Thursday, 24 March 2016

Oh, bother!

No.4 section in two pieces.
The reality was the bank was blessed with some rather colourful language. To say I was cross was a gross under-statement. This was no fishing accident, this was down to pure stupidity on my part. I can't even play the novice card, I should have thought about what I was doing. Attempting to reposition thirty or forty feet of pole over the rollers by the thin end is insane.

What is done is done, so what are the options? Well, I could just buy a replacement section, I could have it 'professionally' repaired, or I could repair it myself. The cost of a new No.4 section is £69.99.  As the pole section is not that expensive a professional repair would probably cost a good percentage of that. By the time delivery and collection costs are factored into the mix the total may well exceed the cost of buying a new section. If this was a more expensive section I would have had no hesitation getting it professionally repaired. As it is, this is a section that has already had a repair and maybe the best bet would be to buy another section...

...But that would be no fun!

A typical repair kit
Repairing a carbon fibre pole is fairly straightforward, but like anything, it is all about the preparation. There is a kit available from that will provide everything you need to make a wrap repair to the pole, but that is the easy bit. I do not advocate anyone attempting this if you have not got the skill or equipment to build an accurate jig.

The MDF jig for holding the pole sections
The jig is what will hold the sections together, in perfect alignment and the repair will only be as good as the jig. The jig is built from three pieces of 18mm MDF screwed together with a middle section removed to enable the broken section to be wrapped. The size is not critical but for this section, the two sides of the jig, that support the pole, are spaced apart by a third, narrower, piece of 18mm MDF that is laminated between the other two, to space the otter boards a consistent distance apart.

There is a video on-line that explains the process but be aware this video is out of date, and I could not find any diagrams of the jig as mentioned. The timings and quantities are wrong too, for the resin supplied in the kit. Check the instructions on the bottles of hardener and resin. 


Making my jig

The side sections were squared, and dimensioned to be identical, from a piece of 18mm MDF. The third section needs to be at least 100mm narrower. All three parts were aligned and screwed together so the top edges are absolutely parallel. Four holes were bored through the jig. These are used to pass cable ties through to secure broken pole sections and hold them in perfect alignment. I made my jig so it was big enough to hold the sections rigidly in position.


Let's mend the pole section!

Before fitting the broken pole sections to the jig, the area to be repaired was keyed with abrasive, ready to accept the resin.

The keyed surface ready for joining
Cleaning the surface with isopropyl alcohol
Once fitted in the jig, the repair surface was cleaned with isopropyl alcohol. The kit has three wipes for this purpose, if you don't have any to hand in liquid form. When the area was clean, it was given a single coat of resin. The resin is mixed to a ratio of 100 parts resin, 30 parts hardener by weight. I used my cheap Slater kitchen scales (I bought for bait making) to do this job. Be as accurate as you can and mix the two components thoroughly making sure there is no residue in the corners of the mixing container untouched. If you are using the cups and 'lolly' sticks, provided in the kit, cut the round ends of the sticks off, at a slight angle, and smooth the freshly cut ends with abrasive paper. This will allow the stick to get to all the resin in the bottom of the cup, where the bottom meets the walls.

I mix my resin in a stainless steel cup (chutney bowl). Note the modified 'lolly' stick
I applied a coat of resin to the repair area, slightly wider than the carbon fibre sheet used to wrap the joint. This needs to be a good coverage but not too thick. Any build-up is smoothed out by laying it off with the brush. This was left for an hour or two to go tacky. Keep an eye on it, this tacky state can happen quicker or slower depending on temperature. Once it has reached the tacky stage, I mixed a second batch of resin.

The first coat of resin is applied
The length of materiel needed was calculated - twice circumference of the pole at the break to give the length of material required to make two wraps of the pole - 2 (2πr). After cutting the material to length the edge was aligned along the centre-line of the pole and pressed onto the tacky resin coat. It was wrapped around the pole once. This was then coated with more resin. The material and wrapped around the pole for a second time and more resin is applied to cover the whole section. A reel of clear shrink tape is supplied with the kit. This was used to wrap the repair as tightly as possible. It is held in position at each end with adhesive tape. This stuff does not shrink very much, but it is enough to squeeze the excess resin out of the cloth and consolidate the joint. The tape must not be over heated or it will stick to the resin. I used a temperature controlled hot air blower set at 120ºC but a domestic hair dryer or a hot-air gun set at the low setting should be good enough. The repaired section will cure in a matter of hours.

Wrapped and bound with heat -shrunk tape
Curing will take longer in a cooler environment. in the middle of summer when the ambient temperature is high, the resin can go off very quickly - sometimes too quick. The best working temperature is in the high teens (Centigrade). Curing can be speeded up by heating but I prefer to just let it cure in its own time. Overnight is usually the best bet, as I did here, there is no rush.  When it has cured, the shrink tape can be removed.  

Removing the shrink-tape after the resin has cured
At this stage the repair is structurally sound. The shrink-tape was removed and the pole section released from the jig by carefully removing the cable ties that were keeping it aligned throughout the repair and curing process. Next it was time to make it look pretty. I sanded the joint smooth working my way down through the grits. That is starting with the low numbered sheets and working towards the higher numbers; the higher the number, the finer the grit. Sand with care not to go through the resin coat or you will have to apply more and wait for that to cure before continuing. Sand 'wet' with the finer grits to get a really smooth finish. You can then use a buffing compound (there is one supplied with the kit) or use a chrome polish to get it to a dull sheen. This is fine but it shows the weave of the repair cloth. I decided to take the finish one stage further.

Ready to go - I might polish it later, but that will do to give it a try
Once the repair had been flattened, I painted it black to cover the weave. Several thin applications were made and rubbed down between coats. That's it, job done and saved myself a few quid. There was plenty of material left in the kit to make a couple more repairs so I set to and fixed that rod my brother broke a few months ago...