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Old Mar 10, 2008, 11:28 AM
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Jim Connell's Avatar
Edmonton, Alberta, Canada
Joined Apr 2001
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Question
What balsa thickness should I use to plank my planes fuselage?

Hi Everyone

Iíve decided that on my current build (RBC Spitfire) I will attempt to plank the fuselage instead of using the provided pre-sized sheeting pieces. (Too many curves on this plane.) And although Iíve read a fair amount about the process Iím wondering just what thickness of balsa I should be planking with. The sheeting provided in the kit is about 1/16 inch, but Iím wondering if it would be a good idea to plank this with slightly thicker balsa, say 3/32 inch and then sand it down.

Thanks for any help you can provide.

Jim Connell
Edmonton, Alberta, Canada
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Old Mar 10, 2008, 11:40 AM
Kansas is windy.
pburress's Avatar
Wichita, KS
Joined Jun 2003
1,538 Posts
I'd say stick with 1/16. 3/32 weighs 50% more, and there will be no (useable) strength gain. 1/16 will be plenty strong. FWIW, I built a fuse for the Earl Stahl P51 at 40" which requires planking and used 1/16. Putting the 3/32" and sanding it down is an idea, but why not just take your time with the 1/16 in the first place? Less sanding, strong enough, and probably less weight.

BTW, I'm not familiar with this model so I cannot comment on the pros and cons of planking vs sheeting in this one...

Good luck,

Phil
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Old Mar 10, 2008, 11:41 AM
Zor
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Ontario,Canada
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Quote:
Originally Posted by Jim Connell
Hi Everyone

Iíve decided that on my current build (RBC Spitfire) I will attempt to plank the fuselage instead of using the provided pre-sized sheeting pieces. (Too many curves on this plane.) And although Iíve read a fair amount about the process Iím wondering just what thickness of balsa I should be planking with. The sheeting provided in the kit is about 1/16 inch, but Iím wondering if it would be a good idea to plank this with slightly thicker balsa, say 3/32 inch and then sand it down.

Thanks for any help you can provide.

Jim Connell
Edmonton, Alberta, Canada
Jim Connell, Hello,

I would think that 3/32" sheeting would be even more difficult to bend to the curves than 1/16".

You also indicae that the sheeting is already cut to shape which is time saving and hopefully accurate to fit.

If you buy some 3/32" check the hardness. Heavier and stiffer sheeting can become a big prolem to curve and fit.

I would go with the suplied material.

Cheers,

Zor
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Old Mar 10, 2008, 11:47 AM
Kansas is windy.
pburress's Avatar
Wichita, KS
Joined Jun 2003
1,538 Posts
I'd have to agree with Zor and encourage you to use the intended process and supplied sheets. Perhaps start another thread asking about sheeting tips? I do know that the longer you soak it, the more pliable it is. Maybe soak a sheet overnight and see how it feels in the morning.... For that matter it would be easy enough to soak a test non-kit sheet and see how it goes, without committing.
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Old Mar 10, 2008, 12:52 PM
Zor
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Quote:
Originally Posted by pburress
I'd have to agree with Zor and encourage you to use the intended process and supplied sheets. Perhaps start another thread asking about sheeting tips? I do know that the longer you soak it, the more pliable it is. Maybe soak a sheet overnight and see how it feels in the morning.... For that matter it would be easy enough to soak a test non-kit sheet and see how it goes, without committing.
Very good idea from pburress.

Zor
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Old Mar 10, 2008, 02:48 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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I think you guys are not familiar with the idea of planking. It uses wood applied in narrow strips and each strip is tapered as required so it builds up the compound curves in a manner much like a barrel of curved staves forms the compound curves of the barrel..... but without the iron bands in our case... Another good example is cedar strip canoes or kayaks. It's a whole different method than sheeting. It's also very time consuming since on a model that uses 1/16 sheeting the planks will be only about 1/4 wide.

For planking you'll want to use 3/32 since you will HAVE to sand it down to remove the ridges and blend the shaping. Also you'll need to find a glue that sands at least as well as the wood or you'll have raised glue lines. That means definetly no CA other than for tacking the back side of the planks to the frame. And no PVA or aliphatic resin glues since they sand about as well as rubber.

The time honored glue for balsa planking is Sigment or Ambroid. It sands just as easily as the wood so the planks will be wonderfully fair.
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Old Mar 10, 2008, 04:53 PM
Zor
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Quote:
Originally Posted by BMatthews
I think you guys are not familiar with the idea of planking. It uses wood applied in narrow strips and each strip is tapered as required so it builds up the compound curves in a manner much like a barrel of curved staves forms the compound curves of the barrel..... but without the iron bands in our case... Another good example is cedar strip canoes or kayaks. It's a whole different method than sheeting. It's also very time consuming since on a model that uses 1/16 sheeting the planks will be only about 1/4 wide.

For planking you'll want to use 3/32 since you will HAVE to sand it down to remove the ridges and blend the shaping. Also you'll need to find a glue that sands at least as well as the wood or you'll have raised glue lines. That means definetly no CA other than for tacking the back side of the planks to the frame. And no PVA or aliphatic resin glues since they sand about as well as rubber.

The time honored glue for balsa planking is Sigment or Ambroid. It sands just as easily as the wood so the planks will be wonderfully fair.
Hello All,

Elaborating a bit on BMatthews posting _ _ _ _

If the curved surface is a flat sheet bent in one direction only, something like the surface of a pipe or tube or the surface of a cone, planking is practical if the radius is not too small. The bend should be a curve crosswise to the grain. The wood grain would run lengthwise along the tube.

If the curved surface is a coumpound curve, like the surface of a sphere, it is bent in two directions. Then planking is the only way and the grain has to be bent.

If the radius of curvature is very small, carving may be the only solution.

Zor
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Old Mar 11, 2008, 02:06 AM
hul
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Switzerland
Joined Mar 2003
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is this for the 1100mm Spitfire http://www.rbckits.com/shop/index.ph...d&productId=17 ?
I'd definitely go with 1/16", use really light/soft wood for the top and medium and/or slightly thicker wood for the bottom of the nose (if you land on the belly). Adjust the strip width to the curvature; the sides are usually reasonably flat and can takes strips of 1/2". Take care to avoid offsets between adjoining strips. It's not too hard to do, but takes patience to get each strip adjusted right.
There are a few pictures of the process in the build thread of my Bf109: http://www.rcgroups.com/forums/showthread.php?t=767775

Hans
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Old Mar 11, 2008, 08:56 AM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
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Based on some experience planking curved fuselages, I'm in agreement with your first idea and B Matthews: 3/32" is the right thickness for planking a plane this size. If you go to planking as thin as 1/16" you will end up with a wavy gravy fuselage surface since some of the planking will end up too thin after sanding and will warp when it's finished.

Myself, I'd go with 1/8" that was a few steps shy of soft. I use a razor plane to trim edges for a better fit but don't go crazy. I like the idea of cutting away some of the formers after to create more of a monocoque fuselage. Covering with glass is a good idea and will provide a lot of strength.

As BMatt says, the glue is also very important. I'd even avoid the CA for tacking.

Here is a thread on planking by the master, Chris Williams (no relation):

http://www.rcgroups.com/forums/showthread.php?t=691489

His models are larger but the same principles hold true. As far as planking being slow, check out how many gliders Chris builds and how fast. Amazing.
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Old Mar 11, 2008, 01:03 PM
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Jim Connell's Avatar
Edmonton, Alberta, Canada
Joined Apr 2001
264 Posts
Planking information

Hi

First of all thanks to everyone that has taken the time to help me get started with my first planking job. To answer your question hul, yes that is the RBC kit that I am working on. One of the reasons that I will not be using the kits supplied sheeting is that the entire front end will be heavily modified. (See http://www.rcgroups.com/forums/showthread.php?t=491200 for a hint as to how much if interested)

I think that after everything is said and done I will try to use the 3/32 inch thick balsa in strips of ľ inch wide. I particularly appreciate the tip (thanks BMatthews ) to use the appropriate glue, of which I will start looking for. I figure the worst that could happen is that the end result is too much and I am left with a larger than normal sanding job. (Although I find sanding to be very therapeutic for some reason.)

Thank you all once again and wish me luck in attempting this first time building skill. If you have an additional tips on this process please do not hesitate to add them to this thread.

Jim Connell
Edmonton, Alberta, Canada
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Old Mar 11, 2008, 04:04 PM
slow but inefficient
Ron Williams's Avatar
Riverhead NY USA
Joined Dec 2000
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Ambroid has been hard to find lately; it is available from Peck Polymers. They're RCGroups sponsors.
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Old Mar 11, 2008, 07:34 PM
B for Bruce
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The 'Wack, BC, Canada
Joined Oct 2002
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Jim, a trick you can do with the Ambroid is to thin it with acetone or lacquer thinner and "dope" it on paying particular attention to force it into the inter-plank cracks. It's a lot easier to do that than to glue each plank for the whole length as you go.

While Ron is right to warn you about using CA even for tacking the planks to the frames I think the big worry there is that some of the CA will get to the joints and cause issues when you're trying to sand it. However if you use some medium or thick viscosity you can place the planks and hold them in place for a moment while the dabs of CA set with very little worry about getting any into the plank to plank joint. BUT DO BE CAREFUL! CA sands about as well as steel!

Otherwise it'll be Ambroid, pins and rubber bands aplenty!
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Old Mar 11, 2008, 09:08 PM
KE your cub.
Curare's Avatar
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heh, ron I wish you'd told me that BEFORE I'd planked the nose of my last ship.

stupid CA.
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Old Mar 12, 2008, 07:08 AM
Zor
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Quote:
Originally Posted by BMatthews
Jim, a trick you can do with the Ambroid is to thin it with acetone or lacquer thinner and "dope" it on paying particular attention to force it into the inter-plank cracks. It's a lot easier to do that than to glue each plank for the whole length as you go.
>
> Etc _ _ _
>
BUT DO BE CAREFUL! CA sands about as well as steel!

Otherwise it'll be Ambroid, pins and rubber bands aplenty!
Hi BMatthews,

I just wish to clarify or confirm my understanding.

As you say [with the Ambroid is to thin it with acetone or lacquer thinner and "dope" it on], I think you are suggesting to thin the Ambroid with acetone or lacquer thinner but not with dope.

I read [and "dope" it on] as meaning "paint it" or "apply it".

Do I understand properly? or do you suggest to thin the Ambroid with "lacquer thinner and dope".

Few hobbyist would care to be really clear about this but I have an area of my Skybolt I wish to plank.

I am also concerned about the rubber bands getting glued on.
Somehow, I usually find a solution. Perhaps put wax paper under the rubber bands ! ! !

Thanks de Zor
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Last edited by Zor; Mar 12, 2008 at 07:19 AM.
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Old Mar 12, 2008, 07:26 AM
Zor
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Quote:
Originally Posted by Curare
heh, ron I wish you'd told me that BEFORE I'd planked the nose of my last ship.

stupid CA.
-----------------

I assume "stupid Cyano Acrylate" ? ? ?

Zor
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