I always hear this phrase ¨I am going to buld it light¨ But what exactly does it mean? What do you guys do to shed the ounces. My first kit was a Funky 40 from CA models, its a 3d machine that looks like swiss cheese bc of all the wood they cut out of the kit to lighten it. For the motor I have on it, it has marginal pull out power. I am sure I built it a little heavy as it was my first kit. I am thinking about buying another kit and trying to build it as light as possible.

So how do you guys keep your birds skinny? I am wanting to cut the weight down as much as possible and cut out every thing that is not absolutely necessary. Below is a pic of the plane ready to cover.

Hi!
Take away as much unnecessary material as possible...Always ask yourself: "Do I really need this?" And choose material wisely! Simple as that!

Regards!
Jan Karlsson
Sweden

There isn't much of anything left to remove from the airframe.

If this is an electric or small glow powered plane (slow flying ), fit the pieces and use ONE DROP of thin CA to glue each joint. The joint is not as strong, however, the covering will provide some additional strength.

Minimize any epoxy used.

Use a light weight film covering - do not use paint if at all possible. If you have to use paint, remember, clear is the lightest of paints (dope ) and colors add weight rapidly. Check the weight per sq ft/yd between different colors on the coverings - there is a weight difference between colors also.

Do not add weight to balance the plane, shift the battery (or use a larger battery), and receiver, or use a larger/heavier motor. You want any added weight to be "working" weight, not dead weight.

When you build light, you often times can not build as strong. You will not be able to do hard/rough landings and your violent manuvers will have to be minimized/eliminated.

MOST people, when building light, use contest grade balsa (4 - 6 lb balsa ), thinner thicknesses and a light weight covering. Unfortunately, the majority of kits have balsa in the 8 - 10 lb range and the parts are typically thicker than you would want to keep everything light. Scratch builders keep EVERYTHING at the minimum weight/thickness needed to do the job.

I do a fair amount of sctatch building and frequently make "balsa plywood" for pieces that do not require the strength (or weight ) of light ply (fuselage formers in back of the trailing edge of the wing ). I also do things like using balsa for spars instead of basswood or spruce, HOWEVER, I do reenforce them with carbon fiber to maintain strength. Other things I do is to increase the spacing between ribs slightly to eliminate a rib or two and I look for areas that I can use lighter/thinner materials with minimal sacrificing of strength (1/32" sheeting instead of 1/16" sheeting, 3/16" square balsa instead of 1/4" square balsa, 1/16" thick wing ribs instead of 3/32" or 1/8" thick ribs ). You get the general idea. Each item by itself doesn't account for much weight, but together, they can (and usually do ) add up to some significant weight savings.

If you want to invest the time (and money ), you can frequently scratch build an identical kit plane and the scratch built will be several ounces lighter than the kit plane.

A few of the planes I've built have a high wing loading so I reduced weight by doing the following:
-Use mini servos instead of standard.
-Use light foamy type wheels.
-Go very gently with the fiberglass and only reinforce the firewall.
-Blance with the battery.
-If painting, use sanding sealer so the wood doesn't soak up too much the poly or fiberglass.
-Use thinner sheeting.
-Use 1 aileron servo instead of two. Not always practical though.
-Go a little smaller with the fuel tank. Careful with that one!
-Hollow out the ribs and formers before you start bulding.
-Use nylon pushrods rather than metal.
-Instead of using an EZ fueler, fill through the carb line.

Glues are another area of weight saving. Avoid epoxy except where you need it like the firewall and stab. CA will be lighter.
Landing gear and wheels as mentioned. NiMHD batteries or Lithium will be lighter than NiCd too.

I saved a pound on my GP Patty by dumping the wheelpants and using CF gear instead of the stock one.

Hope this helps.

Pete

change to light weight wheels instead of the supplied ones.

Is it possible to use someting like varnish or a wood sealer on the firewall in order to fuel proof it instead of using epoxy. I tend to think it would be a little weak, but it seems like you could save a lot of weight using a sealer instead of epoxy to fuelproof.

Although the question is how to build lighter in general. This particular kit is a 40 sized 3d plane that will go through the typical stresses of 3D flying so it needs to be strong and light. I want my cake and eat it too.

I'll tell you what I said when people were having their Funtana 90's blowing up in mid-air...

You're building a Ballerina. When it's done, it will be light and agile... And Fragile!

If you ask a Ballerina to play pro football, something's gonna break!

Now, you COULD add some carbon fiber strips to both sides of the wing, and a few other strategic places, but for the most part, the lighter you build, the weaker the structure.

And you can use polyurethane to fuelproof, but thinned down epoxy will be just as light really.

Hi!
I just pour on thin ca glue......
Regards!
Jan K
Sweden

WHat ratio are you using to thin down the epoxy. Is it OK to use the thinned down epoxy on the firewall or do you need more gusto there.

Thinned down epoxy is fine for the firewall. I usually thin the epoxy with about 10% acetone (by volume ) when applying it to the firewall. Be advised that it will take SIGNIFICANTLY longer to dry - typically 24 - 48 hours depending on temperature and humidity.

Any place its balsa to balsa use thin ca. Ply to balsa med ca or epoxy. Don't overload the area to be glued just enough to do the job. The biggest weight saving tip. Build light in the tail. Most of the time every once you save in the tail means 4 onces of weight saved in the nose. Since most people tend to build tailheavy planes and stick lead in the nose to balance.-Mike

If your airplane has a great deal of sheet balsa or plywood use lightning holes wherever possible. Typically many kits use plywood for strength in some areas and they usually overdo it. Some of the extra plywood weight can be removed by holes in the center area.

Building light is all in your technique. How much adhesive you use to join each piece of wood can play a major part in weight control. When sheeting foam core wings, you should WEIGH THE SHEETING to ensure that the weight of the sheeting for the left wing is very close to the weight of the right wing (this will help avoid having to add too much weight to a wing tip for lateral balance.)

Check out this thread for some ideas.... [link=http://www.rcuniverse.com/forum/m_1504703/anchors_1504703/mpage_1/key_totally/anchor/tm.htm#1504703]Great Planes EXTRA 60 size.....totally 3D[/link]

Minimize the lumber, use glue wisely - just enough to do the job, use lightweight equipment and hardware(or eliminate it altogether if possible), remove material where it's not needed, use CF tubing instead of ply, minimize the length of pushrods, expand the spacing for ribs, bulkheads, etc(you can actually do away with most fuselage formers&bulkheads), use nylon or aluminum hardware instead of steel(better yet - get rid of the hardware, some re-design required), use thinner wood for the sheeting, or get rid of the sheeting, and if all else fails - ADD MORE POWER! <grunt, grunt!>

What about using fuel proof dope for fuel proofing?

By the way, congrats on the CA model. Maybe you could use a bigger engine and practise throttle control with it. I'm building a .40 sized CA Widebody and putting a Saito .72 on it. I'm using a Hitec 55 mini servo for throttle and Dubro foam wheels. Another weight saver is not using a tail wheel assembly. Those weigh a lot. I'm going to make a tail wheel with just wire. I may epoxy that into the rudder or put a screw into the fuselage for the wire to turn around. I won't use a collar, and will bend the wire 90 degrees instead to retain the wheel. Collars weigh a lot too.

I always cut down my axles after fitting the wheels and collars. That extra axle material weighs a lot if you hold it in your hand after cutting.