flight characteristics since I don't do much of any aerobatics with it.
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Old Aug 14, 2009, 11:16 AM
Where'd The Wise Men Go?!?
AC5FF's Avatar
United States, NE, Bellevue
Joined Sep 2007
2,969 Posts
My wing (52") gained around 10g if I remember right.
I used the Krylon spray and had to do two or three coats to get a good covering.

IMHO between this one and others that I have painted the extra weight from paint didn't effect things enough for me to be worried about...
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Old Aug 15, 2009, 12:18 AM
'FPV'er...not a "LOS'er
Vantasstic's Avatar
Las Vegas, NV
Joined Sep 2003
18,240 Posts
Quote:
Originally Posted by Tom Frank
THANKS! I probably spent as much time painting the bird as I did building it!

I used acrylic paint from Michaels, three shades of brown and some black for feather highlights. I D/L probably a dozen eagle pics off the net to see what the real deal looks like up close, and they vary depending on the age of the bird. Younger ones are mostly shades of mottled lighter brown. They don't even get the white head and tail plumage until about 5 years old, and by then the feathers also darken to dark brown/black.

I wanted the thicker wing section (i.e. the "arms" of the bird) to look darker in the air since thats they way they look when I see them flying here. The thicker foam there does just that even though the light brown in the pics don't look that way. I brushed on the based colors for the three layers (tok 2-3 thin coats to get uniform color), then with a very stiff bristle brush, dabbed on the mottled look with a different shades of brown or black to get the look I wanted. I did it rather haphazardly and randomly... I didn't want to definite shaped pattern to show. Ditto for the body.

The feathers at the TE took the most time. I used thinned black for the feather "veins", brushing outward on each side of the feather center, again with a stiff bristle brush. Then, when finished with that, I just dragged the brush the length of each feather to make the shaft while the pint was still wet to them off.

The head and feet detail is just freehand lines with a large black Sharpie pen, adding the eye, beak, and feet color with a small brush afterwards.

It looks really nice in the air. I was flying it at a local park earlier this summer, and people walking by all looked up, pointing and amazed at an eagle flying only about 200 feet up! They didn't see me off to the side with my TX, and I had throttle down to the point where you could not hear or even see the prop. They were completely fooled!
Wow...thanks for the information. As I go back and look at your pictures I'm really impressed with the outcome.
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Old Aug 16, 2009, 12:06 PM
If it wasn't for the foam
PA
Joined Dec 2004
522 Posts
I have a FFF vulture wing from an earlier project. It's about the right size for my eagle, so I thought I'd put it to good use. I'm worried about finding the right CG. Will the CG for that wing be the same on my eagle as it was on a plane having more plane-like proportions?

If so, I can just mark it where it balances on the other plane, and use that point for balancing the eagle. If anything, that should give me a slightly forward CG, as the other plane has a few degrees AOI, and the eagle will have none.

Does that make sense, or not? I'm thinking it will be a good starting point, but not necessarily the real deal.
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