using expanding foam in built up wings
 

Hi Guys. I recently acquired a 100" edge. The previous owner had the plane and wings stores in a back shed. On closer inspection I've found that one wing was a source of mouse food. It appears that they have gnawed their way through a lot of the formers towards the wing tips - from about 3/4 of the wing down. The structural integerity of the wing seems fine, but I would like to offer some reinforcement to the ends of the wing.
Can I insert some of that expanding foam into the wings to give some added support? I could do this by applying a long nozzel to the end of the wing and draw the foam nozzel back towards the wing opening. I am concerned though that the foam will expand and push or distort the top and bottom of the wing where it's not sheeted. Any idea's would be great.

RE: using expanding foam in built up wings
 

From what I understand about the product you are considering, I think it's likely it would expand so much, that it would destroy the wing; or, it would certainly distort it. You call them bulkheads but I assume you are talking about the wing ribs. Do I understand you to be saying 75% of them have been chewed on. The purpose of the ribs is to hold the structural parts of the wing in position and maintain the shape of the airfoil. I have no idea of the depth of the damage done. The mice probably used existing lightening holes in the ribs to gain access to the areas of the wings they damaged. How much they made these holes larger and how much this has weakend the structure is anyones guess.

My thoughts on making repairs would be the removal of the covering in the damaged areas to gain access and patching the damage. This won't be easy as you may not know what the damage ribs looked like before they were turned into mouse terds.

Sorry, but, I don't see a simple fix here.

RE: using expanding foam in built up wings
 

I would go to the nearest model flying field at the end of the day on a weekend where there are a lot of flyers and rummage in the trash cans for trashed/crashed balsa airplanes. Take all you can as you may need to do a lot of experimentation. Pick up the wing parts and take it home and spray the expanding foam inside the wing as an experiment and see if the expansion distorts/damages/ bulges the wing at all. If there is distortion/damage/bulging, then try drilling escape holes on the underside of the wing surface and see at your next experiment if the escape/relief holes will allow the expanding foam to escape and stop the distortion/bulging of the wing. If it does then you have the solution. It is always a good idea to pick up crashed balsa airplanes for your experimental repair jobs. Nothing beats trying it on a real balsa airplane.........even if it is a crashed version. 'Nuff said.
God Bless y'all, always
larry

RE: using expanding foam in built up wings
 

The Dow Chemical Company makes a product called "Great Stuff" polyurithane foam in a can. There is expanding and non-expanding versions and can be found in most any home improvement/hardware store. I used the expanding type around a pre-hung garage entrance door once and had to beat the bejesus out of the door frame with a 2 x 4 and a hammer so that the door would close. I have not tried the non-expanding type but that should do the job. It should add a-lot of structural integrety to your wings and sticks like CA glue. Good idea. If you buy the expanding stuff just save yourself a-lot of time and money and trash the plane or build a new wing. You WILL ruin your wing with the expanding stuff no matter how many holes you drill in the covering. Trust me.

Bill

RE: using expanding foam in built up wings
 

Hi it won't do any damage if you do it carefully.When you look inside the wingroot you know what you see in terms of structure.Insert the long nozzle and give it a 1/2 second squirt,watch and wait for a minute.It's infinately recoated as far as adhesion is concerned so be patient.Keep that up till eventually pops out at you and trim it off.It can't expand and trap itself in a cavity if you are carefull.

RE: using expanding foam in built up wings
 

Seriously mate, don't try it.

Expanding foam does just that, it expands.
And when you think it's finished, it expands some more......then some more.............then snaps through your sheeting and ruins the remaining good ribs.
This stuff will not come away from balsa easy, so effectively if your plan goes south, your stuffed.

Do yourself a favour, remove the covering, inspect the damage with your eyeballs, and make new ribs etc if need be.
I serioulsy doubt mice would eat the ribs and leave the spars intact.
Don't risk trashing a 100" edge plus your engine & radio gear doing a dodgy fix.

Just my 2c

RE: using expanding foam in built up wings
 

I agree with Krener. Don't do it.

I use that expanding foam to fill sheeted retract areas. The way I do it now is to sheet one side, fill with foam, let sit for 24 hours, cut off the excess and sheet the other side.

The REASON I do it that way is because the first time I tried it, both sides were sheeted, the hole was cut for the gear and I added the foam. The next morning, all of the sheeting had busted open from the expansion.

Ribs do very little structurally. If mice have eaten holes in them it should really be no problem. I have often cut out a LOT of the centers of solid ribs for lightening with no ill effects.

RE: using expanding foam in built up wings
 

You might want to consider the amount of weight you would be adding, too. Though it is foam, it is much heavier foam than that used to make foam wings. And if you put it in one wing only, you will need to add about the same amount of weight to the other side. I saw a trainer which someone had used this stuff to reinforce the firewall and it was very heavy in the nose. Not a big problem with the trainer, I suppose, but you might not want the added baggage, especially out on the wing tips. Rebuilding the wing is not as big an issue as you might think; and it is a better option IMHO because you will be able to see ALL the damage that needs to be dealt with. Good luck, Dzl

RE: using expanding foam in built up wings
 

Thanks guys. you have all been really helpful. I can see quite well down into the wing and the only areas affected are the wing ribs. The main spar on the leading edge is fine as is the wing tube area. The mice have gnored around the lightening holes in the wing ribs effecting about the last 4 - 5 ribs - about 20% of the wing from the tip. Some of the ribs are lightly gnored and 2 or 3 have been chewed quite bad. I dont really want to remove the covering as it's a custom job and I dont fancy having to replace it. I think I'll take Larrys advice first and try it on a wrecked wing to see how the foam behaves. Thanks again.

RE: using expanding foam in built up wings
 

Honestly, don't worry about it. If it were inboard there still wouldn't be much concern, but outboard you have nothing to worry about at all

RE: using expanding foam in built up wings
 

I think minn is right but if you feel the need to reinforce it have a go with foam.It's not heavy and those who say it is have never taken the trouble to break a piece off and feel it.It stops re-acting as soon as the air supply is cut off so don't bother waiting 24hrs for the brain surgeon to arrive and give it a squirt mate,works wonders:)

RE: using expanding foam in built up wings
 

You can use those long mini control rod plastic tubes they use for small electric park flyer RC airplanes as tube extensions to pinpoint the 1/2 second foam squirt exactly on the bullseye area you are targeting with the foam squirt. Seriously, experiment first with crashed balsa wings retrieved from the model field trash cans. I see them all the time, especially on a busy weekend. No harm, no foul.
larry

RE: using expanding foam in built up wings
 

I have heard of guys using it on model boats that were epoxied with all ply construction. One guy said he had literally popped a boat apart from over expansion, I had one that almost did it. I managed to dig it out before it broke it. It was years ago, some type of spray can stuff..

RE: using expanding foam in built up wings
 

I did some serious damge to a full size fiberglass boat using expanding foam.
Al I've seen two model boats totally distroyed... be careful.
Because it expands in all directions as it dries doesn't necessarily mean that it'll expand towards the opening.
Quite the contary, it expands equal emounts in all directions.
Boom!

RE: using expanding foam in built up wings
 

Exactly.

Imagine putting a balloon in there and inflating it. Sure, some of it will protrude through openings, but the bulk of it will stay put and expand.