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Old Mar 28, 2010, 04:18 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
Maybe we could work out a deal where we fly these things with "Vote for..." logos on them and get a per flight royalty?

But at any rate, your parts look like they will work to me.

It occurs to me that I did have a problem with the elevons fluttering at first. I had the servos mounted near the inboard ends at first and the flutter was probably a result of the large areas on the ends. I moved the servos out on the wing to put them close to the center of the elevon's length and that solved the problem.

I'll have to put up some brief construction notes on the things I learned the hard way...

Jack
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Old Mar 28, 2010, 05:02 PM
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doggit's Avatar
northenden, manchester, england
Joined May 2009
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thanks for the servo tip jack, i will put them more or less in the centre, and going to order my motor tomorrow and i am going to get this one i think http://www.giantcod.co.uk/epower-221...tor-p-212.html
carl
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Old Mar 28, 2010, 06:10 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Carl,

I think that motor will work fine.

I was flying mine a little heavier than most will be flown. That was, in part, due to the 4S A123 battery packs I used. Those are 1100 mAh and weigh about 175 grams. You can see them in the photos above, they are not small in any sense of the word.

I like to fly a DPR-100 power data recorder occasionally to see what is going on the power system in flight. Here is the summary of the flight data seen in the graph below.

Time: 5:05
Charge: 673 mAh
Current Max: 16.60 A
Avg: 7.96 A
Voltage Max: 13.40 V
Avg: 11.02 V
Min: 9.85 V
Power Max: 179.44 W
Avg: 82.81 W

With the motor you are looking at, you can draw about 14A continuous and with a 3S LiPO battery at 10V that will be about 140 Watts (14A x 10V = 140 Watts). So if you compare that to what I was using with the DAT-750 (an 80 gram motor) and with my AUW of about 28 oz., you can see you'll be fine.

The graphing is eye candy for the insatiably curious. But the number speak for themselves.

Jack
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Old Mar 29, 2010, 03:02 PM
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northenden, manchester, england
Joined May 2009
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well i am in the process of gorilla glueing the coro together at the moment, and just ordered this motor http://www.giantcod.co.uk/221720t-86...-p-402409.html and a couple of the recommended 11x4.7 sf props too, not sure about the mount yet for the motor, i hope it will be here in the next couple of days, but i am thinking of the stick mount method jack used, with screws through the square stick
carl
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Old Mar 29, 2010, 06:45 PM
nickeast
Stuart,FL
Joined Mar 2009
557 Posts
Jack,

Weather report for sunny FL .... NOT.... high winds ad RAIN.... I really like this plane... can you give us tips on the coro gluing process.... I have not had the "sitckability" that I need yet.....

Carl, as usual you have a very nice build going..... Sorry about the UK Spring... seems the weather is bad everywhere

Nick
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Old Mar 29, 2010, 07:12 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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This is a good mount for motors up to 28mm or so:

http://www.allerc.com/product_info.php?products_id=2386

or this one:

http://www.rcdude.com/servlet/the-25...k-Mount/Detail

or this one:

http://www.rcdude.com/servlet/the-11...r-Mount/Detail

or this one:

http://www.aero-nuts.com/product_inf...roducts_id=345

So many good mounts, so little time...

And I finally found the info on the mount I used for the DAT-750, I found it at the LHS and it is the E-flite EFLM1915N stick mount. It has a flat face that works well with the flat mount that comes with the DAT-750 motors:

http://www.horizonhobby.com/Products...rodID=EFLM1915

I also noticed that Horizon Hobby has a good deal on the GWS EMM28TA mounts, six mounts for $5:

http://www.horizonhobby.com/Products...dID=GWSEMM28TA

Jack
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Old Mar 29, 2010, 07:29 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
Here is a photo of the servo location used on SpaFFFnutz #1. The servos were moved out to mid span on the elevons to alleviate a flutter in flight problem. Servo extensions had to be added. Mounting ears were cut off of servos, pockets were routed in FFF to expose coro layer, servos were hot glued in place.

The damage on #1 that finally caught up with it. The occasional prop strike and brittleness in the cold started the cracks. Then they would run when it "came to a sudden stop" occasionally.

The final outrage was a full throttle nose first impact at the hands of another pilot that started a crack that ran along side the center filler almost all the way to the nose.

The plane was actually flown with that crack in it, it would not handle more than the minimum throttle or it would turn into a blur of flapping and fluttering parts. We let he limp past in review, rendered full honors, and then put her down. It was having to shoot you own dog. Sob!

Jack
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Old Mar 29, 2010, 07:55 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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PU Gluing FFF to Coroplast

Here is my technique for gluing the KFm taco shell onto the coro center panel.

0 - If your going to add skewers to the prop slot, do it first.

1 - Position both strips, touching, in alignment, etc., and then use a Ultra-Fine Permanent Ink Sharpie to draw a line on the coro along the back edge of the step to mark the FFF's final position. Also mark the center joint where the two strips will meet. Just do the strips on the top side of the wing first.

2 - With the lines marked on both sides of the top, lay a yardstick over the line on one side so the alcohol does not erase it and scrub the gluing area with a piece of Levis-like rough cloth with some alcohol poured onto it. This is to degrease the coro.

3 - Take a sheet of 60 or 80 grit open grain woodworking sandpaper, fold it into a thirds (like a letter for mailing in an envelope) then fold that in half. Use that to rough up the degreased coro in front of the yardstick to the leading edge. Scrub it up good, cross your tracks. Then give another light cleaning with the alcohol dampened rag to remove the loose stuff.

Gluing the KFm strips down will be done in four steps, top right, bottom right, top left, bottom left.

4 - I use Gorilla Quick PUb (GQPU), that comes out of the bottle in a thin stringy stream a little smaller than a pencil lead. Lay the back side of the top right strip flat and run a string of GQPU around the perimeter about 3/8-1/2" in from the edge. Then continue to run beads at that spacing until you get to center of the strip.

5 - Take a flexible plastic spreader (cut from snap on can lids) and spread that lightly out to the edge and back in to the center. Take the plant misting sprayer with water and spray a fine mist of water on the GQPU and also on the cleanned and sanded surface that it will contact.

6 - Use the spreader lightly to spread the water that is on the GQPU.

7 - Position the folded KFm taco shell back on the coro center panel so that it is in perfect alignment with the lines you drew in step 1. The coro will not be firmly butted into the fold in the FFF, that is OK, you just want to get it on your marks.

8 - Lay a straight, flat, 1 x 3 or 1 x4 plank on top of the folder back and positioned FFF and start stacking heavy stuff on it. I use a supply of depleted SLA batteries that I happen to have. The goal is to ensure that the FFF and coro are in full contact full length. Position the board even with the step so you can keep an eye on the line and not lose the register there.

9 - In 15 minutes you can blot up any water that is forced out along the step. If the GQPU is foaming out, those can be picked off easily at this point. I use a propellor blade to do that.

10 - After 30-45 minutes you can unweight it and move on. I do the back side of that same strip next. Then I do the top and then the bottom of the other side, same steps each time.

Jack
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Old Mar 29, 2010, 08:12 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Reinforcing Prop Slot with Skewers

The prop slot can take a beating as my photos show. I am putting skewer inside the corrugations there to strengthen that.

The first skewers have to be put in place before you glue the KFm strips on or you won't have access to the holes.

The bamboo skewers are in the food section or maybe at the Dollar store and are the size that are a little larger than a toothpick. They are about 0.140-0.150" or 3.5mm in diameter. Buy a bag or bundle of them.

Slide a skewer into the still closed/not cut corrugation along the front of the prop slot. If you can't slide it most of the way in easily, use the 60/80 grit sanding pad to fine tune the diameter or look for one that fits. Snip the sharp pointed end off and slide the skewer into the coro. Then test fit another skewer and use it to push the first one further in. Then take a piece of 1/8" brazing rod or coat hanger and push both of the skewers until they are centered over the prop slot.

Take more skewers and cut them into 3" long lengths. Slide those into the open corrugations in the prop slot to reinforce them. I did six rows on each side, sliding them in flush with the coro after the photo was taken.

The skewers only add about 12-15 grams to the build, don't worry about it.

Struggle with your self control, fight it off and win if you think it is a good idea to put skewers in every corrugation. You get that much bamboo on the plane and it may get swatted out of the air by a hungry panda bear.

Jack
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Old Mar 29, 2010, 08:18 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
My camera died today. Along with my plan to shoot photos and post details and photos of the build in progress.

As you can see in my last post, I have cut the coro and fff, put the skewers in the coro, and have the FFF GQPU glued in place.

I spend most of the day digging out my old camera, getting the batteries going, and managed to get back on track a little bit. I hope to back fill the thread with a sequence of build details and photos to help the people that are new to this. I know very well the aqony of lusting to build, reading a thread, and just not knowing what to do next so I want to be helpful.

Jack
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Old Mar 30, 2010, 02:59 AM
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northenden, manchester, england
Joined May 2009
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hi jack, just wondering what cog you have on yours, i will measure and put in the cg calculator and hopefully they both come to the same figure
carl
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Old Mar 30, 2010, 04:34 AM
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Chalmette, Louisiana. Mostly warm, sometimes 14-feet underwater!!
Joined Jan 2010
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Get that camera going Jack. Your step-by-step, with photos, on the Divinity thread, was the ultimate guide for me!

I have printed the 32 pages of tiled plans. If I took the full plans to Kinko's or similar store, How big of a sheet would it require? How much do they normally charge for these bigole sheets?
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Old Mar 30, 2010, 07:23 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
doggit,

I disassembled #1 yesterday to get the parts off and didn't think to see exactly where the CG was on that. I remember I ran it through the flying wing CG calculator here and that turned out to be a good starting point for me:

http://fwcg.3dzone.dk/?wing_span=48&...ow_mac_lines=0

That link will bring up the calculator with the SpaFFFnutz dimensions already filled in. That shows about 7" back from the nose for a 15%/maiden flight CG and 7.5" for a 20% CG. And that worked fine for me.

That first video in post #2 is the maiden flight and I started with a low power test glide over the tall weeds. You can see there what I consider a good behavior for a test glide, a short distance of level descending glide and then the nose slowly dropping. The fall to one side is incidental but that would have me looking for maybe a little turn to the right on launch too. And, as you can see in the video the launch was done with less than full power went very nicely. A little up and down as I found the stick, a gentle climb, and a gentle turn to the right.

Jack
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Old Mar 30, 2010, 08:39 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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bigoledude,

If you look at the File > Document Properties it will tell you the size of that white area the parts were drawn on. It is 61-1/2" by 38" on the parts drawing document but the parts themselves do not fill the entire area as you can see. I have to do it that way to get the parts so that they can be printed and scaled up and down. I have to draw them full sized and that is what really drives the paper size, how much room is needed to fit all the parts into.

When you want to print that at home you can zoom out to see the full page and then step through the page starting with page one. If you make a note of what pages have the parts line on them and only print those pages you can save a lot of paper. As I see it for my printer I only have to print the following pages:

pages (total)
4-6 (3)
10-13 (4)
15 (1)
18-24 (7)
26-27 (2)
29-32 (4)
(21)

When I print those I see a black border all the way around and I trim the first row of pages I printed to the border line on the right.

Then I lay the first page on the second page, overlapping the left edge and aligned with the left border of the second page and any parts lines. I stick those in alignment with bits of clear Duck brand standard grade package sealing tape (from Wal-Mart) and continue to the right to the end of the first row. You end up with five separate groups of taped together pages and one single loose page

Then start with the stuff from two 2 and higher rows and trim them to the border at the top. Lay those in alignment on the bottom of the row one pages, again aligning the parts lines.

Continue that and you'll have a big sheet that is part of the drawing area and it will have some holes or gaps in it but you should see all the parts.

Then start laying long strips of the clear tape on each of the page overlaps. Then turn it over and tape the overlaps on the back. Then lay tape centered on the part outlines on the front to give you thicker and stronger edges for the parts templates.

Finally, get it on a cutting mat or a surface you can cut on and use straight edges to cut the parts templates free from the taped together conglomeration of pages and you are a done deal. For future builds it will save you a lot of time.

As far as the Kinko thing I have never done that so I'm not sure how it would work. You don't need the entire 61-1/2" so if you can take the drawing file to them on a disc or memory card maybe they can frame and print it selectively with their software there. If you use "D" sized 22 x 34 paper and printer three overlapping sheets from left to right and with the 34" side vertical, it would give you the whole drawing I think.

Or maybe they can print the whole thing on one bigger piece of paper. But the important thing is that they do it with out scaling the parts to fit on the paper, they have to be printed full sized to work.

Let us know how that works out if you got to Kinkos. If you can find an old school blueprint shop or drafting shop that makes blueprints, maybe they can do it for you.

Jack
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Old Mar 30, 2010, 10:49 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
DAT-750 Motors Found In Stock!

The DAT-750 is in stock here (82 pieces). I had not used this dealer before but placed an order this morning.

http://www.r2hobbies.com/eng/proddet...=rcps81529_750

They are polite, quickly responded to my email, are in Hong Kong instead of mainland China and that seems to sometimes bring you better results than you get from the mainland guys.

The motor will be about $16 shipped, I ordered a couple of other things I needed too.

Jack
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