Parkflyer33

[Fredrum]

Having just finished an extended, although sporadic, build on Jemima, I decided that I wanted to build something as fast and as simple as possible with which I could just nip down to the local park to get a bit flying in when I felt like it rather than having to wait for the weekend to get to the club field, not to mention having to wait for a flying spot. Being a beginner, I would also have to wait for an instructor to become available to take me up with the buddy box, which eats into his time as well.

I will be still going down that route once I get around to getting a new receiver for Jemima, but in the meantime, I would like to get a bit of practice in. I have been flying my Vapor at the indoor meetings lately and I think I’ve gained enough confidence to enable me to lurch for the sky by myself, and if the worst happens, I won’t have invested a huge amount of time or money in my incipient bin bag full of sticks.

I was curious to see just how fast I could build a working model from scratch, so here goes.

I started early afternoon with a few blank sheets of paper and drew up the wing, tail feathers and fuselage. Starting with the wing, some spars were stripped up and a pair of rib templates made up in ply. A set of over-sized rib blanks were cut out including holes for the threaded rods. Bolted all the blanks between the templates and planed & sanded them to shape. This went extremely quickly. The only slightly time consuming part was adjusting the spar cutouts for a snug fit.

The wings were built in one piece to be separated later. The leading edge sheet, lower cap strips and trailing edge sheet were pinned down and glued together. The bottom spars were glued to LE sheet & cap strips. Ribs were centered on the cap strips and glued down. The LE sheet was pulled up at the front and glued in the hand, one rib at a time starting from the centre. The dihedral ribs were set with a jig and the tip ribs angled outwards by eye (TLAR).

Top spar added followed by shear webs, top sheeting and cap strips. The front of the LE sheeting was sanded back flush with the front of the ribs and a 3mm false LE was glued on followed by a 6mm leading edge. The LE was planed to section and the wing sanded, cut in half and the dihedral ribs sanded on the shooting board. It was early evening by this time and I was pretty pleased with progress. At this stage, all the balsa came from what I had to hand.

Thus endeth the first day.

Edited By Fredrum on 17/03/2016 12:22:03

[Andy G.]

Good progress for just one day!

[IanN]

Designing and building. That's PROPER modelling

Looks good, very tidy job - what's the wingspan?

[Fredrum]

Thanks guys, although the word ‘designing’ is a bit strong. I drew up a plan with only the minimum of information needed i.e. simple lines for the wing structure and fuselage outline and internal structure. I settled on a 33” wingspan because it fits on two A3 sheets joined end to end and relied on the ‘that looks about right’ school of engineering. I agonized for ages on the clever name

I’m hoping for an AUW of around 500g. Many times you read about model designers saying ‘if it looks right, it will fly right’… works for me.

Incidentally, I find shrink film quite expensive. In keeping with the ‘fast & cheap’ ethos of this build, any advice on alternative coverings would be most welcome.

[Eagle 899]

Posted by Fredrum on 18/03/2016 11:03:10:

Incidentally, I find shrink film quite expensive. In keeping with the ‘fast & cheap’ ethos of this build, any advice on alternative coverings would be most welcome.

Try HK film, it's very good and cheap

[Ken Lighten]

+1 for HK film, very easy to use and cheap (my Marabu is covered with it - see Forum members new models)

Ken

[IanN]

Posted by Fredrum on 18/03/2016 11:03:10:

Thanks guys, although the word ‘designing’ is a bit strong.

I drew up a plan with only the minimum of information needed i.e. simple lines for the wing structure and fuselage outline and internal structure. I settled on a 33” wingspan because it fits on two A3 sheets joined end to end and relied on the ‘that looks about right’ school of engineering.

Yep, that's it - the definition of designing, right there in a nutshell

[Dave Brooks]

Looks like a neat job. Will be following with interest to see how it turns out. I have had some success with similar home brewed parkfly designs based on the 'looks about right' principle so no reason why it won't work out. If you really want to keep away from commercially produced covering it is possible to manage using brown packing paper adhered using thinned pva glue. It will also shrink slightly under a coat of thinned pva and can be superficially waterproofed using tape. This method has worked out well for covering foam cores but must admit I've not yet tried it on balsa frames. Yours look rather good and would doubtlessly end up with a better finish from a proper covering job so I suspect the previous recommendations are better. The primary advantages to the 'post office' method is that you can do a lot of wings for two quid's worth of brown paper and tape and can get hold of the materials at the nearest pound shop.

Good luck with the rest of the build!

[Fredrum]

The Marabu looks good Ken. Do you know what kind of temperatures you used on the film in relation to, say, Monokote?

[Stephen Jones]

Hi Fredrum,

Nice build so far ,

I remember my 1st design Many Many years ago in fact i was a teenager with no real money but a few left overs from keil kraft model kits .

And not having learnt any aerodynamics i just drew something that looked right to me .

Well all the proportions where of coarse wrong .

But it flew and very well .

It wasn't until i rediscovering that plan i realized that i had in fact designed a Tandem wing plane ( flying flea) .

Good Luck Steve.

[Fredrum]

Thanks Steve. I have an OD parasol wing, open cockpit job that I've had on the drawing board for over a year and the fuselage looks uncannily like Peter Miller's Ballerina. As they say, there is nothing new under the sun.

Had some 'me' time today so:

One fuselage side frame...

...two fuselage side frames.

Outlines sanded to shape. Nose sections filled with 3mm sheet & added some bracing under the tailplane. Just makin’ it up as I go along.

Glued one side frame down onto some 1mm sheet the cut around the edges and added hardwood veneer doublers for the wing hold-down dowel gussets. Apart from the 1mm skin and the 3mm infill, everything so far is from 5mm sq sticks. The thick bits are two sticks glued together and the bracing is one stick stripped in half.

No more for tonight; ran out of glue

Edited By Fredrum on 19/03/2016 12:26:30

Edited By Fredrum on 19/03/2016 12:27:04

[Fredrum]

Posted by Dave Brooks on 18/03/2016 20:08:50:

Looks like a neat job. Will be following with interest to see how it turns out. I have had some success with similar home brewed parkfly designs based on the 'looks about right' principle so no reason why it won't work out. If you really want to keep away from commercially produced covering it is possible to manage using brown packing paper adhered using thinned pva glue. It will also shrink slightly under a coat of thinned pva and can be superficially waterproofed using tape. This method has worked out well for covering foam cores but must admit I've not yet tried it on balsa frames. Yours look rather good and would doubtlessly end up with a better finish from a proper covering job so I suspect the previous recommendations are better. The primary advantages to the 'post office' method is that you can do a lot of wings for two quid's worth of brown paper and tape and can get hold of the materials at the nearest pound shop.

Good luck with the rest of the build!

 

Hi Dave. For some reason, I've only just seen your post. Thanks for the advice. The HK covering looks good, but if I get to the covering stage and I still don't want to buy some stuff, might build up a dummy structure and have a go at your post office method. In fact, it's probably worth having a go at it anyway. Cheers

 

Edited By Fredrum on 19/03/2016 12:42:29

[Stephen Jones]

Looking very well thought out so far .

There is nothing wrong with brown paper it can add extra strength while still being light .

 

Can also be painted .

And at 30" this is a light model. Did i mention very cheep too .

Steve

 

 

Steve

 

Edited By Stephen Jones on 19/03/2016 16:52:08

[Fredrum]

How does it go over open structures Steve? That's a very interesting model BTW, what is it? I don't see any elevators. Is that a variable incidence wing? How does it fly?

[Ken Lighten]

Hi Fredrum, I used 100 degrees for tacking and 120/130 for shrinking, seemed to work, it also shrunk really easily with a heat gun - I'll see how it fairs as time goes on with sagging etc but looks good so far!

Ken

[Stephen Jones]

Posted by Fredrum on 19/03/2016 22:05:11:

How does it go over open structures Steve? That's a very interesting model BTW, what is it? I don't see any elevators. Is that a variable incidence wing? How does it fly?

Hi ,

It goes well over open structures , Here is one of many Videos of it ,

 

I was the only one down at our field so i hung my camera around my neck and kept the flying at low level so that it would be captured by the camera.

 

Steve

 

Edited By Stephen Jones on 19/03/2016 23:35:58

[Fredrum]

That's a fascinating model Steve. Did you do a build thread for it? It would make a great free plan (any lurking editors listening?).

[Fredrum]

I see that one of the mods has changed the description of this thread. I was wondering how long I would get away with it. I’ll try to behave myself in the future.

As a matter of fact, down our way, the new one is almost as good

Here's a fin and rudder. Am I forgiven?

[Stephen Jones]

Posted by Fredrum on 20/03/2016 04:30:13:

That's a fascinating model Steve. Did you do a build thread for it? It would make a great free plan (any lurking editors listening?).

Thanks , I have already been down that road ,

Anyway here is the build thread it will also show you how i applied the paper covering.

Steve

[Fredrum]

Very interesting Steve. It's good to see people experimenting. Well done.

[Fredrum]

After considering aerodynamics, moment arms and other scientific stuff too complicated to mention, the chords of the tailplane and elevator were determined by the size of the fin and rudder and the span was a bit smaller than an A4 sheet.

All framed up.

This is probably the only bit of metalwork on the model. I had originally planned to drill the holes for the wire elevator joiner, separate the elevators then glue in the joiner. It then occurred to me that I could just embed the wire and keep the leading edge intact thereby keeping everything aligned as built. I’m sure I’m not the first one to do this.

All sanded, elevator tapered, leading edges of both parts shaped and the elevator trailing edges separated.

[Fredrum]

The tailplane has been slotted to take the fin.

Gussets and veneer doublers fitted for the hold-down dowels and the holes drilled.

There are only two formers proper in the fuselage. Each member of the formers was made of 5mm sq. strip split in half which was cut to length, shifted 5mm then glued with thin CA to make lap joints.

Glued onto one fuselage side…

... other side added.

Tapered tailpost added and tail drawn in and glued. Upper cross brace glued in. I will leave the cross brace near the tail until fitting the tailplane to ensure alignment. The ply motor mounting former will have to wait until I get the motor so I can do all the gubbins before gluing it in.

Underside cross braces glued in.

Edited By Fredrum on 26/03/2016 04:16:35

[Fredrum]

I have ordered the internals, so I can get back to the fuse when they arrive. I’m using a Turnigy Park300 1380kV motor, 12A ESC and 1000mAh 2s battery with 8x6 prop.

Seeing as how I have some time on my hands, I figured that I would keep the wings separate for ease of storage so I had to come up with a joining system.

A dihedral brace was made from 3mm ply which was glued into one wing. A piece of thin ply was glued over the two main spars of the other wing to make up a box to receive the other side of the brace. Because the brace is 2mm thinner than the spars, the space was packed up with some thickish 1.5mm balsa glued to the inside of the ply box cover. Some reinforcement was added around the existing holes at the rear of the centre ribs for a rear anti-twist pin.

There was sufficient friction in the set up to hold the wings together, but I was worried that it may loosen over time, so I glued in some blocks for pins to take a rubber band. The system works very well, but I wonder if anyone can spot the fatal flaw here.

My logic was to put the pin blocks on the outside of the ribs so that the pressure of the rubber band wouldn’t be trying to pull the glue joint apart. Yep, this meant that when I tried to put the wing in place, the pins were outside the fuselage so it was impossible to seat the wing. Duh!

Take 2: The pin blocks were cut out and new blocks glued in spanning the space between the first two ribs on either wing: much more useful. When I drilled the holes for the front pair of pins, I thought I had better check to see if the fit was OK before doing the rear ones. Sure enough, they weren’t sufficiently spaced to fit with in the fuselage, so the holes were filled and re-bored.

Everything so far weighs 130g (4.5oz). I figure that the internals will weigh about as much again, so with top & bottom sheeting, firewall and covering, I’m hoping I can bring it in at around 350g (12.5oz) or even less.

There really isn’t anything more I can do until the gubbins arrive, although I did notice that I had some Monokote left over from my last build which may be just enough to do the flying surfaces, so if I get keen, I might do that in the meantime.

[Fredrum]

Very impressed with HK. Ordered the bits Good Friday & they turned up the following Thursday. The motor arrived in a plastic case with mount, prop saver, prop adapter and spare motor shaft. No ‘O’ rings, but at AU$22, I’m not complaining.

Front former made up in 3mm ply with vents and a hole to take the dowel from the battery hatch. The motor mount holes were packed out at the rear to space the ‘T’ nuts so they didn’t stick out the front plus reinforcing gussets glued in either side. Originally the fuse sides were going to be parallel all the way to the nose, but it looked a bit too boxy so I made the front former square which gave the nose a slight taper which I think looks better and not too hard to pull in.

The framing at the top of the nose section was covered in masking tape (removed before this picture) and a frame for the battery hatch built in-situ. The masking tape provided just the right clearance and also prevented the frame being glued in permanently.

3mm sheeting was added to the hatch frame, front dowel added and everything sanded flush. It's a little bit rough, but it is supposed to be a quickie

I’ve just put all the bits together to see how I’m travelling with the centre of gravity. With the battery right up front and the prop on, the balance is spot on, but once I add the remaining sheeting, control runs & covering, I suspect it will be slightly tail-heavy. The motor will remain uncovered so I can use stand-offs to move it as far forward as necessary to get the balance without adding dead weight.

[fly boy3]

Following with great interest. Fried rum. I love building, and have also used brown paper on larger models to save money. LoL. As a newbie to electrics,wondered if you used the watts/llb method to sort out the motor requirements.Cheersi