Paddle Blade Repairs^

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andreadawn
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Paddle Blade Repairs^

Post by andreadawn » Wed Mar 01, 2006 6:03 pm

I've managed to split one of my Nimbus Mistral fibreglass blades from the top edge towards the spine for about 4-5 cms (incompetence, rather than a reflection on the quality of the paddles ! ).

The blades are very thin and fragile feeling towards the edges. The split is rather ragged and I cannot seem to get the two sides of the split to push back together neatly. I suspect some cutting would be needed but then a repair job would probably be beyond my skills.

It's a four piece paddle which Nimbus don't do anymore with this design, but was my favourite so I'm loathe to bin it.

Is it realistic to try and repair it, and if so, any suggestions on the best method?

Thanks,

Andrea.

.

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ChrisS
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Post by ChrisS » Wed Mar 01, 2006 6:46 pm

Jim will probably give you a professional answer.

But if it was my paddle I would first of all drill a small hole at the end of the split to prevent it from getting any worse. Then I would enlarge the split to make a clear gap. Put some selotape over the hole and the split on the side where you would most like a smooth finish and then fill the hole and split with thickened epoxy. Araldite might do. Finally cover the filled area with some glass tape or cloth and resin.

Chris Bolton
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Epoxy repair

Post by Chris Bolton » Wed Mar 01, 2006 10:33 pm

As Chris S says, with some possible additions:

- chamfer the edges of the hole (to maybe 30 degrees from the surface), so that the infill has more area to key to.

- to thicken the epoxy, don't use a filler powder, use glass mat cut up so that all the bits are just 2 to 3 mm long.

- after filling the gap, use Sellotape on the top side as well (optional)

- when it's cured, sand back to the original profile

A variation would be to use kevlar instead of glass, but if you do that you won't be able to sand it smooth and will have to rely on Sellotape

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Jim
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Post by Jim » Thu Mar 02, 2006 12:43 pm

I'm not sure of the construction of these paddles (solid or foam core) and I'm not entirely certain I understand the description of the damage, can you post a photo of it?

Chris and Chris describe quite normal methods of repair but obviously visualised a different split than I did!

Not too certain about the need for drilling a hole to releive the stress concentration in a composite material, it won't do any harm though, although if the split is a delamination as I envisaged you will be struggling to work out where to drill!

JIM

andreadawn
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Post by andreadawn » Thu Mar 02, 2006 1:48 pm

Thanks. I'll see if I can get a photo sorted out. I don't think it's possible to post one directly is it? Do I need a Photobucket account or something similar to link to?

Andrea.

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lister
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Post by lister » Thu Mar 02, 2006 2:01 pm

Hi,

I believe you will require a inernet based photo album. I use
http://www.imageshack.net. Its really simple to use, and when the photo is uploaded you can just copy and paste a 'link to forum' and the picture will appear on this site.

They also have a handy image resizer for you to download and use. It means you can resize the picture and upload it with 2 clicks of the mouse!

Lister
The sunshine is always better in sunshine vally.

andreadawn
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Post by andreadawn » Thu Mar 02, 2006 3:26 pm

Image

Image

Not sure if this helps. Solid or foam core? Please excuse my gross ignorance of such matters. I don't know!

Feel free to tell me to bin it!

Andrea.

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MikeB
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Post by MikeB » Thu Mar 02, 2006 4:01 pm

Oh dear. Well, my first reaction involves the bin - - -

But - in days past I've successfully done repairs to glass boats by the method of opening the crack with a thin, round file. Roughen the surface(s) with sandpaper or similar to create a key for the new resin and wipe down with acetone to remove dust and the waxy deposit that come out of f/glass.

Then apply a bit of parcel tape to one side. When I was repairing glass boats, that was the gelled side and the idea was to create a nice smooth surface without having to sand afterwards. In this case it'll just be to create a decent surface and stop the gel "falling through" as it sets,

Now fill the opened crack with gel. Once it's set, apply f/glass (I used to use the woven tape rather than the chopped mat as it's a better finish).

IIRC the process was first a small bit, then covered that with a bigger bit. You must do the layering process in one go so that the layers bond. You could do both sides of course, but do one side first - let it harden - then do the other. A little light sanding with wet'n'dry used wet will smooth down the edges.

There are some relevant articles / links in the Almanac/DIY & Repairs page which might be worth a look at if you've not done so yet.

In this case though, I have to question whether the repair will be effective long term and wonder whether the weight imbalance so created will be a problem? I suppose you could always do the other blade too - - -

I guess you've asked Knoydart whether there is any chance of getting a new blade??

Edited to add: There's an outfit called Brite Water listed in the Almanac/DIY page - they offer boat repairs, so might be worth asking about repairing the paddle????

Mike.

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Jim
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Post by Jim » Thu Mar 02, 2006 10:43 pm

Ouch!

First off the Chris' visualised the damage right, I didn't! The blade is solid, an alternative lightweight construction is to have 2 fibreglass skins around a foam core - these can delaminate if you bash them hard enough forming a totally different looking split!

Second off, ignore Mikes advice re: gel (sorry Mike!)

I am 90% certain that we are looking at an epoxy matrix rather than a polyester one so polyester gelcoat or gelcoat filler is 90% likely to be unsuitable repair material, coupled with the fact that gelcoat is decorative and has no place in this type of structural repair!

You can repair this blade but it will be heavier than the one on the other end, OK perhaps for a spare, but if it's your main paddle you would be better off speaking to a dealer about getting a replacement blade (professionally or as a self replacement kit).

To repair first you would need to tidy up the split - the ends of the fibres were interwoven but won't push back together now so you'll have to use a needle file or hacksaw blade to smooth the edges so you can get them in line (it looks like you've started with the pliers...). if you can do this at an angle near the spine to create an overlap all well and good!

Then you want to abrade a fairly large area at least an inch either side of the split if trying to be weight conscious, for more strength you would probably want to have at least 2" either side of the split. Do this on both sides of the blade. You need to select a glass cloth to use for the structural repair - all the fibres are cut in the split and simply filling will not provide anywhere near the strength. I would expect something like a 165g/sqm woven rovings would be about right. For the drive side you might want to try something finer as the patches will be raised - 50g/sqm will be nearer to flush and may prove strong enough but we are into suck it and see territory. Fibreglass tape could be used rather than cloth - ifit was a straight split this would be ideal, since it waves a bit you might want to use a couple of lengths so you can "follow" the crack line with it - use 2" tape to provide 1" overlap each side of the crack. If you want more strength use 3 layers, one with 1/2" overlap to the left, and the other with 1/2" to the right (will overlap each other by 1") and then one on top centred over the crack (will overlap a further 1/2" onto each of the previous strips. This technique will "feather" the patch so you don't get one big step. If you use cloth and want more than 1 layer, make the first layer 1/2" smaller all round than the second to get a feathering effect.

Like I say, for the drive face I would look to use a single layer of finer cloth or just 1 strip of tape to avoid changing the surface too much.

You will also need a small repair pack of epoxy resin, something to mix it in (most places provide graduated pots to help you measure it - by volume, not weight like polyester) and a cheap 2" brush. Thinners (as sold by the supplier, or cellulose) are useful to wipe the area after sanding and clean the brush, but you could just use a tak rag for the wipe and bin the brush when you are done. Skin doesn't like epoxy, wear latex gloves, if you have barrier cream use some of that too!

When everything is prepared (blade sanded and glass fibre bits cut to size ready) mix a little resin - because it's by volume it's easy to mix more later so don't do too much to start with. paint resin THINLY onto the sanded area, really don't make it wet, just moist! Carefully lay the first bit of glass in place - try and avoid having to smooth it out with your fingers by getting it laid right firsttime. Then with the brush damp but not dripping, use a stippling action on the glass fibre to wet it from the top - you should notice that it changes from white to clear as the resin from below seeps up and fresh resin penetrates down. When the first (if you go for multiple layers) layer or piece is clear, lay the next piece on top and repeat the process, if using 3 layers of tape repeat once more! The trick here is to use just enough resin to make the glass fibre turn clear, be careful and thorough not to leave dry patches (white areas) but really do try not to get the job running with resin! If you have some way of supporting the paddle so you can flip it over and do the drive face just carry on and do it, the layers you put on already won't drop off unless they are swimming in resin!

Leave to set (8 hours or so for a good cure), if you keep it warm the resin will cure better. Gently try flexing the blade and see if the repair seems weak or if it creates a stiff point on the blade. If it's too flexible you will need to abrade the epoxy you put on very thoroughly before you can lay up more layers on top because as it cures it develops a waxy surface which nothing sticks to (it sands off OK).

I once did a similar repair to Neil Farmers Werner Wenatches and he got a few more river trips before he broke the repair - they were abused much more than sea paddles would be so your repair might last a while if it doesn't unbalance the paddle too much.

I go on at length there about using minimum resin. Too much or too little resin will make the repair weak, however if you get all the glass to turn clear you will have enough for a strong job. Also resin is heavy so applying more than you absolutely require is undesirable. Many people lash resin on expecting it to work miracles - it's weak without fibres and you want to maximise the fibres/resin ratio.

I haven't mentioned filling the slight gap the cleaned up split will leave - I wouldn't bother! You may get a slight void but as you have a discontinuity there already the danger it poses is delamination, but you will probably find enough resin seeps into the gap to pretty much eliminate the void. If it worries you, use an epoxy filler (Chris B's chopped fibres mix might work), I'd suggest a low density one, or epoxy repair putty perhaps (this is most of my repair kit these days), and then start laminating straight away whilst it is still 'wet' or tacky.

You have probably read than and decided to replace the blade - it's the best solution!

JIM

Chris Bolton
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More thoughts

Post by Chris Bolton » Thu Mar 02, 2006 10:50 pm

Andrea,

Looking at the photo, I don't think it has a foam core. It has a substantial spine, so the blade isn't taking much of the longitudinal bending, which means that there isn't much load across the break in normal paddling, and your patch won't have to be very strong to have a chance of working.

I'd go with Mike's suggestion of a small file to open up the slot: you'll never get the sides to close together, and you wouldn't get a good bond to them as they are.

I would disagree with Mike about using gel; it doesn't have much strength and it's designed to set tacky if exposed to air. I would use straightforward resin (epoxy if you can get it, but measure the proportions carefully, and polyester if you can't get epoxy) and reinforce it as I described in my first post. You'll probably find that a length of wire or something is usefull to push the resin / fibres into the enlarged crack.

If you're concerned about leaving the exposed ends of the fibres exposed to water (which is one reason for using gel when building a boat) just paint a bit of resin onto the surface after you've sanded it flat.

Good luck!

PS - written at the same time as Jim's, so some overlap in what we say. I'll go with his superior knowledge in saying it's probably epoxy, in which case I agree you need epoxy to repair it. I would still attempt to do all the repair inside the enlarged split, not on the surface.

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MikeB
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Post by MikeB » Thu Mar 02, 2006 11:00 pm

For each and every expert, there is an equal and opposite expert - - - ;-)

I suppose some form of filler would serve to fill in the gap, thickened gel or whatever - I'd have thought the edges wouldn't go back together sufficiently well without opening themm up tho.

How about we break the other blade, repair one in one fashion, repair the other in the other - and then wait and see what happens?

One for the Almanac I think.

Mike

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Jim
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Re: More thoughts

Post by Jim » Thu Mar 02, 2006 11:47 pm

Chris Bolton wrote:PS - written at the same time as Jim's, so some overlap in what we say. I'll go with his superior knowledge in saying it's probably epoxy, in which case I agree you need epoxy to repair it. I would still attempt to do all the repair inside the enlarged split, not on the surface.
I'm guessing at epoxy, Lendal and Werner seem to use it so why not Nimbus? Someone could probably look up the specs on their website if they have one and take the guessing out :D

As for repair inside vs outside - I am more familiar with river blades which tend to take a lot more knocks, I was trying to work out how much load there is on a sea blade just paddling. I still think you need to rebuild some longitudinal strands over the gap, perhaps though just one layer of tape on the back would be enough and fill the face smooth? My thoughts were that the face will actually be in tension so a thin layer there should do maximum good from a strength point of view, but obviously spoil the flow over the blade.

Now Mike, you did ask for this bit! As resident paddle breaker, would you like to supply us with some broken blades courtesy of your destructive backside? :-)

JIM

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MikeB
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Re: More thoughts

Post by MikeB » Fri Mar 03, 2006 12:22 am

Jim wrote: Now Mike, you did ask for this bit! As resident paddle breaker, would you like to supply us with some broken blades courtesy of your destructive backside? :-)

JIM
Touche!

andreadawn
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Post by andreadawn » Fri Mar 03, 2006 3:09 pm

Thank you for the very detailed replies.

I'm afraid I'm going to be a bit of a let down and not even attempt to repair it. I'll see if DF can do anything about replacing the blade next time I'm in Knoydart.

In the meantime I'll have to make do with my Nimbus Chinooks, an even skinnier version of the above blades or my new Kinetic Touring; very nice.

Andrea.

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MikeB
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Post by MikeB » Fri Mar 03, 2006 4:08 pm

andreadawn wrote: my new Kinetic Touring; very nice.

Andrea.
They are, aren't they.

Mike.

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