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Repairing Fibreglass Mouldings

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Cliff Bastow07/12/2017 21:07:54
809 forum posts
426 photos

wp_20171207_20_48_34_pro.jpgreferring to my earlier post about the demise of my HE111, I have been reassessing the damage and it might just be repairable.

My problem is that all of the moldings for the upper and lower cowls are damaged. They have both had the fronts smashed out which I think i can repair by epoxy gluing a plywood disc in the front, but they all have several splits and cracks as show in the photo.

Any advice on the best way to go about repairing these please?

Flyer07/12/2017 21:15:49
509 forum posts
72 photos

LIghtweigt glass cloth and resin on inside, and a little P38 filler; after a rub down would be like new, with little additional weight.


Colin Carpenter07/12/2017 21:18:08
546 forum posts
35 photos

Same procedure for epoxy or polyester resin. Use clear tape on the outside to pull the damage together. Use thin pieces of ply to bridge where necessary. Patch repair with thin cloth on the inside. Remove tape and fill cracks , sand and repaint . Repaired many a racing model boat in this fashion. Colin

Cliff Bastow07/12/2017 21:58:33
809 forum posts
426 photos

Thanks for that guys, I will have a go, especially as Ripmax want £59.99 per side for replacements, So thats £119.98 in total just for the cowlings!

bert baker07/12/2017 23:26:54
1288 forum posts
277 photos

I haven't tried this but have often wondered on internal repairs if a ballon could be used to keep pressure on the repair whilst it is curing

jrman08/12/2017 00:15:00
333 forum posts
3 photos

On a similar repair I drilled small holes either side of the cracks and used thin plastic coated garden wire twisted through the holes to stitch the cracks together before tacking with cyano, removed the wire and lined the inside with lightweight glass cloth and finishing resin. The outside of the cracks and small holes were then filled with micro balloons and finishing resin .Using the wire enables you to pull the cracks together as tightly as necessary which I found easier than using tape.

onetenor08/12/2017 00:55:06
1893 forum posts

If you use the holes method dremel some shallow grooves between them either side of the crack then use thin fishing line pulled tight and laid in the grooves.Not forgetting to drill a hole at or just beyond the crack to stop it travelling on. Glass cloth and resin or whatever inside and filler of choice outside.leave the thread in place for extra support..Sand and paint.

Good luck John Mantova O/T

Peter Christy08/12/2017 08:48:30
1387 forum posts

I had to do a similar repair on my Skydancer. First of all, I glued the broken bits and splits together using thin cyano, then layered the inside with lightweight fibreglass cloth and resin. Finally, rub down the outside and fill where required before re-painting.

Using cyano to do a preliminary repair ensures that the cowl can be handled easily whilst applying the fibreglass to make the job permanent.



Alan Hilton08/12/2017 09:28:15
80 forum posts

I second the cyno method it has worked well for me in the past .You can even use cyno to wet the cloth /mat instead of resin if you want a quick job .The important thing is to use the correct resin, epoxy won’t stick to polyester


Engine Doctor08/12/2017 09:30:23
2208 forum posts
20 photos

yes plus 1 for the cyano to hold it while doing repair. Any large holes can be covered with doing film then a piece of litho plate to keep shape while glass sand teen set. Ronseal 2k wood filler is good for finishing the surface and is lighter and sands easier than car body filler.

Andy Green08/12/2017 09:32:52
2279 forum posts
67 photos
2 articles

Don't be put off that things will have to get worse before they get better, you need to get to the detail of any damage.

Its more important at this stage to get it back into shape / alignment, so don't be afraid to drill it and screw wood / wire into it to get it to hold its shape.

Having to fill a couple of additional holes is a small price to pay to know its right.


Philflyer08/12/2017 11:12:23
109 forum posts
74 photos

Bert. Yes a balloon is good for putting pressure on a structure to hold it while setting - but inflated with a little water instead of air. Gravity does the pressure bit so it must be positioned well for it to work. I used it to repair a twinstar foam fuz with lightweight filler. Got the idea from something similar I did in the Falklands after the war to repair a (real) Phantoms wing . Used big rubbish bags taped together, laid over the top of the fibreglass repairs and covered with 10 cms of oil absorbing compound (like sand but bigger grains). It lasted until the fleet was scrapped many years later.

Danny Fenton08/12/2017 11:25:09
9068 forum posts
3928 photos

Not sure if it has been mentioned already but you do need to work out if the resin is epoxy or polyester, they don't bond well if you mix them.

Depending on the age sniff the inside of the cowl, if you cannot smell the polyester, sand a small patch inside of the cowl, and sniff it. You will smell polyester easily epoxy doesn't really smell.



J D 808/12/2017 13:58:03
1124 forum posts
65 photos

Hi Philflyer. A friend of mine [ Navy ] was there when the 4 remaining Phantoms did their final formation fly past. He said one went on one engine and another with undercarrage unable to retract.

Later after anything usefull had been removed ground crews were let loose to do whatever they liked with the hapless aircraft. Sledgehammers,axe's even bulldozers were pressed into service before the remains were shoved into a ditch.

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