1/4 scale PUCARA

[Karl mander]

Attached are a couple of pictures of my current project a 12ft span Pucara.

The model has taken an age to build, for me anyway, it has not been a particularly enjoyable project.

Designed by Falcon aviation it's not how I would normally build which has caused the delay.

I originally intended to put two zenoah 62s with reduction drives on it, however I can only put a 24" prop on it so I've decided to use two quadra 100s with 24 x 14 three blade props.

The retracts have come from my Dornier 335.

[David Brown]

That's looking impressive Karl, I am still amazed how quick you build these large aircraft.

[Alan Cantwell 1131]

Superb, one piece wing again?

[Dave Osborne]

Very interesting. I have been thinking about building a Pucara myself and had made some enquiries with Falcon Aviation about the kit but I understand that the kit is still quite new so I assume yours is the only one under way? I would be really interested in any information or experience you have to share especially on the method used to construct the model and its scale fidelity. Also my web searches so far have gained little in the way of detailed information other than a collection of photos and drawings. The type of info I am looking for relates to some of the more detailed aspects such as landing gear function, flap function / hinging etc and I was contemplating trying to contact FMA to see if they would help.

Any info you have would be welcome.

Cheers Dave.

[Alan Cantwell 1131]

If you go to the AGM, i think they have one in captivity

[Dave Osborne]

Alan
Sorry what is the AGM? The LMA Annual General Meeting?

I know there is an example in the museum Cosford and I plan a trip there at some time but its often difficult to get up close and get a really close look and get under the skin a bit so to speak.

cheers Dave

[Rob Buckley]

Dave, yes it is, see 'upcoming events' above.

After last year's AGM a few of us were discussing another big Pucara that's in build, so went to the appropriate hangar & hopped over the barrier to have a look at the fullsize. We didn't touch & didn't get shouted at, and I've not been thrown out since!

Be warned though, it's dog rough (as would you be if you'd had its' life!)

[Alan Cantwell 1131]

If you phone the museum, mention the LMA, and maybe give a small donation, the museum Might give you access, we were all over the mosquito, both inside, and outside, they were very helpfull

[Karl mander]

Pucara update.!

Its been covered and now painted, I can't show it fully as I'm unable to downsize it.

I've also shown a picture of one of the quadra 100 that I'm fitting. You may notice that I've fitted a zenoah prop driver to it, as the original quadra one use's a 3/8 bolt and isn't really big enough to hold the prop secure.

I've painted it in the colours of the Uruguay air force.
This is a great video of one flying, excuse the cold play music, although it makes me wish I'd done better in school as the pilot must be having fun.

https://youtu.be/SY4elYsLym4

I'm guessing it's going to come out at about 40kg.

In relation to the kit it was sold as a prototype and as such expected somethings better than others. The wings and tail feathers were a dream to put together, the nacelles were fabricated in the shed.
The plan shows a different number of fuselage formers than is in the kit.
There is no scale detail, it's up to the builder.

[Karl mander]

Painting completed so I managed to put the model together.
I've made a plug for the canopy which needs a little fine fettling.
I think its going to need the power from the was quadra engines to fly acrobatically, it's a big model!

[stuart knowles 1611]

Hi Karl,
Post a few details on how you intend to do the canopy as you go along please. I have a need for one, not quite so big but far beyond the 'normal' rage, 1/3rd Bede BD8. Initially I made a plug from blue foam and glassed it with finishing cloth, but then realised that it wouldn't stand either the heat or the pressure (double fail) plus the size of the sheet to be vac form would be so big that I've no chance of getting it hot enough. Its been getting a 'good coat of looking at' for a few months now but no inspiration so far. I need an injection of 'shedology'

Liking the Pucara, it looks to be a Beast!
regards

stu k

[Karl mander]

Hi Stu

To be honest this is uncharted territory for me in the production of a plug for the canopy.

I took my plug to a company in Stoke(acc plastics) who stated that they may be able to produce a canopy but that I needed a better finish on it.
Due to work etc I probably won't take it back to them until near Christmas.
My plug is also made of blue foam, I'm pretty happy that it is strong enough.

Yes the pucara is finally coming together, it seems to have taken an age due to all the work I've had to do on it.

With no hardware in it, it seems very tail heavy, hopefully this will change as the engines etc get fitted.
Its got two enormous aluminium poles going through the wing, although super strong it's a tad heavy.

Karl

[stuart knowles 1611]

Interesting that they think it will be strong enough. What about heat resistance, the plastic has to be pretty hot, even though it cool quickly, I feared that there might be some shrinkage. Apparently blue foam skimmed with car body filler is OK - it would mean a remake on my plug though

[Steve Vodrey]

Hey up.
An alternative, i'm told is to make the plug from wood, jelutong is particularly suitable as it is easier to work with and provides a smooth heat resistant finish....

[Phil Clark]

Blue foam will crush under the pressure & the heat will distort the finishing cloth so you'll end up with a woven glass effect on the inside of the canopy (been there, done that!!)

Any type of timber is also not much use. Timber has a grain to it and this will raise slightly when subjected to heat so you'll get a wood grain effect on the inside. It works OK on coloured formings, but not on clear.

For a 1 off, try aerated concrete covered in 1/4" of car body filler. The aerated concrete (therolite turbo building blocks) can be hand shaped with a panel saw & a surform. Cut & shape it 1/4" under-size all over than 'ice' in a really heavy layer of body filler before sanding to final shape (The body filler will resist the heat & has no grain so won't mark the inside of the canopy). The final surface need only be sanded to around 400 grade paper........if it's too smooth, the heated canopy will stick. All you have to be careful with using this method is that the blocks are 100% dry.........most builders merchants store them outdoors, so you have to dry them before use. Once dry, simply bond the necessary number together with foaming PU adhesive.

Remember to seal the flat bottom of the pattern with a few coats of resin. If you don't, as soon as the vaccum is turned on, all dust from the bottom of the pattern will be sucked out and it'll stick to the underside of the plastic & get trapped between it & the plug ruining the canopy.

Phil

[Karl mander]

Thanks for the advice gents, much appreciated, due to work commitments I'm struggling for time for the next few weeks.
Hopefully be near completion in the new year.

[Karl mander]

After many many hours of work the pucara is finally coming together.

I've had it together in the garden today and had the engines running.
There's definately a lot of power, even though the engines were over propped.
I was pleased that the prop drivers worked.
The retracts and front leg have been recycled from the Dornier 335 as are the rear retracts.
The rear legs were made by the engineering maestro Tony Thompson.
As I'm struggling to upload pictures onto the site I've posted some pictures onto my new Facebook page.

[Karl mander]

Pucara yesterday in the garden trying out the engines with cut down props. Sounds fantastic.
The canopy is fibreglass made from a home made mold.
I'll see how it flies before going to the effort of smoothing the plug and having the transparent canopy made.

[Karl mander]

Maiden fight conducted last week - no issues at all flies fantastic on two zenoah 62.
Below is the link to the you tube video

https://youtu.be/mbJQ31n_u4M


Karl

[Euan Galloway]

Karl well done I really admire your projects and the fact you do all the work yourself and not with unlimited budgets teams of builders etc and they work , so whats next ????
cheers Euan.