Projects

man launches glider seat logoMembers of SEAT build & fly mostly gliders (F3B, F3F, F3J, scale) and the satisfaction of designing and buidling a competitive composite glider is a wonderful experience.

Crucial to the process is an understanding of aerodynamics, 3d modelling, CAD & CNC, moulding and attention to detail. Shown below are a few details of our club projects with an aim of encouraging more of this activity.

clamps used to join top and bottom

Here you'll find information related to the stuff we build.

The Machine | The Nexor | DIY Winch Parachute | Fixing a Furio

The Machine

kermit-green shiny gliderThe Machine is a fully-molded 3D- modelled and CNC-cut 3.1m span F3B glider. Designers Marcus Stent, Bruce Nye, Stephen Boag & Tim Lennon wanted a leading-edge-technology glider that could compete with the Estrellas and Furios being flown in F3B comps around the globe.

3.050m span  280mm root chord generates a 70dm2 wing, so at 2.3 kg AUW, the wing loading is low.

The first step was defining the aerofoil and after a few trips to Profili the 'foil was imported into Rhino 3D to bind the sections onto the 2 rails (LE & TE).

The spar is on the 1/4 chord line and extends to tips.  This improves twisting moments and stiffness.  Elliptical wing planform. 2.4GHz friendly nose.

New building materials and processes should see all 93gm carbon models with AUW (flying) of around 2-2.1kg without too much effort.

The fuselage is based on a minimalist approach to reduce the frontal/ wetted area and yet house relatively standard radio gear (JR368s, 4-cell batt pack).

The numerous plugs were machined from clear acrylic and hand-finished.

How numerous?

Molds were then made from these very accurate plugs. Molds are supported with 1" box steel frames; it's handy to have experienced engineers and fitter/ turners in the team!

huge flap deflectionStephen's lime-green and electric-blue version is Machine # 5 in an on-going build series. Each build sees small improvements made to the lay-up, hinging & production process. Weights vary according to lay-up; the lightest yet was Bruce's carbon D-box with an AUW of around 2.0Kg.

Stephen flew his Kermit-green Machine at Jerilderie 2009 as a 3rd back-up model and Bruce flew his to 1st place at the 2007 Victorian Mt Hollowback F3F comp.

Further experiments with CG & model set-up including ballast loads will push the design envelope. Early signs are, at 2.3Kg it's a winner!

For an extensive collection of build pics check out our Flickr Set.

The Nexor

A fully-molded 3.4 metre competition thermal glider developed during the summer of 2008/9.

green gel coat is 1st layerRapidly-prototyped using cheap MDF as the plug material; a move inspired to some degree by the success of the F3F Martinet from CCM (although the CCM approach used MDF to make the molds without an intermediate plug process).

The relatively cheap material allowed costs to go towards a high-quality but easy to fabricate mold.

Chris and bruce insert carbon sockFrom Go to Whoa in 7 weeks!

 


650g carbon used to strengthen the moldscnc machine posied after cutting mdf wing plugsBruce's prototype was named "Nexor" as a tribute to its gliding ability (it stays up so long it makes your neck sore ;0)

The Nexor was maidened at the Milang F3J International in March 2009 and performed on a par with commercial models 4x the price!

The plugs have been passed-on to a colleague interstate so expect a fleet of Nexors over the next flying season.

Stay tuned for further Nexoriffic developments to expand the flight envelope. See more pictures and info on our Flickr Nexor Set.

Nexor F3J MDF plugs on Vimeo.

Taslotto

Continuing the theme of using MDF as the plug material, the Taslotto F3B ship is based on HN-483 sections and built in one-piece. The Taslotto uses the same v-tail fuselage as the Nexor. More details and pics to come

Make your own winch parachute

hands form the chute canopyThe photos and captions should give you a good guide to how to make your own parachute that is inexpensive, rugged AND pops like a rifle shot after a good ping.

This version is single colour which we have found is fine in terms of visibility.

bricklayer's lineItems needed:

Tools:

paper templet hexagon The paper template is a hexagon, 285mm diameter.

F3B rules dictate a "5 dm minimum area".

Just use a compass, draw a circle and then draw 3 lines across the centre and then join the adjacent perimeter lines producing 6 equilateral triangles.

Use the template to cut out your 'chute material:

jig for marking 285mm lengths Make a simple jig to help you mark out 9x 285mm lengths of line:

wind the cord around nails Wind line around the nails to give you 9 lengths of 285mm:

mark the line at each nail Mark the line at each nail. Then unravel the line:

draw pencil guids on the 'chute to assist in laying the line Use pencil guides to assist in laying-out the line on the 'chute:

tape the cord down Use masking tape to hold the line down while you lay it out:

more cord layout Your aim is to ensure all lengths are equal; get it wrong here and your chute can rotate on launch/ in the air and spin the lines which can reduce line lifespan:

more cord layout See the 3 loops? The final run is to return to the origin:

cut the cord at the origin Once back at the start, cut the cord flush:

all lines laid out Lines laid out and taped down. The tape is removed later after stitching. A better soultion would be to stick the line down with 3M77; the tape can cause the sewing machine needle to veer off:

unfurl the chute after all taped Unfurl the 'chute and check the geometry:

sew through the line and chute Use a straight-line stitch and attach the lines to the 'chute. Leave a gap of no thread across 25 mm of the uppermost cord at the chute apex; this is the loop through which you feed the hook-attachment loop:

once done unfurl again
Once all lines are done, unfurl again to check geometry and re-do any poor stitching:

reinforce high-stress areas Reinforce the cord intersection. Also reinforce the high stress areas:

attach cord to hook To attach the 'chute to the line; firstly thread the line through a strand of nylon piping and tie off. 3mm nylon piping from marine stores with the centre removed works well for all lines up to 1.8mm.

attach cord to hook Arrange the 'chute cord to create a loop:

attach cord to hook Loop made:

attach cord to hook Pass line through 'chute cord and secure as shown:

attach cord to hook To attach line to fuselage follow these steps:

attach cord to hook Feed nylon loop (shown in white) through unstitched apex of parachute and then attach to towhook:

attach cord to hook All done! The ' chute takes massive launches and reliably pops-off. The method illustrated allows the 'chute to cling to the fuselage on launch, thus reducing drag.

Credits:
Bruce Nye for design and techniques, Chris Adams for photos and captions.


 

New life for a Furio wing.

Furio & Ellipse 4 X-tail resting

Report: Chris Adams
If you've ever stuck your high-tech moulded pride and joy into a fence, tree, rock outcrop or indeed, heaven forbid, another glider, then this "renovation rescue" might prove useful. The following sequence is this author's approach to re-building a busted bird.

The Breta Nyx Furio is a thoroughbred F3B glider which excels in all flight envelopes largley thanks to the HN483 wing section and the refined wing planform. An opportunity came along for the author to purchase a rather battered set of wings that, with a little time, epoxy, carbon cloth & paint could be a viable 2nd set.

The 2nd-hand wings arrived beautifully wrapped which is sweet irony when you consider the state of them ;0)

Right-hand panel looked good until further inspection revealed a busted spar near the tip stripes. The left panel had a complete tip broken off & several "horse bites" as well as a "free-floating aileron".

I'd hate to see the other guy!

Time to examine in detail and piece it back together! A good tip is to focus on each break and not attack everything at once.

Cut the inspection hatch. Retain the cut piece so you can fit it later.

The spar cap was broken underneath. The solution was to add a new one AND with laminated splints of fibral-bonded carbon & thin ply (tongue depressors are good for this).

Dremel out a furrow in the top cap. The masking tape is vital to keep the disc in the right place. The radius of the grinding wheel allows the new carbon to fit without introducing sharp stress points.

In addition to the cap, 2 splints were added fore & aft of the main spar as a precaution.

With that done, make up a handy tool from hardwood.

To help mount the top hatch cut out earlier, make a ledge that follows around the edge of the hole. Now take the tool and hook under the balsa ledges while they're glued. The ledges are simply glued with cyano & accelerator.

Replace the top skin, then apply a layer of 3/4oz 'glass & automotive filler.

Spray with automotive acrylic 50% thinned (with acrylic thinner). 5 coats used here. Colour-matched by the local auto paint shop. It's expensive but what can you do?! This blue doesn't come in a spray can round these parts ;0)

Next-up, the other severed limb! Splints were needed for main spar x2, sub-spar & aileron. The main spar of the Furio is simply a 1/2" balsa shear-web with carbon caps. The main spar here had 2" missing so it was thought prudent to use sturdy 3/8" sqr. spruce bonded in front of the busted spar.

Splints rolled in cloth and epoxy. The aileron needed less support, with just 1 face covered.

After the epoxy had set, in a similar way to the other panel, the main spar was "re-capped".

1.4oz glass then a liberal application of filler.

Ditto top-surface.

Stand back and admire your work. You need to do this from time-to -time!

Next-up, the horse bite. Big horse!

More splints and an internal skin of balsa & 1.4oz cloth top & bottom. The balsa/cloth skin goes INSIDE while wet with resin and hung upside-down with lead weights to allow the skin to conform to the airfoil. Do top THEN 24hrs later do the bottom. The rolled splint goes in wet with the last internal skin so it adheres to it. Generous overlaps along the wing of around 1 1/2" each side.

Looks macabre but works a treat. The strings and knots stay with your wing forever! Once set, cut off strings, sand flush and add balsa sheet infill flush with surfaces.

To finish off the radius of the leading edge accurately, simply wrap 3M Book Tape along the leading edge around a lot of epoxy/ filler bog mix. The epoxy sets, the tape is removed and the leading edge is strong and aerodynamically pure.

Balsa infill done, cloth top/bottom done, filler drying....time to sit back and admire!

Sanded and filled and sanded and painted using colour matched acrylic. The tiger stripes were replaced and conveniently hide a few blemishes. The aileron hinge was repaired using Sellotape Diamond. The tip panel still had the original hinge in place which was a blessing. The wings were polished using heavy duty car polish.

All-up, a restored wing. You're probably wondering about the added weight. It gained 4 oz all up. 2 oz was paint! More paint could be added if the exisiting flaws were an issue...they're not ;0)

These wings ended-up 80g lighter than the old pair! As for flight performance they are flawless. These won't see DS abuse but will get merciless F3B launches.

Mssion accomplished.

 

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