RES Vs. Full House.

[FairlyFaded]

Hello, i am thinking about building a thermal ship and have one fairly simple question. What are the advantages and disadvantages of RES ships in the 3m size (like the AVA). Coming from the dlg scene I had thought most large ships would be full house, but this seems to not be the case. Can one get by fine just with RES or should i go full house like the Supra? thanks!

michael

[Hostage-46]

It all depends on what you want to do. Are you into contests? What kind of conditions do you fly in? You can certainly "get by fine" with an RES Ship. I'm partial to my Ava, the EZ Bubble dancer, Topaz, Soprano are also popular.

The AVA has no real vices. It's a delight to fly, has an incredible speed range, launches and lands well. In my mind the only disadvantage is in the landing circle on a gusty day.

RES is a great way to get into a bigger model. Less hassle on setup, less cost, ... less is more!

[davidjensen]

They don't call it "Full House" for nothing. The extra control surfaces give the pilot more control.

[kablair]

If you are truly building a ship, then I would start with a RES - a Houston Hawk is best. If you absolutely insist on building a full-house ship, then I would start with a Genie.

I've built several woodie full house ships and, except for Fred China's Runaway, they have all suffered from being too heavy and imprecise. I'm sure some of that is due to my building skills, but there's just less forgiveness available in these.

On the other hand, if you're willing to make the plunge into composite construction, the Genie is an absoultely outstanding plane. I'm 3/4 of the way through my second one and I've already cut the cores for my 3rd one. However, as Harley has noted, this is not a floater butterfly so don't expect it to work like a Supra.

I guess I am making an unfair assumption that you are not already an accomplished builder - if you are, then the Supra will surely be a great plane. In fact, that will be the next full-house ship I tackle. But if you're just getting started, you'll find the incredibly detailed instructions and build logs for the Genie to be an outstanding learning experience that prepares you to take that next step.


If all this foam cutting, carbon layup, vacuum bagging stuff is more than you want to bite off, then a RES can not be beat. I love my Houston Hawk. It takes full pedal launches and 200' zooms (measured with my Zlog). I've worked thermals 40' off the ground during contests, and I've been able to work lift and still penetrate in 15 mph winds. I still haven't been able to get my Super AVA as high as my Hawk - the Hawk has gotten to 1823', the AVA has only gotten to 1754'. And for landing, the spoilers drop it quite effectively - very suprising how well they work when you compare their size to the AVA.

The Hawk literally falls together. Jack Womacks instructions and pictures here on RC Groups and on the Houston Hawks website tell you everything you need to build it. It is a very straightforward, no surprises build.


If you're looking for a fast and simple build to get started with, I can't think of anything better than a Houston Hawk. If you already have all the cutting and bagging equipment, then the Genie is a great first full-house plane.

You've probably noticed I also have an AVA; as great a plane as it is, and it is beautifully built and flies great - I still enjoy my Hawk better just because I built it myself.


Good luck on whatever you choose and let us know how you progress!
-Keith

[Andy W]

Nothing wrong with RES.. I too have an AVA (mine is electric) and it's the nicest sailplane I own. I am putting together a full-house Topaz as well..
..a

[rdeis]

The main difference is that full house airplanes can alter their airfoil to suit the conditions, RES airplanes can't.

That typicly gives full-house airplanes a wider speed range, and the size of the speed range (fast for penetration and searching, slow in the lift) is key to modern soaring.

But the new generation of large RES airplanes fly sooo well that it's probably more a matter of matching the airplane to your style and getting to know it unless you usually fly windy or turbulent air.

[ChuckA]

They don't call it "Full House" for nothing. The extra control surfaces give the pilot more control.

And more opportunity's to screw up. I find that, on the average, I can do as well with my RES as with my unlimited sailplanes as long as the landing task doesn't use tricky landing zones like Visalia. Flaps let me search more sky and trim for the available lift AS LONG AS I REMEMBER TO SET THE CORRECT FLAPS. But then flaps can actually hurt if mis-set. I don't do inverted flight or aerobatics with my sailplanes so the lack of ailerons doesn't hurt.

[FairlyFaded]

Thanks for all of the great opinions guys! Looks like i will go with RES-seeing as i dont really plan on putting my head to far into competitive flight right now. Why is it that full house is so much better for landing though? with my RE dlgs (no spoilers of course) i have no problem getting the glider back into my hand. Does it get much harder to control the larger ships during landing?

Kablair: thanks for the great post. I am going to be using full composite construction for what ever i end up building. I sort of skipped balsa construction and went right to foam and fg/carb/kev. etc. I do really love balsa planes, but thats not really were my area of expertise is. So now im thinking i will model my plane off of the AVA and the Hawk-only in foam and kevlar/carbon.

I have one more question about larger composite ships. With dlg's the use of carbon rods for spars is very common. They are both easy to install and ridiculously strong compared to carbon skins. However, i dont see this used for the large planes, instead they go with a large rectangular carbon cap. Why is this so? Is there any good reason for not using a number of rods instead of a thick cap? (after all rods would be far easier to tapper then a cap). thanks guys!

michael

[O.L. Adcock]

Michael, it's the 100+ pounds of stress in the center section on lauch. Solid round carbon rods big enough to take the load would weigh a ton. You are assuming DLG's are optimized when all the classes are stuck using what's available instead of what's best. As for the landings, speed is the problem. Glass/carbon skinned open class, you're looking at 7+ oz/sq/ft loading. Without 90 degree flaps it's not going to slow down like a DLG. An open class ship at 7 or so wing loading and 90 degree flaps, you can set them in your hand as light as a feather.....O.L.

[FairlyFaded]

solid carbon rods would actually weigh less then half as much as the equivalent normal carbon spar cap. Good carbon rods can do something like 250,000psi in compression were as most other normal (prepreg etc.) caps will be able to do 100k if your lucky.
heres info on carbon rods vs other things.
http://www.continuo.com/marske/ARTICLES/Carbon%20rods/carbon.htm
So in your opinion would you say a nice big spoiler like that on the ava would be enough then to handle landings? (Im sure it would seeing as so many RES gliders are out there :D )

The only problem i can see with using the carbon rods would be that you cant put a balsa center near the middle to handle the compression like you can with the supra design. I think i have a way to fix that though. thanks for the info O.L.

michael

[O.L. Adcock]

Yep, Michael, you are talking "good" carbon cpmpared to "bad"....I don't use the bad! :) I assumed you were talking solid carbon rods. Solid carbon is 2/3rds the mass of fiberglass and probably 10 times what balsa or ply shear would be with carbon caps making a structure much lighter for it's weight then solid carbon. Some might be using poor prepreg, but not all....O.L.

[O.L. Adcock]

Michael, That's a good link to what they are doing in full scale. The carbon rods typically available for us modelers may or may not be of that quality. My bet is most are not. Here is a link to the material I cap spars with: http://www.gordoncomposites.com/prodlamspecs.htm The numbers are comparable to those you quoted cause it is also a pultruded laminant. Much higher then any wet lay up or prepreg you'll see...O.L.

[kablair]

Michael,

I'm certainly not a designer, but I am an engineer and I suspect that cost and design may be why you don't see many planes with the same type of embedded carbon rods as in DLG's.

Without getting into a ton of detail, a 3m RES has a serious design constraint relative to DLG's - the wing almost always needs to come apart into 2 or 3 pieces. This means there has to be some type of joiner system at the spar. Either in the center (2 pc wing) or at the tip panels (3 pc wing).

For the 2 pc wing, the maximum load will be taken by the joiner rod since it's in the middle and it becomes the design constraint. Metal rods in K&S brass tubes are strong, durable, readily available, and economical. Embedded in a pool of epoxy, the load can be readily transferred to the spar system.

For the 3 pc wing there is another issue - for many aerodynamic reasons, the wing thickness decreases going out to the tips. If a carbon tube is used, which is necessarily of constant diameter that is sized based on the tip panel joiner, then the center of the wing will require additional support. Actually, regardless of the wing sectioning, a rod/tube needs to be a constant diamater in a changing thickness wing. With flat spar caps, the thickness can be adjusted through the shear webs.

But the real reason may be cost. The further away the load carrying material is from the neutral axis (midpoint of the wing height), the less of it that is needed. Flat spar caps maximize the load carrying ability for the material used. Round rod/tubes would have half their material near the neutral axis and not providing much to the load carrying capability. This could be inefficient from a cost standpoint....



Actually, I did look into doing just this with my latest Genie - that is until I faced the issues above; especially the cost! :eek:


I'll be real interested in what you come up with as a design. I like the composite planes too, but there don't seem to be many composite RES designs out there.



Oh, one last point regarding the RES vs. Open, the RES planes (and pilots) are figuring out that in some contest conditions, the low wing loading of a RES makes it the better plane even in the Open rounds. I've done it, and seen it.


-Keith

[markdrela]

solid carbon rods would actually weigh less then half as much as the equivalent normal carbon spar cap. Good carbon rods can do something like 250,000psi in compression were as most other normal (prepreg etc.) caps will be able to do 100k if your lucky. If the spar design is sound, with proper shear webs, etc, then the carbon sparcaps will need to be sized for stiffness, not for strength. So the max allowable stress of the sparcap material is mostly irrelevant. If you want to reduce spar weight, you'll need to go to high-modulus carbon.

BTW, both CST and ACP make tapered precured carbon strips which are very convenient for sparcaps --- certainly more convenient than dealing with bundles of individual rods.

[O.L. Adcock]

Keith, I agree 100%.....Hard to take out piloting skills when making choices as 2 meters have won open classes too! :) Doc, I agree......What many forget is you can use the best stuff in poor ways and vice versa....O.L.

[rdeis]

Does it get much harder to control the larger ships during landing?


I don't know that it's necessarily harder, but the RES and Full house approaches are very different, and using the wrong type of approach makes it really hard to hit the spot.

RES birds land more like full scale birds in that you set up a nice shallow, reasonably fast approach (to keep control authority up), and use the spoilers to kill altitude. They tend to touch down lightly and slide.

Full house airplanes tend to approach on a much steeper glideslope and slower speed. You fly the nose right straight in to the spot with all 3 control channels and it gently dorks with very little slide.

I'm much better at the former, so I land RES better, but there's a guy in the club here that puts his nose right in to the spot more often than not. Wow.

(And of course the guys that approach to shallow and fast and dork it really hard.. Ouch..)

[Andy W]

RES birds land more like full scale birds in that you set up a nice shallow, reasonably fast approach (to keep control authority up), and use the spoilers to kill altitude. They tend to touch down lightly and slide.

Full house airplanes tend to approach on a much steeper glideslope and slower speed. You fly the nose right straight in to the spot with all 3 control channels and it gently dorks with very little slide.


Approach speed depends on attitude more than whether it's RES or full-house. I have my AVA set with elevator compensation so that the nose rises as spoiler is dialed in. Full spoiler causes the model to come to a screeching halt, I swear you could hand-catch it, it slows so much. Obviously, you're not hitting that much spoiler when you're a couple of feet off the deck, but you get the idea - you can slow an RES model just as well as full-house.

Again, I have both, and each works in different situations. I prefer full-house when it's windy..
..a

[OVSS Boss]

It is all a control issue and how much you want. Both aircraft take energy management to fly good consistent landing patterns, the RES to a greater degree. The unlimited ship does have the ability to get draggy with out loosing lift, the RES is killing lift with every increment of spoiler added. The Ava's, Danny's, and Soprano's all have very large spoilers and can be almost over effective, as Andy said, your stab compensation has to set precisely cause if not they can really loose attitude quick.

They both are fun, and there are days that RES ships can be lethal in the right hands. In many cases, they fly so softly that many guys get the float syndrome going, i.e. it will stay up for ever all I have to do is fly slow. Well, they all come down with out air, they just look slower doing it. Even an Ava needs to search and be flown to be effective.

Marc

[AMBeck]

Back to the carbon rods, one thing that big, high aspect ratio wings need is torsional stiffness. Carbon rods aren't very good at keeping a wing from twisting. You need the wing skins to take that load. With small, low aspect ratio wings, this isn't as much of a problem.

[ChuckA]

Full house airplanes tend to approach on a much steeper glideslope and slower speed. You fly the nose right straight in to the spot with all 3 control channels and it gently dorks with very little slide.


Gentle dork? Never seen one. :)

[rdeis]

Most dorks seem to be recovery from a mistake-- but this guy touches down at what looks like 45* with scarcely a "bonk". It's amazing...

Approach speed depends on attitude more than whether it's RES or full-house.

Absolutely-- what I meant was that the most reliable landing patterns tend to be different. Since the full house airplanes can dive steeply and slowly, and generally have more control authority, they can approach in a steep slow aproach. RES has less control authority so it prefers to be faster, and with large spoilers it will fall flat out of the sky even in on a quick, shallow approach.

[FairlyFaded]

Thanks for all of the information guys! So, unfortunately, i think im going to have to give up on the carbon rods and go with the tried and true caps. Here are a few problems i see with the rods.

1) This is for sure the biggest, that being the joining issue. The only way i can think of making a joiner would require the spars strength to be bunched up (like that in a cap), this makes the use of spaced out rods not so great.

2) The stretch factor, i dont want a wing that can bend into a O.

3) One has to use small rods in order to not have to worry about shear (when gluing them to foam, you could however wrap the rods in kevlar with a flap on one side to make their surface area greater), many small rods would be a pain.

It is really to bad that the rods wont work seeing as how strong they are, but maybe on a later plane ill try.

thanks for the help guys.