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1/2A Planker Finish

Old 03-22-2009, 07:23 PM
  #1  
jetpack
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Default 1/2A Planker Finish

What would your favorite method of finishing a planker such as this? Tissue, Silkspan, UltraCote, etc...

I would like to add the graphics also, and somewhat of a nice finish with no grain showing.

What would be a good wing building proceedure? Should it be sanded to a slight airfoil shape or the edges simply rounded? Should this be done to the tail also?

What do you prefer for hinging the elevator?

I guess I should ask "How would you build it?"[8D]

It would be good to do one up nicely for looks and good flying, instead of the usuall "hit the corners with sandpaper, seal it and go fly" approach.
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Old 03-22-2009, 08:21 PM
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Default RE: 1/2A Planker Finish

How fancy you want to get on shaping the planks to more closely resemble airfoils is up to you. But truthfully it won't make any difference to the flying in the end. However by removing a lot of the wood you will both make it a bit lighter and a lot weaker. If the goal for this is to fly it only occasionally and with care then no problem. If it's to train a newbie or three then it's a bad choice to get too aggresive. But given all the requirements for finish this sounds like it won't be used for newbies. So sand away.

Tissue and dope would be my suggestion. The tissue adds strength and seals over the grain all at the same time. For a true show finish I'd suggest a coat or two of sanding sealer made using thin clear dope and talcum powder. A coat or two of very thin clear to seal the wood Then apply a coat of the sanding sealer and let dry well. This mix sands beautifully and fills well. Start with thin clear and add powder until it's about like cream. Work it into the wood but not too much or it'll "curdle" as the solvent flashes off. After sanding apply another coat of medium thin clear to seal the sealer.... Then apply tissue, dampen it with a very light water mist so it goes limp and use raw thinner to re-melt the last coat of dope and seal down the tissue. It may blush but that's OK. The next coat of sealing clear will cure that. But it shouldn't blush unless you're doing this on a really bad day. From there it depends on what you want for a finish. Either apply color dope or wait for it to finally stop smelling and then use some other form of finish or you may opt for an all tissue finish and clear dope for a different look. Both options can look great. The coloured tissue will be lighter but that's your choice.

..... at least that's how I'd do this. Especially if this is intended as a show piece.
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Old 03-22-2009, 08:21 PM
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Default RE: 1/2A Planker Finish

Most folks just sanded the balsa smooth and used dope for a finish.
First a coat or two of sealer letting dry completely then sanding between coats after which several coats of clear, again sanding between coats. The clear has no pigment and weighs less. Sealer can be made using clear dope with a tablespoon of baby powder mixed in it. Using available lighting, see how it looks before you add colored dope. When it meets your approval then the prep work is done and you can then use the colored dope.
Only use enough color to make it look great and after letting it dry completely, add a coat or two of clear to give it a deeper gloss.

Many of these type original kits used a cloth hinge. it was simply a piece of thin cotton cloth a half inch wide and about six inches long and you would cut it to length for each half of the elevator and glue it into place, trying not to get much glue in the center where it will bend.

It will look better if you round the LE and sand the rest of the wing into an airfoil.

Before you glue the wing to the bottom of the fuse, mark the centerline on the wing and poke the ends of a couple of toothpicks to act as dowels where the wing joins the fuse strengthening the joint.

Covering with light tissue could add minimal weight and make your prep work less before doping. The tissue seals easier than the wood grain.

Love to see you do a build thread for it!

Lots of these planes were marketed to use .020-.075 CID engines. Can you imagine what a Norvel .074 would do on a plane like this?
Of course the engines of the day had much less power than the modern Norvels.

Robert

P.S. BMatthews beat me to it!

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Old 03-22-2009, 08:31 PM
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Default RE: 1/2A Planker Finish

I just type faster.... And obviously great minds think alike!
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Old 03-22-2009, 09:08 PM
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Default RE: 1/2A Planker Finish

If the wing is a 1/4" slab, it can be airfoiled.....but a C/L plane with a wing that twists in flight is worthless. If the wing is 1/8" slab, just round the edges. Planes like this tend to get beat up if they get flown, so I wouldn't invest too much time into the finish. I'd cover the wing with film and do the rest of the plane with epoxy paint.
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Old 03-22-2009, 10:06 PM
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Default RE: 1/2A Planker Finish


ORIGINAL: combatpigg

If the wing is a 1/4" slab, it can be airfoiled.....but a C/L plane with a wing that twists in flight is worthless. If the wing is 1/8" slab, just round the edges. Planes like this tend to get beat up if they get flown, so I wouldn't invest too much time into the finish. I'd cover the wing with film and do the rest of the plane with epoxy paint.
This is not an original kit. Sort of a 'short' kit offered on that big auction site. They seem to be pretty acurate to the originals but I betcha that wing ain't but 1/8" in thckness. The first one I started with was 3/16" down from a 1/4" on the original and from the factory it was airfoiled in shape but for having to round the LE. One also has to supply the hardware including the wire for the landing gear.
The reason why I chose to reccomend the airfoil shape was just for looks and no more.

What jetpack could do to improve what he already has is to add another thickness to the wing to make it 3/16" or 1/4" thick and then sanding the airfoil, in doing so improve the looks and function of the whole aircraft.


BMatthews, I consider what you say to be very worthwhile and for you to agree with me a real compliment and an honor! Thanks!


Robert
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Old 03-22-2009, 10:42 PM
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Default RE: 1/2A Planker Finish

jetpack -

Bruce and Robert pretty well covered the bases (no pun intended).

Use butyrate to finish with - nitrate dope is not fuel proof. Much of the dope on the market today is high shrink. If you use it, dope half the wing on top, then do the bottom. Doping only one side and letting it set can curl the wood if its been sanded thin.

You can get low shrink butyrate from SIG called Lite-Coat. I believe the colors are low shrink.

Colored tissue with a clear coat finish looks pretty sharp.

andrew
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Old 03-23-2009, 03:22 PM
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Default RE: 1/2A Planker Finish

I get quarts of butyrate dope from the local General Aviation field. There's a supply store right there and a quart of clear is a bit cheaper than other sources since there is no shipping.


ORIGINAL: Andrew

jetpack -

Bruce and Robert pretty well covered the bases (no pun intended).

Use butyrate to finish with - nitrate dope is not fuel proof. Much of the dope on the market today is high shrink. If you use it, dope half the wing on top, then do the bottom. Doping only one side and letting it set can curl the wood if its been sanded thin.

You can get low shrink butyrate from SIG called Lite-Coat. I believe the colors are low shrink.

Colored tissue with a clear coat finish looks pretty sharp.

andrew
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Old 03-25-2009, 12:47 PM
  #9  
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Default RE: 1/2A Planker Finish

Dope and tissue is the standard. I would also suggest looking into sprays like Coverite 21st Century, and LustreKote. That dope fried it's share of brain cells in the early years, and it cost more than the sprays. It really is what you like to work with, but I would just spray and fly.
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Old 03-25-2009, 09:36 PM
  #10  
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Default RE: 1/2A Planker Finish

Last but not least... trace all the parts... these are getting hard to find.
Bob
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Old 03-26-2009, 11:37 AM
  #11  
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Default RE: 1/2A Planker Finish

If you start with Butyrate, stay with butyrate. Butyrate dope takes months to really gas-off (dry). Applying an iron-on or fast drying paint over it will often cause bubbles due to layer separation when gas is trapped between. This may take weeks to become noticeable.

If you are going to mix finishing products, use Nitrate for the first layers because it dries faster. Once you use another product over Nitrate, stay with it.

I would suggest several base coats, sanding well, another coat, then apply tissue with thinner so it seals from the bottom, then more clear or sealer, sanding, one more clear, then color.

Some have been successful using Rustoleum colors (not clear, nor metalics) over base Nitrate sealer coats.

These are only opinions, some have been successful with other combinations.

George
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Old 03-26-2009, 12:26 PM
  #12  
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Default RE: 1/2A Planker Finish

........one coat of rattle can primer, one coat of Klasskote [very fuel proof] epoxy paint and you're done. Nothing that comes out of a spray can is fuel proof. Dope isn't fuel proof, either. 2 part paint systems are as close to true fuel proofness as it gets. They will dull from fuel exposure but not come off on your cleaning rag and become a gooey mess. Full respirators with charcoal filters must be used, but they should be used for all hobby paints, regardless.
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