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OME's Lawn Dart Build


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I had a search around and came up with this design. It's made from Depron, but corflute is half the price.

https://www.youtube.com/watch?v=MGCBfFOSgGI:578

 

I hauled out my old modelling stuff and found a 6V brushed motor from a foamy glider I once had. I've got a couple of radios systems, but I think I'll just start off with rudder and elevator. I'll use Ni-Cads, because I've got the charging equipment. I've got various types of hinges and control rod ends. I'm going to use mini servos, although I do have a handful of normal-sized ones. I've got axle clamps and collars. And I have plenty of hot glue sticks.

 

I downloaded the templates and had them printed at OfficeWorks (40 cents). I got the corflute from Bunnings at $9, but I'll need another $6 sheet for the top and bottom of the fuselage. I'll get down my box of aged balsa, or maybe just use some ply for the firewall and landing gear block. I have some Williams Brothers Antique wheels that might not be too heavy.

1588229223649.png.596d0f4d4f4a515f065055ae54a23db9.png

 

So far, I've made templates for the fuselage components and nested them on the corflute sheet.

1588229307261.thumb.png.cd7bf6aa312fb68c918f2989c3b732e9.png 1588229336663.thumb.png.c544f086c6256d77ebdd784b618181ae.png

 

The fuselage came out at 645 mm. If I wanted a length to wingspan ratio of 1:1.5, I'd need about 970 mm. The standard sheet is 900 mm, so I'll have to accept a 1:1.4 ratio. I think that's still withing the correct range for this type of plane, especially with a Clarke-Y shape.

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Snap or flick rolls are usually done just with elevator and rudder, it stalls and literally flicks around, a horizontal spin. That's big machines as well as little :oh yeah:

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At this stage there are no ailerons, so snap rolls are out of the question, unless I twist the wing by accident.

If you're not fitting ailerons, you may want to add a little more dihedral than shown in the video, only an extra inch per side, but that will make it a little more stable while giving better roll response.

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OK. I'll look into that. I was thinking of adding a flat centre-section to increase the wingspan to get the 1: 1.5 ratio. I could make another wing with the dihedral starting from the outboard ends of the centre-section. If the plan calls for 7 degrees of dihedral now, how many degrees do you suggest to increase it to?

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Seven degrees?

Video didn't look like that much, that said, fifteen degrees would be a nice stable platform so it matches what I was thinking by doubling what was shown in the video.

If you wanted to extend the wing with a centre section, I would look at having the tips at a similar height as they would have been if from a single 15º dihedral at the centre.

ie; the outer panels would have more angle to them to reach the same point. (this is called polyhedral)

Polyhedral wings can range in their dynamic, but a good all round concept from a weight, strength and stability standpoint is for the centre section to be at least one third of the overall span.

Any less and the span loading at the joint is almost as high (from a modelling view) as a single dihedral joint.

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Where did you get the templates to download?

 

Open the Youtube file and you will find a link to the plans in the info underneath. You can download the plans in A3 or A4 size. Four sheets for A4 and two for A3. I'm using the bigger A3 size and it cost me 40 cents at Officer Works to get the two sheets printed. I'm using 5 mm corflute from Bunnings @ $9 per sheet (99 x 600). You need two sheets because the plans don't have a drawing for the belly and top skins. One sheet will give you the wings and fuselage sides and bulkbeads. The other sheet is needed for belly and top skins and for wing spars. The video shows the use of a balsa strip to strengthen main spar. I'm going to use a bamboo garden stake. No use wasting good balsa on a lawn dart!

 

Depron from Bunnings is about $16 per sheet. I scored some Depron, so I think I'll use the A4 plans, which I printed myself, to make a silhouette glider for my grandson. I'll use corflute for the wings and tailplane.

 

Instead of hauling out my box of balsa, I used some 3 mm ply for bulkhead A and for the dihedral brace. I also made the tail skid from balsa. I'll probably dig out some 5 mm ply for the landing gear block. If you have a bandsaw or scoll saw, it makes it easier to cut out the shapes. You'll need some sticky tape to seal the edges of the fin, tailplane and possibly front of the fuselage after you cut them, otherwise they will trap the oncoming air. Also, if using corflute, cut any vertical bulkhead with the tubes of the corflute running top to bottom. That makes the piece more crush resistant due to the strength of a column.

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Ultra high quality hot glue gun stuff from the $2 shop. C'mon! It's a lawn dart, not a Concurs d'Elegance entrant.

 

By the way. I looked at the A4 print out. It is provides the same sized pieces as the A3 print. You just have another section of fuselage to join to the front and rear.

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A half-price aeroplane made from plastic cardboard, and held together with sticky tape, and glue from a $2 shop! What could possibly go wrong?

 

Boeing and Cessna will be in touch with you shortly, they're desperately looking for ways to cut production costs!

 

I had to close my eyes several times during that video, when I saw the way that Russian laddie uses trimming knives - aimed directly at his fingers whilst cutting!!

 

He obviously never got taught the old adage - "Cut towards your chum, not towards your thumb!!"

 

I didn't see the wing attachment method in this video, but in another video, he attaches the wing with two rubber bands! Does this design utilise the same wing attachment system?

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Don't forget that this is a trainer, and a bit of fun to make during lockdown. Better to buckle a half-priced lawn dart than a $1000 thing of beauty.

 

No doubt there will be a few more rubber bands used to ensure wing security, but some much larger balsa and plywood jobbies hold their wings on with a couple of nylon screws, so what's wrong with some rubber bands?

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Every rubber band I go to utilise, generally snaps as soon as I stretch it! I have yet to find a rubber band actually made of durable rubber!

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Rubber or plastic screws are fine.

 

Esp for a trainer, they act as a simple fuse and take the impact well. Esp with a foamy, you can do lots of abuse and get back flying in minutes.

 

Much better than a black bag for the balsa debris.

 

Have fun

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Every rubber band I go to utilise, generally snaps as soon as I stretch it! I have yet to find a rubber band actually made of durable rubber!

Made own rubber bands for holding shoulder pad on wee daughter's violin longggggggg ago. Can't remember where I got the 'rubber'...it was round in section, like white spaghetti...but if you can find something like that, you just slice the ends flat and join with superglue. It's a nice demonstration of just how strong that stuff is on a tightly pressed nonporous joint.

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Every rubber band I go to utilise, generally snaps as soon as I stretch it!

You are supposed to roll it on ... not stretch it over.

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Someone dared ask for me to update this build. I've cut the fuselage sides; rudder/fin and tailpane/elevator. I've found a small prop for the brushed motor. I just need to make a tight fit for the prop on the motor's output shaft. I was digging through my 30-year-old bits'n'pieces box and found some pin hinges for the rudder, and some flat hinges for the elevator. The bulkheads and floors have been glued together with hot glue.

 

Since I'm spending the day home-schooling my grandson, I'm not moving forward with the plane construction. However, he and I have nearly finished a puppet of the character in his English writing work. I'm not impressed with the lack of information that the school has given in relation to teaching arithmetic. If I knew what the leanring path was that he had to travel I'd be more at ease with teaching him.

 

Here's where I'm up to with the plane:

1588848822651.thumb.png.58554624445f85f979069db5e9f6d0f9.png

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Someone dared ask for me to update this build. I've cut the fuselage sides; rudder/fin and tailpane/elevator. I've found a small prop for the brushed motor. I just need to make a tight fit for the prop on the motor's output shaft. I was digging through my 30-year-old bits'n'pieces box and found some pin hinges for the rudder, and some flat hinges for the elevator. The bulkheads and floors have been glued together with hot glue.

 

Since I'm spending the day home-schooling my grandson, I'm not moving forward with the plane construction. However, he and I have nearly finished a puppet of the character in his English writing work. I'm not impressed with the lack of information that the school has given in relation to teaching arithmetic. If I knew what the leanring path was that he had to travel I'd be more at ease with teaching him.

 

Here's where I'm up to with the plane:

[ATTACH type=full" width="556px" alt="1588848822651.png]53012[/ATTACH]

Jeez, that brings back memories. Balsa instead of corflute but the layout is exactly the same for your basic trainer.

 

And yes rubber bands were common to hold the wings on - only really flash people used nylon bolts...

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AND

Nylon bolts don,t give, when one wing hits the dirt.

Scratch one wing.

Rubber bands do let the wing twist allowing the wing to survive

. Just a little.

spacesailor

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[ATTACH type=full" width="556px" alt="1588848822651.png]53012[/ATTACH]

 

I'm looking at the build up photo, and assuming that the 'airfoil' shape on the top of the cabin is later cut off, and the one piece wing sat on the now flat top?

Just seemed odd to include that shape only to cut it off later?

The alternative is that you have a two piece wing sliding onto a spar of some type? (not a very durable idea for a trainer)

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Yes, the aerofoil shape in the plan is simply there to show the thickness of the spars. The centre section box is hollow which allows the dihedral brace to set the dihedral and lets the wing sit on the top of the fuselage. I'll tape the wing joint with 100 mph tape.

 

I used to have a glider with a main and rear spar which slid into tubes on the opposite wing. These had a tendency to come loose through wear. Joining wings like that is OK if you have to transport the plane. It makes for a smaller bundle, but I've just got to go though my side fence to get into the park I want to fly in.

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Come on, it should have had its first crash by now!

 

Festina lente, my son. Festina lente. Rome wasn't burnt in a day.

 

I got this done today. That hot glue makes great filets.

1589091758958.thumb.png.04006467882b1b1459df9919cd26fcf9.png 1589091787893.thumb.png.668cc298d530a8afab9e6473aa58147d.png

 

Pylon 500 said, "I'm assuming that the 'airfoil' shape on the top of the cabin is later cut off, and the one piece wing sat on the now flat top?"

 

I had a look at the plan and the fuselage and realised that you are correct. I'll cut the aerofoil shaped bit off along a line from the rear cabin bulkhead to the front one. The wing will then rest on the top of the fuselage sides.

 

The wings should be made today (Monday 11/5/20)

Edited by old man emu
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