Scale Soaring UK

Well it had to happen. After 20 years of joyous flying in all conditions in every corner of the country, I stupidly stuffed my 4m ASH25 into the ground last August. Nasty turbulence at Leek turned a fast pass at +3m height into a sudden stop at -25cm. A photo in RCM&E shows the carnage.

The bits (and there were many) have been in the workshop long enough. Looking over them last week, I decided it's worth fixing as the wings are virtually unscathed. So all I need to do is make a new fus.

I'll change a few things just to add interest, the main one being to mold the fus using the lost foam technique. I made some fuselages like this decades ago but they were pretty primitive. Hopefully I can refine my technique. I'm inspired by Roo, and how believably fast he makes his fuselages. I'm also determined to do a better paint job than my usual satin finish - I want GLEAMING! And I'm going to vac-form a canopy too - I always meant to do one for the ASH25 but had so much fun flying it I never bothered.

First question - I'm planning to make the fuselage plug from XPS (extruded polystyrene) foam, the kind available in 6mm - 30mm thick sheets for electric underfloor heating. Is this the best stuff to use? I like its small-cell texture and it shouldn't break off in lumps like EPS (expanded polystyrene).

Second question - can you hot-wire cut XPS for foam wing cores? If so I'll buy plenty for future foam-veneered wing projects.

Meantime I've drawn up a new fuselage plan and practiced some composite layups. I plan to use 2 layers of 200gsm twill glass cloth either side of 175gsm Diolen - an aramid cloth similar to Kevlar but cheaper. First samples seem great. Light and stiff but with an extra resilience due to the Diolen. The Diolen cloth is a nightmare to cut (it just fluffs up!) but it wets out OK and seems to bond well to the glass. It cuts better after the epoxy has set.

I'm a dead slow builder as I overthink stuff and have very little spare time but I hope to make a start on the foam plug before new year.

Rog

Good luck with your project Roger, I used EPS on my 17 fuz, wouldn't use it again to flexible, had to stiffen the plug with carbon to keep it straight. have been using XPS for foam wings for years, first in green then blue, they have stopped making blue now, grey is the new colour, it cuts much better than EPS but does require a bit more heat in the wire, it also carves and sands better than EPS, you could bring the model to Eden next year, no pressure then
Chris

Chris Bowles wrote: ↑24 Dec 2019, 09:12 ... you could bring the model to Eden next year, no pressure then
Chris

I'll do my best!

Hi roger glad you are inspired by my builds and I hope l can help if possible. I have used blue foam on my 1/4 models it is easier to carve but really hard to remove. I remove it by hand so it was really hard to remove and did not melt very much with chemicals like petrol ect. My bigger models are Wight polystyrene foam it is harder to carve right but is easyer to remove it will melt with petrol. So I will now only use white foam now.plus it is cheaper. Blue foam is getting really hard to find you can still get it but it is now gray in colour. The last time I asked it was £250 order . Wight foam will have more flexibility so it will need a jig and I layed carbon tape along the tail boom then let it set first. I then add 4 layers of glass cloth of about 200gm plane weave. You will lose some weight when you sand but you can add inside more glass or carbon if needs be. I whould consider not using kelver. Best of luck Roo

Thanks for those tips Roo.

The best searches for XPS foam included underfloor insulation . The boards are usually 120cm x 60cm and from 6mm to 50mm thick. Unfortunately they are typically sold in packs of boards to cover a large area, and for my small project I only wanted a single 120cm x 60cm board of 50mm thickness. The cheapest place I could find that would sell a single board was ezheat on ebay. Prompt, free delivery, well packaged, all good.

One board cost £15 but if you buy more the unit cost goes down. It was blue by the way. For info, the new grey stuff contains graphite which will likely increase density - not a good thing if you're using it for foam wing cores.

In terms of lay-up, I'm pleased with the 200gsm twill glass / 200gsm Diolen / 200gsm twill glass test piece I made. The Diolen adds a lot of resilience to the lay-up. When I hit it with a hammer, like you do, the glass eventually splintered and tore but the layer of Diolen held it together. If the fuselage feels a bit too flexy I could always lay up another layer inside.

I'm back to work now so may not get much done for a few weeks....such is life.

Roo/ Roger, I have found that cellouse thinners will remove XPS foam, it dosen't dissolve it, but turns it into a thick paste, which is very small is size, compared to the plug, also insulationsuperstore, advertise XPS foam, Danosa Danopren, 1.25×60×5, 8 sheets for £41, we have a store near by, so will check it out, and let you know
Chris

Thanks Chris - that is a great deal from Insulation Superstore, especially of you can collect locally. Please let us know what the quality is like.

I assume you wrap your foam plug in parcel tape before glassing to make it slightly easier to clean out the foam? Either way, it sounds messy!

Cheers,
Rog

Hi Roger, yes I normally wrap the foam plug in parcel tape, and give it a coat of release agent, makes it easier to remove in the boom area, where there is not a lot of room, it's not that messy, once the front end is clear, stand the fuz up on its tail, in a container, pour in some thinners and wait, best of luck

Hi Roger, took a trip to the superstore, more like a small building, no stock, to bulky to store, we can get it for you, carriage extra, quoted £55 for delivery, needs to be but on a pallet, so pallet charge, tried a few more firms, all the same, apart from one that wanted to charge £80 delivery, so your price looks reasonable
Chris

Chris Bowles wrote: ↑11 Jan 2020, 18:28 Hi Roger, took a trip to the superstore, more like a small building, no stock, to bulky to store, we can get it for you, carriage extra, quoted £55 for delivery, needs to be but on a pallet, so pallet charge, tried a few more firms, all the same, apart from one that wanted to charge £80 delivery, so your price looks reasonable
Chris

That's useful to know, Chris.

It's a shame that although builder's often use materials that look very cheap to modellers, you need to buy a shed-load to get these savings!

In one of those lovely quirks of fate, I stumbled on a bunch of offcuts poking out of a skip outside the school's DT department this week. They are now in my workshop.

This is all the proof I need that god is an aeromodeller.

The World's Slowest Builder? Could be.

Anyway I've started on the replacement forward fuselage (the tail section is detachable behind the wing TE and survived the crash ).

First I sketched a side view and plan view of the fus and lofted some cross-sections.

There are many ways to transfer these 2D drawings into foam.

You could just get a big lump of foam, transfer the top and side profiles onto it, bandsaw around these, then get creative with a sanding block to create the contours. But I didn't think I'd be able to get enough cross-sectional symmetry to be happy enough with the end product.

At the other end of the spectrum you could cut many (say, 20mm thick) formers and sandwich these together. This would massively reduce the amount of sanding and ensure good profile accuracy. It would also take blummin' ages.

In the end I decided to cut a 50mm thick central keel to capture the side profile, then fill out with 50mm thick half-formers either side. Yeah this means there are some big steps between adjacent formers, but I reckon there are enough reference points to help me keep the profile accurate when sanding.

So.. over to the scroll saw, and about 2 hours later I have a little kit of foam parts. Must say, this pink foam is fab to work with - so easy to cut/sand but stiff enough to stay straight and rigid.

A couple of hours later the whole lot is glued with PVA, taking obsessive care to check alignment/symmetry.

The next step is to get jiggy with a sanding block and blend all those formers to a smooth flowing shape.... BUT maybe not for 6 weeks as I'm back to work Monday.

Rog, I'm glad to see that someone else resorts to a big roll of paper and a good old lead pencil.
Brian.

I can't drive CAD either Brian, so roll of wallpaper backing plain paper, rulers, squares and a pencil for me too.

John M

CAD is great for some things but for simple-one-offs like a model glider I actually prefer the creative freedom of a pencil running over paper. It gets my hands more in touch with the 2D shapes before they become 3D forms. It's a tactile thing and also a nostalgic thing - takes me back to a happy childhood of endlessly doodling planes.

Great to see that you have made a start and it's looking good. I myself always shape from a side and top profile the same way we made surfboards. There is a method we shape what we call the rails what you call the side profile of a glider. But there is meny ways to skin and cat. I myself use pen and paper still works.

Crikey I've had fun!
Shaping the pink foam of the new front fuselage section went really well, working methodically with a serious of chamfers on each side to keep it symmetrical. It was so pleasurable to see the stepped sections blend into a smooth 3D form.

I then worked on either end. I'm fitting a FES so screwed the motor bulkhead to the front. After laminating up a block of balsa I turned a spinner using my electric drill as a kind of lathe. Not sure what I'll do next - either glass the balsa, fill, paint and use it as the spinner or use it as a plug and vac-form a plastic spinner off it.

At the back of the new front fuselage section I'll fix in a former so that it can bolt to the original rear fuselage section (which survived the crash). This former is cut from 9mm ply and profiled around the rear fuselage section, before fixing to the end of the front section foam plug. The profiling took a while due to the angle of the join, but after an hour of trimming I think it should give a smooth blend. Anyway, why rush? I just love being in my workshop.

Next time I'll tackle the wing roots.

Looking great Rog!

Out of interest, what did you use to shape your foam? I find permablocks a little too coarse.

Ell.

All very cunning Rog. Nice neat workmanship.
Brian.

Elliot Howells wrote: ↑18 Mar 2020, 08:17 Looking great Rog!

Out of interest, what did you use to shape your foam? I find permablocks a little too coarse.

Ell.

Cheers folks.

I used a long Permagrit to get the bulk off then stroked it with a 6"x6" pad of 240 grit, curved in my hand. I wait until the hour before sunset because the low, warm light casts really useful shadows revealing highspots. The strip-lighting in my workshop is no good for this.

Just heard schools closed so hoping to get more time in the workshop between remotely-taught lessons.

Board manufacturers shaping blocks of foam have white painted walls with waist level strip lights to complement a waist level saw horse type of supports. They use an electric plane with multiple blades for taking away large amounts of foam, most diy electric planes will only have the one blade and rip the foam.

I can believe it Mark. Lighting is so important to a good job.

Did a little more today - made the fuselage root ribs from 6mm liteply with carbon. Also glassed and polished the spinner. The plan was to vac-form acetate over it but I now fancy something stronger and more resilient so may mold it from GRP. Something to mull over as I fall asleep.

Progress inches on, glacially.

With the foam fus plug 95% shaped, I switched to the wing root structure which is built separately to ensure accurate alignment of wing joiners and auto-connecting electrics.

The wing ribs are 1mm undersize all round to allow for the thickness of the glass skin when joined to the fuselage.

I moulded the glass wing joiner outer tube around the wing joiner itself.

Then it was time to cut the canopy and wing roots out of the foam plug. I wanted this to be done really accurately. In the case of the wings this was to hit the 1.6 deg longitudinal dihedral I found worked best in the original model. In the case of the canopy it’s because I love a beautifully fitted canopy. Is it just me that always looks first at the canopy when judging the workmanship of a model?

So I spent most of the morning making a jig then trimming, rechecking, fiddling, trimming etc... Honestly, I think I have undiagnosed OCD.

Then the plug was fitted into the jig and I reached for my sharpest hacksaw (yep I could have Hotwire cut it but I had stupidly left my paper templates attached to the foam formers, which would have stopped the wire in its tracks)

The cutting itself went well...just took my time and checked the saw was progressing symmetrically.

I’ve eyeballed it and measured it from every angle and I am 100% happy with the profile symmetry of the fuselage. This is not like me. Usually stuff goes wrong.

I test slid the wing root structure in place and it’s a satisfying fit. I now need to finish this structure before gluing into the main plug. Then it’s the canopy surround for which I have a cunning plan.

Well I hope it's better than one of Baldrick's !!!



BC

More cunning than a cunning fox with a degree in cunningness from Oxford University.

Funny how sometimes model-building gallops on in leaps and bounds with lost of obvious progress, and other times you plug away for ages with nothing to show for it. This last week has been one of those other times.

Any road, I got the wing root centre section all finished and glassed with 200gsm, then sorted the nut and bolt that attach the front and back fuselage sections.

I also hollowed out the fuselage under the wing roots to leave about a half inch wall thickness, so that the servo wiring could pass through.

Then I masked off the area and applied polyurethane glue, possibly the best glue ever invented except that (a) it foams as it dries and gets EVERYWHERE, (b) it is quite pricey, (c) it gives you cancer, as it admits on the label with remarkable honestly.

I'm using the Everbuild brand of polyurethane.

Then lots of slightly panicky rigging and jigging to check all the angles were true before the glue grips. Yep, all good.
(Also...an excuse for a sneaky bench-fly )

After lunch I’ll fit the deck above the wing roots and then I can actually start glassing the fuselage, which is good because if I leave it much longer it will be more dented than my car...

Front fuselage foam work now basically done, after adding foam fillets under the wing roots, then filling and final sanding. Polyfilla worked well - it sands about the same rate as the foam.
I used the shallow evening sunlight as it shows up every imperfection. And crikey the wing roots look rough! I’ll rework them with micro balloons after I’ve got the first layer of cloth on.

I’ve just parcel-taped the fuselage so I can mould the cockpit rim, and made a former for this too.

Was disappointed that the tape ended up with wrinkles (like you do when you try to get a flat material to take up a compound curve) but am hoping this won’t show through the glass cloth too badly.

May need a break now due to work, but hope to inch the project forwards whenever I can steal a minute.

Hey Rog, that's coming along lovely!

I presume you'll be removing the foam with solvent? Is the tape just stop excess epoxy soaking through to the foam then? Intriguing...

Hope it's as nice for you up there as it is down here.

Ell.

Rog,

I've always used parcel tape to protect my foam canopy plugs and it's fine - on a 'normal' canopy. When it came to the 100 plug, the acute compound curves were a nightmare - the tape actually lifting off in places after a little time.

I found a very good solution in giving the plug three coats of undiluted PVA, brushed on and allowed to dry thoroughly between coats and that completely protected the foam from polyester resin - and we all know what that does to foam.

It was only cheapo builders PVA that I used (or maybe my granddaughter's creative learning stuff - can't remember, but I will undoubtedly be found out in due course if it was the latter!).

Some useful tips gents - thanks. Yeah Ell, weather is glorious - but I'm stuck inside teaching!

Interested to hear your tape lifted, Robbie. I hoovered the foam with a brush fitting before taping it and found the tape stuck really well (such that when I tried to reposition it it tried to take a chunk out!)

I'm not worried about the polyester dissolving the foam...as I'm using epoxy. But I will forever remember that sick feeling when my dad and I tried to join the foam veneer wings of our first model, a Cambria Capstan, using polyester resin! It just ate it's way through the cores. Ugh. Upsetting.

So yes, the tape is just there to prevent the foam sucking up all my precious epoxy, which would then become a nightmare to remove. I'll chisel out most of it then use maybe petrol to wipe out the last bits. Will test first though as petrol is pretty aggressive stuff.

Cockpit surround moulded this evening.
Two layers of 200gsm glass (top one larger to reduce taper the strength) spot glued in place with cyano.

Then on to some proper glasswork at last!

The glass soaked out well and conformed amazingly to the tight curves around the wing root leading edge. I assumed I’d need to snip it here or there, but this twill weave really does take curves.

Then on with the waxed card to give a smooth finish to the cockpit ledge, then a layer of cling film, then masking tape to pull it all down tight.
Hoping for a reasonably sharp edge to the cockpit opening with no air bubbles.
Fun times!

So yesterday went well - removing the tape this evening revealed a beautiful crisp shiny cockpit rim, requiring almost no trimming. Check me out, master composite expert.

But then this evening I was back to my usual form - learning from mistakes!

The plan was to lay up 2 layers of 200gsm glass over the whole of the fuselage except the deck above the wing roots. However, it turns out those little wrinkles in the parcel tape not only show through the cloth, but seem exaggerated by it. So I only did one layer, and used the spare resin to glass the canopy plug.

When it’s cured I’ll have to sand out the bumps in the glass before I lay on the second layer. The fus should still be plenty strong as I hope to lay 200gsm Diolen inside after I’ve cleared out the foam.

You live and you learn, as my gran used to say.

Half an hour sanding got rid of all the bumps in the first layer of glass due to wrinkled parcel tape.
The next layer of glass went on much better and is now sunbathing outside. Going onto glass it takes much less epoxy than onto foam. I used exactly 1:1 epoxy:glass today.

Any views on how many layers of glass for a modestly-sized fuselage? I’m thinking 200 glass + 200 glass + 175 Diolen.

I can always add more inside if it feels squishy.

Hi Roger, looking good, following with interest, when I did my ASW 17 fuz, used 5 layers 160, plus 1, 80 topcoat, this was from the trailing edge area, up to the nose, behind the trailing edge,down to 4 × 160, + 1, 80, this made a firm to squeeze fuz
Chris

Thanks Chris, I was hoping you’d reply. So that’s a total of 880gsm in the nose of your ASW17.
I think I’ll finish with some 100gsm glass on the outside, which will take less filler to finish than the 200gsm. I’d rather have glass than filler. My total thickness with the Diolen will then be nearly 700gsm...not far off your thickness.

I must say I’m finding this glasswork really therapeutic.

Hi roger I use about 4 or 5 layers of 190 cloth. It may need more adding later when the foam is removed but I add this to the inside. 4 to 5 layers is ok for the back end but can be a bit thin on the front end .I do it this way because it is easy to make a lost foam fuz too heavy.

Thanks Roo. That's really interesting - you use a similar overall thickness to Chris - about 900gsm total. I expect I'll be adding more layers to the inside after I've removed the foam.

I've been learning loads from this website recently: http://www.lefevere.eu/modellflug/how-t ... -fuselage/

It's inspiring what wonderful standards they achieve with relatively low-tech equipment (no CNC or digital printers) and affordable materials. The emphasis is on strong, robust, light, practically-sized models designed to be flown hard off the slope or the flat.

Here's an example of their fuselage lay-up (shown in the attached drawing). Starting from the outside and working inwards...

160gsm
280 gsm(at 45 deg)
280 gsm

Although this only totals 720 gsm, they also use some bands of uni-directional glass rovings running lengthwise along the side of the front fuselage, and glass rovings around the cockpit opening.

Interestingly they avoid carbon, and give some convincing reasons for this on their website.

Moving on...I‘m now up to 3 layers of 200gsm cloth on the outside, rubbing down lightly after each and the surface finish has improved every time.
I then screeded the whole fus and canopy mould with microballoons. Afterwards, I thought....why did I do that? There was no trace of the grain of the cloth and I should probably just have gone to a coat of primer. Anyway, by the time I’d rubbed it back there was almost none of the microballoons left, so I’ll just consider that as my 60 mins exercise for today.

Then it was time to tackle the cockpit lip.
Rather than just have a, say, 10mm wide flat lip like Pat Teakle models for example, I wanted to create a square crossection ridge, rebated back from the edge by about 5mm. This was partly to make it more scale, but mostly because I believe life should be hard. I could then mould the canopy frame around that, so that it would locate really positively onto the fuselage.

First I marked where I wanted this ridge to be...

Then, I stuck depron (ok...it’s pizza packaging) onto the fuselage with double-sided tape. This was trimmed back flush with the fuselage edge, then a channel cut out where the ridge would be. I made a little trimming tool to keep it accurate.

Many metres of epoxy-soaked 12k carbon tows were looped into this channel and packed down tight. I levelled off the top with some microballoons, then layed a waxed template on top to (he said hopefully) get a flat smooth finish to the top of ridge.

I’m not sure this whole approach will work because the foam may get well impregnated with epoxy and take some removing, but my hope is that it will sand easily off to reveal the ledge I so want.

Then at last I can cut the centre of the cockpit out and start mining foam. I should be good at this...my grandad was a miner.

Well that worked fine...a good solid carbon ridge with a neat and accurate edge. Not perfect, but should tidy up ok.

Now the fun bit... excavating the foam.

It went brilliantly, coming out so cleanly without any messy solvents. Waxing the tape probably helped.

I was really glad I had a strong cockpit edge to work against with my chisel. A thin glass edge would have been very vulnerable.

Surprising how much weight there is in the foam...it dropped from 500g to 400g when foam removed.

In terms of rigidity, it is rock solid around the cockpit edge thanks to the carbon, but about as squishy as an orange squash bottle on the skin itself. So next step is to lay up 200gsm Diolen internally.

Diolen in. I used a cloth template to get a good fit.

When it’s cured I’ll see if it’s still squishy and add another layer if needed.

In the end I added 2 layers of 200gsm Diolen, which added to 3 layers of 200gsm glass brings it to a total of 5 layers and 1000gsm wall thickness.

It feels very strong and possibly too stiff. I think a fuselage needs a little flex in it to absorb landings (unconvinced? Watch me land). I also noticed it’s way harder to achieve a 1:1 resin to cloth weight ratio when working inside the fuselage rather than outside it. Pulling cloth around convex curves it’s much easier to wet out than pushing it into concave ones. My last layer of Diolen inside took 2:1 resin to cloth. The fus is still fairly light though.

I’m happy that the main glasswork is done now on the front fuselage, so this afternoon was just skimming the joins to the rear fuselage and wings with filler.

I had some spare epoxy so moulded a tray for the Lipo too from scraps of Diolen.

Not sure what next. Probably make the canopy frame.

So...the plan was to spend half an hour or so rubbing down the filler to get a decent blend between the wings and fuselage parts. Then the OCD kicked in. 3 hours later I’m satisfied with the finish.

To reward myself, I decided to make the canopy frame. Now remember that carbon ridge around the cockpit edge? Well this is where we have to mould an n-shaped canopy frame to fit over it.

First off, loosely cover the fuselage with a couple of layers of cling film.

Plan A was to lay a few strips of 200gsm glass cloth over the ridge, then squish down with foam and a hardboard template, to make the cloth conform to the cockpit ridge.

Whenever you call something plan A, it’s instantly doomed, isn’t it.

Well the foam didn’t work because no matter how hard I compressed it down onto the cockpit rim, it would not squeeze tightly into the corner.

Plan B... Abandon foam. Roll modelling clay sausages and push these over the glass cloth before clamping on the hardboard template. Seemed worth a try.

Strips of cloth applied, roughly 3 layers. A nice chance to use up a bunch of off cuts (well I do live inYorkshire.)

Then a layer of cling film, then the modelling clay, carefully nipped around the cockpit ridge.

Finally, hardboard template clamped in place, then off to my solar-powered thermo-cure system i.e. on the bench in the sun.

I’ll check it this evening before it fully sets then run some carbon tows around the outside for added rigidity. Not sure how to thicken up the frame edge to give gluing area for the canopy. May use 1/8” balsa. Ah yes, I remember balsa....

Hi Rog, at least you have some decent clamps to hand, always like a plan B
Chris

Well that went REALLY well. Just peeled off most of the modelling clay to reveal a light, snug-fitting canopy frame. Needs a tidy up, then I’ll run some carbon tows around it to stiffen and thicken up the edge.

Never mind the canopy frame. Why do I have a chunk of smashed foam glider in the background?

For many years a good friend from Holland has come over and holidayed in our village. He flies mostly small electric foamies but I’ve tempted him into slope soaring. Last August he brought the model in the photo and asked if i could get it to fly. We chucked it off the cliff above our house into a fresh and lifty breeze. It took me seconds to realise it was a total pig, flying very fast but with sluggish responses in every axis and the worst stall of any object I have ever steered with thumbs. I fought it for 2 minutes until eventually it ignored all controls and dived downwards to a place I had only ever been to in my darkest nightmares - the impenetrable and precipitous wood at the base of the cliff. I’m amazed really that I’ve flown here for 20 years and never once crashed a model into this most inaccessible of places.

Skirting around the top of the cliff, we glimpsed the model lodged in a tree about 400ft below. There is no way down, so we spent a few hours trying to climb up from below, returning with only grazed knees and hands torn by brambles. I waited until the leave-fall of Autumn and tried again, but was defeated again by the nearly vertical slippy bank side.

Fast forward to this afternoon and a neighbour passed the model over the hedge by my workshop. He’d been exploring the caves in the cliff and had stumbled upon these sad looking remnants. His son, (half Olympic gymnast, half goat) had somehow managed to reach it.

So, that’s about as happy an ending as I could hope for.

I have, let me see....NO intention of fixing it, but am happy that it is no longer littering the hillside.

Goodness, what an exciting life you lead Rog!
Brian.

B Sharp wrote: ↑08 May 2020, 22:36 Goodness, what an exciting life you lead Rog!
Brian.

Ah, the retrieval of wayward models....a challenge as old as aeromodelling itself.

Cockpit tray moulded and fixed to frame. Just going to run some cf tows around the outside to stiffen it and give more gluing area for canopy.
I seem to be stuck in an endless circle of filling/sanding with the fuselage. Just when I think I’m ready to spray, the light catches an imperfection. At some point I just need to man-up and shoot some primer at it.

Looking good Roger, only problem is you see more defects after spraying on primer !!!

Hi roger I use isopon reface great stuff. Looking good

Chris - I know! It's going to look SO BAD when sprayed.

Roo- thanks for the tip. I've never sprayed 2K and don't think my health could handle it now. So I'll probably use a rattle-can primer and just accept it is an inferior result.

Rog, another option is to brush on 2K primer over the worst areas. You need to do some industrial-scale flatting, but you can start coarse (120) and work your way to fine (600). This will leave you with a surface with all but the largest imperfections filled. Aerosol primer is so thin in order to get it out of the can, that it's about as much use as a chocolate teapot...

Hi roger I do not spray it I brush it on .it sands really easy. Stopped using micro balloons has it makes me feel ill when sanding even with a mask. Also I use 2k stopper to fill small holes.

Thanks Chris and Roo. That’s good to know. I’ll order some. I assume although it’s polyester based it’s compatible with epoxy GRP.

Interesting what you say Roo about the microballoons becoming a problem for you. I’d never realised until I read the label last week that you should have a mask on before you open the tub.
It’s true, and worrying, when they say that whatever material you work with ends up inside you.
With composites in particular people develop sensitisation over time, to the point where even a trace of the substance will trigger an allergic-type response.
And it’s harder than ever to get PPE at the moment for some reason?

I use this stuff, especially as it's available in white...!

https://classiccarpaintsdirect.com/shop ... rimer-kit/

Thanks again Chris. Good enough for you.... definitely good enough for me!

The primer went on a treat. It’s a funny thing primer, you buy nice quality stuff, apply it with great care, then spend hours trying to rub most of it off. I was pretty happy with the finish though, which had removed all trace of sandpaper scratches and evidence of pinholes.

And next...one of the very few modelling jobs that still fills me with fear...spraying topcoat.

This time I would get it right. I would mask the model meticulously. I would hoover all dust from my workshop with forensic rigour. I would avoid overspray by making a screen. I would prewarm my rattlecan in hot water. I would shake the can vigorously until my arm ached. I even sat myself comfortably on a plastic box so I could focus on applying those even coats from 20cm.

It was all going so well. I sat back to admire that gleaming, run-free finish I have long dreamt about. And with a loud bang the plastic box under me exploded into bits, I fell backwards and deftly kicked the gleaming fuselage into the curtains. Ruined it is, ruined. I’ll have to wait until it dries then rub it down and start over. With a stronger seat.

Roger,
Best laid plans!! Should have passed on that extra helping at lunch

I feel for you Roger. My painting adventures usually come to an equally sticky, albeit perhaps less painful, end. For example:
http://www.bartonhewsons.uk/home/model ... lcano.html

Trevor

I'm with you on the spraying gloss thing Rog. I've never done an aircraft which didn't need a rub-back and respray at some point in the finishing. Tough luck mate!
Brian.

Thanks for your commiseration gents! It somehow helps knowing I’m not the only one struggling with spraying.
The annoying thing is that I had, momentarily, achieved that mirror finish I’ve long hankered for.

Never mind, I consoled myself by flying gentle laps around our field as the sun set with my little Hangar 9 Taylorcraft, my first fly since lockdown. I keep forgetting how much sheer fun you can have with small models on a calm day. Why do we build such big heavy expensive models again?

Meantime the painted fus has sun bathed all day so will hopefully harden off and sand back reasonably well.

Rog, you're just a beginner when it comes to disasters, I could tell you stories that would make your toes curl!

He told me, and my toes are still curled......



BC

Can any of you beat this disaster of mine?

I had just finished my latest pride and joy.The massive (to a 10year old boy) KeilKraft Topper.It was as I remember a massive 40" wing span. I had just that day finished it in British racing green dope brushed on. With fine lines of gold flash also brushed on running under the cockpit and down to the tail which was a 'V' tail. My colour scheme left a little to be desired but I was only 10. In those days I would use every penny of my pocket money and birthday money buying the needs to finish my latest and of coarse my best project to date. After putting it all together to show it off to the visiters at the family tea get together I took it into my mothers 'best' room and nestled it onto her settee befor returning to the party. A little later my elder brother who had just taken a new girlfriend began a play fight with her, and she making a girly scream ran off. The rest of us stayied at the party and the tea table. Brother came back into the room and beckoned me out, He took me into the best room where my pride and joy was re-kitted into many many bits of broken balsa on the floor. He had chased this girl into the darkend room and play thrown her onto the settee and my model Ahhaaaaaa.
With the remenesing of this story and while you all have a chuckle I'm going to find a darkend corner somwhere and have a cry.

Oh Terry I feel your pain. It somehow made it worse knowing where the story was going! We should start a thread of people’s biggest modelling bloopers. It would be much more interesting than this thread!

Actually one of my bloopers would be when I maidened this model 20 years ago. I was so wowed by its speed and agility that I outside looped it on its first flight, the canopy popped off followed by the battery and I watched as my new free flight model carved a neat parabola into the hillside. Amazingly the Kevlar held the fuselage together and it just had a few scratches to the paintwork.

After stripping right back, re-priming and re-glossing I’ve got a finish I’m happy with.

It’s actually really shiny so I’m not sure whether to
a) cut back with 1200 used wet and then polish it up,
b) just spray it with lacquer,
c) not even risk the lacquer?

If I cocked it up again I honestly think I’d cry...

More phots

Hi Roger, looking very smart, I know your problem, you get a nice finish, and think about a coat of lacquer, only to find there is a reaction

Hi Rog, the ASH is getting there. Paint, lacquer- I hate them, but they are necessary on a scalie. I try not to go for a super shiny finish, even on a glass ship, as it tends to make the model look like a toy. If I order gloss paint I tend to ask for it to knocked back about 10% to give me a gloss rather than a shine. I think it looks more like the machines I see at gliding clubs.
Brian.

Thanks for your input gents.

Is the point of the lacquer to increase the scratch-resistance of the gloss paint, or to restore its shine if you've cut back the gloss with wet and dry?

The purpose of lacquer is to immortalise the dirty thumbprints that you missed...

Today was going to be the day when I vac-formed my first flawless gleaming canopy.
It didn’t quite turn out like that.
I practiced on some white HIPS plastic, overheated it and melted my former.

So this is why people send stuff to Sarik.

Will have to mend my former and start over. > sigh <

oh Rog, I feel your pain.

At least you didn't fall off your stool this time! I fell off mine t'other day, nearly flattened my wilga before it gets finished... That'll teach me to lash up temporary sitting down structures.

As an aside, I used you r parcel tape technique to take a female mould of the 213 before I cut it, it worked way better than I could have imagined - ta!

Deep breath, sand, seal and send to Sarik then.

Ell.

Cheers Ell.
I’m pretty philosophical... setbacks are all part of the creative process. I don’t mind as long as I learn from them, f’rinstance 3 layers of 200gsm cloth is not strong enough for my school vacforming machine!

I may try it manually with a heat gun and simple wooden frame to hold the plastic.

Happy to hear your moulding went well. It can be very satisfying. You must be pretty much ready to test fly it.

After my utter fail with the vac forming machine, I spent a few hours with filler repairing the plug and adding another few layers of 200gsm then filling and smoothing. Fun times.

I decided that simpler is better and that I’d just pull the heated plastic down over the plug with brute force, all the time blasting it with a heat gun.

This seemed like a 3 handed job so I enlisted my youngest, Kitty, to help. I rubbed down the plug with sunflower oil to make it easier to remove the canopy, clamped the plastic sheet between two timber battens, and Kitty got medieval with the heat gun.

The first attempt was ok but the second was much better when we heated the plastic until it was really saggy and soft.

Not perfect, but ok for test flying. I’m happy to be learning a new skill and think I could do better next time.

I’ll add a little cockpit detail then trim the canopy and glue to the frame.

Nice job of the canopy. It's not easy to get it right first time. I use a gas camping cooker to heat the plastic has it will heat all the plastic in one go and finish off with heat gun. Great Job. Roo

Cheers Roo. To be honest if I hadn’t seen you pull canopies it I wouldn’t have bothered trying! So thanks for the inspiration.

I had one piece of plastic left....and you know how it goes...you just have to have one last go, don’t you? Third time lucky - it’s just about perfect (I’ve had worse commercial canopies).

Couldn’t resist a bit of cockpit detail, even though it’s a very semi-scale model. After that I settled in for a couple of hours painstakingly trimming the canopy to fit the frame. Ooh, I do love a nice tight-fitting canopy, so this job is perfectionist nirvana. Then it was time for a quick round of Hunt the Canopy Glue (I won) and it’s now all glued in place, drying in the workshop.

I also made up and fitted a sprung canopy latch from some old transmitter aerial tubing and a ballpoint pen spring, which is operated by pull wire exiting the fuselage under the wing root trailing edge.

Tomorrow I’ll mask and spray the canopy frame and prop blades, then check the electrics all work and adjust C of G. If the weather’s ok I’m hoping to test fly on the Long Myndd this weekend, with prop removed.

Prop blades sprayed white after a tickle with 240 grit to give the paint a key. Did some other blades while I’m on...

Finished.

Last jobs were to spray the canopy frame and check the CG was where I’d designed it to be (based on the original fuselage). It was spot on.

I also checked the electrics really thoroughly last night, wiggling all wires and connections to check for reliability. That was lucky... I found intermittent faults on rudder and one flap...traced to accident damage to the wiring. I slept on it then woke up this morning and replaced the entire wiring loom inside the fuselage. Better safe than sorry, (as wise, risk-averse people say).

So here’s the old and new front fuselage sections. (The new one is at the bottom of the photo )

Next photo will hopefully be atop the Long Mynd before I throw it off....

Perfect conditions on the Mynd and it flew straight out of my hand just like the original. I moved the CG back 2mm after the first flight for a more neutral feel.

Thanks to everyone who's shared tips and inspiration.

Rog

Well done Roger, thanks for sharing the rebuild, Terry.

Couple more photos, from a friendly passer-by.

Fun times.

I’ve decided to build a new rudder. Nothing horrendously wrong with the existing one other than it’s built-up and film covered and I can afford to make a stronger/heavier rudder now that I have a motor in the nose.

I wanted a nice glass finish so first thoughts were to strip off the film and then cover the original balsa structure each side with grp sheet, fabricated beforehand on plate glass. I know a few folk experimented with this method in the 80s.

So I waxed a handy sheet of glass, sprayed it with acrylic white and then laid up two layers of 100gsm cloth (weave at 45 deg to each other) and an equal weight of epoxy resin. The idea was to make a light, tough, shiny grp skin that would need no further painting after gluing to the fin structure.

Not so much. Peeling the grp skin away from the glass revealed lots of pin holes (see photo). I may explore this approach again some day, but I’ve decided to go a different way with this rudder....

So instead I’m going to laminate the glass skin directly onto a blue foam core. No fancy vacuum bagging, in fact I didn’t even hotwire the core - I’m just cutting one side from a block, then glassing it, then cutting the other and glassing it.

The idea is to get a strong, glass-looking rudder with a quick low-tech approach.

Here’s the core with one side cut away, then sanded smooth.

Here it is stuck with double sided tape to a flat board (I noticed it warped slightly when cut/sanded). Two 100gsm cloth skins prepared, weave at 45 deg.

And here it is 5 mins later after cloth applied with resin.

I find it takes about 1.2 : 1 resin to cloth (by weight) when applying to highly absorbent surfaces like foam.

Since deciding to go with a foam core I’ve spent just over an hour on it to this point.

I skinned the second side of the rudder yesterday and today sanded it to a smooth finish using 240 grit (wet).

I am chuffed to bits with the finished result. It has a rock hard, smooth skin, sharp, tough and straight trailing edge, it will not bend or twist, and it weighs just a few grams more than the old wooden rudder. Best of all, it took just an hour and a half to make. What IS happening? Nothing I build ever goes that quickly!

Will definitely be using this method again for fins, rudders and tailplanes. May reduce the 2 layers of 100gsm to 1 x 100gsm + 1 x 50gsm because this rudder is needlessly strong.

A quick update on this model. With its new front fuselage pod and canopy and now an entirely new rear boom and tail unit, this model (like Trigger’s broom!) doesn’t have much to do with an ASH25 any more. Maybe more JS3 Rapture?
Anyway, after its re-maiden at the Eden Valley event a couple of weeks back, I flew it for 2 hours this evening tweaking the CG and surface trims and am now delighted with how it handles.
All that remains is to crash test it…which I’ll no doubt do in due course