MIXMASTER

My Feedback: (15)

I would like the opinion of 3-D'ers who huck it DOD and have flown many glow size and giant scale. Are giant scale planes (50cc & up) more stable for DOD 3-D than glow size? I'm particularly interested in how the giants seem to stay put in hovers/harriers DOD in more wind than a glow could take. I can do all out DOD 3-D with glows when its 5-10MPH winds or less, hovering tail touches, TR'ing tail touches, drag the tail harriers. One thing I would like to be able to do is hold my planes in one area when hovering but when the winds are above 5-10, the planes just drift away as soon as the nose is up in a hover, even harriers become a lot more "rocky" in this much wind. A couple of my giant scale friends (specially the 33% & up) hold their planes in one location while hovering in wind conditions that I cannot do the same with glows. I know one technique used is is holding some up-elevator and keeping the plane tilted slightly into the wind, I've tried this but it didnt work for me, is there a way to make smaller planes hold or is it a must to have giant scale?

Bob_S

It is all about scale. 10 mph wind has much less effect on a 35% plane than it does on a 60 size glow plane. Works the same in 3D as it does in precision; the bigger the less effect the wind has.

MIXMASTER

My Feedback: (15)

I think I agree with you, I just did some basic math: .60 size plane with 65 " wing and 7 lbs vs. 35% with 110" wing and 25 lbs. The 35% has almost 4 times the mass or weight but less than 2X the surface area. Does that make sense? I always thought a giant scale would be equally affected by the wind because of the much larger surface area, but when you consider the weight, it has much more mass per square inch. again, does that sound right?

Bob_S

Sounds right to me. Fly a 10 oz foamie in 20 mph for a good example of scale. No compare that to a full scale plane where 20 mph is nothing.

GmanBill

My Feedback: (10)

Also the bigger they are the less twitchy, I love my big stuff on the deck, they also do everything much more smooth and slow. If you had a 4 minute routine with a 50cc size plane that same routine would be about 12 minutes with a 40% plane.

MIXMASTER

My Feedback: (15)

I've never heard it explained that way before, but it gives me a good perception of it. I remember reading an article that states the wing loading of a giant scale is higher than smaller planes but they still float(if not too heavy) like a foamy. The higher wing loading and higher mass/per/sq. inch of surface area seems to make sense, but I dont understand how the wing loading can be higher & still fly "light" like they do.

JoeAirPort

My Feedback: (41)

Part of your issue with stationary hovers is proper stick controls and the other part is instability of smaller planes. The smaller planes are very hard to 3D because they get so twitchy in high alpha. In fact the small planes are harder to do anything IMO. That's why I am at 50cc right now. The bigger I went the better they flew. Also don't underestimate your buddys' flying skills. Holding a stationary hover in a wind takes good stick control. I actually don't do much of that myself. I prefer to let the thing torque roll accross the field. It looks much cooler and is very fun to do. As far as glow, I got out of it since the 80"+ inch planes are all gas. I don't like anything smaller so I don't have any glow right now.

The glow engine is kind of a pain for 3D from my experience. I always had engine issues since I was always pushing them and heating them up (overheating Moki's). Also all the glow planes were designed for the fuel tank in the nose, I can't stand having all that weight in the nose changing trims as it gets consumed. So I would mount the tanks on CG, which is never very easy, then I would need fuel reg's or pumps to keep the engine from going lean in uplines. So I was always always fighting the lack fuel delievery systems in glow engines. Lastly, even with the tank in the nose, the engine would still change mixture as the tank emptied out (went lean). Then you would have to over richen the engine with the tank full to get it to stay running near the end of the flight. With gas all these issues are gone. Not to mention I go to the gas station and spend less than $2.00 to fly the entire weekend. If I run out at the field, I go to the gas station 2 minutes away. I got gas, and I'm happy.

sukhoi26mx

My Feedback: (1)

The reason is cubic loading. Wing loading is an effective tool to predict flight performance and compare models in a very small window of weight/size, but when comparing airplanes of vastly different sizes, we need to normalize the numbers and cubic loading calculators are the tool for that.

For more basic understanding, consider a one inch cube. Let's assume it has a mass of 1 oz., and obviously has an area of a square inch (per side), and a volume of 1 cubic inch. As we increase its size to 2x2 (doubling its length as we might with an airplanes wingspan) the area (per side) of that 2x2x2 cube increases to 4 sq.in., but its volume increases to 8 cubic inches, and its mass to 8 oz (eight of those square cubes.) Again doubling the cube side length to 4 inches increases the area to 16 square inches, but its volume to 64 cubic inches, and thus the mass is 64 ounces. So the area goes up by the square, while the mass increases by the cube.

The same thing happens when we scale airplanes. For instance, it is not uncommon for a giant-scale airplane to have a wing loading (which is weight in ounces divided by the wing area in square foot) of 30+ ounces per square feet. A similar "feeling" foamy will rarely have a wing loading of more than 3-4 oz./sq.ft. The difference can be found in the larger airplanes ability to carry weight while retaining the same "feel", and drives back to the point that weight (and the models ability to carry weight) increases cubically while area increases by the square when scaling models.

So, the solution is to normalize the numbers taking into account the larger aircrafts ability to carry a higher wing loading (as a result of the scaling stuff above), so we can accurately compare the flying performance of a wide variety of different sized models. The common method for that is to first raise the wing area in square feet to the 1.5 power. That new number is divided into the weight in ounces, and the result is the cubic loading. We've been using this method for years, and it seems to be reasonably accurate when scaling all sizes of model airplanes.

For simplicity, here's a calculator I like to use.

http://www.ef-uk.net/data/wcl.htm

Hope that helps and that I didn't muddy the waters too much!

Scott

MIXMASTER

My Feedback: (15)

I can see there are different techniques to hovering, I tend to let it TR and have learned to deal with that. Only when its light winds I can stop the TR with aileron input and hover stationary, well almost, it still moves a bit but much less than in windy conditions and gives me more time to "tail touch". My friends with the giants mainly hold non-TR hovers and can hold steady on days when I get pushed away pretty fast. I can start a hover low , but its gone too far away to see well in a few seconds. I miss out on some of the fun those windier days but I feel that my skills are equal to my friends, I do everything they do, but have to be patient & wait for a better window. I don't think anything less of their ability just because a 40% can take more wind, they didnt just magically start 3-D'ing simply because they could afford one, they were good flyers before that. I'm learning a lot from this thread about why the giants handle better in more wind,I do understand that you still have to be a very good flyer with major "cahoonies" to huck it DOD! Talk about PUCKER!!

MIXMASTER

My Feedback: (15)

That's getting to a level where I might hurt myself thinking about it! I want to know just enough to have fun! Actually, I think I do understand it basically,I think my explanation(simple as it is) brings it down to "laymens" terms. Its mass and sq. inches(area).
Even though a 40% has a larger area for the wind to push against(in 3-D flight)it also has a mass that is much more in relation to its area than a smaller plane. The air molecule size being fixed is another mind bender for me, not that it's always the same size, its how it affects various size aircraft. The Discovery Channel had a show that made it easier to understand, they were developing "nano" size surveillence aircraft and found that it was like flying in syrup or under water due to the relationship of size vs. air molecules.

MikeEast

My Feedback: (3)

To answer your question, generally speaking if the design is good the planes are MUCH easier to fly, especially 3D as they get larger.

A 50CC plane is much easier to 3D than a say SHowtime and a 35% plane is 10 times easier than a 50CC plane, except for the Extreme Flight 50CC Yak. It flies like a 35% plane. Then you take another leap when you go 40%.

The bottom line in laymans terms is that the larger the plane the more time you feel like you have. The smaller planes react much more quickly than the larger ones. If you built 2 planes one with a say 68" wing and an identical replica that is scaled up exactly in every way, the larger plane is going to "feel" better. It going to feel smoother, its going to feel like you have more time. Youa re going to feel that it responds to your inputs and actually does what you ask it to do where a smaller plane is twitchy and a little unpredictable.

I go back and forth up and down all the time and no matter what plane I fly, it is always a relief to get back to a well built 35% plane. I feel like I am not fighting the plane and I can just relax and do my thing without fighting the plane.

MIXMASTER

My Feedback: (15)

After a weekend of camping & flying it reinforces all the above posts, all day my friends were DOD & tail touching with their 35 & 40%, I tried a couple hovers, started a few feet up, they said my plane was gone in a second after the nose went up, I hang with it, torque rolling & moving at 10-15 MPH away, but its not long before the fence comes up or its just too far to do it safely. In the evening around sunset, it calmed down and I kept it below 6" for minutes it seemed, even they said it was cool, did 3-4 tail touches while TR'ing, I love that stuff! The next day (Monday-holiday!) it was windy again but I tried to keep it "hangin" into the wind, it seemed to work best in HA KE, I could hold in one place better that way than facing the wind straight up. But the same thing always happens when I go straight up,its by-by in a second. I had my DVD cam and someone else had a cassette cam, hope to get copies on DVD of my flying, I always film my friends but never seem to get my flying captured.
Mike East: thanks again for the tip about Windows Movie Maker, been using it ever since, have edited several videos now & enjoy using it. Now if I could figure out how to make them small enough to e-mail, they're at least 10MB or more even after extensive cutting. I wanted to send then to RCU & U-Tube but my my browsers will not send files that large.

pizza

My Feedback: (24)

I have flown and own everything from foamies to over 40% gas. best 3dr for me is my diablotin super with os46 on a cf pipe has 1.5m wing oversize controls and weighs 4lb. all other so called 3d glow 40 -120 size I have tried are the most difficult to 3d. foamies are too sensitive, big stuff is almost as easy but too expensive and dangerous for spectators = not enjoyable, not suitable for practice or everyday tail touching.

MIXMASTER

My Feedback: (15)

I hear you on that, the $$ puts them out of my reach and I think they are more dangerous when you look at just 3-D flying. "Pucker factor" is relative to your bank account too,(safety aside). The Diabolitin is only 4lbs with almost 60" wing???? I would think it would get blown away in hovers in almost any wind at all?

pizza

My Feedback: (24)

yes it does get bounced around but not like you think - most 3d stuff you get a little wind and its over - the Diablotin is the biggest floater you will ever fly but is very easy to control in wind. many times over the years I have shown up at a fun fly somewhere and it was blowin 30+ with 40 pilots and nothin in the air - I will launch it by hand down wind so it will drift up and away then land verticle at 1/2 throttle pin it to the ground walk over and pick it up. flying in high wind is most enjoyable for me you just switch into that mode and perform manuvers like rolling harriers down the runway slow then fly backwards back down the runway while rolling. In my opinion if you cannot be comfortable and take some chances you won't advance in skill, the Diablotin is very forgiving, predictable and when you crash is easy to repair - is made entirely from 4lb balsa - the covering keeps everything in place - is stiff yet will flex some to minimize damage. The Diablotin costs about $100 more than other 3d arf kits because of expensive balsa, but these other lazer cut ply kits weigh twice as much and fly like a brick. I test fly all popular 3d planes that show up at our field - u can do's, hangtime, funtana, etc they scare the hell out of me not because of poor design but power to weight to size is way out of wack for safe down on the deck stuff. really don't understand why this all balsa design has not caught on when everything else has been tried and tested. people keep showing up week after week with these lazer cut 3d arfs and stuff them into big round can - just like the big stuff one small dork and they expload. I see many young promissing kids show up after a few months with a big gas plane because they are told the bigger the better - it is easy with the big one and this is true somewhat but all it takes is for engine to quit just once they loose their life savings and you never see them again - tragic.

MIXMASTER

My Feedback: (15)

You mean a vertical(hover like) landing in 30+??!! It would be moving at 30MPH. I know what you mean about just having fun on windy days, I used to hand launch my 5lb Su-Do-Khoi into the worst wind and still have fun, I needed spoilerons to get her down though, in that kind of wind it would not come down. Seems like since I got into 3-D hard core, I always want light wind conditions so I can do it all right in front of me. Once the plane is floating on thrust, it becomes more like a kite or balloon, doesnt take much wind to move it. Thats why I envy the giant scale planes, they dont seem to get pushed around nearly as much.

yakman

Two planes hovering. One twice the size of the other. Both take a wind bump on the tail and both their tails move 5". Looking from vertical, the smaller plane is now at a greater angle than the big plane before they got bumped. Therefore it needs more correction and is more likely to move from its position. This can be applied to high alpha precision flying etc etc.

Just another factor to consider.

Big planes are much smoother.

MIXMASTER

My Feedback: (15)

Yep, that makes sense too. From all the previous posts, this one makes it pretty clear too: As the size doubles in area, the mass is cubed. That explains why you dont see full scales hovering DOD,there is a point where you lose that thrust/weight advantage that certain giant scale gassers have. Another way of looking at is you dont see many single engine small aricraft in the air when its very windy, but the major airliners are up there no matter what. The wind affects them both, but the small aircraft passengers would be tossed around the cabin while the commercial passenger wouldnt even be aware the pilot has made a correction.

MIXMASTER

My Feedback: (15)

I have 16 flights on the Double Vision & I'm beginning to realize a few things,yes the difference is in favor of the larger planes, it takes a lot less correction input to 3-D this beautiful flying bipe, I feel like I can relax more and just do the maneuvers. It harriers effortlessly, slow down, pull up & its in a harrier, no rocking, no struggle to keep it level! The TR's feels about the same, it rolls pretty fast but I'm used to that , one thing I'm not used to is having the aileron authority to do a reverse TR, I actually did one whole roll with right aileron-amazing! I also went back to school & tried some stationary hovering while leaning into the wind, not with the DV, with an old beat up U Can Do on a more windy day. I found out that once you get into the near vertical attitude, keeping it there is not that hard to do, I was holding the Do in place in a 10-15 head wind, it did move around some, but nothing like when its vertical,you dont have to deal with the TR which is harder IMO. Just concentrate on keeping the wings level and work the elevator & throttle to maintain the "lean". I'm having fun now!!!!

JoeAirPort

My Feedback: (41)

You are flying one of the best 3D ARF's out there. Very good choice.

Try some harriers on that baby. It'll do everything well from what I've heard and seen on vid's.

MIXMASTER

My Feedback: (15)

Harriers are childs play with the DV, it locks in even at shallow angles & just stays put as I advance throttle, all the way to a hover, very cool, & the first plane I've had that doesnt yaw with throttle. The thing holds KE without rudder, maybe just a little but unbelievable KE performance. Cant wait for the DA50 to break in.