efish

My Feedback: (5)

Hi Everyone, just built an LST and its a load of fun. I know there's a build thread, but it's really long and I'm not sure if this post should go there.

Anyhow, my question relates to the AUW weight of the plane. I think the indicative weights were from about 20 to 28 oz. Maidened mine yesterday with an Enya 0.09 with a AUW (dry weight) of about 15.5 oz. Way too much engine! Swapped out the engine last night for an 0.061 Big Mig. Just got back from the field and the AUW with a half tank of fuel is just under 14 oz. Performance was expectedly hot - did most of my mild test flying with the engine at idle and it defintiely will need plenty of down thrust. Will probably just put a Wasp in since its still overpowered. I've hovered other planes about this weight with the Big Mig before!

I built the plane with the wood sizes indicated, added doublers where I thought necessary and used epoxy on critical joints. Some things that might have lightened the plane: 1. converted the plane to a tail dragger with steerable tail wheel 2. used a spectra pull-pull system 3. used a CF linkage to the the torque rods 4. only put in one set of sheer webs 5. Thanks to a photocopier glitch, my fuselgae is about an inch shorter than what it should be.

But I'm running flaperons (probably unnecessary), a heavish receiver and 8g servos (as opposed to my usual 6g ones). Wood was the cheapest I could scrounge lying around the LHS (think it's at least 10 yrs old). Not exceptiuonally heavy but definitely not contest grade. Construction seems more than adequate and I can see the plane doing some cartwheels on the ground with little or no damage.

I thought the scale was off, but I've checked it with a commercially packed bag of flour.

My building skills are rudimentary at best, so I'm just trying to understand what I've done (or not done!)

Thanks.

skaliwag

My Feedback: (1)

We should all have this weight "problem".

ptulmer

My Feedback: (5)

It would weigh more and fly better if you put covering on it...


ok, I can see you used something clear, doculam or similar? That will save LOADS of weight over $kote. Personally, I think you just have the right attitude about building 1/2a. It's not like most anything else. Everything extra you put on them reduces performance measurably. With a little attention to the weights of equipment, alot of fat can be shed!

combatpigg

My Feedback: (3)

That's a nice looking plane. I don't see how a plane that size could end up weighing much more than a pound, unless you were to use full size radio gear.

efish

My Feedback: (5)

Hey, don't get me wrong, - I'm real happy it's light.

Keeps the stall speed down so its perfect for a trainer. Just went for another couple of flights and it flies about as slow as the engine will let it! Right now, even with the engine on idle and 5% nitro, it's still coming in a little quick for my girlfriend who's moving on from a slowstick.

PT, yes, that's some doculam equivalent. No one's heard of doculam locally, but this is the same sort of stuff, only Korean made. Took weeks to track down, but now I've got a lifetime supply!

Was just wondering why I came in at about half the targetted weight?!

combatpigg

My Feedback: (3)

If you're using all modern 1/2A sized gear, the only way to make a plane that size come out at 28 ozs is to TIG WELD it out of aluminum round stock, or build it out of 1/16" plywood and spruce, then cover it with silk and give it several dunkings in a vat of epoxy paint

BMatthews

It sounds like much of your gear and stuff is quite light. Also it's not uncommon to add 2 oz worth of weight to a model of this sort if you use Monokote. That film you found may well be far lighter.

Also I'd bet that your wood is lighter than you think by the sounds of it.

efish

My Feedback: (5)

Thanks guys. Perhaps the cheapo old balsa I found is lighter than I thought! The Doculam is definitely great for keeping weight down. I was using World Models lite covering before this (not the lightest, but the cheapest) but I the Doculam is even lighter.

While I think I still prefer flying something quicker and more responsive such as the DNU, the LST makes for a very pleasant change of pace. With the right prop, it just sort of floats around gently, plus its really cool to be able to look up and see through the ribs! Based on my experiences with the GWS estarter, it should be pretty competent with basic aerobatics too. Power is certainly no issue.

Swapped out the biggish receiver for a lighter electron 6 I had lying around; could go lighter, but really don't see a need to. A 1 oz tank gives me about a 10 minute (trainer type) flight time.

Will put it to its intended use next weekend - a buddy boxed trainer.

Bipe Flyer

The 20oz weight I put on the plan was to accommodate a something like a Hitec 555 flight pack, which uses 17g servos and a 250mAh NiCad pack, Monokote or Ultracote etc. Some of the guys used full sized radio gear, which can add more than half a pound, as well as aluminum gear. Remember too, that this has a 40" span and is larger than most 1/2A planes.

I think you did very well to come out at the weight that you did. Good wood, not beefing up the design, making it a tail dragger, light covering, micro radio gear and park flyer wheels all contribute to yours being lighter than some of the other builds. Something else that is often overlooked is that pushrods, especially nyrod style, are very heavy and add weight where you least want it - at the tail - often requiring lead to be added to the nose. The pull-pull setup you are using on both the elevator and rudder is a real weight saver.