Low spots on wing sheeting.... what to do? My ARC Akrobat.

[Paul Taylor]

I am almost done with the cowl. I just need to glass it. As it stands right now, it looks like I saved about 1/2 oz by dumping the ugly plastic cowl.

Now on to the wing of this ARC Akrobat. Help!

The weight in the wing tip was a tire weight that was about 2.5 inches long and was held in by what look liked a half of tube of Ambroid glue. I cut it out and will install a weight tip box. By removing the glob of glue and weight it took off about 2 oz off the wing.

So now to some help. I am not sure how, but the wing has 3 low spots in the sheeting. Maybe poor construction or just age. But I think I would do more damage if I tried to remove all the sheeting. As I see it I have three options.
1. Remove all the sheeting and put on new wood.
2. Cut out the bad spots and splice in new wood.
3. Use sheet rock spackle and fill in the low spots.

I also have a small hole that I think I can just glue in a patch. This are the only problems I see with the wing. I could not build one this straight.

Also I think the bell crank and leadouts will go. Put in a 4 inch BC and it looks like the leadouts were soldered and they do not look like the right size lead out wire.

Any way what to do with the low spots in the sheeting?

[Leo Mehl]

I am almost done with the cowl. I just need to glass it. As it stands right now, it looks like I saved about 1/2 oz by dumping the ugly plastic cowl.

Now on to the wing of this ARC Akrobat. Help!

The weight in the wing tip was a tire weight that was about 2.5 inches long and was held in by what look liked a half of tube of Ambroid glue. I cut it out and will install a weight tip box. By removing the glob of glue and weight it took off about 2 oz off the wing.

So now to some help. I am not sure how, but the wing has 3 low spots in the sheeting. Maybe poor construction or just age. But I think I would do more damage if I tried to remove all the sheeting. As I see it I have three options.
1. Remove all the sheeting and put on new wood.
2. Cut out the bad spots and splice in new wood.
3. Use sheet rock spackle and fill in the low spots.

I also have a small hole that I think I can just glue in a patch. This are the only problems I see with the wing. I could not build one this straight.

Also I think the bell crank and leadouts will go. Put in a 4 inch BC and it looks like the leadouts were soldered and they do not look like the right size lead out wire.

Any way what to do with the low spots in the sheeting?

In My case these low spots are supposed to be there. I don't know about you but I can't see them anyway!

[Paul Taylor]

That is not true Leo, I have seen your planes up close. Your stuff is nothing like this bundle of wood.

[Leo Mehl]

That is not true Leo, I have seen your planes up close. Your stuff is nothing like this bundle of wood.

I actually carve them in and then go over the plane ane fill them in before I paint. It take longer to paint when you do this. Just a hint!

[Serge_Krauss]

I wouldn't have posted this opinion, except that I've recently seen some critical areas of ARF model sheeting removed for bellcranck access and replaced. One builder cut out a patch with broad saw-tooth cuts at each span-wise end, kind of like this, but with sharper, deeper cuts:.

________
\          /
/ <---->\
\          /
/______\

He replaced pieces or patched the openings with new ones using CyA cement, which hardened up the local areas, perhaps creating stress risers, but certainly not reducing strength at the seams. I've tried balsa surface patches, but the aliphatic resin glues haven't sanded well for me. Some recommend epoxy of other glues mixed with a high volume of microballoons. I think I'd try the cutting and patching. FWIW.

SK

[Mark Scarborough]

If you really feel the need to correct it, Im not sure that putting a patch in is going to be all that beneficial, but its really the only option in my book. filling it with anything is going to be heavier, harder to make look right, and not as satisfactory IMHO.
what I have done when replacing sheeting is to carefully cut the area you want to replace, many light passes with the xacto, then glue a tab of 1/16 under the sheeting where you cut so that when you install a new peice, it will have a glue ledge to set on, and it also makes a better joint.
I think were it my plane I would be sanding some radius into the leading edge too. that looks pretty sharp from the pictures.

[Alan Hahn]

What ARC Akrobat? Never heard of it.

added:

I reread the original post---I gather this is an old model built by a modeler--not a commercial ARF/ARC!

[Bill Little]

As Ty mentioned above, you can pop out dings with a damp rag and an iron.  I don't know if you can raise a low spot like that, though.  Don't know abut the others, but light weight spackle will fill in the low spots and not add a ton of weight.  It *will* add weight, though.  But don't feel like the lone ranger, I know countless top ranked builders who keep light weight spackle on the building board......  it ain't the first choice, but when nothing else will work.  Cutting out the wood and using glue to add the splice back in will also add *some* weight.  If you do it right, block sand down when it dries, most of it will be sanded off, and feather in the edges.

Unless you are going after the Walker Cup with this plane, Paul, I would go with the light weight spackle. 
And light weight isn't what some of the Walker Trophy Winners had, anyway.  A well trimmed plane, *slightly heavy*, will out perform a crooked, out of trim, feather weight. 

Mongo

[EddyR]

Paul    You are putting good work on top of bad work. Looking at the wing closely it looks like there are places where the leading edge sheeting is not touching the ribs. Also the builder forced the sheeting over the ribs and cracked it. The wood was to hard or not wet enough to bend. The build looks like a builder with out a lot of experience. Your efforts would be better spent on a new model. You can finish up the model with out doing much to it and it will fly the same as if you do all this work. If you need a model to fly I would just fill the low spots and cracks and sand it all smooth with a long block sander. Replace the leadouts. If you can't build a straight wing get a used ARF wing and build a model around it. My ARF Nobler wing was better than I could have built it. It is now waiting for a future project.
Ed

[Paul Taylor]

Thanks guys for all the in put. This will not a world beater and I will not put a front row finish on it.(not that I could any way) Monokote and rattle can is my plan. I have never built a full fuse plane before. I am learning a lot as I go and you guys are my teacher, for that I am thankful. I now will learn how the controls go together is a fuse plane.

Where did I put that jar of spackle.

[Andrew Tinsley]

  I have had some (limited) success with applying water with a syringe (just to control the amount!). Once the low area is thoroughly wet make up a thick balsa wedge and gently force it between the sheeting. When dry, the sheeting will have been raised. The snag with this technique is that it is difficult to get the correct amount of "raising". On the several occasions that I have done this, I have overdone it! Luckily I was able to sand the area back to flat, but the sheeting was then on the thin side!

Regards,

Andrew.

[Shultzie]

Probably waaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaay to late, however without seeing it up close and personal..
.  However FIRST N' FORMOST....
Carefully dampen ONLY THAT LOW SPOT AREA FIRST.....then grab either your old moneycoat'  iron or heat gun and carefully try to swell it....up n' out!

KEEP A PEELED EYEBALL ON YOUR PROGRESS!!! (Years at the old Wind tunnel flutter model area we often got off the hook...with this "moisture-n-ironing measure (if we were lucky...Otherwise a replaced sheet of balsa sounds the way to go, Maybe?

[Larry Cunningham]

Good advice, all.

Here's another trick I have used for correcting a hole repair or low spot, say due
to planking over and gluing to a rib which is slightly lower on its perimeter than
it should be: use a thicker patch..

For example, with 1/16" planking, add the repair with 3/32" - then use a good flat
sanding bar to sand it all down to perfectly flat.

And my method for getting a good fit on the patch: 1) cut the patch piece first,
making sure it is larger and overlaps the area by a reasonable amount (say 1/4"
at least), 2) apply the tiniest dab of thick CA to the diametrical corners of the
patch piece, on its bottom surface, 3) very carefully place the patch in position,
with the tiny dabs of CA on opposite corners holding it in place, 4) using a
fresh, sharp #11 exacto blade, carefully cut around the edges of the patch
piece, and remove it and the planking below it, 5) separate the removed planking
piece from any cut away planking attached to it.

Now, reapply the patch piece and it should fit tightly. I normally use thick CA
for rib contact areas which are unreachable, and thin CA for the edges. When the
thicker material is sanded flat, you can make the patch nearly invisible.

Patching is one thing I have done a bit of; I had some extremely soft (and light)
planking near the wing root on the LE planking of one wing and it was so thin and
fragile that I kept breaking holes with my thumb. That where I learned the thicker
patch piece trick..

Good luck!

L.

"I know what pleasure is, for I have done good work." -Robert Louis Stevenson