Cessna 152 Aerobat

[reg shaw]

Agreed Ton, keep posting, its great to see an in depth tutorial on the art of Fibreglass

Ian.

[john stones 1 - Moderator]

Yes I agree

And now I know why glass cowls cost a bit quite a bit of work involved.

John

[Colin Leighfield]

This is building at a level I haven't achieved yet, skill and patience.

[Tony F]

Absolutely fantastic to watch , amazing Richie !!! Makes my build thread look so amateur. Your explanation to us on this process is easy , informative and you make a great teacher. Can't wait for the next installment.

Tony

[Richie Carey Maddog Designs UK]

Thank you gentlemen for your kind words.

Well here we go, this is the moment of truth will it separate cleanly or will it be a total disaster and stick resulting in a bin the lot job and start again scenario (Yes the disaster scenario has happened on more that one occasion usually because I have tried to cheat or cut corners)

Start by removing the screws from the base that hold the centre section and side supports in place.

Next very gently insert an old chisel between the mould and the centre section, do this a little at a time moving around the mould as you do it, you should hear a little cracking sound each time you insert the chisel which indicates that the mould and the centre section are separating. Don’t be tempted to force them apart as this will only end in tears, even when you see a small gap appear just carry on with small gentle movement until the centre section can be lifted away.

Now you can breath a sigh of relief

Gently remove the plasticine with the dowel tool you made earlier.

Now use a nylon brush to clean away any remaining small pieces of plasticine (if you don’t have a nylon brush, you can use an old tooth brush)

Plug the screw holes in the base with plasticine.

And now we are back to the wax, you should apply another four coats again leaving 45mins before buffing between coats. I can not emphasise enough the importance of the waxing process because if you try to cheat here, I guarantee that it will bite you and stick with disastrous consequences.

[Richie Carey Maddog Designs UK]

Now lay-up the second half of the split mould in exactly the same way as the first side, now hold your breath and hope it all goes according to plan. On second thoughts don’t hold your breath as I will be leaving this over night to fully cure.

Next if all goes well, I will fit the securing nuts n bolts, then lay-up a Cessna cowl for my prototype just in time for my laser cut bits n bobs arriving on Friday.

[Richie Carey Maddog Designs UK]

Ok, I did say at the start of this thread that it would be a warts and all blog, well here is the first wart.

Removing the first half of the split mould and this is what was revealed, a red gooey mess.

‘Disaster’ well not quite, what had happened was, the paint had melted under the heat of the laying up process. However it wasn’t as bad as it looks as most of the heat produced during lay-up was when I was applying the two layers of chopped mat so fortunately the get coat had cured so the only problem I had was sticky red paint all over the surface of the mould which I quickly removed with some acetone based wax remover.

How did this happen? Inpatients, plain and simple, I hadn’t allowed enough time for the paint to harden before I applied the polyester resin. I had simply cut corners and I should have known better as this has happened before.

I wasn’t quite so fortunate with the second half of the mould, the cowl plug was well and truly stuck and no amount of tugging would release it. There was only one option, dig it out, which involves total destruction of the cowl plug. Anyway I managed to most all of the cowl plug with the exception of a layer of rock hard body filler and epoxy resin which was stuck firmly to the surface of the mould.

As I mentioned earlier, this has happened before so I already had the perfect tool to chip it away from the mould.

Here is the tool I used, an old propeller sharpened at one end and a makeshift handle at the other end.

The propeller is hard enough to chip away the body filler and epoxy but soft enough not to damage the mould surface.

Progress was slow but chipping away for an hour or so and the job was almost done. Just a little more to do.

Once all of the body filler and epoxy had been removed, I cleaned the paint off with the acetone based wax remover.

Here are the two halves after a good cleaning. Pheeew I recon I got off lightly as this could have been so much worse.

Luckily the only casualty in all of this was the cowl plug which is now ready for the bin.

[Danny Fenton]

Excellent information and I like the warts and all approach, great to see.

Cheers

Danny

[Josip Vrandecic -Mes]

Mr Richie , hat of....I ran out of breath...

Rgds

Jo

[Richie Carey Maddog Designs UK]

Thanks Danny,

Thanks Jo,

Last job, fit all of the securing nuts and bolts then trim the edges of the split mould with a grinder.

Now the mould is ready for some more ‘wax on wax off’ as Mr. Miyagi (The Karate Kid) would say. It’s a new mould so it’s a minimum of 7 coats of wax, again allowing 45mins before buffing between coats which I will do tonight whilst I am watching TV so that it will be ready for laying up the cowl for the prototype tomorrow.

[Richie Carey Maddog Designs UK]

Look what the postman delivered to me this morning, balsa from Slec and laser cutting from Laser Craft.

They say that patient is a virtue, so I will open the boxes later, yeah right. Where’s me knife so that I can get in to this lot.

Ooooh all the light-ply, birch-ply and balsa laser cut bits for two Cessna prototypes I just could not resist having a little play with them. Cheers Dylan (Laser Craft), excellent job young man.

Right, where is my glue, No, stop Richie! You have a cowl to finish and an epoxy undercarriage to start before you get stuck into this lot. But, but. Never mind but, you have work to do.

[Tony Bennett]

he he he

you could not resist could you.

[Richie Carey Maddog Designs UK]

Hahaha It just wouldn’t be right not to look though sir.

Richie

[Richie Carey Maddog Designs UK]

Mix up some gel coat and apply a thin even layer using a sponge brush, brushing from the front of the cowl to the rear, again avoid using up and down brush strokes when applying gel coat.

Next cut out some 160g or 165g woven glass cloth, you want the cloth to be over size so that when they are applied they overlap each other by about 1” you will need enough cloth for two layers.

2 front pieces

4 top/bottom pieces

4 side pieces

And 1 two inch strip that goes around the rear of the cowl to add strength.

Mix up some general purpose polyester resin and apply the cloth using a stipple motion.

You want to apply the cloth one piece at a time ensuring the cloth is thoroughly wetted and there is no air trapped under the cloth, apply the cloth in this sequence, making sure that they overlap each other.

Front

Bottom

Top

Side

Side

Repeat for the second layer of cloth, then finish with the 2” strengthening strip around the rear of the cowl. Now leave it to cure.

Whilst the resin is still green (still soft but not sticky) cut off the excess cloth with a sharp scalpel. Now leave overnight to full cure.

That’s the cowl complete and will be ready to remove from the mould tomorrow.

Next I will tackle the epoxy undercarriage, but first its time to play with the laser cut bits and bobs that came this morning he he he.

[Tony Bennett]

looking very nice sir.

cant wait to see the finished product.

[Richie Carey Maddog Designs UK]

Ok, here we go, time to see what we have.

Well it does need a bit of refinement and new moulds made for the production kits but it fits over the bulkhead perfectly and it looks the part so this one will do for the prototype.

Now I can put it to one side until the fuselage has been built.

[Tony Bennett]

yay

well done.

looks good too.

[Nev]

Nice job and a great thread.

The amount of work involved would put me off trying but I suppose once you have the hang of it it's not so daunting. Thanks for including so much detail.

[Richie Carey Maddog Designs UK]

Cheers Tony.

Thanks Nev, yes there is quite a lot of work involved but that the bit I like and your spot on, once you have done it a couple of times its not half as daunting as it looks. It’s the waiting for things to cure I struggle with.

Richie

[Richie Carey Maddog Designs UK]

Well here we go with the epoxy undercarriage, now there are loads of different ways this can be done using specialist tools, vacuum bagging, moulding press etc etc, what I will do here is show how it can be done in your workshop with minimal tools.

First you will need to make a simple mould in the shape of the undercarriage, this can be made out of any thing you want as long as it will hold its shape. I chose plywood and foam because I have plenty of both.

Find two pieces of birch ply wood.

Next apply some double sided tape to one piece of ply, remove the tape backing and stick both pieces together.

Trace the shape of the undercarriage on the ply wood.

Cut it out with a band saw or jigsaw.

Finish off with a sander.

Using double sided tape stick the two pieces of ply to a bock of polystyrene

Cut the foam block to shape with a hot wire.

And that’s all you need to lay-up the undercarriage.

Cut some fibreglass tape (I used two” wing bandage tape for this one) in to strips long enough so that about 1” to 2” is hanging over the edge of the mould.

Roll out some draftsman tracing paper, the opaque plastic stuff you can get from your local art materials shops.

Cut it in half.

Now mix up some epoxy resin (slow setting).

These are the tools you will require to lay-up the undercarriage.

1 3” sponge brush

1 fibreglass roller.

1 car screen squeegee.

Pour some epoxy resin on to one half of the draftsman tracing paper

Spread it over the paper in a even coat.

Now using the glass tape build up the undercarriage flat on your board, making sure the glass tape is wetted and firmly rolled as each piece of glass cloth is laid up.

Now place the second half of the paper over the undercarriage and pull the squeegee firmly over the undercarriage squeezing out ant trapped air as you go. Do this a few times just to make sure you have removed all of the air bubbles.

Finally drape the undercarriage over the mould making sure that it is flat. Use some masking tape to hold the ends in place until the epoxy cures.

[Richie Carey Maddog Designs UK]

After leaving the undercarriage over night to fully cure trim off the ends.

Now mark a cut line on the underside of the U/C and using a diamond tile cutter cut off the excess.

Sand the U/C flat.

Now repeat on the other side.

Mark and cut the U/C to the correct size.

Using a washer mark the U/C where it is to be rounded off.

And round off on a disk sander.

Now using one of those nifty little sanding things of which the name eludes me at the moment, sand the sharp edges off the U/C.

That’s the undercarriage and cowl all done, next job is to build the fuselage decking jigs, then I can crack on with building the Cessna prototype.

[Tony Bennett]

flap wheel sir.

looking impressive so far young man.

you make it all look so easy.

[Martian]

Excellent step by step guide Richie

[Richie Carey Maddog Designs UK]

Cheers martin

Thanks Tony I would have tried all day to remember that, ‘Flap wheel’

Well I have almost finished the decking jigs so I thought id treat myself and have a quick preview, its all held together with masking tape, I cant wait to put it together properly.

Richie

[Dylan Reynolds LaserCraft Services]

Looking good Richie