Keel strips^

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tomthehaggis
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Keel strips^

Post by tomthehaggis » Sat Feb 23, 2008 9:23 pm

I want to fit a keel strip, and was just wondering...I've found this kevlar tape on the internet (from www.mailspeedmarine.com - which after trawling the internet, was cheapest site I could find for most marine related things) for £10 per 1.5m x 75mm from a company called PSP, who make loads of different types of tape. I was wondering if anybody has used this kevlar tape, and how to do it? i.e. is it self adhesive (I'm thinking probably not), or do you use resin/hardener as you would with fibre glass? If so, does the tape abosrb the epoxy like glass?

I know the subject comes up in various shapes and forms occasionally, but I thought a post completely on the matter would be good (for me at least) and also I can't find my OP with the keel strip article in it! So I wanted to ask people.

Any advice would be much appreciated!
Tom
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Cornholio
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Post by Cornholio » Sat Feb 23, 2008 11:32 pm

"God tells me he can get me out of this mess, but he's pretty sure you're f****d..."

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chris-uk
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Post by chris-uk » Sun Feb 24, 2008 9:06 am

is it self adhesive (I'm thinking probably not), or do you use resin/hardener as you would with fibre glass? If so, does the tape abosrb the epoxy like glass?
It isn't self adhesive. You would need to infuse it with resin in the same way that you would with glass, only Kevlar is much harder work to properly wet out by hand. An alternative would be to buy a powdered carbon that you mix into the resin and can then apply along the keel (after maskingit off), or over the whole of the bottom of your boat if you wish. You may need to look hard to find the powdered carbon though, and I don't have any suggestions as I haven't used it myself, but apparently it is well worth the effort.

Chris

OGB
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Post by OGB » Sun Feb 24, 2008 8:00 pm

I'm currently experimenting with a self-adhesive tape that is sold to protect the leading edge of wooden propellors (aircraft). It's thicker than a single strip of glass, easier to apply and replace, and costs about £1 per foot (2" wide). So far it has stayed on, but I've got a few more longer term tests to do before I'd recommend it.
If anyone wants to help out, see www.LightAero.co.uk and search for Fasson Stoneguard prop tape.

tomthehaggis
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Post by tomthehaggis » Sun Feb 24, 2008 8:17 pm

Corholio, good links, read them through, helpful stuff.

Chris, yea I couldn't find carbon powder anywhere either after a quick search. Do you know anyone that's done it? I was surprised at the powder aspect because I thought the strength in epoxy/fibre mixes came from the actual fibre (i.e. glass/carbon/kevlar/etc), so surely getting rid of that fibre would sacrifice the strength?

Also, found OP issue 6 with keel strip article, so bit more clued up. Thanks for the help!
Tom
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Jim
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Post by Jim » Sun Feb 24, 2008 9:11 pm

The fibres provide stiffness, for your keel strip you are more interested in abrasion resistance so carbon powder is probably fine (I have no experience with it. What Chris says is generally on the money, you work with Kevlar just the same as glass tape, but it is more difficult to wet out properly and harder to tell when you have wet it out properly (glass goes clear, kevlar stays yellow).

If you want a relatively easy kit, have a look at skid plate kits for open canoes - there probably isn't enough to do the whole keel of your sea boat in one kit (they just do the ends of canoes usually), but it will give you a good idea of the bits you need. That said the canoe skid plates tend to end up much wider than you need.

Jim

SJ
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Post by SJ » Mon Feb 25, 2008 10:52 am

My attempt at this is described at http://icefloerefurb.blogspot.com/2007_ ... chive.html.

I used glass tape, following recommendations from the guys at P&H. It seems to have worked OK.

Cheers,

Sean

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chris-uk
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Post by chris-uk » Mon Feb 25, 2008 11:12 am

Chris, yea I couldn't find carbon powder anywhere either after a quick search.
I've only heard of it being done in the States, so I'm afraid I don't know where to suggest looking. Jim's explanation of fibre V's powder is spot on.

Chris

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geyrfugl
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Post by geyrfugl » Tue Feb 26, 2008 10:39 am

Try googling graphite rather than carbon.

I use West system epoxy for my boats, and graphite powder is one of
the standard additives. Its purpose is not to provide more strength or
abrasion resistance, but to lower the friction so your keel strip tends
to slide over things taking less damage. You should be able to get it
at the same place you get your glass tape and epoxy. I used two-inch
glass tape, wet out with plain epoxy, and fill-coated with the epoxy
graphite mix. You could wet out with the graphite mix, but it's a bit
harder to see what you are doing with black goo than clear ! I got a
nice enough result without using masking tape, but I don't seem to
have a photo of the result - I'll see if I can take one shortly.

BTW, the graphite comes in tubs which would be enough for several
dozen keelstrips - you don't need to add much. You can increase the
abrasion resistance by adding amorphous silica. This produces a whiter
mix - it might come out a yucky inconsistent grey if you use both, I
haven't tried that.

A final idea is to use hexagonal Boron Nitride or "white graphite". This
will give you a nicer match for colour if you don't want a black strip,
and has the same effect in reducing friction. It's a lot harder to get
hold of though ... if you find a supplier, let me know ! It is used as a
lubricant (like graphite), but also in cosmetics ....

Andy

tomthehaggis
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Post by tomthehaggis » Wed Feb 27, 2008 9:57 am

Thanks for all the posts, the info/experiences were all really useful. After having a wee think, I think for simplicity and doing what I know people have success with, I'll:

- use the kevlar tape, wetted out with standard epoxy mix, no additives;
- use 2 layers on the areas at highest risk (ends);
- use a white gelcoat colouring to match the boat (I don't like the idea of contrasting as it seems a bit "I've got a keel strip"!) - not going to use either carbon or graphite powder because of the supply and colour issues respectively;
- until reading up about it, I hadn't thought of the masking tape bit, so that's useful.

Pretty standard, despite the alternative approaches offered, but hopefully it'll save me and my boat from unintentionally wetting ourselves sometime! The outcome will be on my blog, if people are interested in finding out how it goes. Happy Paddling...
Tom
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al27
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Post by al27 » Wed Feb 27, 2008 11:31 am

Hi Tom.
Don't use a polyester gelcoat over the epoxy, the two generally don't like each other (although if you are set on this route, you can get vinylester gelcoats that are compatable with epoxy, or SP do an epoxy that is compatible with poly gelcoat). The main reason for using a gelcoat is for the shiny finish (from a female mould), which is not an issue here as you are putting it on last. You can get pigments for epoxy, and the epoxy will be far stronger than the gelcoat anyway. And epoxy self levels better as well. The finished appearance will be about the same.

Al.

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Jim
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Post by Jim » Wed Feb 27, 2008 1:09 pm

I assumed Tom meant pigment by the phrase "gelcoat colouring"? I hope so for the reasons Al mentions, plus the fact that curing gelcoat in air is an advanced skill.

I have been using tangerine pigment in epoxy on my sea king, it's not colour matched, I was just in the chandlers and spotted that it looked similar to my boat, my keel strip (glass) is invisible as a result. Well, sort of! Does anyone know if I ever posted up my keel strip photos? Suspect I may have forgotten about it!

tomthehaggis
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aah

Post by tomthehaggis » Thu Feb 28, 2008 9:39 am

Aah, ok, a few more questions then:

1) Maybe just no gel coat, and 2 layers of epoxy if that is going to be stronger with a similar finish. Do people have any recommendations for a nice finish for the epoxy? If it's just painted on for the second layer then it should be an alright finish no?
2) Does anyone have any idea how much I should use? I've found some on the www.cfsnet.co.uk website, £75 for 5kg resin + 1kg hardener - from what I've read, I take it this will be more than enough to do 2 coats of epoxy, including the first 1 wetting out kevlar tape??
3) So I can just add pigment (yea Jim, gelcoat colouring) to the epoxy?

Sorry for what might seem like daft questions but I haven't got much experience with fibreglass, retrofitting, etc.

Happy paddling...
Tom
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lennart
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Post by lennart » Thu Feb 28, 2008 10:20 am

hi
at your second question;
I think that you can build a complete boat with that kind on quantaty about 10 % I think could be enough. the west website recond that about 1 kg should cover 8.5 m2.

good luck with the work,

some tips:
wear good gloves,
watch your eyes.
wear a mask while sanding.
try a bit before you do your boat.
be sure you are ready before you start mixing :
surface good, clean
all the tools nearby
etc.

I think you will have enough time to do 1 coat from back to front.
but it makes a mess when you are not finished in time.

working in low temperatures (as far as possible) gives you a lot more time. I found that it made mine wrok generaly the best in low temps and warming it after i had finised.
Propper Writing in English, how do you do that, with dyslexia, bad hand eye coordination, ect. and in a foreign language
sorry fore all the mistakes.

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Post by SJ » Thu Feb 28, 2008 10:31 am

1) Just painted on should be fine. I believe that you'll need to key the first layer by sanding lightly before applying the second layer.
2) My keel strip used less than half a kilo of resin.
3) I've never tried using pigments with epoxy. I'm told that it weakens the resin slightly but not enough to be a problem (unless you add far too much pigment).

Getting kevlar tape to stay in place while the resin sets can be a problem. It has a tendency to spring back up again at the worst moment! I've had some success with using clingfilm to protect the repair and then adhesive tape over the clingfilm to hold the kevlar down. For concave areas you can use some ethafoam or similar on top of the clingfilm to fill the cavity and press the kevlar into place. The ethafoam blocks are held in place with adhesive tape while the epoxy sets.

Wetting out kevlar can be a pain. I would use unpigmented resin for the first layer, so that you can see clearly whether the kevlar is properly wetted.

Epoxy resin is quite nasty stuff. Double gloves and a well ventilated workspace are a good idea, although the fumes aren't as noticeable as with polyester.

[All advice given in good faith, from years of patching up slalom boats and more recent experience in fixing my sea boat. I hope that it helps but this is only from my experience.]

tomthehaggis
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thanks

Post by tomthehaggis » Thu Feb 28, 2008 12:37 pm

Great, thanks for the further advice lennart/SJ. I'm off to order things. Will put a wee update on when it's all done!

Happy paddling...
Tom
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"Blessed are those with no expectations for they are never disappointed"

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Jim
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Post by Jim » Thu Feb 28, 2008 8:46 pm

1 kg of epoxy will more than do the job, use as little as you need to to just wet the cloth out enough - if you use 1kg of resin, you will have increased the weight of your boat by about 1.1 kg assuming you also use 100g of tape...

What do you mean by 2 layers?
2 layers of tape or one layer of tape with 2 coats of resin? The latter might be useful to get a smoother finish in which case applying it after the first layer has cured will be sensible (sand enough to get a mechanical bond). If it's the former you are thinking of, just start the second layer right away whilst the first is wet.

Don't worry about working in the cold with epoxy, room temperature is just fine, pour it into a roller tray and it won't set faster than you can use it - working in a hot boatyard in the middle oif summer we used to rarely get epoxy to exotherm if we weren't fast enough or had mixed too much, but I must stress that this was under sweat shop conditions! Epoxy will be a bit thicker in cold temperatures and you want it thin to wet out the kevlar. If you have the option of using extra slow hardener it will be slightly thinner, stay workable even longer, and will require at least room temperature to cure, but I recommend heating the work space overnight when you finish anyway to get a decent cure (use a safe type of heater and beware of solvents).

Don't be afraid to mix pigment in, you only need a tiny amount and as noted earlier, you aren't looking for exceptional tensile performance from the keel strip! There are probably different pigments to work chemically with different resins but for a keel strip I just wouldn't worry about it!

Jim

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