I am thinking about putting a keel strip on one of my boats. It is a Kajaksport Viviane so it is a pretty fast boat and that is what I got it for. It has some wear in the gel coat in several places along the keel line which is why I am considering this in the first place.
Do you think that a keel strip would add enough drag / frictional resistance to make a difference in the boat’s speed? Since that is what I got this boat for I would not want to add one if it would make an appreciable difference.
My guess is that it would add some drag but not sure if it would be enough to really make any sort of difference. Maybe I’m wrong.
Matt
Potential products for keel strips?
I imagine from a technical point of view, any keel strip would have some sort of measurable drag effect, but my guess is it would be negligible in all circumstances outside of racing.
In an earlier thread there was discussion on several products available for potential in the field repair use. I have never seen or used any of these products, but in reading about them wondered if they also could be applied to hulls as keel strips. It appears that if they would work in that scenario, they would produce a smooth skin tight surface that would reduce any drag factor for being a keel strip. Maybe others who know or use these products could shed some light on this.
Some of the products discussed:
http://www.hippopatch.com/index_002.htm
http://www.mobilehomerepair.com/stickit.html
http://www.densona.com/DensoProducts.htm
If it were me
I would repair the gel and try and avoid repetitive beach landings where the keel slams into the sand.
Drag
Will not cause noticable drag. VF
After a closer look
my keel is also getting some nasty scratches with very little contact with sand bars and surf landings.
I only remember pulling myself over one sand bar with shells.
good question about keel strips. right now I would probably stick to repairing scratches once a year, hmmm, or if it gets worse consider a keel strip.
added weight
A keel strip added by a novice will add 2-3 pounds to the boat with most of the weight being at the neds of the boat. Newton will tell you the more mass, the more energy needed to get that mass moving. So your turning will definitely be affected; the boat will not want to come around as easily. If they are scratches, leave them be, if you have gouges down to the fabric or gel coat chips, those are worth fixing. I would only add a keel strip if you plan on beating the boat and it doesn’t sound like that’s your intentions.
I wonder if, after going to the trouble
of adding the strip, you wouldn’t find that other wear areas started to appear, laterally to the strip.
Probably the lightest possible strip would be carbon fiber and resin, but while the carbon would be “slippery” as it wore away, it isn’t hard.
S-glass is the hardest cloth one might use for a strip, but of course it is relatively heavy.
In general, Nylon, Kevlar, polyester are going to wear fuzzy to some extent, although polyester and vinyl ester resin might fuzz less.
And, of course, one might use a plastic or wood strip applied with resin.
But I tend to side with those who would just patch the gelcoat as needed. And, a little bit of exposure of the underlying glass cloth isn’t going to hurt anything. Main goal is to paddle.
Might depend how well you do it
I’ve seen lumpy, bulky keelstrips. I’ve also seen fairly clean additions. The added drag may depend on how good a job you do and how thick the strip is.
An alternative is to add a nonfabric keel strip of graphite-silica-epoxy mix. You can sand that one to be streamlined.
That’s what I use
Non-fabric. I mix up some epoxy in a cup add silica until it’s almost unworkable, thin slightly with white pigment, and apply. When dry, I sand out any lumpyness, and I’m good for another 3 years or so of beach landings & bouncing off rocks. Much tougher stuff than gelcoat.
Silica Mix
Wayne:
Being a novice at gel-coat repair and the different epoxies, silica, etc are unfamiliar to me. I do have a few chips off my gel coat at the keel and would like to use your mixture for a repair. Could you give me particulars about the expoxy, silica and pigment you use? I presume the pigment is white gel-coat pigment, correct? What type of epoxy, and silica? Where could I find the silica?
Thanks!
Keel strip
– Last Updated: Aug-10-08 8:00 PM EST –
I use MAS medium cure epoxy and fumed silica, and any old pigment I can find at the marine store. I got all my stuff at West Marine.
The brand of epoxy really doesn't matter so much. I prefer to use real epoxy rather than the cheaper vinylester or polyester resins, because I think it lasts longer, and doesn't crack as easily.
One note of caution, though: if you're going to use fumed silica, wear a respirator. The stuff is pretty dangerous to inhale (Think asbestos). I prefer to mix it outdoors if possible, so that I don't let any loose in my basement. Of course, you can't do that on a windy day, because your silica will all blow away on you.
Gorilla tape is pretty amazing stuff
Try a temporary keel strip of Gorilla tape to see if it creates significant drag. If it does, you can always take it off.
I got the idea from a customer who said he used it on his entire hull!
I wouldn’t go that far, but we tried it as a keel strip on one of our livery tandems because they take a lot of abuse along the keel line from being run up on the shore and dragged over rocks & shells.
After four weeks the Gorilla tape shows no signs of peeling and it is absorbing a lot of the scratches. When a section got too chewed up I just put a strip on over it and it’s still holding up so well we’re planning to do the rest of the tandems.
I’d be interested in hearing other people’s experience with this stuff. It’s definitely replacing duct tape in my emergency repair kit!
IF You
actually NEED a keel strip for the way and the places You paddle
Then any imagined or not imagined drag doesn’t really matter.
If You don’t need one for Your type of paddling…then it’s just cosmetic…and You could use a magic marker or sharpie if You wanted. easier touch up…and from a distance on the car or on the water, it would look like the real thing (maybe)
Best wishes
Roy
Utility…
My potential desires for a keel are strip are for utility only.
The boat I would put it on is about 10 years old. It has several places along the keel that are chipped down to the glass.
I could re-gel coat and repair the areas which would take a long time and may not hold well (already tried this at the bow and it is chipping off already…maybe I used too much hardner or maybe this is just a bit harder place to repair for a new glass worker like myself).
I once had a boat I bought used that had gel coat wear on the keel at the bow.
I never really worried about it until one day when my front hatch was filled with several quarts of water.
Upon later inspection I realized that the wear on the gel coat had actually been so extensive that the glass unerneath wore through. Not a good situation.
I now am more concerned about such wear in order to prevent this sort of thing from happening again.
It just seems that a keel strip would be easier, stronger, and have more longevity than repairing all the spots along the keel that are chipped.
Matt
Matt
Since
– Last Updated: Aug-14-08 1:44 AM EST –
thats the case...then ..You need to repair all the chips before You put on the keel strip anyway...
so what's all this silliness about concern over drag?
either You need a keel strip or You don't
If You need one.....then do it while the weather is conducive....
It's a very simple job, just takes a little time and some patience.
10 Years is not that old of boat...if your patching jobs are not done corectly and they worry You....Take it to someone to do the job or else use the boat to practice on and learn how to do repairs.
The question is not about drag......The real question is about if You need a keel strip or Not.....
Best wishes....(remember it's not a race boat and never will be)
Roy
I’ll think about it…
My current gel may hold up well enough.
Just curious about the drag issue. Obviously one of the factors that determine boat speed is frictional resistance. It would seem that this would increase it, but was not sure whether it would be “statistically significant.”
Part of the reason I ask is due to some comments I heard a few years ago. I was getting my gel on my keel repaired by the guy who does reapairs for SK GA on Tybee Island (Mike Robinson I think is his name).
He told me that another option was just to add a keel strip. He then went on to tell me that some people feel it changes the boat’s dynamics a bit.
He told me that Dale Williams (who he said is like the princess and the pea when it comes to his boat and its handling) feels that they change the handling of the boat and make them track stronger. He also said it might add some drag. I thought this was an interesting statement from Dale and wondered to what extent it was true. Dale is a pretty darn good paddler and a true expert. His opinion carries weight.
Actually…the Viviane is a viable race boat and I am considering doing some racing with it. This is why I ask about drag. You don’t see race boats with keels strips.
We’ll see. It’s all good.
thanks
Matt
Not noticible.
“So your turning will definitely be affected; the boat will not want to come around as easily.”
2-3 pounds on a 50 lb boat will not be noticed.