Icare Sail­fish F3K 900mm

This small dis­cus-launched glider is per­fect for catch­ing ther­mals!

Electric Flight - - CONTENTS - By An­drew Grif­fith

This small dis­cus­launched glider is per­fect for catch­ing ther­mals!

I love glid­ers! I got my start in RC fly­ing glid­ers, and I have an ar­ray of glid­ers on shelves in my garage that I fly on and off through­out the year, in­clud­ing high-start and winch-launched glid­ers, scale sailplanes for aero­tow­ing, and even mo­tor glid­ers. What I don’t (or didn’t) have is a dis­cus-launched glider (DLG). And then along came the op­por­tu­nity to re­view the Sail­fish 900mm DLG from Icare-icarus in Que­bec, Canada.

The Sail­fish is avail­able as ei­ther a kit or a plug-and-fly (PNF) ver­sion. The lat­ter is fully built and in­cludes the ser­vos and pushrods in­stalled and ad­justed, a re­ceiver Lipo bat­tery, and a USB bat­tery charger. You add a mi­cro re­ceiver and then go fly. I was given the choice and de­cided to build the kit. No need to ad­just your glasses; I learned to fly when there were only two choices: build your own kit or pay some­one to do so, and the lawn-mow­ing money only went so far. I was thrilled to re­ceive the kit ver­sion and see how glider kits had changed over the years. I opted for the bat­tery and ser­vos that they use with the PNF be­cause I know they fit, and I or­dered a mi­cro re­ceiver.

The Sail­fish uses a sim­ple 2-chan­nel sys­tem con­sist­ing of just rud­der and el­e­va­tor con­trols. The Sail­fish can be built by any­one that has ever built or re­paired a wood model and can be flown by those with min­i­mal flight ex­pe­ri­ence; it is, how­ever, a re­lax­ing ev­ery­day flier even for more ex­pe­ri­enced pi­lots.

UNIQUE FEA­TURES

The Sail­fish is a dis­cus-launched (or DLG) F3K glider. The name is de­rived from the sport of dis­cus throw­ing, and to launch the plane, you hold a peg on the wingtip and use the ro­ta­tion of your body and arm to throw the glider as high as you can. I’ve seen ac­com­plished DLG com­pe­ti­tion pi­lots hurl the larger 1.5m DLGS as high as 300 or 400 feet!

The first unique fea­ture of the Sail­fish is the lack of an instruction man­ual. I’ve seen this be­fore, and I won­der if it will be a trend. You as­sem­ble the Sail­fish af­ter watch­ing a five-part video se­ries on Youtube. Each video is ap­prox­i­mately 30 min­utes long and cov­ers a ma­jor assem­bly step. There are no voice in­struc­tions in the videos, they are set to re­lax­ing mu­sic and the in­for­ma­tion is pre­sented in a com­pletely vis­ual yet ef­fec­tive for­mat. I found my­self in the shop with my ipad, watch­ing the full video through once, then start­ing over and com­plet­ing each step while paus­ing the video be­tween steps.

Other than the ra­dio equip­ment, the kit comes with ev­ery­thing you need, in­clud­ing cov­er­ing ma­te­rial and even a bot­tle of glue.

The Sail­fish uses a care­fully con­sid­ered com­bi­na­tion of ma­te­ri­als so that it is both as light as pos­si­ble yet strong enough to sur­vive the rig­ors of many re­peated and of­ten vi­o­lent dis­cus launches. The wing is con­structed out of balsa-wood ribs with car­bon-fiber spars as well as car­bon lead­ing and trail­ing edges, and built over a pro­vided wing jig. Wood gus­sets and car­bon-fiber parts in all the right places en­sure a sturdy assem­bly with a min­i­mum of weight. De­spite be­ing a kit, there is a jig pro­vided to build the wing, and since the Sail­fish lacks ailerons and spoil­ers, the wing con­struc­tion is quite sim­ple.

The fuse­lage con­sists of a car­bon rod that ex­tends from the fiber­glass pod and holds the tail feath­ers in place. A min­i­mum amount of room is pro­vided that is just enough to hold the two sub-mi­cro ser­vos, a small re­ceiver, and a Lipo flight bat­tery.

The tail feath­ers are made out of bal­sawood slab, and the rud­der and el­e­va­tor are hinged with the pro­vided heat-shrink cov­er­ing ma­te­rial. I would love to say that I changed the cov­er­ing to white on the el­e­va­tor be­cause it looks bet­ter, but the truth is I had my iron too hot and man­gled the first piece of cov­er­ing.

Since ev­ery gram mat­ters, there are no markings to ap­ply. When com­pleted, the trans­par­ent yel­low cov­er­ing looks great. Just be care­ful not to make a mess be­cause the translu­cent cov­er­ing will show any mis­takes you make.

IN THE AIR

A na­tional cham­pion sailplane pilot once told me, “If you want to learn how to read the air and work min­i­mal lift, get your­self a DLG and prac­tice, prac­tice, prac­tice!” I never fully ap­pre­ci­ated that un­til I spent the bet­ter part of a day fly­ing the Sail­fish. Find­ing a ther­mal and harnessing na­ture to climb and ex­tend a flight is some­thing that never loses its thrill. While it

took me sev­eral tries of launch­ing and walk­ing, I slowly re­fined my technique to max­i­mize my launches and then to find lift and stay up for in­creas­ingly longer flights.

All of a sud­den, on one of my launches, I no­ticed that I wasn’t com­ing down for sev­eral min­utes and, in fact, had caught a baby ther­mal form­ing at ground level. Ther­mals are like bub­bles in a fish tank: They start small at the bot­tom and ex­pand as they rise and the air pres­sure low­ers—mean­ing that at ground level, the area of lift is at its small­est and most dif­fi­cult to hook. Ris­ing col­umns of bugs or cir­cling birds of­ten in­di­cate the pres­ence of a ther­mal, but the truly gifted sailplane pi­lots have an un­canny sense of when a ther­mal is go­ing to form and are able to throw their DLG straight into lift.

GEN­ERAL FLIGHT PER­FOR­MANCE

Sta­bil­ity: The Sail­fish is ex­tremely light, and while the de­sign is sta­ble in dead air, the 125g glider doesn’t hold its own well when the wind picks up. Track­ing: While lack of ailerons will take some get­ting used to by those un­fa­mil­iar with fly­ing rud­der only, the Sail­fish tracks well and goes where you point it. Aerobatics: The Sail­fish isn’t de­signed for aerobatics, and the lack of ailerons lim­its what it can do. That said, I tried a few flights do­ing sev­eral loops and even a bar­rel roll or two us­ing full rud­der and up-el­e­va­tor. While aerobatics aren’t its in­tended pur­pose, fly­ing the Sail­fish doesn’t have be bor­ing ei­ther. Glide and stall per­for­mance: The minis­cule wing load­ing makes the Sail­fish nearly im­pos­si­ble to stall, and when it does, the nose drops and it keeps fly­ing. Glid­ing is where the Sail­fish ex­cels, and with some prac­tice, I was hit­ting flights of 10 min­utes and more.

PILOT DEBRIEFING

While a 2-chan­nel glider doesn’t need much in the way of fancy pro­gram­ming, I did set up my Spek­trum DX9 to con­trol the rud­der with both the aileron and the rud­der stick. I also set up a rud­der off­set be­cause my throw­ing mo­tion was pulling the Sail­fish to the left each launch. The rud­der mix gave me some right rud­der on a switch dur­ing launch, and with a lit­tle tin­ker­ing, I was mak­ing nice straight launches.

Left: An easy-to-use jig is in­cluded to en­sure that the ribs are both square to the spar and per­fectly spaced out.

Above: The solid pieces are lam­i­nated on ei­ther side of the cutout piece and form a strong but light mount for the hor­i­zon­tal sta­bi­lizer.

The sta­bi­lizer and el­e­va­tor are sim­ple slab com­po­nents with a car­bon-re­in­force­ment rod em­bed­ded in the sta­bi­lizer. There are no hinges as the el­e­va­tor is hinged by the cov­er­ing ma­te­rial.

The com­pact size of the Sail­fish makes it easy to bring to the field no mat­ter what else I am fly­ing. The translu­cent cov­er­ing looks spec­tac­u­lar on sunny days and is vis­i­ble when it’s over­cast.

I in­stalled the car­bon­fiber con­trol horns with Zap gel af­ter I re­moved the cov­er­ing from the glu­ing area us­ing an old sol­der­ing iron.

Above: The car­bon-fiber tail boom is slot­ted on this side for the rud­der pushrod. The whole assem­bly is rigid when all the com­po­nents have been in­stalled. Left: The cov­er­ing ma­te­rial ar­rived in sheets that were sized with enough over­lap to do a proper...

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