Parkflyer33

[Stephen Jones]

Looking good you are nearly there now .

Looks like we share something in common even if it is just the chaos in the background.

I covered this one in brown paper too.

What is the wing span of yours ?

Steve

[Fredrum]

Hi FB3, thanks for your interest. Once I had worked out the size of the plane, I looked at similar existing planes and figured that the AUW would be around 500g (17oz). I used Web-O-Calc to determine motor size, ESC & battery requirements, prop size and lots of other info. Some of the motor Kv recommendations were not available, so I entered the Kv & current specs of some available motors until something worked out.

As the build goes along, it's looking like the finished weight may be as little as 350g (12oz). I just plugged the new numbers in and the software recalculated. As it happens, the same motor would work fine for both weights, but the prop size would be different. I found it very easy to use.

I also used this online calculator to determine the servo power requirements. I wanted to keep this plane as light as possible and found that 1.8kg mini servos provide more than enough power to handle the flight loads and they only weigh 11g (0.38oz) each.

BTW, if you're interested in model design, there's a great article here.

[Fredrum]

Posted by Stephen Jones on 04/04/2016 23:45:18:

Looking good you are nearly there now .

Looks like we share something in common even if it is just the chaos in the background.

I covered this one in brown paper too.

What is the wing span of yours ?

Steve

Snap! If I wasn't in a different hemisphere, you think I'd been peeking in your workshop window

[Stephen Jones]

Posted by Fredrum on 05/04/2016 13:38:14:

Snap! If I wasn't in a different hemisphere, you think I'd been peeking in your workshop window

LOL,

Never mind looking through my window you would of needed a time machine i made that in 2011.

Thats the thing with trainers / cabin cruisers they all look very similar

Its the un-canny clutter in the background that make the two scene look alike .

Steve

[fly boy3]

Hi Redrum, sorry for late reply, but thanks for the info. The link to model design was very interesting indeed. Thanks again. Cheers

[Fredrum]

Work has kept me away from modeling for a couple of weeks but I managed a bit of workshop time this afternoon.

Battery tray made up and supports fitted into the sides of the nose.

Velcro added to the battery tray & assembly glued in place. Servo tray and control runs fitted. Luckily, I had some bits of snake left over from my previous build that were just the right length. It doesn’t look much, but this was surprisingly time-consuming. BTW, the motor bolts won’t be projecting into the battery bay like this. I’m intending to use brass tubes to position the motor forward to balance the model then cut the bolts to length after trimming the thrust lines.

The underside shot shows the battery strap clamped in place with a piece of balsa let in to the cross braces under the tray.

Last job of the evening was to align the wings & tail. A little bit sanding of the seats here and there and all’s fine.

 

Edited By Fredrum on 25/04/2016 22:54:52

[Stephen Jones]

Hi,

I was about to ask if there was any up dates on you're build ,

Looking good,

are you a free flightier by any chance as you're method of connecting the wings together looks like something a free flight model would use.

Steve

[Fredrum]

Thanks Steve. The only free flight I have done is some indoor rubber models, but I will undoubtedly build an outdoor model at some stage, probably rubber duration.

It's interesting how little information I've been able to find on how to hold two piece wings together. In all the magazine build articles, this aspect is always skipped over so I just figured this was a simple way to do it.

[Fredrum]

Sorry Steve, I forgot to answer your question from a few weeks ago: she's 33" span.

Bottom sheeting added.

The top sheeting marks the end of the woodwork. Now I have to work out a reasonably attractive scheme for the wings & tail using left-over scraps of Monocote. In the meantime, I'll have an experiment with brown paper as suggested for the fuselage.

[Simon Chaddock]

Fredrum

That all looks very neat.

You did ask for comments about the dihedral brace on your two part wing.

With sheeting back to the spar and about 1"(?) deep those wing panels look both strong and stiff.

Your dihedral brace is only half(?) the wing depth, narrow (and ply!) and at the point of the maximum bending moment.

If you loaded the wing at the centre and lifted it by its tips where would expect it to break?

My guess is it would fail at well under half the load the wing could bear if it was built in one piece.

Whilst the current join it should be adequate just remember it is quite possible to pull 12g in even quite a modest model plane.

Lets say your complete fuselage (with battery) weighs 8oz. At 12 g it would "weigh" the equivalent of 6 lbs!

Unless you are absolutely stuck for space I would 'bandage' the join with glass cloth and resin so in effect it becomes a 'one piece' wing.

Of course I could be completely wrong!

Edited By Simon Chaddock on 28/04/2016 14:52:39

[Stephen Jones]

Hi Fredrum,

I agree with Simon, it is a nice looking model and with a wing span of only 33" i would be inclined to glue the two halfs together and then bandage them as i did on mine.

This is mine covered in brown paper then painted.

Steve

[Fredrum]

Thanks for the advice guys, much appreciated and you are probably right. At the moment, the plane won't be flown under any stressful conditions (apart from my inevitable dodgy landings) so it will mostly be just easy circuits and eights and if the wing join fails, and the plane survives, I will do some mods. At the moment, the whole thing weighs about 280g (10oz) with all it's bits so it's looking like quite a light model, around 7oz/sqft. I have just put all the bits in and picked it up by the tips and it seems OK. Time will tell I suppose.

A bit further down the track, I might want to get a bit more adventurous so I will build an aileron wing for it and I will certainly be taking your excellent advice and beefing up the wing join. I'm curious to see how it goes and how long it stays intact. I'm partially trying out some ideas in preparation for some more ambitious projects in the future, which probably won't involve ply wing joiners

Nice covering job Steve.

[Stephen Jones]

Posted by Fredrum on 29/04/2016 01:27:55:

Nice covering job Steve.

Thanks Fredrum ,

Any news on this one .

It`s probably too late now,

But just looking at you're wing retaining dowels , If they where longer they could of passed through holes in you're servo mounting plate and that would of added more strength . while still allowing the wings to be split after being removed.

Just a thought, Steve

[Fredrum]

That's a great idea. Could be of use for the aileron wing.

It also occurs to me that if I had spaced the dowels accurately, they could have butted up against the inside of the wing seat (perhaps lined with thin ply to act as a bearing surface) to stop the wings separating with the added advantage of the wings being automatically centred on the fuselage.

I'm finding 'me' time a little hard to come by at the moment, but I'm hoping to get started on the covering tomorrow. Stay tuned!

[Fredrum]

The bottom of the wings covered in Monokote offcuts.

Enough left on the roll to cover the upper surfaces (just).

Nearly there. Off to get some brown paper tomorrow to see it I can make it work for the fuselage & tail.

[Fredrum]

OK, so I've just bottled it on the covering. I tried to order a servo, props and some covering from HK a few days ago and two of those items were on backorder. Experience tells me that this can be a bit of a black hole and I was all ready to try out the brown paper system, but I checked today and everything was available from my local warehouse so I ordered. I figured that as the wing was covered in film, it might look a bit weird with the fuse & tail in brown paper if I didn't do a great job of it. I'm still keen to look into it and have made up some dummy structures.

Steve, I had a look at your build blog and I was curious about how you glued the brown paper to the framework. Did you use Poly C for that as well or thinned PVA?

[Stephen Jones]

Hi Fredrum,

I use film covering and there is no shame in bottling out of trying brown paper ,

Its just that i don`t like it when film covering bobbles up over a solid structure or sags on a open structure ,

I have been meaning to do a blog on how i use brown paper as a covering alterative but as there has been so many that have done the same i did not bother.

Here is a link to one i did earlier .

I do not glue the paper in place i just wet the contact points with neat Poly C , then place the damp paper on top .

It is important that the paper is not wet , So it depends on how big you're sheet of paper is going to be or how big you can effectively Handle.

So small pieces of paper can be laid on top of a plastic bag and the diluted Poly C painted onto it . When the paper has fully soaked up the Poly C then use an old debit card to swipe over the paper to squeeze out the excess water .

Then the damp paper can be applied.

On larger projects i buy a cat litter tray to use as a bath to soak the paper in and draw the excess water out upon removing the paper by sliding it over the edge of the litter tray and between a plastic ruler .

Like most things it is easier for me to do it than it is for me to explain it

Steve.

[Stephen Jones]

I have found that PVA solution will dry hard and so not good for open structures , where as the Poly C solution will allow some flexibility.

Steve

[Malcolm Fisher]

I have used brown paper on a multitude of different models and always used thinned PVA or wallpaper paste for the adhesive. I think I prefer wallpaper paste such as Polycell and use this as a sealing coat on the paper before applying dope, paint or varnish. It doesn't seem to matter whether the structure is open or "solid" in my experience.

Malcolm

[Fredrum]

Thanks guys. Will definitely be trying the brown paper bizzo in the future. In fact, you can see the roll I bought the other day in background of some of these pics.

New elevators with wider trailing edge with ribs set in for a stronger joint.

All covered, motor stand-offs fitted. Electronics installed. All up weight is 380g (13.4 oz). It’s very slightly tail heavy at the moment. If I can get some longer 1/8” screws I’ll move the motor forward.

There is some twist on the left elevator because of the covering; the shrinkage is very aggressive. If I redo the tail feathers (which I may have to do) I will shrink the covering with an iron rather than the heat gun. This will result in the covering sticking to all the structure underneath, but I could live with that.

I know it was supposed to be a quick roughie, but I just couldn’t help myself. It took a lot longer than I intended. Overall I’m pretty happy with it, but here are some design changes I would make if doing another one:

Rethink the tail end to make the linkages a bit easier to get at. I might even go with the Tyro idea and have the tailplane underneath the fuselage.

Extend the length of the rudder so there is a bit more meat below the control horn.

Extend the nose about an inch.

Work out a more robust wing joining system, possibly using carbon fibre (I’m still keen on the two-piece idea).

Just need a good day for flying and then start thinking about the aileron wing once I have a few hours up.

[Stephen Jones]

Hey that looks neat , you wont lose that in the long grass, or the dark clouds .

Steve.

[Stephen Jones]

Any news on this one Yet.

Steve

[Fredrum]

I haven't flown it yet. I'm a bit nervous about the wing joiner after discussing it with some of you and my buddy hasn't been available to maiden it for me. I'm hoping to get a bit of time this weekend to look at the wing and hopefully have it airborne soon.

Cheers

[Stephen Jones]

Posted by Fredrum on 23/07/2016 04:22:41:

I haven't flown it yet. I'm a bit nervous about the wing joiner after discussing it with some of you and my buddy hasn't been available to maiden it for me. I'm hoping to get a bit of time this weekend to look at the wing and hopefully have it airborne soon.

Cheers

It is understandable to be nervous about maiden something you have created your self . But you built it to fly and enjoy. So i would hold the palms of you're hands out and lift the model fully flight ready by placing you're hands under both wings about midway and then gentle bounce the model up and down over the bed . that way only low G forces will be put on the wings and if it cracks or breaks at least it does not have far to fall and will have a soft bed to land on.

Also while holding the model at approximately 45 degrees power up the motor to see if the motor has the power to hold the model in the air . Don't let go of it of coarse you are just judging if there is sufficient power .

And choose a field with lots of long grass so if something should go wrong the long grass will soften the landing.

Personally i don't think you will have a problem.

Good Luck and Safe Landings. Steve

[Fredrum]

Sorry for the late reply Steve. Work has been pretty nuts lately so I haven’t had much time for model-related stuff. Thanks for your advice, that’s very encouraging.

I checked the wing in the way you suggested and it felt quite stable so I took it down to the park to do a glide test. Unfortunately, being a bit hesitant about hurling it, I didn’t throw it fast enough to generate lift and it just nose-dived into the grass. The only damage to the plane was - (you’ll never guess) - the wing joiner.

Took a day off on the weekend to sort it out. Decided to use telescoping square brass tubes for the joiner. Cut away the covering and cut a square hole in the first two ribs at the required angle.

The ends of the outer tubes were cut along the corners for a short way, pinched in and soldered to stop the inner tube sliding right through.

The inner was inserted into the outers and the whole assembly inserted and epoxied while the wings were clamped together. Thin ply doublers were epoxied into each rib for reinforcement. All that’s left now is to patch up the covering.

The joiner isn’t very long, but with a model of such low wing loading, I think it will be more than adequate. This was far more complicated than what I had intended for this model, but the join is now very strong and alignment is good. It seems a bit of overkill to have a two piece wing on a model of this size, but it will pack down into a much more convenient space and the experience will be useful on future models.

While I was at it, I knocked up some new elevators. Just waiting now for some good weather.