Built Up -> Sheeted -> Molded

[rrowley]

I currently have planes with built up type wings, some call them gas bags, they don't penetrate real well into the wind, but fly fine.

Is the next step a foam core, wood sheeted wing type of plane? I assume that these planes have a more modern airfoil and are able to hold it more accurately than a build up wing. The advantage that I see to these planes are that they don't cost quite as much as ones that are fully molded.

Then you have the fully molded sailplane, I guess from the price that these are the state of the art in modern sailplanes, with the best performance of any of the planes.

I guess that I have 3 questions;

1. Have I got the progression correct; as my skills improve would you would expect to move through all three of these types of planes?

2. Is the foam core, wood sheeted type of plane necessary to the process? I guess that it allows you learn full pedal launches and flying faster without putting an extremely expensive plane in the air, just a moderately expensive one.

3. What are the disadvantages to the sheeted wing type plane. Is the performance of a fully molded plane that much greater than a sheeted wing plane?


Just trying to figure out the classes of planes.

Thanks

[schrederman]

Not too many folks sheeting wings, these days. The next step in my progression is foam wings with fiberglass skins that are molded in vacuum bags, I have one that was done by Fred Sage, and it flys great!!! I am going to do some of this type of construction soon. I will tell you that whatever you are comfortable with or like, is the thing to do. It's a hobby. Think outside the box a bit and you might just be the next guy to come up with a really new construction method. It happens...keep us posted. If you decide to go the vacuum bag route, there are lots of web sites with pictures and instructions. The molded stuff is expensive. If you have lots of disposable income...enjoy. They come ready to install the radio.

Jack Womack

Real men scratch build...or scratch and build as Bill Grenoble says...:D

[Masterpiece]

There are a few more types of wing types. You could add built up wings with molded carbon D boxes and carbon capped ribs. A bit fancy but are found on a couple of planes such as the Omega 3 / Highlight Extreme, Hybrid and Graphites used in F3J for added lightness and stiffness. This would lie between sheeted wings and fully composite molded wings, but closer to molded wings if not compatible with molded.

Another wing type would be lazer wings made with blue foam ribs and sheeted D box and trailing edge. This would come in close to the built up wings. Though I have been told that they are lighter than built up.

A great read for anybody looking at foam wings is "Building RC foam models" (or something like that) by Nexus books. You can get it at most hobby shops and it has something for everybody. I have made plenty of foam wings in the past but I have learnt some new thing already from this book. I'm going to be making some pylon wings soon so that is why I am reading it.

Later,
Glen

[Jack Hyde]

How are you launching?
Are you flying contests or just for fun (like me)?
A balsa wing with sheeting over the ribs from the LE back about 1/3 of the chord then covered with Monocote will fly the about the same as a molded wing of the same airfoil, weight , rigidity. The airfoil on the molded wing will more closely fit the design airfoil and will maybe be stronger, less prone to damage such as punctures. It is difficult to make a balsa wing with ailerons and flaps that is as slick, light and strong as a molded wing.
A foam wing covered with glass/kevlar/carbon cloth is nearly as accurate as a molded wing and is competitive in strength, weight, ruggedness and usually is less expensive. I like them because they are very tough and I love ailerons and flaps.
If you are launching with a histart at the nearby soccer field and flying a Gentle Lady in wind you can go to a balsa wing plane with a faster airfoil and be happy. If you are flying 3 meter full house planes in contests and getting beat by 5 pts by a guy with a $2000 moldy every month you may want a moldy (not necessarily need one, you could try practicing instead).
As with most things the more you pay the less benefit per $. At the high end you have to be looking for small benefits that are worth the money to you - winning contests.

[leverick]

I'm in the same boat as RRowley on this one. I've logged many hours over the last year on my 2 meter and DLG RES ships and I'm looking for more in my next ship in terms of performance be it bagged/sheeted/ or molded.

BACKGROUND

I started RC sailplane flying in early 02 in Phoenix AZ hooking up with an outstanding club (www.casl.net) home to many experienced, dedicated and helpful pilots. I had a very accelerated learning curve flying with the help of the club members supplimented by 10 years of hang gliding experience. RC sailplane flying gives me the "fix" I have always craved , but with my feet on the ground and without the major time commitment that hang gliding requires.

We now live on a remote ranch in Northern New Mexico with awesome thermal, slope flying conditions available almost daily. If its not a good convection day then the wind is blowing from the west and I have a 1000 ft westerly facing ridge I hi start to from the bottom about 5 minutes from the house. In addition our house sits on top of a 100 foot north facing ridge that allows me to step outside and toss the DLG when the wind is from the north and ridge soar to my hearts content while sitting on my back porch. Long story short, I'm blessed to get lots of big air with no hassles at all other then laying out the hi start on good calm convective days or walking out the door with the DLG.

Summary

I'm limited here in that I need a BIGGER GLIDER that I can see from greater distance and with better performace to allow me to range around the valley I fly in, HOWEVER it needs to be accomidating to hi-starting. The 3 meter molded ships are ok but I don't need to be competitive since I don't compete. Being a sport flyer, its hard to justify the big dollars. The ideal ship for me is a bagged/sheeted wing 120 inch or better full house ship thats in the 40- 80 oz. that I can Hi- Start AND is forgiving and rugged enough to learn full house flying on. I would like to inquire for suggestions on larger bagged/sheeted wing ships that are moderatly priced.

Thanks, Leverick

[Ollie]

CNC molded wings do not necessarily guarantee the best performance. Dr. Mark Drela has designed some very high performance airfoils for built up construction. The AG34 thru AG37 airfoils can be guilt using ribs, spars and partial sheeting and then film covered without any sag between the ribs.

Four things are required for high performance: Airfoils designed for the wing chord and airspeed. Wing planforms, twist and airfoil blending for an elliptical lift distribution. Accurate profiles. Structures that are strong and stiff enough. Dr. Drela's designs have proved that CNC molded technology isn't the only way. See:
http://www.charlesriverrc.org/articles.htm

[Jack Hyde]

Leverick,
One plane that fits your wants is the Mantis - 3m, 60 ozs, very strong and rugged. At $450 its one of the least expensive top quality full house planes. I have been flying them for 3 years and can't seem to wreck it and its been thru lots of big crashes.
I lived at Ojo Caliente, NM for 10 yrs. Know where that is?

[rrowley]

I think that this is very good discussion of the topic, here are some more facts:

Currently I use a big hi-start (NSP Pinnacle L) that I think could launch most of the models we have been talking about. We also have a winch at the sod farm but I haven't used it yet. I would like to compete at the club level.

Here are a couple of planes that we could compare, both are from NSP and I have other examples that we could discuss. Both have the same airfoil (SD7037), about the same wingspan (120-121) and about the same weight (68 - 65). But they are $200 different in price.

They are the Saphire ($389) and the Victory C ($595).

How much different would the performance be? Would it be half again better, I wouldn't think so.

Would something in the Saphire class be the next step? So that if (when) an accident occurs I am learning on a less expensive ship. Save the good one for another couple of seasons when I get better?

Thanks

Rod

[Ollie]

Who wins contests is very, very seldom a matter of what the winners are flying. Here are the things that matter the most in the order of importance:

1. Landing practise.
2. Landing practise.
3. Landing practise.
4. Knowing where the lift is before launching.
5. A helpful timer.
6. Thermalling skill.
7. Adjusting skill (fine tuning).
8. Familiarity with the plane's handling.
.
.
.
.
.
n. Which technology and design.

The best pilots can spot the average pilot the height of a towering zoom and still beat them. The best pilots can fly a Gentle Lady against the average pilot flying the most expensive all molded ship in 15 MPH winds and still beat the average pilot. The best pilots can sky out from weak lift encountered in the landing pattern that the average pilot flies through without even recognizing the lift.

So, invest in your skills and don't obsess on equipment.

[RCheroske]

rrowley, two things determine what level plane to get. Your pocket book and wing loading.

Generally the better a pilot you are, the heavier the sailplane you can fly. ( as per wing loading )

The more expensive planes are built very light and very stiff so they are very reponsive to lift and control inputs.

So comparing the Victory and the Sapphire side by side on paper, I see that the Victory is lighter with a lighter wingloading and lighter wings so to me that says that the Victory will be more responsive to lift and control inputs than the Sapphire.

(That also means that for some people, the Sapphire will more more stable, easier to fly and not as twitchy as the Victory)

[leverick]

Good, feedback on the "what ingredients do you need for contests" The limited competetion I was exposed to, it was indeed landing skills and knowing where to find lift that seperated the really good pilots from the others. Type of planes really didn't weigh in that heavy.

Would anyone have any suggestions on 100-120 inch foam winged gliders similar to the searcher at www.jancomodels.com?

[Ollie]

In my opinion, you will be hard pressed to find another foam winged model with the friendly handling and performance of the Searcher RES at such a reasonably low price.

There is the Sierra but it lacks the spiral stability you will probably want. By the time you add the cost of three more micro servos it will cost as much as the Searcher.

There is the Thermic 2.5 meter RES. It may be the best buy at roughly half the cost of the Searcher RES. I seriously doubt that its wing is as strong as the Searcher's but, I haven't tested them to prove my supposition.

The Art Hobby High Aspect 3.1 meter sailplane is new and I am not even sure if it is available. It is advertised at $369. It looks like it will be very high performance. If you want to take a chance by being one of the first to try it, then you might get a great value. It is full house and there will be the cost of additional servos to the tune of about $100. It will require more concentration and skill to fly than the Searcher.

[Masterpiece]

Hi,

I think that Ollie said it all. I have a JK Thermic 2.5m and though I haven't flown it yet I can ensure you that it is a great plane for the cost. Ollie is right about the Thermic not being as strong as the Searcher. The wing joiners are 4mm carbon rods and this shows that this plane is really for light thermal work and NOT Speed runs or F3F turn (ha ha :p definately NOT). The wing panels are well strong enough though, and VERY LIGHT. It should be a great plane to fly .......... soon. As the instruction say "for hi starts but not for winch work"

BTW .... my Thermic is set up with flaps and ailerons as well as the V tail ruddervators. I probably don't need the flaps BUT then I want a plane I can land at my feet everytime and on command.

Later,
Glen

[davidleitch]

Interesting discussion.

I would have guessed that thermalling skill was closer to landing practices than Ollie shows, but its encouraging to see landing given such a high priority since it is the easiest thing to practice.

By and large moldies have one advantage over built up planes, and that is strength. You won't see too many built up planes in hotliner style aerobatics or at dynamic soaring contests.

Its also hard to beat an "in the mold" paint job but that doesn't have much impact on performance.

later
dave

[R. Carver]

Originally posted by davidleitch
Interesting discussion.

I would have guessed that thermalling skill was closer to landing practices than Ollie shows, but its encouraging to see landing given such a high priority since it is the easiest thing to practice.

By and large moldies have one advantage over built up planes, and that is strength. You won't see too many built up planes in hotliner style aerobatics or at dynamic soaring contests.

Its also hard to beat an "in the mold" paint job but that doesn't have much impact on performance.

later
dave

You can't beat the prefab of a moldie, either. Drop in your servos and RX, program your TX and fly!