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Old Jan 23, 2007, 10:44 PM
Watts is where its at!
racerxky's Avatar
United States, WA, Seattle
Joined Oct 2004
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Chanute F3P

I have been working on an F3P monoplane design for a while now. Its called the Chanute F3P and its outline is based on the Cadcor Chanute unlimited aerobatic aircraft. Its got a very distinctive platform and just looked appealing to me.



I built the my first prototype for Chitty3D and managed to place second in the Intermediate Pattern contest with it. I'm pretty pleased with my showing as someone new to the sport. I feel downright luck to have walked away with some prizes.

I got some people to fly the prototype. Going to a contest and having other more experienced pilots fly my airplane was a great experience. Sounds cheesy, I know but thats the way it is. You gotta get off your butt and go to these things or you wont learn anything.

The first thing every other pilot said was that my linkages were sloppy. I had good geometry on the Elevator/Rudder but the lines just wouldn't stay tight. The bowsies were slipping and it made is hard to get good centering or to trim it out. I saw Mike Hammel from FancyFoam.com using a neat little trick. He had some short segments of aluminum tube he was using to crimp the pull pull cable. I tried this out myself and its very simple and effective. The good news is the Chanute has lots of elevator and rudder authority so I'm not messing with the tail areas or moments.

The ailerons in particular were a disaster. I blame the builder, he sucks ;-). No really, they were the worst ailerons I have ever set up. At first the roll rate was way too slow. I increased the throws and tried to clear out the hinge line but it never did roll fast. Its not that the ailerons are too small either I just wasn't getting enough deflection. One thing that became clear for me was that all the airplanes with tabs on the ailerons rolled faster than those without. So the next version will have tabs and a slightly reshaped wing for a faster roll rate.

The hinges on the ailerons were a big problem. I did them as one of the final steps in assembly and this was a big mistake. From now on the hinges are going to be done first, on a flat surface, before paint or anything else. I have a Dremel now so I'm going to try routing the hinge lines. I'm going to go back to single beveled surfaces with Blenderm + a bit of hinge material at the hinge control horn itself. I used some 3mm wide strips of CA hinge material and they tended to pull out or break the foam. The CA hinges need more grab to no pull loose.

Did you know they make 1/2 inch wide Blenderm?

The CG turned out to be further back that I expected. I'm going to move the rudder and elevator servos further back in the next version. Sticking the servos in with RCZ-56 worked really well and I had no problems with them coming loose at all.

I saw a really neat trick for servo guides. Just cut up a pin hinge and CA it into the fuse, its got a tube that fits the 1mm carbon rod perfectly. Fancy Foam is actually sending these hinges as parts in their kits. This would have helped my aileron setup a lot because the rods were flexing quite a bit.

The all EPP motor mount worked well. I think it was finally starting to come loose at the end of day 2. It could be stiffer if the motor was on a little bit of light ply. So a little improvement is needed there but its a proven idea.

Crash wise the airplane held up pretty well. I tore one wing off when I clipped a wall and then again in a mid air. The other wing folded up when someone else was flying it inverted. The wing needs that flat rod in it to stand up to the torture. Midwest makes a 0.5mm thick flat rod that I'm going to use next time to keep the weight down.

The doubled up elevator seems to cause more problems than its worth. Its going to be reworked to have a carbon strip as a brace. I don't think that will save any weight but it should clean up the airflow back there. Looking at other winning airplanes its kind of surprising how much flex is acceptable for precision flying.

I'm building 5 degrees of right thrust into the plans. I needs it and thats just a round number to start at.

Since the plans need to be modified and I need to build a v0.2 prototype so it will be a little while before I can post them here. In the meantime you can check out the build photos over on Flickr.
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Last edited by racerxky; Apr 02, 2007 at 07:57 PM. Reason: err elevator not aileron
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Old Jan 23, 2007, 10:51 PM
Watts is where its at!
racerxky's Avatar
United States, WA, Seattle
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Some specs of the prototype:

Power: Park 250, GWS 8x4DD prop, Hyperion 300mah 2S packs
Equipment: Thunderbird 9 esc, Dymond 4.7 servos, AR6000 Rx
All Up Weight: 145g (5.11 oz)
Wing Loading: 9.61 g/dm^2 (3.15 oz/ft^2)
Cubic Wing Loading: 2.47
Span: 804mm
Length: 840mm
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Old Jan 24, 2007, 03:13 AM
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That's nicely different!

A few comments:
Do you currently have any external bracing? I can't see any in the photo but maybe you have bracing on the underside. You'd save weight and end up with a stiffer plane if you use carbon or thread to brace the wing, tail and fuselage rather than adding carbon strip to the surface itself. It's a little more work but not much. The thread approach adds virtually no weight and gives an incredibly stiff and resilient airframe. The carbon should be less prone to hanger rash and is possibly even stiffer but weighs a few grams.

Blenderm is available in 1/2" but doesn't seem to be as easy to get your hands on.
Of course you can always cut the usual 1" stuff down the middle!

How do you find the Park 250 for this size and weight of plane?
Bear in mind that the side thrust required will vary depending on the prop used.

When you post plans make sure I add a link in the F3P plans sticky!

Aidan
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Old Jan 24, 2007, 08:11 AM
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I finished my Chanute also. There are no spars in the wing on mine, only the Vecht X bracing. So far its proven to be a very nice plane. Just have to work on my linkages. The plane slows down very well in level flight, without any of that tail down harrier charectoristics. It flys straight and slow. Im still adjusting and trimming, but should have video once its all trimmed out.
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Old Jan 24, 2007, 08:33 AM
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Great job Racer! Its nice to see someone who is designing an F3P airplane and actually using it for what it was designed for - Competing! and big congratulations for your placing in the intermediate contest.

I wish I could have been there in person to participate with ya'll.

Awesome paintwork Bryan!
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Old Jan 24, 2007, 08:37 AM
Watts is where its at!
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Here is a shot of the bracing:



I am impressed with the Park 250 with the 8x4. On the 7x3.5 its got enough power for F3P but not for freestyle. On the 8x4 is will hover right down to the end of the pack. It doesn't really get that hot, just warm. It's small, light and cheap.

I may go to the Axi 2203/45 for freestyle. Several people were running this motor at the event. It is a little bit heavier but it seems to get good run times and make lots of power.

Either of these motors will make you happy on a 5oz airplane.

Here is a shot of the motor mount I made entirely out of EPP. Its got the Park250's motor mount embedded between the top two layers. The wheel pants are also EPP.



The prototype before this used the same sort of mount and it had a linkage failure in the downline of a stall turn. It went straight in from the top of the OKC armory and the nose didn't break.
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Old Jan 24, 2007, 01:29 PM
pad
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quite heavy for this small wingspan ... with your equipment I think it isnīt difficult save weight between 125-135g

try prop 8/4,3 ... it is lighter than 8/4 and I think you will be satisfied

about engine mount - I am not sure you can keep exactly right position of engine and to change position softly

for freestyle I think the plane will not be rigid enough

good idea is to use epp block to keep gear legs crossing fuselage, reinforcement on horizontal part of fuselage is needless (- if you are using carbon wire with diameter 1,5mm)
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Old Jan 24, 2007, 01:54 PM
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Quote:
Originally Posted by pad
quite heavy for this small wingspan ... with your equipment I think it isnīt difficult save weight between 125-135g

try prop 8/4,3 ... it is lighter than 8/4 and I think you will be satisfied
changing a 8x4 HD for a 8x4.3 RS prop is not a like-for-like change. It will greatly increase the load on the motor. Having the right prop for the power system and airframe is, in my opinion, far more important than the 1 or 2 grams you'll save.
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Old Jan 24, 2007, 01:54 PM
Watts is where its at!
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Thanks Matchless!

Pad, I will be shooting for 135g next time. I have removed some Depron from the design and some other improvements should make it lighter.

The 8x4.3 prop is about 2g lighter than the 8x4DD but it draws more amps so I am a little scared of it. If you want to save weight and just fly the F3P sequence the 7x3.5 will work well.

The wing has a very wide chord so it has a lot of area despite the span. Wing loading is what counts. I have reduced the area somewhat on the new plans but at 135g the wing loading will be lower then the first version.

I will be adding some 0.5 x 3mm carbon strip to the wing and this should make it stiffer. I promise some more detailed construction photos for the next one.

The gear setup does use 1.5mm rods, its going to be redesigned for the next version. It was a pain to install, it could have been lighter and it got in the way of any kind of aileron pull-pull setup. The next version will address these issues.
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Old Jan 24, 2007, 01:58 PM
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Great paint job Bryan!

Is the lamination on the outboard LE just a 3 layer sandwich? What's the reasoning behind putting it outboard only? To prevent tip stalling?

Aidan
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Old Jan 24, 2007, 02:05 PM
Watts is where its at!
racerxky's Avatar
United States, WA, Seattle
Joined Oct 2004
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Quote:
Originally Posted by Aio_1
Great paint job Bryan!

Is the lamination on the outboard LE just a 3 layer sandwich? What's the reasoning behind putting it outboard only? To prevent tip stalling?

Aidan
Its 3 layers. That was the idea, to fight tip stall. Its really stable in a harrier. It did do some funny things that I cant really explain. When Sean was flying it he had it in a tight flat turn. He said it was stalling on the outboard wing.

I don't know if it was caused by the SFG's though. On the next one I wont slant the SFG's and they wont be on the ailerons. I need to eliminate as much weirdness as I can for testing.
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Old Jan 24, 2007, 02:35 PM
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plan's?
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Old Jan 24, 2007, 10:28 PM
Watts is where its at!
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Got Pulley?

I have been on a maddening search for a small pulley. This is my best effort so far. It works well, is easy to make and uses common materials.

Materials:
  • 1/16" Aluminum Tubing, available at HobbyLobby or your LHS, I got K&S brand.
  • Piano Wire, it needs to fit inside the aluminum tube, I got the smallest stuff available at my LHS.
  • 2 of the black rubber grommets that come with the Dubro EZ connectors.

You have to ream out the grommets with a 1/16" drill bit to let them slide over the tube.

Slide them together and secure with a drop of CA at either end.

Then slide the rig onto the wire. It needs to be cut on the wire to keep the ends open. If you cut it too long you can clean up the end with a Dremel and a sanding disk. A short length of the wire can be used as an axle.

If there is a downside to this its that you need 0.5mm carbon rod for an axle and thats a kind of rare size. Three of them don't register any weight on my scale. They have a nice deep groove and they spin freely.
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Old Jan 24, 2007, 11:48 PM
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great idea!
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Old Jan 25, 2007, 12:02 AM
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Amarillo Intl, Texas, United States
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Looks fantastic, Racer. I may try out a Chanute next when one of my Blings needs to be retired.

I hear you on the need for a carbon strip in the wing. On both of my Blings I went with a 1mmx3mm carbon strip (shockflyer stuff) and it really stiffens it up a lot. The mistake I made was cutting the strip a little short. Thinking I would save a few grams by going a little shorter, I found that the wing tends to fold/bend just outboard of the bracing and carbon strip. Next time I'll just run the strip to within 3/4" or so of the wingtips. I simply cut a slit, inster the strip, put a small drop of foamsafe every 2" or so, and then use that 1/4" of blenderm (just cut the 1/2" blenderm in two) on the top and bottom of the strip. Nice neat, and clean. Here's a pic of how mine had come out: http://www.rcgroups.com/forums/showp...3&postcount=90


What are the pulleys for? Trying to do pull/pull on the ailerons? I think Mike Fwilly has a nice done a setup that worked well with a little pulley.

Sorry to miss you guys at the Chitty event...my work schedule got in the way this year.
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Last edited by Lance; Jan 25, 2007 at 08:07 AM. Reason: Edited "ChaNute" to appease the desires of the allmighty Chinnman! :)
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