How to lighten a plane?

[Vinman]

Any body have any other tips to lighten a plane? I'm working on a Top Flite Elder 40. Got a AXI 2826/12 for it. That's what HL said to go with. I'm trying to lighten the plane a little. The back of the fuse is a open frame. But the rest is solid. Question is can I cut open holes in the sides,top and bottom of the fuse for less weight and how much can I cut without weaking the fuse? Any idea's? What do you do to lighten your planes? Vin

[flyranger]

During construction, use as little glue as possible. Instead of 30 minute epoxy, use thick CA. Instead of 5 min expoxy use thick CA. Instead of monokote, use transparent monokote. During the build, mark the balance point on the fuse sides. Make sure as you go along that servo placement, motor, battery placement range yield a balance. Don't wait to check balance until you strap on the wing!! Check balance as you go along. Forget about tail wheel (or front wheel steering - don't remember if it was a part of this model) adds weight precisely where you don't want it - near the tail. If you do add lightening holes, make the holes round, not rectangular, as this will help in maintaining strength. The laser cut fuse sides I have seen use rounded edges in the cutouts even when they seem to be rectangular in shape. Make your cuts inbetween the fuse formers, then add some 1/8 in balsa stiffeners to the fuse formers to compensate. Dave Brown or DuBro Lite Flite wheels. Wings on the 40 size models use spruce and basswood. You could try using the same size in balsa backed up with carbon fiber rods. Hope this helps.;)

[rcers]

Question is can I cut open holes in the sides,top and bottom of the fuse for less weight and how much can I cut without weaking the fuse? Any idea's? What do you do to lighten your planes?
Holes in balsa just don't make that much difference. I once had a wonderful laser cut kit. it had holes everywhere. I took all of the pieces and weighed them. They were 9grams. Now granted it was on a small AUW plane of 8oz. But considering the holes cut that was very little difference.

So here is how you save real numbers in weight. Replace ply with balsa (where you can). Replace real ply with lite ply. Replace heavy balsa with lighter. Thick balsa with thinner stuff. Replace doublers with balsa, and use smaller doublers.

Use lighter batteries, motors, spinners, props, servos and receivers. That makes a huge difference.

Use smaller wire or CF landing gear. Use light wheels. Keep the pushrods and likages short and light. You can use CF here too.

Use Epoxy sparingly, it is OK to use only on the firewall. CA for everything else. Very sparing on glue. Tight joints and tiny amounts of glue are good.

Use light covering.

Think big stuff, not holes in balsa.

[flypaper 2]

Only three places need strength. Firewall, landing gear mount and wing saddle. Build the rest as light as you possiby can.

[Oldpilot]

COVER with Oracover Lite or Hobby-Lobbys Polycover. Much lighter than other normal films.

[FinnFlyer]

I don't know if this is practical or even on topic, but this looks to be the appropriate place to post such an idea.

I have thought about different ways of lightening an airplane. This is one.

Has anyone ever considered using some sort of Helium ballast built into any/all voids? If you get the ballast to acheive positive lift with whatever substance you make the bladder with, wouldn't it lighten an airplane?

It probably wouldn't work with an ARF, but integrating into a kit should be possible.

I'm curious to hear feedback, let me know what you think.

[rcers]

If you get the ballast to acheive positive lift with whatever substance you make the bladder with, wouldn't it lighten an airplane?
I think the issue would be the material required for an air-tight seal throghout the entire plane would weigh more than the <1oz of lift provided.

Mike

[FinnFlyer]

I wasn't thinking of sealing the airplane. More like installing very thin skinned balloons, connected by a small tube to one another, in between the wing ribs on a balsa kit.
In fact you would not want the plane sealed tight. It would need to release air when helium is pumped in to inflate said bladders.
The helium would leak out over time so it would be a good idea to be able to refill such a system.
I just used the dead space in between wing ribs as an example, they could go anywhere. But the wings are on the C.G., so that is another thing to consider.

[rcers]

Yep but the bladders would add more weight than the helium would displace (I think). Hydrogen might displace the weight of the bladders, but I really don't know if it would do more than an 1oz.

[Vinman]

Lots of great info guys. But I'm with rcers on the helium. The weight of the bladders would be more then the left provided.

[clipper]

the gas would be gone in a short time and you would be left with the empty bladders. sorry to deflate your bubble.

[goplug]

I sometimes (laminate several layers) cross grain balsa when replacing plywood. It makes it stronger and lighter.

[FinnFlyer]

Just brainstorming everyone. It may not be practical, but it was a thought out of the "box".:D

[Dereck]

Any body have any other tips to lighten a plane? I'm working on a Top Flite Elder 40. Got a AXI 2826/12 for it. That's what HL said to go with. I'm trying to lighten the plane a little. The back of the fuse is a open frame. But the rest is solid. Question is can I cut open holes in the sides,top and bottom of the fuse for less weight and how much can I cut without weaking the fuse? Any idea's? What do you do to lighten your planes? Vin

I lay the plan out, prop the cowl up on the drawing and put my own structure behind it!

Sometimes, I even make my model the same shape as theirs!

Sheet is mostly out, as is Liteply. Any areas of them can be replaced by open-frame structures made from stripwood. For Liteply sides, I'd use 1/4 x 1/8" spruce longerons with ditto sized balsa uprights, for example.

Ply doublers - 1/64" ply. it's there to provide a hard surface to glue to, and to tie all the other parts together, so any more material between its outer skins is just more weight.

Wings - 1/16" balsa will do for ribs, and I fly a 5.5lb fully aerobatic ship with 1/4 x 1/8" spruce mainspars.

The only ply you really need is 1/8" Birch ply - Liteply is not good for much really, apart from BARF and diecut part production. You don't need much of it, and in the above aerobatic model, I have a 700W Hacker on the front of a 1/8 ply firewall that's mostly holes.

Tailfeathers can always be thoughtfully lightened, though pay attention to selecting spar wood that is straight grained and stiff.

For good ideas, some of the old timer designs had really good structures - too many modern kits have structures designed for easy assembly, but mostly cheap production.

Your Elder could come out really light, especially if you're after a flight pattern like the model looks right doing.

There's an old saying from the control line aerobatic world - "it is easier to take one gram off 100 parts of a model than to try and take 100gram off a finished model"

Don't forget the covering - Monokote is one step lighter than tarpaulin!

Good luck

Dereck

[Sky Sharkster]

A suggestion; Try a pull-pull control system with kevlar thread for the rudder and elevator. Not only is it much lighter than nyrods but looks more realistic on a Vintage type model. Another option is balsa pushrods with thread-wrapped ends.
Make all your joints tight and use just enough glue to hold-em. Adhesive weigh builds up fast! Ron

[Dereck]

Good one Ron! I once build a Flair Magnatilla - sort of pseudo WW1 that looks little like a Focker Eindecker - and rigged the back end with closed loop to both rudder and the seperate elevators. Looked great with all those 6 wires vibrating in the propwash. Kevlar was a brilliant idea for closed loop controls - I had to use old control line stranded wire and I don't think the RX aerial really liked it in the midst of all that wire :(

If you use closed loop, treat them like the real thing - the wires started at the bottom of the control stick, went under the pilot's seat, and hence more or less in as straight a line as possible to the control horns. Following that idea often makes it real easy to do, though you can place the servos aft of the 'pilot's seat' position.

If you want a real good lightweight pilot bust who looks the part, "Pete's Pilots" in England will ship over here and do a great job. Most of my models are flown by "Pete's" I think he has a website now, which is good for him - try googling him.

If you want to save some more, stay off the Monokote. Fibrafilm / Micafilm is far lighter, stiffens up the open frames well but needs determination to apply. If you have to go with conventional heatshrink plastic, English "Solarfilm" is still the lightest outside of Microlite/SoLite - the latter is possibly a tad too light for a model this size. I've used it on a 550 square inch aerobatic just fine though.

D

[ForestCam]

I don't know if this is practical or even on topic, but this looks to be the appropriate place to post such an idea.

I have thought about different ways of lightening an airplane. This is one.

Has anyone ever considered using some sort of Helium ballast built into any/all voids? If you get the ballast to acheive positive lift with whatever substance you make the bladder with, wouldn't it lighten an airplane?

It probably wouldn't work with an ARF, but integrating into a kit should be possible.

I'm curious to hear feedback, let me know what you think.

You could have one big bladder, do away with the wings and fuse. (that'd save a LOT of weight right there) put a couple of motors on the sides and a gondola on the bottom for the radio gear.
:p

[Rugar]

You could always use Lighter fluid. :D

[50+AirYears]

Don't forget sandpaper and elbow grease!