How much weight would sheeting add?
 

Hello,

I'm nota beginner to the hobby, but a beginner to sheeting. I want to sheet the wing of my extra 300, as I'm using a bigger engine than called for, so thats not a problem. I want to make it a little stronger, and not so light and delicate. I'm thinking of 1/16" or 3/32". I've sheeted only aP-40, so my experience is lower. Any ideas for this?

Thanks

RE: How much weight would sheeting add?
 

The weight you will pick up from sheeting depend upon the density of the wood as much as the thickness. Balsa wood density is figured out as pounds/cubic foot. 6-8 lb wood is considered light (contest balsa), but you can find wood as heavy as 18 lbs/ft^3 which is fine for certain limited applications.

RE: How much weight would sheeting add?
 

That's a tough question because it depends...........

I've been selecting balsa by weight since the 60s. Used to troll the LHSs with my triner scale.

You will be amazed at how much balsa sheet varies in weight. A couple of the supply houses used to hand pick it for you on request, then for extra bucks. They also sell "contest balsa". You really have to buy about half again the amount you think you need just to match weights.

anyway..............

Figure out what the wood you are going to use weighs. Figure out the area you'll wind up covering. Then you got the info to figure out what your covering is going to add.

RE: How much weight would sheeting add?
 

What size airplane?

What is the recomended engine?

What is the engine you intend to use?

Without that information its almost impossible to make a subjective recomendation. However in most cases when folks begin reinforcing for the sake of reinforcment its usually a mistake every time.

I,ve no idea what size airplane we are talking about but consider even if some reinforcment is required it may not even be the wing but possibly in the firewall area.

To answer your question doing a fully sheeted wing over a lightlty built type will add considerable weight.

Improving an airplane by strengthing where it is not needed is always a bad idea.

John

RE: How much weight would sheeting add?
 

Oh yeah, forgot..........

I think contest balsa is usually considered to be 4-6 pounds per cubic foot. Not much help, that little tidbit, is it.

I will tell ya' this. I used to build control line stunters that were around 600sq-in. That's about what our 60size are today, give or take. They would come out around 36-40some ounces, ready to fuel up and fly. With careful wood selection and sensible gluing, you're actually not going to hurt that sucker much at all.

RE: How much weight would sheeting add?
 

Info on the plane:

.60 GP Extra 300
64" Wingspan
Calls for .91-1.25 4 stroke........61-.91 2 stroke. My option are an OS 1.08 2 stroke, and Saito 100.
Not looking for extreme aerobatics, I would rather have a stronger airplane than one I pick up and it snaps in half.

I think the LE and TE sheeting is 1/16", so it would only be 1/16" thickness (3/32" is typically used today)


Thanks

RE: How much weight would sheeting add?
 

After looking around, I was kinda looking towards Midwest balsa sheeting.

RE: How much weight would sheeting add?
 

4-6 lbs, not ounces. And pretty much not available.

As to the project plane. Add a lot of weight (too much structure, too heavy an engine, huge airborne pack, too much finish, etc, etc.) and it will be a snapping beast that is unpleasant to fly.

RE: How much weight would sheeting add?
 

GP estimates the all up weight to be 7 - 7 1/2 lbs.

I just weighed a piece of Bud Nosen Models AAA Balsa wood sheet 1/16" x 4" x 36" (144 sq. in. or 1 square ft.) - it weighs .7 oz. Calculate the area to be covered in sq. ft. and multiple by .7 oz.

RE: How much weight would sheeting add?
 

i dont think you really need to sheet it, it will just make it heavier than needed, id put the saito 100 in it or just throw the 108 in it if you want, maybe beaf up the firewall alittle but putting a bigger engine and more sheeting is going to = a heavy plane

RE: How much weight would sheeting add?
 

So will me sheeting it make it fly different and not as fun to fly even if it only added maybe .5 oz?

Thanks</p>

RE: How much weight would sheeting add?
 

That airplane will handle the proposed engines fine. If you must do anything perhaps stiffen the nose cell slightly but agine don,t get silly about it.

That wing is fine. Its a conventional D tube section that adds all the torsional stiffness needed. Adding additional open bay sheeting aft of the spar will add nothing to bending strength.

Don,t do it, its a waste of time, effort, money and for what? A heavier airplane. Do take the time to learn good throttle skills.


John

RE: How much weight would sheeting add?
 

Yes, yes and that .5oz figure is a journey through fantasyland.

RE: How much weight would sheeting add?
 

Thanks for the replies. I'm not as concerned about adding some what, if I make that extra weight up with a bigger engine, but want more strength, if that means giving up some aerobatic style flying. With the right engine, it should still fly like an extra, but like JohnBuckner said, it will make a bit of difference.

I'm still considering it. Its kinda tough to decide, because its not a very big area of the wing being sheeted. Its gonna be covered in ultracote, which is pretty light covering.

Thanks.

RE: How much weight would sheeting add?
 

For a completely different point of view ...

If the plane is fully sheeted, you are not limited by covering it with a film (or fabric). Sheeting gives rise to painting and some really creative creative alternatives.

RE: How much weight would sheeting add?
 

I had one of these planes. It's light, but very well engineered to be strong.

I had a YS 91AC on mine which has a lot more power than your Saito 100 and never had a problem.

That said, I also like a sheeted wing, I didn't sheet the wing on mine, but as long as you don't intend to do 3D, the extra weight won't be a problem.

It's an easy mod also, just add the LE sheeting as per the plans, but skip the TE sheeting and the cap strips. Butt-glue two sheets together into a single wide sheet and glue it from the spar to the TE and trim off any excess.

RE: How much weight would sheeting add?
 

Over the years I've pondered the strength vs. weight question constantly only to find that reputable designers and kit manufacturers have done the engineering pretty well. Try to keep in mind that every ounce you add increases the wing loading and will result in higher takeoff and landing speeds and less crisp manuvers. And it's hard to know the final weight until you're truly finished which may involve adding 1/2 pound of noseweight to balance out that 'extra strength' you've built in.

Personally, I would not fully sheet a wing that does not call for it. And even if you use 1/16 balsa if you paint it, it will be very heavy. I'd rather see smaller modifications on a wing like fiberglassing the center section or adding a few more shear webs along the spar. These mods do add strength but very little weight. Of course it's all subjective and if it makes you 'feel better' go ahead and try it!

RE: How much weight would sheeting add?
 

What kind?
The forces of flight will only bend or twist the wing.
If either effect happens really fast and strong, then you have flutter.

Check this post and its attachments:

http://www.rcuniverse.com/forum/fb.asp?m=9279316

Some reading on sheeting:

http://www.airfieldmodels.com/inform...kins/index.htm

http://www.airfieldmodels.com/inform...ruction/07.htm

http://www.airfieldmodels.com/inform..._points/02.htm

RE: How much weight would sheeting add?
 

I seriously doubt any real "engineering" is done on any of these kits or designs.

Show me the calculations.

RE: How much weight would sheeting add?
 

I can't show you any numbers, but if you look at (and build) earlier GP kits, and then see the newer techniques used in the Extra, it is VERY obvious that there were some new engineers on the R&D staff.

RE: How much weight would sheeting add?
 

Designers perhaps, but doubtful they are engineers. Most model design is done by inspection. Looking at what others have done, and copying what looks like it works.

Back to the sheeting question, if you sheet you would be better off with 3/32 wood of very low density than 1/16" wood of higher density. Plus have material to sand. Avoid using CA glues on the skins, model airplane cement sands best and is easier to control it's application

All things equal (in density), sheeting that is 50% thicker is more than twice as resistant to localized buckling.

RE: How much weight would sheeting add?
 

Designers, engineers - Semantics

The easiest and best sheeting to use (thickness-wise) is whatever is presently used for the center, LE and TE sheeting and the Cap Strips (which if my memory serves me correctly is 3/32" on that plane). Since the rest of the wing is designed around that sheeting, everything else will line up with it.

RE: How much weight would sheeting add?
 

I think the aircraft will perform poorly with the additional weight of the oversized engine and sheeting. You would be better off building it lighly, and using a smaller engine.

RE: How much weight would sheeting add?
 

Well, all of GP ARFS are sheeted foam, and I would say the wing without sheeting would weigh the same if not a little more than the piece of foam does.

No, I will not be doing 3d type stuff, just simple aerobatics.

So If I decide to sheet it, should I replace the LE sheeting with 3/32", and do all 3/32"? Or do all 1/16"?

Thanks for the links on sheeting, it helps alot.

Jason

RE: How much weight would sheeting add?
 

A small 60 size kit from Texas Twins, fully sheeted but foam core wings. Glassed using 1/2oz glass and Deft Sanding Lacquer to lay the glass. Painted with Klass Kote paint. Small plane, heavy for it's size, used an SK .91 for power, Outstanding flying machine. As strong as it was it didn't hold up all that well when the RX went out in it during flight.
Mid West makes the stiffest and heaviest balsa in the land. You may want to place an order for contest grade wood from Lone Star Balsa, buy a bunch of different sheeting and sticks so you have it on hand for future use.