I have a side by side Rapier delta that uses two I rvine 46s.THis afternoon i crashed it on take off on its maiden flight.The damage is immense<due to its high weight and high lift off speed>but it is repairable.Upon studying the video footage of the accident it appears that the starboard engine was slow to reach t/o power.I used a rolling t/o and fed the power in gradually,our strip is not the longest and the end was looming up fast-I firewalled both engines.The starboard engine then came on to full power quite aggressively and swung the model off to the left.I was now at the end of the runway with no choice but to shut the throttles and run off the end at hidiously high speed,or go for it!I went for it only to be greeted with what looked like the yawing incipient stage of a left spin which In the heat of the moment i corrected with elevon-only to have it yaw horribly to the right and over on its back to a very nasty mess!The wing loading is 36 oz/sq.ft wet and weighs 177oz -again wet. Was it not flying fast enough? <ie it had a yawing motion at t/o that was aggrevated by elevon input>or was there insufficient rudder/fin area?DOES ANYBODY HAVE ANY USEFUL INFORMATION REGARDING FIN AREAS ON DELTAS??????Regards Marc

Takeoff and landing are not the best flight modes for low aspect ratio deltas. At low speeds and high angles of attack the induced drag is very large indeed. This makes them slow to accelerate on takeoff and their glide ratio extremely steep on landing approach. A high wing loading for a delta just makes matters worse. The vertical tail is blanketed by the high angle of attack and the vertical tail's effectiveness is further reduced by the very short tail moment arm. It's hard to imagine a vertical tail that is large enough to be all that effective under the circumstances. A side-by-side twin can cause serious yaw and roll at slow speeds if the engines aren't pulling evenly. When you put all of these adverse odds together you have no room for error. You might ask yourself if the advantages of a delta outweigh the disadvantages in this particular configuration and operating environment.

Constructive suggestions:
1. Tandem push-pull engines.
2. Instead of putting a huge vertical tail on it, put the added area into a larger wing to reduce the wing loading.
3. Add flaps over the center 1/3 of the span.
4. Extend the runway.
5. Locate the fuel tank over the CG and use pumps.
6. Increase the span rather than the chord to increase the aspect ratio.
7. Use an airfoil with a drooped leading edge.
8. Put the structure on a diet to reduce weight where possible.
9. Put the rear wheels just outside the arc of the pusher prop to protect the prop during high angles of rotation on take off and landing.

Is this the Balsacraft Rapier you are talking about? 11 lb would give the Rapier that I am thinking about around 36oz wing loading. If so, HOLY B'JESUS that's heavy. My Rapier with gear, enlarged vstab (built strong enough to take tailsitter landing stresses) and Supertigre 90 weighs exactly half that dry. Weight seems to be the "heaviest" issue here. You've just got to put that plane on a diet. If you can't get it under about 7lb dry It is just going to be a real pig in the air and really difficult to deadstick.

I was thinking of doing a side-by-side twin like you did myself. One way alot of twins deal with the assymtrical thrust in case of an engine out situaltion is to mount the engines with a couple of degrees tow-out. Mounting the engines as close together as possible will help with that too.

Marc,
Your email address returned an undeliverable message and RCU gave me the message that you do not want to recieve email through them, so I will post my email response to you here.
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Marc,
Isn't RCU great. I am also involved in another thread. A guy in Austria built a turboprop model with variable pitch prop blades. He didn't have enough pitch and the first flight was a bit of a diaster. Now, myself (Minneapolis, Minnesota US), a commercial turbo pilot from Nova Scotia, Canada, and a guy in Ireland are helping him out. It's a near Utopia here online!

My Rapier cannot rotate on takoff. Instead, it relies totally on its positive-incident stance to lift off when a fast enough ground speed is reached. It works really nicely too. There are no poor handling qualities with this configuration. It is very stable taxiing, taking off and rolling out after landing (just make sure the nose gear is angled back some, because forward angled nose-gear causes a pole-vault effect and "bucking bronco" landings). Since the picture taken with the Jett 50 engine on it, I have mounted a Supertigre 90. With the 90, I have even done a few zero-roll takoffs due to the higher incidence needed for clearance of the 14" props that the 90 swings.

The underside rudder might be a problem for a gear setup like mine. Since rotation is impossible with the wheels at the trailing edge, you have to rely on incidence for lifting off. 10 degrees incidence should be enough, but you may need a really long nose gear to get that if the underside rear fin is too tall.

Craig

one things i've found with deltas....
i had a quicky delta, flew real nice untill it went dead and you just couldnt slow it with out a sipn.
when i looked over the leading edge at about 30 degrees i saw no sign of the fins.. its the same on a standard Rapier.....
I gave it Diamond dust ones and could see a nice amount past 30 degrees, stall speed droped to walking pace...
Deltas have huge vortexts behind the wing and your little fins are sitting here, hold the plane at 30 degrees and if you see fin your about right, its out of that vortex and working again. Both my Outlaw and Diamond Dust have this and show no spinning at stall.

Dear Phiilybaby,Please ,where do i obtain a diamond dust(I've heard it called a diamond lill) delta? is it a self build plan?,is it an artf?,where ,Please?What about the "outlaw"-same question applies.Kindest regards Marc Sommer

they are still at www.diamonddustrc.com
there isnt a UK importer, you have to order from US, they dont cost a whole lot. the other option is the Whiplash which will be imported to UK soon.
Jeff Gilbert makes a few planes, the Diamond Dust is the fast delta, the Diamond Ulimited is a stick fuz comp fun fly, and Lill rippy is another version of that.
this is what you get in the kit, there isnt much, dont cover it in solar film, it'll tear and you loose it. use a fabric, i have film on mine and fabric on the bottom. i lost the bottom sheeting in a dive.
you can easly build the plane in a day. its built light, keep it that way. 2.5lsb all up is common in US, mine is just shy of 3 with a MVVS 40 and extra balsa capping strips and radio bay.
dont put the aerial in the recomneded tube, personaly i feel when you line it up with the LE you'll loose radio.


Outlaw is all balsa and ply, its like building in a pic frame, but the meathod works well, ends up strong and light. engine insalation is strange so a remote needle is the way to go. its a very quick plane and you need very good reflexes to fly it. i built mine in 2 days. its on a 36 and tuned pipe, and its great fun to chuck it about.

the Outlaw is capable of more nutty stuff than the Dust, but the dust is faster and smoother to fly. both mine have the same full speed and sudden 90 degree direction change ability. tho the Outlaw will flat spin all day thats fun
theres a vid of my outlaw on the rcflyers web site doing its back flips


ps. turn your pm feature on. much better to be sending info percific to you, right to your own RCU page, rather than bore the rest of the readers with it. RCU will mail you and let you know you have a message waiting just like forum posts

Just found out you can get the Outlaw kit here
http://www.ecubedrc.com/kits.htm

I have just finished building a Stingray Delta from Model Airplane News plans (from 1985..), that is a .40 delta design with fixed undercarriage, and a sentral fin (no rudder). I was concerned that the fin would be easy to break, during transport and storage, so i mounted removeable winglets instead. Each winglet is just a little smaller (area and hight) than the original fin. I wonder if anyone can predict the behaviour of the delta with winglets instead of a sentral fin?? Another thing a dont understand is the reflex up-trim of the elevons. Is the model to be balanced in such a way that it will fly straight with up trims, or is the model to be balanced with neutral elevons and just use the uptrim at slow (high AOA) flying?

Thanks!

I don't know if this will do, but I know this is a flying wing not a delta. A delta is swept back about 50 to 60 degrees a side.
Darryl

Delta or flying wing, i think of it as a flying wing with a delta configuration, a tailess design..

The reflex is normal for any flying wing.. set it for the specs for the plane, then experiment with it to suit yours. You will need some reflex.