Hi Folks I have recently bought a 7ft fibreglass observatory which came in two pieces, the dome and the bottom wall section. I managed to get the dome round the side of the house but the bottom piece was just too bulky and I had to get the angle grinder out and cut it vertically in two and now wondering how to get them back together again. As its a fibreglass observatory I assume I need fibreglass to fix it back again but as the last bit of fibreglassing (is there such a word?) I did was at school some ?@! years ago I`m a bit in the dark what to do next, how,where from etc!!. Any advice from the group most welcome. Cheers Steve
You're not going to get that strenght back just fibreglassing it so I'd suggest some ally strips pop riveted down the sides inside and outside with the ally plating.
You can buy fibreglass matting and compound from car accessories shops and boat building suppliers if you choose to do it that way.
First, DO NOT BUY the glassfibre kits in the high street. They are over fast in their going off. Your resin will last two or three minutes in this heat, about ten in normal temperatures. Purchase some proper resin, matting and catalyst from a professional company. You will have up to an hour working time.
Cut lots of aluminium fingers and drill a 4mm hole in each end of the finger. Get some cellophane and cut long strips that will cover the slot between parts and some to the sides. If the joint butts accurately, you can dispense with the cellophane.
Screw the fingers using short self tappers over the cellophane such to cover the slot and hold the pieces in correct alignment.
Using an angle grinder with a STONE disc, grind out the other side so that the joint tapers over some reasonable area.
Make up a small amount of resin and paint over the joint. Leave to set and then do the same again, having made up some extra resin.
Lay a piece of matting onto the wet resin and stipple the resin in as if you were painting through a template. Short bristles help. Do not use a "painting" motion. If you are brave, you could lay more pieces of matting, but make them different sizes. Do not lay too much in one go.
Make sure that all the matting is fully impregnated and rolled out to remove air bubbles.
Repeat as required until the joint is about level and strong.
Now you can remove the screws and fingers, leaving just the holes to fill.
Finish as required with polyester filler and paint to match.
To do the repair properly requires more or less what you said above but it needs doing from BOTH sides.
Grinding halfway through and taper repairing one side then letting it go off, then removing the strips of aluminium used for joint alignment followed by grinding out the other side and using resin and matting in a similar manner makes for a much stronger joint.
======================= Have you considered adding strengthening flanges to each half through which you could fit coach bolts (or similar) to hold the two parts together? You would then be able to dismantle the base if you ever needed to remove it.
A very big thank you to all of you who took the time to reply. Forgot many years ago how to fibreglass so all this advice extremely helpful. Didnt bank on having to cut the ruddy thing in half and repairing it but there you go. Cheers again Steve
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "The3rd Earl Of Derby" saying something like:
Structural repair theory begins by recognizing the difference between a repair and the original piece. When a part is first fabricated, all the resin in it cures chemically as a single unit regardless of the number or orientation of the reinforcement plies. This is called the primary structure or bond, and it is the strongest form in which a part can exist. Once the part is damaged, all repairs become secondary bonds attached to the original primary structure. In real life, this means that the repair is only as strong as the adhesive used to make it. For this reason, never use a weaker resin than what the part was made with originally. In fact, stronger adhesive resins are sometimes used for repairs. However, even this substitution must be cautiously tested so it does not change the performance of the part.
A proper repair to a composite structure is not gluing by any stretch of the imagination.
Attempting an overlying strip type "repair" to cured surfaces that may contain release agents, or be purely resin in the case of gelcoat is a bodge, pure and simple. Also using resins other than that used in the original layup can cause reinforcement wetting out problems . For instance epoxy resins are not compatible with the reinforcement binder commonly used with polyester resins. Using different reinforcing material, or a different resin chemistry, can also cause differential expansion in extremes of temperature leading to interlaminar shear. Repairing only from one side can result in an unbalanced layup which in extremes of temperature can cause distortion and delamination failures in the area of the repair.
In real life a tapered repair from both sides, which fully exposes the original substrate (matting) and which uses resin similar in composition to the original layup and similar reinforcement will be as strong and possibly even stronger than the original layup.
Hi again I forgot to mention on my original post that the observatory walls appear to have been made in three sections based on the fact that there are three seams on the outside but nothing internally. I simply cut down two of the seams removing one of the sections for it to fit down my drive. I assume when it was manufactured one of the methods mentioned by members of the group above was used to join all three sections and overlayed internally with fibreglass to hide any joints?. Regards Steve
Thanks for the quick reply Matt. Yes thats right just a plane edge not turned up. Is there anywhere you can post pics without having a web site?. Will post some tomorrow if poss. Cheers Steve Ps could send you em directly?
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "The3rd Earl Of Derby" saying something like:
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