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The Vimana89 V-Sliver and RETjet RET Deltas

Vimana89

Well-known member
#1
Overview
This is the official thread to launch my first two successful designs! They are similar enough in build and principle that I decided it would be best to create a single thread for both that can compare their similarities and differences. Both the RETjet and V-Sliver are low aspect(slender), highly swept delta style craft, but unlike most delta RC planes, slender or otherwise, they utilize a simple RET(Rudder, Elevator, Throttle) control scheme that generally requires less build precision and piloting skill. The roll axis on this type of plane is generally extremely sensitive, especially with AET or elevon setups, but the RET scheme tames it somewhat, and the dihedrals add some self-leveling. This eliminates some maneuverability and proper barrel rolls, lowering the plane's flight envelope a bit, but makes the plane more predictable and beginner friendly.

Since the beginning of starting the hobby, I've wanted to mess around with and design highly swept deltas like the HP-115 or Concord. I enjoy building and flying all types of planes, and plan to expand all sorts of ways with the hobby, but most people have that one niche they favor no matter how diversified their tastes. For some, it's flying wings, others are warbird guys, biplane aficionados, etc. For me, it's highly swept delta craft. Here's the theory on slender deltas and how they can fly well at low speeds and high angles of attack. https://en.wikipedia.org/wiki/Concorde#Slender_deltas

The RETjet is a round-backed, elongated teardrop delta shape strongly influenced by the FT Nutball. It has canards that help smooth out pitch and long dihedrals that add a lot of stability and auto-leveling but reduce the high alpha capability of the plane noticeably. The V-Sliver is an extremely slender delta with dihedral only on the very tips of the wings. Both have a high mounted pusher, based on the Kolibri Flyer by @Dr. Looping Looie, and on the "Bixler style" pusher of the FT explorer.



Handling Characteristics
These are based on numerous flights with the prototype versions of both of these planes.

In common: Both have a gentle pitch and touchy roll, common of low aspect planes. The extreme roll tendencies are tamed somewhat by the RET control scheme, but still require a good amount of expo. The ability to barrel roll like an aileron or elevon plane is negated, but these designs can still bank and turn very nimbly. The phrase "Deny The Dip" applies here. As with most any high mounted pusher, these will have a bit of nose-down tendency. Some up elevator trim helps, but mostly, be ready to adjust for a bit of dip on launch and any time you stop giving it a bit of up elevator. Both of these planes, to me, were easier to fly than my experiences with the FT Nutball.

RETjet: The more stable and beginner friendly of the two, this one has minimal wing rock and more robust dihedrals, adding a more noticeable auto-leveling effect. It has a slightly smoother pitch, likely due to the canards, which makes for easier, cleaner loops generally speaking. From my experience, what it gains in stability, it loses in high alpha ability. I believe the long dihedrals create a wing profile that generates greatly reduced vortex lift. Overall, a fun, nimble plane that has a unique look and bridges the gap between more funky and advanced planes and a typical trainer.

V-Sliver: A "wilder ride", but still quite tame. This one is the most slender plane I've seen flying. It has the profile of a classic dart paper plane, or the HP-115, perhaps a bit more swept even. This plane has much more noticeable wing rock, and a bit more roll/bank sensitivity than the RETjet, but is still smooth and pretty easy to handle with a bit of practice. It can bank as well as the RETjet, but can't loop quite as smooth, and has less auto-leveling, since only the very tips of the wings have dihedral. This ends up leading to much better high alpha performance than the RETjet, which leads to a bit more throttle and speed flexibility.I can do some really slow flying with this one. Overall, a high AOA beast with a slightly touchy roll axis and a strikingly slender profile.

Why would you build these?
Most of all, they are fun. They are very fun to fly, and unique in both handling and aesthetics. They are great for a pilot that likes to fly lots of different looking and handling planes to try something novel, and they are a perfect intermediate point between a basic trainer and more advanced elevon deltas and jets. The RETjet is especially good for this purpose, and makes a great second plane. If you can fly a basic trainer with confidence, you can be flying the RETjet next no problem.

The V-Sliver makes a great introduction to high alpha flying and throttle management, and is sure to turn heads with its extra slender profile. It is great for flying and maneuvering in more confined outdoor spaces or roomy indoor areas such as gymnasiums. There is nothing that handles and maneuvers quite the way a super slender delta does, especially at high angles of attack, and despite the non-traditional(for this type of craft) RET control scheme, this plane still gives the full slender delta feel, just minus the barell rolls.
 
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Vimana89

Well-known member
#4
sketches/plans/info V-sliver

Electronics/Non-Foam Parts:
(The following parts list is recommended for the original V-Sliver "parkjet" sized model, with 250 sized motor and 17" wingspan. Any scaled up, scaled down, or otherwise modified models, will be up to the builder to choose compatible and suitable parts, using the original for reference and scale.)

Motor: 250 size; 2205 2300KV(recommended: FT Radial 2205 2300KV), 2804 or 2806 1900KV(recommended: Graupner Ultra 2806 1900KV)
Prop: 5" size; Recommended: Gemfan Hulkies 5x5.5x3(Best performer hands down!! I tried Raycorp 5x4x6, and they look snazzy and run very quiet, but the thrust power was not quite there. I tried Raycorp 5x5.3x3, thinking in theory they should have about the same output as the Hulkies and boy was I wrong, I think they were even weaker than the six blade of lower pitch.)
Motor Mount: 2" size to fit fuselage; Flite Test swappable wood firewall or equivalent (This firewall fits the recommended motors with little to no modification)
Battery: 3s 11.1v 75c 550-850 mAh(Recommended: Tattu 3s 11.1v 650 mAh)
ESC: 20A(Recommended, Flite Test 20A)
Receiver and TX: Any/Preference(Recommended: anything with expo for the rudder)
Servos: Any/Preference
Extenders/Extras: 2x 24" servo extension cable
 

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Vimana89

Well-known member
#7
Updated Sliver build flies, though I could not test its full capabilities due to heavy winds. If I am satisfied with is performance under good conditions, I will update this thread with a full build guide(I have pics of the process), and some measurements that can potentially be developed into plans with some help, or used as a guideline(this is a pretty basic scratch build with some room for variation in little things like the nose and spine vs full box.) I was dumb and didn't double check my channel 2 reversal before maiden launch. Got a couple cosmetic minor dings, but it was error, not build related. Here's a pic before maiden!
 

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Vimana89

Well-known member
#8
Updated V-Sliver exceeds the performance of the prototype across the board in strength, handling, and stability!Wingtips and nose are now strong and durable, wing rock is lessened(30 degree dihedral is perfect). High alpha is about the same, less nose down dip with a bit of trim. Hood scoop looks great and will ensure cool function in hot summer weather, although I may put plastic mesh in mine or something to keep out bits of desert gravel and sand.If you don't fly in these types of conditions it will be perfect as is. This version with the bugs worked out will be the one I release to the community fully. Build guide and dimensions coming soon, with a high probability of plans to follow!
 

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Vimana89

Well-known member
#9
Crude sketches of each part and its dimensions are up! These were made during my last build process, and are up under the sketches/plans/info section. I'm still figuring out how to get proper measurements on the rounded parts of the fuselage(may have to use a string or something), that's why those are missing(I'm no math whizz), but should be able to be approximated and filled in easy, especially with pics of the plane. More detailed sketches and exact measurements on the fuselage may be coming, but better yet, @Grifflyer has offered to help make printable plans.
 

Vimana89

Well-known member
#12
Thanks a lot! This took a lot of trial and error and learning to get running smooth, but the result, once dialed in, is a great little park flyer. High and fast, low and slow, high alpha, it's pretty flexible. Has a unique feel to the handling but nothing intimidating if you've flown a plane or two.