Get Rid of Sheeting Lines on Sheeted Wings?

[pcastine]

Hey guys,

I've built a few giant scale planes before, and I am now just finishing up a 43% Carden Extra. On all my projects, I've used wood glue to join the balsa sheeting together to create the wing skins for the foam cores. I bag the wings and use West Systems epoxy to skin the wings.

On final sanding, it seems I always end up with panel lines on the wings that only show up after covering. I've sanded the surface with 150 up to 400, sprayed with hairspray, and resanded with 600. I thought on this project I had the panel lines gone. But they're still there!!

How do you guys sand the wings so you don't see the lines?

Thanks,

Pete

[MODE 1]

Which way you sanding I don't get lines if I go at 45 degrees with 400 or even worn down 250 and vary the pressure on the pad over the joints for the last part once i know its smooth just to fine tune it more.

you can use a 1000 .........but who wants to spent forever polishing the wood....I dont think more than 400 is needed.

Forgot to ask: What lines are they raised or sunk. Might be your glue type.

[pcastine]

Raised...tried sanding across the grain. Seems that the balsa sands away before the glue line.

[gzkpez]

Not all wood glue works the same. There are some types which sand easier. Also some hobby glues , such as the discontinued pica glue, sanded very easy. I read that Super Phatic an English glue sold by Hobby Lobby might be real good is worth a try a least to test it out. The type, age of glue, and how soon you sand it matter; as well as weather.

Also some brands of sandpaper, such as that white Portuguese stuff, are much sharper and sand our soft wood a little better. Be sure to use fresh sand paper, not like cheap me who uses it till it is just paper.

[Mithrandir]

I use CA, and sand the seams before I sheet the wings with a long and wide sanding block

[Patrick H]

For foam core wings I use no glue to join. Join sheets on outside with packing tape lengthwise and pull off when the wing comes out of the shucks.

[zzw26n]

	Quote: Originally Posted by Patrick H
	For foam core wings I use no glue to join. Join sheets on outside with packing tape lengthwise and pull off when the wing comes out of the shucks.

This is a novel idea, wonder if it works?

[rc4flying]

When are you doing the sanding ?

We glue the sheeting together with TiteBond Wood Glue and do the sanding, right upto the final sanding with 600 grit. All done prior to applying the sheeting to the foam parts. We also do the sanding on a sheet of glass with plenty of vacuming while doing the sanding process.

[SmoothFlying]

I tape the sheets together and then run thin CA down the two sheets to join them together. After joined sand and there are no lines at all. Never get any lines whatsoever.

[jmiracle]

I also don't edge glue the sheeting. But use a polyurethane glue that foams into the seam from below. This leaves no glue ridge on the outer surface so it can be sanded smooth. I also sand at a 45 to the seams to even things out...then finish sand with the grain to remove any cross-grain marks. (They will show under the covering)

The ridges or lines are caused by glue (any kind of glue) changing the density of the wood.....the softer balsa that hasn't been exposed to glue will always sand faster than glue soaked balsa.

[MODE 1]

Something else which doesn't make sense. You glass the wings afterward. This makes the surface the same in hardness so it stands to reason that sanding will not find any hard n soft points to leave lines. You should be getting a finish as smooth as glass after final sanding of the glass. Any high areas would be flattened down to match the surrounding area.

Maybe its the vac bagging making the joints slip slightly. Personally I think bagging wings is unnecessary...but there ya go.

[tl3]

I don't know anyone glassing wings on GS planes.

[MODE 1]

Glass is just extra weight. Not needed if its built strong but if your painting the model ......spose glass is the best idea.

[Walt]

The last plane I covered I had some issue's getting the covering to stick. I actually could see the sheeting slighty swell from the heat I was applying which made the seams show. If you cover in a humid time of the year this seem's to show up more than doing it in the winter..Here in greater Indiana anyway...This particular project was shot with hairspray and sanded to 600 grit. No seams were visable till I started cooking the Monokote and the sheeting seams became visable..Walt

[smokin]

Now, I'm not saying that I am the expert here and that my ideas are going to be correct, but....

I too do NOT glue my sheets together when but-joining for the balsa panels. I use 2"wide masking tape to hold them together. I make sure that the edges have been planed and the but-joints are perfect and then press them lightly together and tape down the seam. This does use a lot of tape! I then glue them to the foam wing panels using Elmers Ultimate PolyUrethane glue. This acts pretty much like gorilla glue but gives me a bit more "workable" time. I rarely even have any of the Urethane come up thru the cracks as my tape lines are jointed very well.

I used to use plain old Elmers white glue to join the balsa together and had no issues with sanding. I just found that this was a step that wasn't necessary and it just added extra (though very little) "glue weight" to the airframe.

I too do most all of my sanding PRIOR to gluing to the foam wing panels. I make certain to use a fresh piece of MDF to sand on as it is smooth and flat. Using a good vacuum cleaner to suck up the excess sand-dust while sanding will eliminate alot of the "pitting" you'll get from continuously sanding. This should eliminate the need to continue the sanding process!!!

Again, this is just the way I do these wings for myself. I'm sure there are many acceptable ways in which to accomplish the desired result.

Good luck on future projects!