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Old Sep 29, 2011, 11:06 PM
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Now your talking Dave. That one looks like something I would like!
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Old Sep 30, 2011, 11:48 AM
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Ashford. Kent. England
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Here is the video of the maiden flight.. this little version is now a lot better.. But it can be a rocket and I had to dial down the control movements which were very strong..
Flying in the video the COG was nose heavy.. At least this is more stable than the previous oval shape..
The heart shape again wins..

in the video I was gradually going back with the battery, finally running out of room on the velcro, the COG still nose heavy..
I was also adjusting the rates to get the rate of roll I liked.. The elevator was left full rate and coped fine even when a bit nose heavy..

Inverted, near the end, and a power off dive test showed the nose dropping when inverted and in the dive it would pull up on its own..sure signs of the trims being set up to hold the nose up

I am pleased with this size now so I wont be scrapping it..

Edit further flights moving the COG back were made.. unfortunately as the COG went back it became more affected by the wind.. easily off ballanced, It is too light, So it needs flying with a slightly forward COG when the wind is up.. here that is every day..
The middle version remains the favorite, its heavy enough that the wind is no problem even when the COG is back at the neutral spot..
.
maiden of the KFm4 "W" wing size15 v3 (7 min 55 sec)
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Old Sep 30, 2011, 06:35 PM
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Nice.
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Old Oct 02, 2011, 06:12 AM
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Here with floats... held on with two strips of velcro...AUW 16oz...4.15ozsqft..

The gear has been moved to the top surface to keep it away from any water/damp.. But I expect I will only use it off the snow when it comes..
The floats are fixed where the wing shape allows, see pic1...they can be moved fore or back to suit .. at the moment they sit angled outward, I dont think that will cause problems, but fitting a wedge to keep them vertical wont be a big job.. likewise, I think the prop will clear the water ok , but again its not too difficult to make a wedge/block to raise them up a bit..
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Old Oct 03, 2011, 04:52 PM
What could possibly go wrong?
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Market Harborough
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Excellent Dave!

I had a similar experiment and found that, on water, it needed the aft part of the floats to have a higher angle, more clearance to allow a bit more rotation on takeoff. It worked, but took a longer take-off run than you'd expect.

Good luck!

Nick
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Old Oct 05, 2011, 06:33 PM
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United States, FL, Mary Esther
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Here's my take on the design. Heart shaped, with ailerons with 20 degrees sweep. Only used KM1 airfoil on the inner wing. Motor moved to 3" in front of leading edge, per Tymbrewolf's suggestion. Cross strut bracing from 1.5mm carbon rod according to original design. I added a strip of foam between the inner wing pieces to provide a stronger structure and to have a horizontal surface to mount the battery and receiver. The landing gear is doubled up FFF with a 5mm carbon strip for reinforcement. I used sections of tie-wrap to protect the bottom of the landing gear and as a tail skid. Finally, I extended the Vertical Stab below the wing, to compensate for the added surface area of the landing gear ahead of the Center of Gravity.

First flights shows that the model is too stable in yaw and roll, and has a sharp nose drop when stalled. I'm going to increase the control surface throws to make it more responsive. Still scratching my head on the nose drop, maybe move the motor back a little and put in a bigger motor. It stalls and drops before entering a hovering attitude.
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Old Oct 07, 2011, 03:09 AM
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After building 4 varieties I will say that its always best to make them with a KFm4 step.. this really adds to the strength , no bracing needed, just some tape reinforcing, and the steps really improve stall and performance..

I recommend the best size as close around a 20" long version, too big is bulky and docile, too small is not stable enough for me..

For shape the heart is best, either with or without the raked forward elevons like the smallest, version3..

I like your rudder going below the W, but I would put its hinge line back at the trailing edge of that center panel fo best effect, then it wouldnt need splitting
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Old Oct 09, 2011, 12:10 PM
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United States, FL, Mary Esther
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I think I will rebuild mine with the KFm4 airfoil. That's the nice thing out foam, it's cheap and quick to experiment with. I'll drop the cross bracing, I mostly just wanted to see what it would do. It adds drag, makes it more complex to build, and is one more thing that can break, so out it goes. The 1" strip that I put below the center wing bend adds a lot of strength to the joint, so that stays.
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Old Oct 10, 2011, 03:28 AM
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The KFm4 build makes for strong joints and a stiff wing without any expensive CF rods to brace.(foam is much cheaper)...I can handle all three sizes by the thick part of the wing , no problem..
Perhaps a bit overkill but I also added colored tape along top and bottom of the joints for extra strength..and decor.....on the bottom the tape prevents landing scrapes..
Also add clear or colored tape along the rear edge and hinge line ... the tape along the back stops stress tears from heavy nose impacts... on all three I only used tape for the hinges and forgot to go all along... I had several impacts with the smallest size and a stress split formed at the rear of the centre untaped part of the W..
Its funny where the stress end up showing, the front hits and the rear end gets pulled apart by the stress of the wing trying to keep going forward.. There was no damages to the front in the impacts.. 3 layers is tough..
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Old Oct 16, 2011, 09:39 AM
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Ashford. Kent. England
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here is the W wing 21" long heart model trying out some floats.. Take off from grass didnt happen, with its high thrust line and no up thrust, the model only rocked forward.. I need to add a wedge to the floats to get the nose up and have some direct lift from the thrust, then perhaps it will move
.
KFm4 "W" wing 21" heart with floats on test (5 min 30 sec)
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Old Oct 17, 2011, 04:36 AM
What could possibly go wrong?
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Market Harborough
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Nice plane Dave!

Definitely a major contribution to the global fun-to-fuss ratio.

High on my list of jobs to do, next time I get time off for good behaviour.

Have you tried flying it through that goalpost?

Cheers

Nick
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Old Oct 18, 2011, 04:43 AM
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Ashford. Kent. England
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Yes , all my models go through ok...lol... Its just sometimes the B***** jumps out of nowhere and gives one a whack...

I am going to add some wheels soon, I will fit a cross plate halfway up the center of the W section and use velcro to hold my UC system on.. either the trike or two wheel option..

UC system here ... http://www.rcgroups.com/forums/showthread.php?t=937395
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Old Oct 18, 2011, 07:13 AM
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Long Valley, NJ, USA
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Hey all,

Inspired by the WattFlyer thread, I tried a Capricorn. Had two 24"x48" pieces of 1/2 insulation foam left over from old projects, so that detrmined the maximum size. Came out at about 42 inches span and 50 inches length.

Estimated AUW is three pounds. Old Hyperion 3025-8 outrunner, 13x6.5 APCE, 3xA123 battery, ICE 75 ESC. Two HS-475 servos on elevons, one Futaba 3003 on rudder. Each HS-475 drives a single pushrod with a fork to two clevises for the inner and outer elevons on each side.

Maiden flight went well despite gusty conditions. At least the wind made it easy to hand launch as it kind of just lifted out of my hand on the awkward - this thing's big - underhand toss. Plenty of power, but could not ROG from the grass; I'm thinking that snow will be fun.

Seemed a little unstable in roll, but that may of been the wind. Also may have been a tad nose heavy. Have to check it all out again in calmer conditions to be sure.

After bringing her home, I noticed that the Blenderm hinges on the outer elevons had stretched about 1/8" and the surfaces were very floppy. (Yes, I was lazy; this one is too big for "foamie hinges.") I've since rehinged the lot with hinge points and hinge glue and everything is as it should be now.

Thanks,

Paul
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Old Oct 19, 2011, 08:25 AM
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Thats a big'n... Ive built and flown the Capricorn but always thought the multi split elevons are a pain, thats why I kept the W wing but altered the proportions so the tip sections are larger.. With my heart shape's bigger tips you only need elevons on them and as you can see from the videos it rolls very well .. A Capricorn with the same sort of center to tip proportions likely would work nicely as well...( oh no! another one worth trying for me)
Another thing is to try using a KFm4 wing section... That has always improved the performance on my models..

You might find that you will prefer a smaller version, as they all seem to go too docile when large and heavy... my bigger heart shape at 26" long is already going too docile for the most fun, but the smaller mid size 21" long is perfect.. again the smallest 15" is too small, too much bothered in the wind and almost too much of a handfull...

Do a power off dive test to sort out the COG,.... power off..dive at 45 degrees.. if it pulls itself up, it is nose heavy, move the COG back a bit, trim out and repeat....and vice versa...
Also go inverted..if the nose drops its nose heavy..
On the heart shape when the COG is spot on the model has an axial roll, and inverted or upright the model is hands off stable.. I never had a model like it..

Foamie hinges... I always use 2" colored or clear packing tape for hinges, going full length top and bottom... see the pics... that works ...
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Last edited by davereap; Oct 19, 2011 at 08:43 AM.
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Old Oct 19, 2011, 11:07 AM
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wheels now added ..I fixed a cross plate near the top centre of the W and that holds the UC system on a couple of velcro strips..
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