** SpaFFFnutz - 48" Coroplast/FFF Hybrid Flying Wing ** - Page 3 - RC Groups
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Mar 30, 2010, 02:17 PM
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doggit's Avatar
thanks for the link jack, i have marked it on the wing, and now waiting to get the motor,
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Mar 30, 2010, 04:42 PM
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Office Max can print a 36" by (any-length) copy. They will charge me $8.00 to print the SpaFFFnutZ (38" X 61 1/2").

They will center the 38" drawing onto the 36" paper. Looking at the PDF drawings, it appears that we have an inch of space around the edges.

The young fellow who I spoke to said that he does these model plane drawings all the time for some "old dudes". Imagine that! Well, he just got another old guy.

Money is certainly an issue for me but, in this case, I consider it worth the cost. He said they can also scale them up or down, to any percentage you want.
Mar 30, 2010, 04:43 PM
jackerbes's Avatar

SpaFFFnutz Build Part 1 - Coroplast Wing Center Panel

OK, Here we go on the SpaFFFnutz build. This will be detailed and in a number of sections. Feel free to fire away if there are any questions.

The text will be interspersed with the file names of the images I am talking about. That helps me upload the right images and will also let you save off the images and the text and correlate the two offline if you want.

SpaFFFnutz Build Part 1 - Coroplast Wing Center Panel


Sheer of coro laying on basement floor, the template for the center panel positioned on the coro. I use a Ultra-Fine tip Sharpie to mark the corners and other cardinal points and will connect the dots with a straight edge. I've found that easier than trying to trace all the way around a template.


The marks are faintly seen and are connected with the long aluminum straight edge. The large size snap off tip utility knife will be used to make the cuts.

Lay the straight edge on the part (not outside of the part) as much as possible so that if the knife wanders it will do it off the part and not onto it.


The white board is 10" x 48" x 1/2" thick vinyl clad particle board shelving. That is positioned under the cut to keep the knife tip from following wood grain. You can feel the vinyl when the cut is deep enough. The vinyl will get scratched up but the board can be used for a long time.

I hold the straight edge down with my right knee and left hand, keep the knife at a right angle to the coro and inclined back 45-60 degrees, and concentrate on keeping the blade flush to the straight edge as I cut. The corrugations at an angle to a cut will make it want to walk away from the guide. I make several short (18" or so long) light cuts all adjacent to where my hand is, then move my hand and knee down and repeat the process. I've found trying to do it in one long continuous cut and hold the straight edge in place is just too hard to do.


Make the final straight trim cuts and you are done for now. I don't cut the prop slot yet.


Lay out the prop slot. Adjust the front edge a little to put it centered on an open area of the coro (not on a rib). The diagonal lines are for the next step.


I use a 1-1/4" hole saw to cut holes for the corners. Cutting a square corner there is an invitation for a crack to start there, make some kind of rounded corner. The curve can be cut free hand too of course.


Use a straight edge and the utility knife to join the holes...


Then make the cuts on the sides to open the prop slot and we are a done deal on the coro center panel.

To be continued...

Mar 30, 2010, 05:03 PM
jackerbes's Avatar

SpaFFFnutz Build Part 2 - Cutt KFm4 Strips

SpaFFFnutz Build Part 2 - Cutt KFm4 Strips

Dow Performance Board III insulation foam (FFF) is used for the KFm strips here. A bundle is 25 continuously joined and folded 24" x 48" sheets. FFF is generally only available in North America and it costs about $35 a bundle.

The template for the KFm strips is a plan view looking down as the KFm strips would be seen on the wing. It is used to lay out the cut so that both KFm strips are cut at the same time from along the folded edge of two adjoining sheets of FFF. The folded edge will form the leading edge of the wing and the finished part is what I call the "KFm4 taco shell."

As long as you work with the full bundle you can cut the pair of KFm strips needed from three sheets of foam. If you separate the foam from the bundle into pairs of sheets, it will take four sheets of FFF to get a pair of KFm strips.

Using the folding edges to form leading edges leaves you with a large amount of unused foam on each of the three sheets But that foam is still useful for other builds. It seems wasteful or inefficient but the stuff only costs about $1.40 a sheet.


The template for the KFm strips is seen laying on top of the bundle of FFF here. Position it parallel to the fold and about 1/4" or one foam thickness back from the folded edge. Use a Ultra -Fine tip Sharpie mark the corners and ends. I usually join the cardinal marks with a straight edge to make sure the part is right before I start cutting.


The top sheet has been lifted up and the template is positioned for marking the second strip. Up where the knife is laying is where the first strip will be cut from. Set the template back from the folded edge 1/4" or so again, mark the corners and ends, and you are ready to start cutting.


The bundle has been repositioned, the top two sheets are laying on the cutting mat, the folded edge it to the left, and the first cut is being made. Lean the utility knife back at an angle as seen there, the more the better. That prevents the tip from snagging the foam at the tip and leaving a jagged cut.


Now the back edge of the KFm strip is being cut. This is the edge that will form the step and be the most visible so you want a clean square cut. I use a series of light and deeper each time cuts about 15-18" long until I feel the cutting mat. Make sure to keep the knife blade inclined well back as you cut to avoid snagging.


And there it is! A KFm4 "taco shell" with the leading edge and two KFm strips cut in one piece.


The foam has been repositioned again, you can see where the first strip was cut out at the top, and the second strip is marked, and ready for cutting here.

After the second is cut, one of the two will have the plastic skin on the inside and one on the outside. Fold the foam side out one back to get the skin on the outside of both strips. If you lay them skin side down and back end of the utility knife up and down the fold line a few times it will crush the foam in the fold a little and make the fold less inclined to spring open.


The bundle is standing on end, you can see where the two strips were cut from the first three sheets of foam. Lots of FFF left there, I think I hear a Divinity 42 or Divinity 32 calling me. Or maybe another Blu Sail II glider, or a Blu Baby... A Revert slope glider, that's it! I need a Revert!


A good start, one center panel, two pairs of KFm4 strips (I cut an extra set while I was at it), ready to move on...


To be continued...
Mar 30, 2010, 05:09 PM
jackerbes's Avatar
bigoledude wrote:

"..Office Max can print a 36" by (any-length) copy..."

OK, that sounds like a good enough deal. Depending on how heavy the paper is, you may want to try taping the template outlines to make more durable templates. But maybe not too. The taping thing can turn into a mess sometimes...

Tell them that the parts are full sized on the drawing file and than you don't want them scaled up or down. If the guy wants to do it and knows how, he can print a small portion of the drawing that is a known size (like the 5-1/2" long wing tip for example) and you can measure that to make sure it is the right size before he prints the full sized sheet.

Have a little tolerance for variations, when I was scaling that up I think the wingspan on that was not precisely 48", it was something like 1/10th of an inch one way or the other. But close enough for this kind of work.

Mar 30, 2010, 05:44 PM
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doggit's Avatar
you been very busy jack, must have took you ages to get all those photos and info together, but it will be a great help to us, and looking forward to when you get to the mounting of your motor, i havent used such a heavy one before so will look forward to seeing how it is done prperly
Mar 30, 2010, 06:55 PM
jackerbes's Avatar
"..must have took you ages to get all those photos and info together..."

Actually it goes pretty quick if I keep the camera handy as I work. And if I remember to use it...

I took some photos of the motor mount on #1 as I did the autopsy on it. The motor mount there is a E-flite EFLM1915 I spotted at the LHS. It lends itself nicely to that flat disc motor mount that comes with the DAT-750.

On #1 I used a 3/8" square stick and glued a piece of tongue depressor to the bottom of that so it would raise the mount up high enough to let the plastic stick mount clear the coro and slide on. I put the mount far enough forward that the rotating bell was 1/4" or so clear of the back edge of the slot.

I routed the foam on the filler panel out down to the coro and laid the stick and mount into a fitted pocket there. Then I drilled two small holes down through the 3/8" square stick and the coro.

On the bottom I made a small doubler out of a piece of a paint stirrer and wrapped that with black tape to match the covering there. A couple of small 1" or so wood or sheet metal screws and washers from the bottom pulled the motor mount down snug and I didn't even glue it in place.

I'll use the same mount on this build as far as I know now.

Mar 31, 2010, 02:50 AM
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doggit's Avatar
jack, thanks for taking the time to do that, it has helped so much, and i am assuming that the motor i have ordered which is 27mm, will suite any 28mm stick mount, if so i am going to look for the same one your showing in your pictures and get a couple, thanks once again for being so helpful
Mar 31, 2010, 09:58 AM
jackerbes's Avatar
You are very welcome, Carl.

All of the smaller motors have mounting holes in the back on a 16mm x 19mm spacing. Those mounts all have holes on the same spacing too so they will work with nearly all of the newer style motors that are made to use the "X" mounts on the firewall. But even the older round firewall mounts on the Tower Pro CD-ROM type motors can be made to work with those mounts with a little drilling and creativity.

Mar 31, 2010, 10:08 AM
jackerbes's Avatar

SpaFFFnutz Build Part 3 - Prepare Coro for Gluing

SpaFFFnutz Build Part 3 - Prepare Coro for Gluing

If you are going to reinforce the edge of the prop slot by sliding skewers into the corrugations, do that before you glue the FFF leading edge in place as it will block the holes. See this post for the details:


Added Note - August 17 2010: I recently added some bamboo skewers to the coro flutes on the back half of the wing. Those were to provide some additional stiffening in that area. I was experiencing some fluttering on the back half of the wing at high speeds and the skewers will help prevent that. The fluttering was only noted at very high power (over 200 Watts and at higher speeds) and reducing throttle to a more sensible level would stop it.

The skewers are best added at this point in the build (before the KFm strips), and the details on doing that can be seen here:



Insert the coro center panel between the layers of the KFm4 strip and slide it forward until it gently contacts the inside of the fold. Slide it right or left to bring the end even with the point of the nose. Lay a board and some weight on it to hold it in place and double check that the folded foam is parallel to the coro from the nose to the wing tip.


As you can see here, there will be a slight gap inside the leading edge at the fold point, that is OK like that. Use the Ultra-Fine tip Sharpie and draw a line along the step and the end at the center line.


Do the same with the right had KFm4 strips and meet the first one flush at the center line and make sure it is parallel to, but not necessarily touching the edge of the coro. Then trace a line along the back edge of the step.


The lines are your reference for prepping the the coro for gluing and also for aligning the FFF when it is glued in place.


Lay a yardstick or something on top of the drawn lines to protect them from being erased by the alcohol. Take a coarse folded cloth like a piece of denim material (I wear a disposable glove) and pour enough alcohol on it to dampen it and scrub the coro right up to the yard stick to degrease it. If the centerline mark gets erased it is OK.

I glue the KFm strips down in four steps, top right, bottom right, then top left, and bottom left.


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 to make a sanding pad. Use that to rough up the degreased coro in front of the yardstick to the leading edge. Rough it up good, crossing your sanding directions. Then give the sanded area another light cleaning with the alcohol dampened rag to remove the loose stuff.


The sanded and degreased area is seen here, the work is not obvious but the prep is the key to getting a good bond between the coro and the FFF. The reference lines are not seen here but are under the yardstick and still visible.


To be continued...
Last edited by jackerbes; Aug 13, 2010 at 08:00 AM.
Mar 31, 2010, 10:11 AM

Looking very good... Spring is soon to come and only light breezes....

Mar 31, 2010, 10:22 AM
jackerbes's Avatar

SpaFFFnutz Build Part 4 - Gluing KFm4 Strips onto Coro

SpaFFFnutz Build Part 4 - Gluing KFm4 Strips onto Coro


I use Gorilla Quick PU glue (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" in from the edge. Then continue to run beads at about that spacing until you get to center of the strip.

Take a flexible plastic spreader like the ones seen there (cut from snap on can lids) and spread that the GQPU lightly out to the edge and back in to the center. Take a plant misting sprayer with water and spray a fine mist of water on the GQPU and also on the cleaned and sanded surface on the coro that the FFF will contact. Use the spreader lightly to spread the water that is on the GQPU.

Spritzing with water is the key to PU glues working well!


Position the folded KFm4 strips back on the coro center panel so that it is in perfect alignment with the lines you drew. The coro will not be firmly butted into the fold of the FFF, that is OK, you just want to get it on your marks.

Lay a straight, flat, 1 x 3 or 1 x 4 plank on top of the folded 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 so you can keep an eye on the step of the FFF and the line and not lose the alignment there. Parts will slide around easily with PU glues so keep an eye on it for the first five minutes or so .

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

After 30-45 minutes you can unweight it and move on. I do the bottom side of the same strip next, repeating all the same cleaning and sanding step for each strip each time.


When the last strip is glued on the bottom, you may to trim the FFF slightly where it meets the first strip or there may be a slight gap there. If it is a gap, we'll fix that later.


This is the wing with the FFF glued on, it is OK to start getting a little excited about this now. This makes a really beautiful wing.


I mentioned there might be a gap where the end of the KFm strips meet on the bottom, I had one and cut a narrow filler strip of FFF that fit nicely. I spritzed the gap with water, put some GQPU on the sides of the filler strip and glued it in place. If the PU oozes out, wipe it off with a wet paper towel. That joint can be further smoothed later and will be covered with colored package sealing tape eventually so it will not be noticeable at all.


The prop slot can get hit by the prop and it can crack the coro there. Especially in cold weather. I have already put two skewers inside the corrugation (beneath where the long skewer is laying) at the front of the prop slot 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.

Slide a skewer into the first 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 on each side of the prop slot to reinforce the edges I did six rows on each side, sliding them in flush with the coro after the photo was taken.

All of the skewers used only add about 12-15 grams to the build, don't worry about the weight.

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.


To be continued...
Mar 31, 2010, 03:47 PM
Registered User
doggit's Avatar
ok the motor was delivered today, but i am kinda disappointed, the way i see it i have the mount it like an inrunner, if i want to use the prop saver adapter, i will have to put the shaft through the hole in the mount with the body of the motor inside the wing, all my other motors hang off the back of the mounts, they did include a prop adapter that has a nut to tighten the prop on to, and also a prop saver adapter but cant use it, here are a couple of not very good pictures of various stuff,
Mar 31, 2010, 04:13 PM
jackerbes's Avatar
It that will clear the motor mount you can mount it with the motor mount under the motor as you see in the first photo. That is on a Divinity 42.

If the motor won't clear the mount that way, you can turn the mount around and put the motor behind it. You'll have to move the mount further forward on the stick then too. You can leave the unused shaft hanging out or trim it shorter. Let me know if you want to know how to do that with a Dremel tool.

Position the mount on the stick to give you the clearance you want on the prop slot.

Then fit a 3mm prop saver like this one:


or like this one if you can find it (the cone shaped nose lets it adapt to different sizes of holes in the props):


When I fit those I put the prop saver all the way back against the magnet housing and then cut the shaft to length. You only want enough shaft in the prop hub to locate it, then the shaft end needs to be cut off and rounded so the prop can tip to the side.

Mar 31, 2010, 04:26 PM
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doggit's Avatar
jack, they supplied me a prop saver adapter like in your link, but the way i see it if i want to use this prop saver then the only way i can do it is to have the main round body of the motor on the inside of the wing, opposite to the way your photo shows, i dont understand why they adverties this thing as an outrunner, i need to wait till the mount arrives and try it, but if i do keep it, will it be ok to mount it as an inrunner, providing there is room, will keep you posted as to the outcome, i may just have to return it and look for a proper outrunner

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