Piper Cub Sailplane - Page 3 - RC Groups
Thread Tools
Sep 29, 2012, 10:11 AM
Retired CAD guy
birdofplay's Avatar
Or you could paint with a water based urethane clear coat 1st then after dry
HIT IT with impunity using regular foam eating types of paint.

Regardles, it's not pink anymore :-)

Terrific work and progress.

Sign up now
to remove ads between posts
Sep 29, 2012, 12:24 PM
Build something.
Nodd's Avatar
Originally Posted by pfrommbe
absolutely stunning!

How do you know the CG will be right without adding lots of weight? Did you do some tests before, or use the original fuselage/geometry as a guide?
No I've not done any calculations or tests to see where the CG will fall. I'm okay with adding weight if necessary. After seeing how nicely my 10 lb Discus flies, with all that stored energy, I'm okay if she ends up a tad on the weighty side. I guess it depends on what I intend to do with her. If she's heavy then she'll make a good slope or aerobatic ship. If she ends up light, then maybe she'll thermal nicely? I expect she'll end up somewhere in-between though. Truth is I'm not all that concerned either way.

Originally Posted by birdofplay
Or you could paint with a water based urethane clear coat 1st then after dry
HIT IT with impunity using regular foam eating types of paint.

Regardles, it's not pink anymore :-)

Terrific work and progress.

That's good advice there Bob. I'm headed to the paint store now so maybe I'll snag a can of water-based urethane & see how that works out on some scrap. Thanks.
Sep 29, 2012, 02:19 PM
Registered User
seeingeyegod's Avatar
smoother than an androids butt.
Sep 29, 2012, 11:20 PM
Build something.
Nodd's Avatar
I found some urethane spray paint at the store but at $12 a can Vs $3 for regular primer, I cheaped-out & went with the primer.

Are we forgetting something?
I was so eager to get her painted I plum forgot about the battery hatch. Its just as well I ran out of paint yesterday. My plan is to make the front canopy removable giving access to the battery tray. Using masking tape I outlined the hatch...

A buddy loaned me a hot-wire foam cutter. Using the tape as a guide I cut the hatch free...

That looks like plenty of access to the battery area...

Now I can get back to painting her...

That's enough primer, I'll let that dry overnight.

The Wing
In the meantime I turned my attention to the wing. I'm planning to add a short center section to the span. First I need to glue two pieces of foam together to get sufficient thickness. Time to break out the Gorilla Glue again...

Spreading the glue evenly...

Adding water to the other piece...

Slap the two pieces together...

...and once again its dinner plate time...

While that dries I started work on the template ribs that'll be used to guide the hot-wire cutter...

Unfortunately my wood-shop is being used as a pint-booth for the fuselage, so now's not the best time to use the belt sander to shape these template ribs. So that's as far as I'm going today. Hoping to get the wing cut tomorrow.
Last edited by Nodd; Sep 29, 2012 at 11:45 PM.
Sep 30, 2012, 07:42 PM
Build something.
Nodd's Avatar
Plan A
Well after my success carving out the fuselage battery hatch I was looking forward to trying the hot-wire gizmo again. I pinned balsa template ribs to both ends of a block of foam...

You maybe wondering what the notch in the rib is all about. Well the Cub's wings use a carbon fiber tube as the main spar. I couldn't come up with an easy way to drill a hole span-wise down the wing piece I was about to make so I decided instead to just cut a slot. I'll use expanding foam or something to fill the slot later on...

So it was time to use the spiffy hot-wire cutter. This was the unfortunate result...

Apparently this isn't as easy as it looks. I'd love to play with this more, definitely want to master this process but in the interest of getting this bird done I switched to...

Plan B
Starting with a new block of foam I broke out the router & cut a slot for the wing-rod...

Now that's a nice clean slot, MUCH better...

Then it was back to my trusty belt-sander to shape the airfoil...

Here's a comparison of the hot-wire wing on the right & the sanded wing on the left...

Don't get me wrong though, I have nothing against hot-wire foam cutting. I'm just not very good at it yet. There's lots of great threads on the subject, I'll read-up on it, practice some & hopefully next time will yield better results.

So here we are test fitting the sanded center section. Looks pretty good to me...

Yellow & Black
Meanwhile back in my wood-shop/paint-booth more progress was made...

While the finish is far from perfect its about what I expected having painted directly on foam. Its certainly plenty good for this silly project...

I'm going to let this paint dry overnight then I'll mask out the rest of the windows & the lightning-bolt graphic & lay down a couple of coats of black.
Last edited by Nodd; Oct 01, 2012 at 11:47 AM.
Oct 01, 2012, 09:26 AM
Registered User
I just love the creativity here, this is what modelling is all about.
The path appears as you go, the essence in the joy of building!
Oct 01, 2012, 10:16 AM
Upwardly Mobile
mikegbogh's Avatar
Originally Posted by Gudmund
I just love the creativity here, this is what modelling is all about.
The path appears as you go, the essence in the joy of building!
Oct 01, 2012, 10:54 AM
Retired CAD guy
birdofplay's Avatar
Not sure what the current cost to H2O based varathane in a brush can is these days.
$12 for spray does sound high.

Light weight spakle make s good filler too.

I like your sander alternative to HW !

Great Progress !


BTW today is moving day.
I'll then be on the road until Saturday.

C U L8r

Oct 01, 2012, 10:12 PM
Build something.
Nodd's Avatar
I've heard spackle mentioned before. I'll have to give that a try next time. That H2O stuff looks interesting too, thanks.

The funny thing about spray painting is you spending hours on end masking & then about 30 seconds spraying...

Yet another template, aren't computers great?..

The idea here is to carefully cut through both the template & the masking tape below...

Peal away the excess tape...

Add the window lines...

Then wrap her up like a last minute birthday present...

20 seconds of spraying...

And we have windows!..

We're not done yet though. Next is the signature Cub, Flash Gordon lightning bolt...

There we have it (the yellow doesn't quite match but what can ya do?)...

Looking pretty snazzy in a Cub sorta way...

Last edited by Nodd; Oct 01, 2012 at 10:43 PM.
Oct 01, 2012, 10:51 PM
A10FLYR's Avatar
You have too much time / energy!! Love it!

(I'll bet you make the colors match!)
Oct 02, 2012, 03:30 AM
Upwardly Mobile
mikegbogh's Avatar
Hi Nodd,
This is lovely and I hope it flies a treat, you going to slope it on the maiden? Going back to the hot wire cutting and templates, looks like the heat melted into the wood templates, you can also try making templates out of malamine veneer , available at kitchen cupboard guys, pcb or fibreglass board, aluminium , all seem to handle the hot wire ok , but must be sanded nice and smooth.
Keep up the great thread
Oct 02, 2012, 11:26 AM
Build something.
Nodd's Avatar
I'm not too worried about matching the yellows. In a way the mismatch helps highlight the bits I built Vs the stock Cub.

I've not decided where I'll maiden her. There's a smallish grass hill I may toss her off to get the trim & whatnot figured out. Proper slope flying is an hour plus away. I have local access to a winch & a few eager tow-plane pilots, so we'll see. I do prefer to get the plane up nice & high on a maiden so there's room to fiddle with the trim.

This & my mirror posts on other RC forums have given me a good idea of what I did wrong with the hot-wire cutting. Stuff like, don't use balsa as a template, its too soft, it'll burn & the wire will snag on it. Use something harder/heat proof. Stick guide T-pins in the leading & trailing edge so the wire has somewhere to rest during the start & exit. Don't cut the spar slot with the wire. All great advice, thank you.
Oct 02, 2012, 12:15 PM
Pedro Salomón
harrier81's Avatar
I cannot wait to see her finished and in the air......
Awesome work...
Oct 02, 2012, 08:23 PM
Build something.
Nodd's Avatar
The Tail
After a little head-scratching I came up with an effective way of squaring up the fuselage to my workbench before attaching the tail...

This should result in a nice level tail that should align with the wing once that's done (waiting on a longer CF wing-rod to arrive)...

The rudder hinge was damaged in a nose-over a while back. I removed it so I could make a proper repair but having it off of there got me to thinking, maybe I should take this opportunity to enlarge the rudder a little...

A fat bulbous nose section, a short-coupled tail-moment & an extended wing are all conspiring to make this puppy a little lacking in yaw authority. More rudder area can only help. So I think that's what I'm going to do, make a slightly larger rudder...

Now that the tail's on I can move ahead & get the rudder & elevator servos mounted & functional. That'll have to wait for the glue to dry though, not sure I'll get to that tonight. We'll have to see.
Oct 02, 2012, 11:21 PM
Build something.
Nodd's Avatar
BIG Rudder
Well I got a little more done tonight after all. Here's the new enlarged rudder...

Figuring a larger surface area will translate into more stress I'm reinforcing the control-horn/tail-wheel area...

Reinforcing glued in place...

Test fit...

I think that should help her track nicely while maintaining the scale tail's looks...

I'll put a few coats of paint on her (won't bore you folks with that process) & that'll do for today.

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Wanted 1/3 World Models Piper Cub or Super Cub ARF NIB learnedinuk Aircraft - Fuel - Airplanes (FS/W) 2 Jun 17, 2012 07:28 PM
Sold Piper Cub LPU davezagwyn Aircraft - Fuel - Airplanes (FS/W) 2 Jun 14, 2012 09:52 PM
For Sale Piper Cub 91 sized ecoliburger Aircraft - Fuel - Airplanes (FS/W) 0 Jun 11, 2012 03:28 PM
Discussion Hobbyking Piper Cub vs Dynam Piper Cub For First Plane? HempfieldHunter Beginner Training Area (Aircraft-Electric) 2 Apr 25, 2012 01:54 PM
Discussion Piper J-2 Cub vs. Piper J-3 Cub Inverted Schizo Giant Scale Airplanes 9 Jan 16, 2007 04:32 PM