repairing model gliders

Stormeflyers

Moulded Model Repairs

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What started out as a superb day at the slope with steady wind and endless lift, with models of all types adorning the launch area; sadly ended abruptly by those immortal kiss of death words..................................."Just one last flight!"

I was blasting my Blade round the sky, letting it scream it's sweet head off in front of a gathering crowd of flying buddies and spectators, when the thought of my next meal suddenly crossed my mind.

So with a flick of a switch, I deployed crow brakes to begin my approach, just as I did that steady wind that blew so true all day suddenly changed direction, no problem I merely altered my course but my new landing strip was now unknown territory.

The Blade landed with ease but this time accompanied by a strange noise............which only I could hear. Collecting my model from the long grass, to my horror I spied one of those "Pet rocks" hiding it's ugly head laughing at me.........................Doh!

I had suddenly lost my appetite and felt decidedly sick looking at the leading edge of the wing, I turned to look at my buddies who were blissfully unaware of my plight; therefore due to their presence thought some composure was called for..................after only ten minutes of kicking and screaming and rolling around on the grass crying "Why me?" I had calmed down.

It was then I got some friendly advice........"That's the problem with moulded models, they aren't very strong when they hit something"
"Hmmnn! I feel a whole lot better for knowing that......................not!"

So off home I trundled feeling as useful as a fart in a space suit. I knew that I could do one of two things, I could sulk for a week or set to repairing the wing................I opted to sulk for a whole week.

One week later a quick phone call was made to Fibretech and the next morning all my resins, cloths and micro balloons were at my doorstep. I scurried into the workshop and laid the wing out to inspect......................"Ouch!"

The leading edge could not be pulled out and the top and bottom skins had de-laminated and felt like mush, so the wing had to be opened up from the underside making my cut slightly wider than the original damage.

Now to put my part time gynaecological skills to good use again, I had now gained good access to the leading edge and top skin due to the underside incision, the leading edge was now simply pulled straight and glued with cyano, which I reinforced with thin carbon rod held with cyano and micro balloons. Through the opening in the wing, I could easily see where the top wing skin had de-laminated.

Here I wicked cyano and stuck the top skins together as best they would then cut some 80gm/sq fibreglass cloth and laid this into the opening and applied resin to reinforce the top section. When set I turned the wing over and used fairing compound to fill any slight imperfections of the wicked skin and rubbed down using wet and dry.

Already the wing was very strong and this was before the wing opening was filled in, all that was needed was to insert the new false skin into the cut out. To make false skins, cover 1/16" balsa with 80gm/sq cloth on one side. When cured make a cardboard template of the wing cut out and transfer to the false skin.

Now for the clever bit..............at strategic points drill tiny holes in the false skin about 1/4" from it's outside edge. Get yourself a thin piece of piano wire and make a 90 degree bend in it. Now insert the false skin into the wing opening cloth side out, making sure the new skin is flush with the original using your piano wire tool to lift the skin flush against the original section.

To bond a false skin to the wing carefully wick only a small section of the repair at a time using cyano then sprinkle micro balloons on top, with a puff of smoke this will set instantly. Repeat until the entire repair is bonded then simply wick cyano and micro balloons to fill the small holes drilled in the false skin and hey presto, you are nearly home and dry! Rub down any excess micro balloons with fine wet and dry.

Now that the false skin is secure cover the whole repair with finishing cloth and wet out with slow curing resin making sure there is an overlap of around 15mm, when cured rub down thoroughly with wet and dry, this is quite time consuming, fill any slight imperfections with fairing compound and yes you guessed it.............................rub down again.

Using an airbrush or aerosol apply white acrylic undercoat to the repair, when dry give this a light sanding with fine wet and dry used wet, you should still see very slight imperfections in the finish, so apply more thin layers of undercoat and repeat the process until satisfied.

Finally when happy with the results give this last undercoat a very light and very wet rub down ready to apply the finishing coat, a good tip is to add a drop of soap to your water...................at long last we are ready to spray the finishing coat. If you really want perfection after about a week, T-cut the top coat and polish to a high shine then stand back and admire.

"We are now finally ready to go to the slope and do it all over again"

If I am ever unlucky enough to hit one of those pet rocks again, I won't add add finishing cloth to the entire repair, this adds very little structural strength to the join of false skin and wing, merely thickening up what is already sound wing section. The bond of cyano and micro balloons is strong but not as strong as the original wing, as the repair is merely a butted joint.

I have thought of a simple method to adopt which would greatly increase the strength of the join. Make additional false skins only this time of 1/32" balsa and frame the inside of the wing cut-out. You would be left with a result like a recessed wing servo opening. The false wing skin would simply drop into your ready made recess. Your wing skin will be flush but more importantly beefed up just where you need it..............."Now why didn't I think of that sooner?"

Like any repair the hardest part was all the rubbing down and fairing in, I would not like to hazard a guess as to how many hours spent and undercoats I have rubbed down to get a mirror finish, if I added all my labour costs it would have been cheaper to buy a new model.................."Doh!"