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FTFC20 - April Showers by Rhaps, Grumman J2F Duck

Rhaps

Well-known member
#1
My entry for FTFC 2020 April Fools Showers is Grumman J2F Duck.
Duck_pic.PNG


I chose this because I like seaplanes and I like biplanes and I like quirky planes and this one ticks all the boxes.
Also I like the possibility of pushing battery pretty far to front :)
And there is of course this:
:

Build won't be master class but maybe "masterish" and will also involve some strange ideas of mine. I will try to build this close to scale but we'll see..
Pilot skill - I have no idea yet - also since I crash all my planes they are pretty much all the same for me anyways.
I'll submit plans if it seems worth it.

Size will be 1000mm - rougly 40 inches - and will use B-pack.
Also lots of cardboard.

I will appreciate any suggestions on the way.
 

Tench745

Well-known member
#3
I've got an old modeling book which has a chapter on scratch-building a styrene Grumman Duck. For years I thought it was something they made up just for the book because it's so odd looking. I look forward to seeing your build.
 

Rhaps

Well-known member
#4
I've always liked the looks of this plane, can't wait to see how it goes!!
I've got an old modeling book which has a chapter on scratch-building a styrene Grumman Duck. For years I thought it was something they made up just for the book because it's so odd looking. I look forward to seeing your build.
I've got an old modeling book which has a chapter on scratch-building a styrene Grumman Duck. For years I thought it was something they made up just for the book because it's so odd looking. I look forward to seeing your build.
Its a bit weird looking plane but the looks can really grow on you.
There is also beauty in functionality, by doing the flat the way it's done gives plane probably more strength than it would have had if float was done with struts. It also gave plane actual landing gear which is pretty rare in seaplanes and even nice cabin.
 

Rhaps

Well-known member
#5
I made a wing, not totally happy with is so I'll redo it.

Meanwhile I present you first version that I made earlier:
Duck_v1.PNG

It was 700 mm and I am pretty happy about the way it looks, but problem is the weight, with hardly larger wing area than mini scout it weighs almost three times as much.
I had somewhat successfully maiden with it but the speed it needed to stay in the air was too much for me (F-powerpack can really move a plane).
It's also very conscious of any wind and we 've had more than enough of that in here lately.
Second flight with moderate winds did not go well (might have also been bad GC - its always more to the front than you think...)
Luckily the critter is pretty tough, It will get second chance if wind goes down anytime in the future.

Anyways on this second version I'm goin to try to make plane as light as possible to get it fly as slow as possible.
Will be interesting to see how many weak points I can indroduce in the process :)
 
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Tench745

Well-known member
#6
That looks really nice, Rhaps.
Next step, simplicate and add lightness!

A side note, I've noticed an increase in less family-friendly language on the forums lately. I don't mind personally, but if we don't police ourselves it can get out of hand pretty quick.
 

Rhaps

Well-known member
#7
That looks really nice, Rhaps.
Next step, simplicate and add lightness!

A side note, I've noticed an increase in less family-friendly language on the forums lately. I don't mind personally, but if we don't police ourselves it can get out of hand pretty quick.
Thanks and apologies and duly noted and fixed
 
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Rhaps

Well-known member
#8
Moving at snails pagebut I finally got wings done.
It was surprisingly hard to get tailing edge step to a height where TE was flush.
First wing failed at that so I had to build another.

I went maybe bit too far removing paper from the top of the bottom foam but I weighed the paper and it's 4 grams/wing half = 16 grams total.
It's probably not worth the hassle because now bottom part doesn't want to stay straight during construction
I still wanted to do it - just to see how difficult it would be and if the wing will still be strong enough.
Besides I don't think extra strength is much needed there, so far my wings have been broken only on from LE ot tips.

For lightness I also used mostly gorilla glue.
Tip on gorilla: After laying glue I wipe it with wet paper towel. With spray bottle everything gets too soggy.

Bottom of the LE is ironed - I think Battleaxe mentioned doing this in some thread.
(On first failed wing I ironed top LE too but then LE would rise too high when folding top of the wing)

Spar has no paper at all, again I felt that it isn't needed, eager to see if I was wrong :)
wing1.PNG

To stop LE from raising I taped it to cutting mat and table (I don't remember where I originally saw this, thanks to whoever you are)
wing2.PNG

Put some mouses to guard gorilla curing
wing3.PNG

Not super proud about servo placement but it will have to do for now.
In retrospect I maybe should have placed servo just standing out from the bottom of the wing like normal people do but I wanted flush wing bottom and the wing wasn't thick enough for standing servo. Oh well....
wing4.PNG

I am slightly worried about ailerons being too small as I don't plan to add ones to top wing.
Also I havent figured too well how I will make wing floats but I reckon those will come after maiden

Cub wing, meet your leaner taller and smoother cousins - don't worry we have all been there:rolleyes:.
wing5.PNG

This wingtip came out pretty nice
wing6.PNG

Aand no I finally I get to do the interesting parts, hull tail and float.
While waiting for tem I present result of my todays flight with version 1:
Duck_v1_2.PNG
Unfortunately that isn't a shark bite, that would be just too cool.
Failed takeoff try presented float to the prop and prop didn't hold itself back.
Luckily this didn't affect anything negatively and the plane actually flew - if not great then at least adequately for me.
So I have actually somewhat high hope that v2 will fly good.
 

Rhaps

Well-known member
#9
Started with the hull. Note the slight raise of tail, more on that when I get to tail feathers.
hull1.PNG hull2.PNG

Complex part, took couple of times to get it right.
hull3.PNG hull4.PNG hull5.PNG hull6.PNG hull7.PNG hull10.PNG
I could have done this also with moulding foam instead of cardboard but that would require precise part and bevelling.
Here it was easy to just cut excess cardboard with scissors.
Then I botched gluing it to the place - seam isn't quite as tight as I had wanted it. Luckily it's not very visible in the bicture :).
Guess version3 of the plane willl have to have one more tab in this part to keep it better in place

Power pod and cowling.
Cowling will kept in place by power pod giving the possibility to change to different color cowling to suit your mood.
hull11.PNG

Current Status - ARF!
hull12.PNG

Looks like plane will definitely be ready for FTFC2021 April showers
 
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Rhaps

Well-known member
#11
You are making GREAT progress! Good work.
Thanks, pep talk is always needed and appreciated :)

Onwards.. or more like tailwards.

I wanted somewhat scale looks so I made2 piece hstab.
Also I didn't want vstab horn to ruin the good looks of the plane (heh).
Thus some 1/16 music wire, q-tips and trendy bendy flitetest pushrods.
tail1.PNG tail2.PNG tail3.PNG tail4.PNG
I coated wires with gorilla glue before i sunk them in stabs. Gorilla really works great here.
You may also notice 2 kinds of glue mess on hstab and hull seam - luckily Gorilla foam is hardly visible in real life and hot glue web can be cleaned.
I used only drops of hot glue to keep parts in place while gg cured (another technique nabbed from FT forums. Thanks to whoever suggested it)

Next is this really annoying piece
tail5.PNG tail6.PNG tail7.PNG tail9.PNG
It didn't come out nearly as well as I wanted but after several failed tries I decided last one would have to do.
These are waiting for their turn in trash bin:
tail10.PNG

I had wished that missing piece under vstab would somehow magically fix itself. Unfortunately it didn't and iI had to do some makeshift solution. Fix was again far from ideal. In retrospect I should have made the tail part of the hull to extend under hstab or just go with simple FT type hstab.
tail11.PNG

And here we are now. Glue smears are not a problem, paint will cover them. I am slightly unhappy about bend on the left side of teh bottom but there is a good chance that the whole plane will resemble pretzel after maiden so I'll let it fly for now (figuratively)
tail12.PNG tail13.PNG tail14.PNG tail15.PNG

Next will be the float - hopefully this week.
 

FishHawk

Well-known member
#12
Thanks, pep talk is always needed and appreciated :)

Onwards.. or more like tailwards.

I wanted somewhat scale looks so I made2 piece hstab.
Also I didn't want vstab horn to ruin the good looks of the plane (heh).
Thus some 1/16 music wire, q-tips and trendy bendy flitetest pushrods.
View attachment 167271 View attachment 167273 View attachment 167274 View attachment 167275
I coated wires with gorilla glue before i sunk them in stabs. Gorilla really works great here.
You may also notice 2 kinds of glue mess on hstab and hull seam - luckily Gorilla foam is hardly visible in real life and hot glue web can be cleaned.
I used only drops of hot glue to keep parts in place while gg cured (another technique nabbed from FT forums. Thanks to whoever suggested it)

Next is this really annoying piece
View attachment 167280 View attachment 167281 View attachment 167282 View attachment 167283
It didn't come out nearly as well as I wanted but after several failed tries I decided last one would have to do.
These are waiting for their turn in trash bin:
View attachment 167286

I had wished that missing piece under vstab would somehow magically fix itself. Unfortunately it didn't and iI had to do some makeshift solution. Fix was again far from ideal. In retrospect I should have made the tail part of the hull to extend under hstab or just go with simple FT type hstab.
View attachment 167289

And here we are now. Glue smears are not a problem, paint will cover them. I am slightly unhappy about bend on the left side of teh bottom but there is a good chance that the whole plane will resemble pretzel after maiden so I'll let it fly for now (figuratively)
View attachment 167290 View attachment 167291 View attachment 167292 View attachment 167294

Next will be the float - hopefully this week.
This is an incredibly complicated build, with numerous compound curves. You are doing a fantastic job. I don't have the nerve or skill to even contemplate something this difficult.
 
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FoamyDM

Building Fool-Flying Noob
#13
Started with the hull. Note the slight raise of tail, more on that when I get to tail feathers.
View attachment 166192 View attachment 166193

Complex part, took couple of times to get it right.
View attachment 166194 View attachment 166195 View attachment 166196 View attachment 166197 View attachment 166198 View attachment 166200
I could have done this also with moulding foam instead of cardboard but that would require precise part and bevelling.
Here it was easy to just cut excess cardboard with scissors.
Then I botched gluing it to the place - seam isn't quite as tight as I had wanted it. Luckily it's not very visible in the bicture :).
Guess version3 of the plane willl have to have one more tab in this part to keep it better in place

Power pod and cowling.
Cowling will kept in place by power pod giving the possibility to change to different color cowling to suit your mood.
View attachment 166201

Current Status - ARF!
View attachment 166202

Looks like plane will definitely be ready for FTFC2021 April showers
Haha, Don't worry. You might still get close. That's happened to me every year but this one. Don't worry, remember, when you get this done you will have a plane to fly when it's raining a little. or you don't have to bring it in in a rainstorm. and if you WP your transmitter... you put on your slicker, or gore-tex and go fly! (unless you have a lake.
 

Rhaps

Well-known member
#14
This is an incredibly complicated build, with numerous compound curves. You are doing a fantastic job. I don't have the nerve or skill to even contemplate something this difficult.
Its just me doing it probably harder than it needs to be but thanks for the compliment nevertheless.
The reason for doing it hard way is partly to find my limits though so failures are also successes (on limit being found :) )
 

Rhaps

Well-known member
#15
Haha, Don't worry. You might still get close. That's happened to me every year but this one. Don't worry, remember, when you get this done you will have a plane to fly when it's raining a little. or you don't have to bring it in in a rainstorm. and if you WP your transmitter... you put on your slicker, or gore-tex and go fly! (unless you have a lake.
Heh thanks :). I was going to do the plane anyways so I figured to join the challenge as it coincidenced with my plans.
Sadly I'm even slover builder than I tought I'd be so now my target is next may.
And yes, flying from a lake was always my plan since my parents live by the lake and in possible(probable) mishap dad can send his rc boat for the rescue
1588111576800.png
 

Rhaps

Well-known member
#16
At this point it really starts to look like I won't get the plane ready by the end of April.
So I hereby declare that May will be called as second April.
I also make reservation for June, it may be third April.
I'm sorry for the inconvenience - you need to edit your calendars - but I'm sure everyone understand the importance of the plane being finished on time.

With that out of the way... progress, plane is now quite floaty!
1589611413667.png

Some stuff on float went better than I expected and of course some did not.
For example I had planned to use popsicle stiks for front attachment but I wasn't sure how i would get a tight fit.
But since I built the float in a bit different order than verison 1 I had the front open and it was easy to fit sticks perfectly.
Also I was stuck with landing gear for a long time. In version 1 axle went through pipe but I had no suitable pipe for thicker axle.
I tried to make one from drinking straw and tape but result was just huge ball of tape.
Then I finally realized that I don't need any pipe, if I fly from water I will remove wheels anyways so I can just put piece of tape over axle hole.
1589612407451.png

Removing paper from top of the beak piece was bit of a pain but in the end very much worth of it, piece folded right how I wanted.
Also I fitting cardboard curve was rather easy. Too bad I lost my patience and made a bit of mess with hot glue. Should have stayed with the gorilla glue.
1589612712923.png
1589612786001.png 1589612818337.png 1589612867606.png 1589612955003.png 1589613009769.png

I was not sure how V bottom for the beak would succeed
In the end the shape could have been bit closer to the original but as a proof of concept I'm pretty happy.

1589613884423.png 1589613948054.png 1589614269937.png

Then I ruined it.
Because I was going to put clear packaging tape over the V part of the bottom I needed to paint the bottom before taping it.
I had used silver paint over cardboard before without priming but it turns out that not all cardboards are created equally.
The cardboard that I used (because it was long enough) didn't really like the waterbased paint :(
1589614316407.png

Luckily after couple of days wors waves settled and i taped the bottom. Not perfect fit but good enough.
Whether cardboard + tape actually holds up on future undoubtetly rough landings remains to be seen.
1589614398292.png 1589614432876.png 1589614479744.png


There is one thing I'm quite unhappy about:
1589615289923.png

I will make some changes in version 3 but I'm not sure where i could meaningful amount of weight.
Oh well - I can always put a bigger engine.
 

Rhaps

Well-known member
#17
Turtling the deck. I originally planned to use cardboard over whole length but fortunately I then came to my senses.
Cardboard isn't actually any lighter than foamboard and it's much more flimsy. I used it in the back because I tought it would go better over stabiilzers. It does but next time I will use foamboard.
1590529064473.png

I made template for fitting lower wing to fuse. It took a bit of effort but in the end it was quite worth the while.
Wing sets quite well.
1590529535867.png 1590529616924.png

I probably should have put bit more effort to top wing attachment and make a jig for it.
In the end I just winged it:rolleyes:.
It _looks_ close to where it should be.

One thing that was kind of unpleasant surprise is that making wing chord longer had consequences (more wing should be good, right?)
I have read that biplane wings should supposedly have distance that is at least same as the wing chord or the airflows may interfere.
Thus I had to raise top wing bit higher than I wanted for the looks.
But then the painter sticks I'm using for struts were too short. Thus I settled for top wing that may be bit too close to bottom wing. Remains to be seen if this will result bad flight characteristics.

Originally I was going to but Argentinian paint scheme but since I had these stickers aroud I decided to fly bit different colors :)

Canopy was at first difficult but then I googled j2f duck canopy and found picture of masking tapes for plastic model canopy.
I used mask bits to make canopy template and it worked surprisingly well.

1590530575544.png 1590530615931.png 1590530660885.png 1590530724374.png

This is the float attachment I'm currently least unhappy with.
Rubberband is attached to stick in the hul. On the other end of the rubberband I have hook that i can attach inside float.
Then I push float back , guide paintersticks on the front inside the hull and rubberband in the back pulls back of the float to the hull.
Good thing about this is that rubberband works as a suspension if front of the float hits the ground.
Bad thing is that if it stretches too much prop will make mincemeat of the float (happened with ver 1).
Also it's clumsy to set up.
Still it gives fairly easy access to the front of the float where the battery will go.
1590531362900.png
If anyone has better idea for this please let me know.

Side floats are still missing but now the plane is closer to completion than ever before
 

Rhaps

Well-known member
#20
Side floats - I can't believe I got them right at the first try...
1591296990574.png 1591298083522.png 1591298140383.png

..prototypes don't count.
1591297060823.png

Interesting thing about build process was that the gluing order matters a lot when doing curves like these (well duh).
I found out that doing spine, then the back and only then gluing front "triangles" produced best result. Initially I tried gluing skin to side formers and witch didn't work well as the rigid sides then prevented smooth curves.
There was also tricks that I figured for cutting the skin: first just score cut outlines, then remove paper from other side, form longidutal curve and only then cut otlines through. Specifically cutting through only after paper was removed made cutting through cleanly much much easier.

In case someone is interested to try building one the pdf for the float is attached.
Build process (this also here for myself in case I'll need to build more of these):
Cut formers and skin, remove paper fom one side of B and C. Glue formers B and C to A , B to front and paper sides facing to middle.
Note that hole on the skin should be on unpapered side. Also lots of bevels, but not on the sides of the skin (refer to picture)
1591298406830.png
Glue spine of former A to skin starting from front former (B) to the end spine.
Glue sides on the stern to the spine, then the stern.
1591298583683.png 1591298865127.png 1591298903670.png 1591299083165.png
After that glue the triangles on the bow starting from middle. Dont burn your fingers.
1591299451112.png
After you have cooled your fingers glue side formers to skin - just a bit of glue.

Before adding bottom skin you should attach struts because it's easier to see where they go when bottom is off.
Struts are bent for 1/16" wire.
(in retrospect: should have ignored scale looks even more and make symmetric floats for spare part logistics)
Cut slots for struts so that the go inside formers B and C
I am using gorilla glue here because it works with metal much better than hot glue (at least for me) I then seal the cut with hot glue.
1591299794357.png

Then its the bottom skin from cardboard.
Make a bend to the cardboard, then glue the bend to the straight part of the keel.
After that glue straight part of the sides - mark beforehand with pen where the glue should go
1591300026681.png
Cut a seam from the front along the bend
Then bend one side of the cardboard to see where you need to remove excess in the middle with hobby scissors.
(Hobby scissors are just like ordinary scissors except that the other household members won't go medieval on you if you use them)
Be very careful to remove cardboard in very small increments because it's very easy to take off too much.
1591300422548.png
Glue the side to the skin when you are happy with the fit
1591300584523.png
Then do the same to the other side. Finally cut excess cardboard with hobby scissors.

I ironed seams a bit but you have to be _very_ careful not to overdo it or you may end with "Mr. Bean tries to fix Whistler's Mother"-situation Do just one to three swipes with not too hot iron.
It is also a good idea to check that all seams are water tight, seal with hot glue or some other preferred method.

Attachment to the wing:
It just so happens that I have these q-tips that are perfect fit for the 1/16" wire.
I cut a seam in them and glued them to wing.
Presto! Removable side floats
1591303415629.png 1591303502510.png 1591303576634.png

I painted the float and then taped the bottom with a clear packaking tape.
(reminder for myself: next time do just the bottom - i turned the tape over to the sides but it doesnt sit and/or hold very well.
Also I put water resistant acrylic coat on floats (whole plane really). I'm hoping it's good enough:censored:

Snakes Floats on a plane:
1591304878345.png 1591304383992.png 1591304483607.png
 

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