Elexaco model, design, build, discussion

[graham_mca]

Hi,
I recently attended an electric fly-in at Appleton WI to take a look at the elexaco comp. they were running during the day. It turned out to be a really fun event with enough of a competitive element to make it worthwhile. Much talking ensued with a guy I hope will join in here and I came away wanting to design a model to compete.

Doing a little research it seems that as an event most of the activity was back in 2000 - 2002 with little being said or done since. This is a shame because it seems to me that as well as a fun, simple and cheap comp. the few models which were designed would make nice little park flyers today too.

So I am designing/building a model to suit the class so that I can take on the Appleton guys next time and I will document it here in the hope that there is interest out there yet.

I will be promoting the competition in our club here (SHARKS, Sheboygan, WI) and hopefully we will see a few models built for next summer. I am hoping to see interest grow north of here in Green Bay too because another chap from there was impressed with what he saw at Appleton.

I will add the rules here as we intend to use them, we have made slight 'modernisation' changes to the originals. If you are flying Elexaco, or want to, I invite your comments here.

Graham

[graham_mca]

I have based the fuselage design on my Hitcher4 electric sailplane design of a few years ago, that model had a particularly small fuselage for it's 72" wingspan and a nice slippery shape.

Here are the fuselage sides with the fuselage edging added to stiffen the 1/16" sides. I realised that the 1/2" x 1/8" strip you see at the nose would not give me enough wood to shape to a round nose ring so I replaced that with 3/8" triangle as in the second photo.

The upper 3/8" triangle is trimmed back to give wider access into the cockpit/battery loading area. I want to avoid having to take the wings off to change the battery.

[graham_mca]

A series of razor saw cuts solved the problem of bending the 3/8" triangle strip to fit the fuselage bottom curve. I run cyano into the cuts after it is glued in place.

Custom jig!
I always mean to make a fuselage building jig but the excitement of wanting to see a new model develop means that I do this instead! But it works nicely all the same

The fuselage is inverted here, the rear end is clamped together after tapering the 1/8" fuselage edging down to nothing to give a 1/8" tailpost. The fuse rear sits on the board and the wing saddle is resting on a 3/16" stick to keep the fuselage sides at an even height.

The 'jig' keeps everything straight and the right width while I add the 1/2" x 1/8" cross braces. I think you can see a temporary cross brace near to the nose which I cyano'ed in place so that I could add the ply nose ring/former later.

[graham_mca]

Ok we are out of the jig now and adding some of the bottom sheeting. From the nose to the rear of the wing this will be 1/8" light crossgrain. Pretty substantial I know but much of it will be sanded away to give a nice rounded profile to the corners and it makes for a strong bottom too.

From there aft the sheeting is 1'16", the step is removed by blending the forward sheeting into the rear in a smooth curve, again removing wood and weight. I think that 1/16" sheet under the nose would be just too delicate.

I build mostly with Elmer's yellowish wood glue, hence the masking tape holding the sheeting on. Thicker cyano would be fine but may give a hard ridge when you sand the curves in.

[graham_mca]

And finally for the moment I have glued the front former/motor mount ring in place. This is a Hitcher4 part cut down so the two upper mounting holes are redundant. The Speed 400 will be mounted with the two holes either side of the centre hole.

I will strengthen the joint with a fillet of glue inside later. The nose will carve/sand down to meet the nose former. I love that part, working away at a boxy lump to find the slender fuselage hidden inside...

I need to go think about the wing now.

Graham

[graham_mca]

Oooops I hit the submit button instead of the manage attachments.... here is the photo now.

[szastoupil]

Hey, that's cheating. It shouldn't be as easy as scaling down plans. It looks like your making very quick progress. What CAD program do you use for your planes?

Scott

[graham_mca]

Did I say scaling down Scott.... I think not
Lets see what I changed.... erm.... wing section, angle of attack, downthrust, fuselage profile, fuselage structure to some degree, tail group from all flying stab to simple elevator, wing structure, wing planform. Heck it was meant to be a scale down but so much stuff had to change.... LOL.

Just back on the PC to lay out the wing ribs now that I have decided to go with a single bolt wing. Rubber bands would be easier and quicker but not so sleek, but maybe preferred? Yes that ? means that I would love to see input here as this progresses.

I use AutoCad 97LT Scott.

[tim hooper]

Looks good, Graham!

It's nice to see a sailplane made out of balsa! Pretty rare these days....

tim

[No Step]

AutoCAD LT 97 ? That's what I use. I can't afford an up grade, besides it works just great.

Elexaco,.. I thought that was an electrified form of 1/2A Texaco, flying oldtimers? You are designing a new plane for this event? I'll be watching with interest. Ya gotta love Speed 400s, besides I have some old motors and controllers without a home.

Fred G.
My stuff: http://mysite.verizon.net/res7oqj1/index.html

[szastoupil]

Just a reference for this build thread and in the spirit of promoting the Elexaco event, here is one of our club members presenting his Elexaco design at a club meeting.
http://www.flyvam.com/?Club_Projects:Valero

Here are pictures of myself and fellow club member at our club Electric Fun Fly that hosted an Elexaco event in 2003.
http://flyvam.com/gallery/electricfunfly03?page=2

I know Graham will be starting thread at some point in time about the Elexaco event itself, but it does not have to use models from the old era. Basically it is a limited motor run event that is similar to the old Texaco with a few basic rules to even the "playing field".

Graham,

I can't wait to see how your model turns out. Our Valaero's sure beats the pants of the Dymond Modelsport Elexaco with the flat bottomed airfoil in weather with any wind. Not to toot my horn or anything.


Scott

[graham_mca]

Hey Tim... yes I know, all of those glass things. Did you ever see my Hitcher4? My proudest moment in kit producing so far was reading the review in QFI (as it was) where the guy took the review model to the mountains of Fiss in Austria and he reported that in light lift the Hitcher4 out-soared everything present That was a balsa electric glider too.

Good to see you here Tim, hope I can keep the standard up there with your quad!

No Step... Hi, I like 97LT, I do have 2000 on the machine but LT does everything I need and I like the clean look with a big drawing area.
>>Elexaco,.. I thought that was an electrified form of 1/2A Texaco, flying oldtimers? You are designing a new plane for this event? <<

Yes, you are right about the origins being tied in with oldtimers I think, but the rules never restricted the model type beyond one key area, so in practice you can fly an old timer (a little Playboy would be nice) or simple electric soarers. This is what I am designing as I build, a 48" direct drive 400 powered three channel soarer, parkflyer, holiday, competition model!

And thanks for chipping in here with an explanation and those great links Scott. If you got my last email... are we a go on those rules? I'll post them here if we are. I can't wait to see this model too Scott... just hope it flies... this thread could be a big embarassment if I launch it and it hits my foot!

[graham_mca]

The forward hatch will be formed from 3/8" balsa... that's a lot of wood but much of it will be planed away to give a pleasing side profile blending down to the nose former (I hope). The forward section, see the saw cut, has been glued to the fuselage.

[graham_mca]

The bottom sheeting is completed and here is the step (a la Hitcher4) where the 1/8 sheet meets the 1/16... a long blend with the sanding block will hide this completely.

And then I developed, drew, printed and cut out the wing ribs.... who needs RTF huh? You may drool over my quarter grain ribs if you must.

The chosen wing section is Selig S3021... or at least it would be if it were a foam/veneer wing, to be more accurate the ribs are S3021... the shape of the covering in between is anybody's guess, but you know what I mean. S3021 will work as well as any open structure wing and better than most. Slimmer than E205 with a nice long Phillips entry I am hoping that it will penetrate nicely on the power phase and glide.

All for now.... oh what is it called? Well it's working title is E-lax, but if it comes down quicker than I expect it could be called Ex-lax.

I had better go after that, Graham

[szastoupil]

Originally Posted by graham_mca

All for now.... oh what is it called? Well it's working title is E-lax, but if it comes down quicker than I expect it could be called Ex-lax.

It looks like you were sleep deprived with that line of thinking.

Scott