DS FLING?

[felix]

Taking the plunge and going to put together a mouldie for summer slope and DS. Intend to use the fling fuse (strong and very slippery) mated up with a sparred and glassed eagle wing.
Got a couple of questions though for the experts:
What should a set the incidence at with speed in mind?
Would an all flying v’tail be the way to go?
Any other advice would be great,cheers all.

[thevon]

Felix, firstly I'm no expert. But I think it's a hard Q to answer, because DS is a term that applies to a wide range of flying conditions. You could be swooshing around with a light DLG in 5 or 10 knots or throwing off a 5kg sled in 40 knots. Completely different planes, totally different experience. My recommendation is concentrate on getting something that scores the most points on the frontside because seriously that's what you'll do most of. Then when the conditions are right and you're at a DS spot that's working, have a dabble. My second advice which I know you won't take is to buy something with a proven track record, rather than making a hybrid. Second hand is great if it's set up to go, has a few dings etc. Or a discounted moldie - check with Falcon Gliders etc. Save yourself lots of heartache.

[felix]

Andrew you are absolutely right there mate and I probably should have been a little clearer.
After seeing marks eagle in action weekly it has proven to be a great plane in light conditions but seriously quick in bigger conditions and the bit of DS we get away with at the corner. Generally it shows a very efficient wing section.
Love the model but think with a slippery fuse, stronger tail, no dihedral, provision for ballast and some strength added to the wing she would be a great little allrounder with good DS potential (with a lot more practice with a foamy on my part). Of course the added weight will reduce the light lift performance.
Best part is the chord is the same on the fling, the fuse length is pretty much spot on and I have the model retired in the shed. I just got a quote from Canterbury sailplanes and I could put the whole model together for under $80. Would make a good cheap step up from the foamies with the added bonus of not getting me shot by the better half ;D

[felix]

just found the plan of the eagle on the canterbury site so will give me a bit more to work with . looking at other designs i think i'll go with an aerodynamically balanced all flying v tail (light and simple).

[sean]

Hi Felix,

Having seen Mark's Eagle go the other day I reckon you couldn't go wrong with one as a versatile all-rounder. Mark's would DS very nicely in light conditions IMO but if you want to go a bit faster the thing to remember is everything needs to be as stiff as possible, in bending and torsion. The whip tailboom and coreflute tail surfaces on Mark's Eagle would give trouble once the speed got up a bit, so replacing the fuse with a glass one sounds like a good idea (except for crash resistance of course...). The all-moving v-tail could be problematic in that it creates a point that can readily flex in turbulence and under high g loadings, a fixed tail would be a safer bet IMO. Also cross-tails seem to track better than v-tails which helps DSing.

Generally the incidence on a fast glider like my Bird is setup 0 - 0 as far as I understand, I guess you'd need to tweak that, but it would make a good starting point.

The turbulence and shear layer on the backside put a lot of additional strains on the airframe compared to going fast on the front (a DS speed of 60mph equals an airspeed of 60 + the windspeed each time it crosses the shear layer, as well as a viloent jolt through the whole airframe). That's why EPP DSers tend to be planks - there's less to twist/bend. But in light air (which is what we get 90% of the time), thanks to a more efficient design the Eagle would probably be much better to DS than a foamy plank.

Sean.

[felix]

Thanks sean some good advice there.
Ok revised plan:
* a fixed cross tail out of lightly glassed balsa
*0 incidence
*Curved carbon main spar shearwebbed and carbon drag spar
*Diagonal fiberglass or balsa wing skin (maybe even double layer of brown paper and pva?)
*Insert a solid fiberglass rod through the carbon tail boom of the fling
*One piece fuse and wing
*lightly glass inner of fuse for a bit more strength

Sound ok and any other tips?

[sean]

Hey Felix, sounds pretty good. With a long tail you want to keep the weight down behind the CG or you could find you need a ton of lead to balance. For wing covering, if it were me I'd use the "new stuff" laminating film - that would keep a degree of crash resistance, and it seems very easy to repair. Also the new stuff adds quite a bit of stiffness to the wing. Fibreglass or balsa would go crunch in a big crash. If you're going to use it learn to DS it's wise to make it as crash resistant as possible .

[felix]

Thanks sean for some more sound advice.
Understand about the crash resistance of laminate over fiberglass/balsa but really want to get some good performance out of this one which is why I am thinking of going as smooth as possible. Really not sure how smooth laminate is compared to glass but am about to cover one of my bees in it so will make a decision then I guess.
I won’t be learning to DS on this one, I will have the heavily modded bee that I’m working on for that which should prove plenty fast enough for awhile. Just after something with a bit more performance over a foamy on the frontside and if the conditions are smooth maybe a little DS if i'm comfortable without the price tag that’ll make me cry when I stack it lol. come summer i will be spending alot of time trying DS so think my skills should improve quickly enough for something a little quicker.

[chamm37]

just remember felix....when you and mark place the order to get the planes, would you be able to pm me and i will give you or mark the money to get me an eagle kit but i am only going to make light as possible so that i can fly around with mark when the wind is close to nothing ;D

[chamm37]

Where are you going to be getting it from?

I would probally get it from modelflight for $145 and it is $15 for postage so= $160 for 1 kit

that is cheaper to buy the kit it self from canturberry sailplanes little alone with postage......when ordering the 3 kits together its only $25 postage on top of the cost of the planes ($460 for the three posted to Queensland here)

What you reakon and anybody else wanna join in on a buy?

[felix]

sorry chris but i have already ordered a wing and aileron set from canterbury for $68 inc. postage.

[felix]

well my wings are here and taking a quick break from my bee build's i started to lay out some sort of plan which has raised more q's then it’s answered.
A few things are very obvious so far:
1.i am going to have a hard time fitting a center mounted aileron servo (the fuse is no wider then a 20c piece!)
2.fuse space will be at a premium when I add the battery, ballast tubes,servos, receiver etc
3.the tailboom is not long enough
4.elevator control routing will be a PITA
5.the wing is very thin so I am really going to have to think about spar placement
6.do I fiberglass the wing, spackle and brown paper it or just go with laminating?

So plan so far is to have the fuse and wing as one piece with access to ballast and servos through a hatch in the bottom of the fuse and canopy. The tail boom will be replaced with a 6” longer, thicker solid carbon boom with a flat 2mm carbon ribbon as an offset “spine” (should get rid of flexing) with the elevator control rod running externally along the boom.
Couple of q’s for the guys with a bit more experience:
1.should I go with an all flying cross tail or fixed? I am thinking an all flying would be best for drag and potential incidence probs but may be easily snagged stripping the elevator servo.
2.are flaperons necessary on a 1.4 mtr glider that will weigh up around 750grams unballasted? If so I will go with twin servos outboard.
3.how smooth is laminating and would I likely notice any performance loss compared with a dead smooth glass or brown paper job?

Any other advice would be greatly appreciated,
Cheers all.

[chamm37]

hows it it coming along mate

[felix]

haven't touched it yet, been getting the bee finished but will be making a start next week. going to take a bit of planning and work to get this one done.

[chamm37]

yer i bet it would