wing tips..solid or ...
 

trying to decide if i should just carve out some wing tips from balsa or do some built up ones instead, the wing will be covered with covering not painted... any advice or opinions?

pros and cons to both?

RE: wing tips..solid or ...
 

Stevem9,
I am assuming you are building a 424 class racer, so I will approach it that way. The last 3 inches of any wingtip can be constructed with any material you want to use (even though the main wing has to maintain the constant thickness and shape for 47.5" and have a minimum of 500 sq. inches of area, as long as you do that, it can be hollow, fiberglass, etc.). The carved balsa tips are pretty easy to make, and allow you to play with the shapes some. By hollowing them out, you will make them lighter but weaker at the same time. If you do hollow them out, I would soak some thin CA into the hollowed out part and allow it to dry completely before attaching then to the wing. This will make them a little stronger. The advantage of a lighter wingtip is that it allows you to roll faster and stop the roll easier since you are moving less mass. And since the airplanes thrust line is the pivot point of the roll, you want to try to keep the mass closer to the center so it is easier to counteract. The pros for balsa would light, easy and inexpensive. The cons would be they are a little more fragile the more material you remove, so you have to balance weight vs. strength.

If you want to go with fiberglass, you would now need to create a plug for the tips, glass, paint, polish and then construct a mold. The pros for this is they will all be identical, light and very strong. The cons are a LOT of work to make and more expensive initially.

The other way is to simply run the wing cores out to the tips and sheet it like the rest of the wing. I actually do this in 424 and clip the tips off at a 45 degree angle so that the top of the wing is flat and the bottom tapers up. You could do any angle or even square if you wanted to here. The pros here are simplicity and the tips are just as strong as the rest of the wing and the ease of construction. The cons would be that you have a solid wingtip, however it is only foam.

You can use covering with any of these methods, but fiberglass is a little tricky to use covering on. You have to hold it in place a longer time while it cools, as fiberglass cools much slower than wood. Depending on how fancy you go with the shape, will determine how difficult it is to cover too! ;)

Good luck, and I hope this helps some. ;)

Edited my typical spelling screw ups!

RE: wing tips..solid or ...
 

thanks, this will for sure be a 424 plane, might transition this year to fast quickie this might be a canidate for it. what about the tips like the predator has..kinda like ribs? not sure what thats called..

RE: wing tips..solid or ...
 

Oops, forgot about that style! I don't use the plastic coverings much, so I didn't think about those! :eek: You can take the wing profile and trace the airfoil onto some 3/32" or 1/8" balsa and then cut it in half. Glue 1/2 onto each wingtip centered and perpendicular to the section and add a few triangular pieces of wood (about 1/2" x 3/32" thick) and glue these to the end of the wing and the 1/2 rib wingtips. You can then round them off some and cover the wings, wrapping the covering around the tips. Pros are again light weight and pretty easy to do. Cons would be damage is easy with a wingtip scrape and if the covering comes loose in flight, the drag induced could make it really interesting to control with the small throws we race with! ;)

If you are laying up the foam wings yourself and may use them in 426, I would suggest using a good epoxy laminating resin and adding a 1/2" x .007 x 48" long uni carbon fiber strips on the high part of the wing, top & bottom. I also laminate 2 strips 2" wide and 2 strips 1 1/2" wide full length of 2 0z. fiberglass to the trailing edge either side of the foam (between the foam & wood) to help the TE transition smoother & really stiffen up the TE. With the fiberglass in the middle of the layup, you can then sand the TE to the fiberglass and make a real sharp TE. ;)

RE: wing tips..solid or ...
 

Steven, I think if you look at the wing tips here you can see what Scott is talking about. Flat 1/8 balsa tip with ribs for a built up tip.

Bob Harris

RE: wing tips..solid or ...
 

ok, since im covering the wing built up tip looks like a fairly simple design, i will have to see if i want to make this a fast quickie plane in the future..

do you guys cap the foam on the wing before adding a solid tip?

RE: wing tips..solid or ...
 

I liked the solid tips. I found that they helped to reduce twisting of the wing,,, grab a built up wing tip wing at the ends and give it a little twist,,, then grab a solid tip wing and try to twist it,,, you will feel a difference. Also i liked the solid tips better for when I needed to add quarters to a tip,,, all I did was cut a slot and tap the quarter(s) into the wood.

No real need to cap the ends if your gonna do solid tips and yes to capping the ends for a built up tip, that will help some, to minimize wing twist.


BV

RE: wing tips..solid or ...
 

I like solid tips. They take banging on the runway better. Are easier to repair after a good runway banging. Also can be shaped easier into a nice aerodynamic shape. Roll inertia is the only downer.

The old runway banger himself.

Denis

RE: wing tips..solid or ...
 

I don't know about you guys, but I set up my race planes to have a pretty mild roll rate anyway.

Since many of us use quarters, etc, stuck on wingtips for balance, I doubt if we'd really notice a roll rate difference from a solid tip. The quarters weigh more than the difference..

RE: wing tips..solid or ...
 

"even though the main wing has to maintain the constant thickness and shape for 47.5" and have a minimum of 500 sq. inches of area, as long as you do that, it can be hollow, fiberglass, etc."

so am i correct in saying the wing tips are calculated in the wing area? so a wing 48" x 9.8" is legal providing the wing tips make up the extra wing area needed for the 500 sq in?

thanks

RE: wing tips..solid or ...
 

The wing tips do not have to completely make up the area difference. But the added span of the tip is used in calculating the area based on the cord and span and must be 500. Because of rounding and shaping you could still wind up with a projected area of less than 500sq.in.

Denis

RE: wing tips..solid or ...
 

If you go the full 52", which you want to do, you can get to a 9 3/4" chord if you don't round the corners at the LE too much.

RE: wing tips..solid or ...
 

thanks everyone, i picked up some balsa going to make som solid tips. seems to be the best choice for me,