my 17’greenland style s&g 4 mm okoume boat is tracky with a straight keel line and moderate deep v hull shape. i am considering cutting a long thin wedge shaped slice out of the bow along the keel line and then sewing it back together to get a little rocker into the bow. is this a wack idea? have you done it?
I’ve been trying to picture this…
…in my head, and I have a couple of questions before I mess up my head even more…
Could you tell us exactly which model boat it is? Or is it one of your own design?
Have you thought about how you would deal with the interior keel fillet during such an operation? In addition to adjusting rocker, how would you go about reshaping the exterior keel and the rest of the hull shape towards the bow, etc.? How much of the bow would you have to totally reshape in order to achieve the increased rocker you desire?
Wood and epoxy is wonderful to work with, in that you can pretty much “sculpt” any shape you like, but I do think that rocker isn’t the only thing you’re going to have to think about reshaping here, and I wonder if you’d be happy with the other shape changes that could result in an operation like this; or what it might take to get to a final shape you’d be happy with. I ask all this, because I know that once a S&G boat is complete, there are lots of forces working together to keep the wood panels very “solid” in their final shape. Adjusting “just rocker” may well require a lot of other adjustments as well. Or, it may not be quite the ordeal I can imagine; I don’t know.
Finally, do you have pictures of the boat as it is now, so that we can try to imagine, along with you, how you might go about such a project?
If you have to do it…
I think I would start by rounding off a little of the stern. The stern has more to do with the hard tracking…
SOF - putting in rocker
not a wacky idea at all. the downside will be that there will be less volume in the bow, usually right where you want it.
ive discussed and recently influenced and witnessed a reskinning where more rocker was put into the whole yak by putting in a longer keel, that in turn pushed up the ends and kept the volume - relashing was necessary - but the boat’s characteristics were radically changed from a train on a track to a much more maneuverable car.
these boats are fairly simple and forgiving - so go for it. If does not work, make the big change and reskin. if it was me, i’d cut at the gunwale, pull back the hull skin, add length, relash and just see if the skin will still fit. if not, add 2 darts at the g/w at ea side.
Build another boat
This is a S n G not SOF right? I think you’re opening yourself up to all sorts of complications, and likely to end up with Franken-kayak. Plus, best case scenario, you’re adding a little rocker at the ends, but keeping the center keel line the same.
I think it would be more fun to just build another boat. And if you really can’t stand your “tracky” one, sell it to finance materials the new one. Building a new boat from plans (cheaper than a kit) would, IMHO be more rewarding, less frustrating, and yield a better boat.
S&G Putting in rocker
oh oh - puddlefish is right - yr were asking about changing sng shapes on an existing boat.
as the bow and stern of most yaks become quite vertical at their termination, there is lots of scope to recut and reshape:
the absolutely most basic is to just cut whatever shape you want, wire the keel edges together as close as they’ll go and then just fill the gap with epoxy mush or tiny panel or pc of wood to be shaped as a bowstem - that’d cover nearly all possibilities.
the other way is to make the cut and then trim off little bits and stop when you can’t close the gap say more than 1/4" - then fill with mush.
in any even, if the upper seams are stiff, you may have to slit them also so that the panel will bend.
if you take small steps, this is a straight forward modification done all the time.
I’ve wondered what would happen if I trimmed the sharp corners at the stern and bow keel of my Merganser 16. It too is a harder tracker than I like (though nice in a beam wind). The keel is also very fine…somehow I managed to glass it that way. I’m thinking that rounding the sharpness and cutting the corners would loosen up the bow and stern.
But I am going to just leave it alone rather than mess it up.
Try posting in www.kayakforum’s Building section, and you might get a response from someone who has actually done this instead of just wondering about it.
what kind of kayak is it to begin with? I’d be tempted to start with a new kayak, the straight keel probably has more to do with being tracky than just the ends.
here are a few pics
the boat is my custom adaptation of a pygmy queen charlotte: lower, narrower, longer keel , deeper v, bulkheads/hatches & inwale added, etc. its a sweet boat but i like to tinker. and i live on a marsh with a lot of winding creeks. [URL=<a href=“http://outdoors.webshots.com/album/187342804Ftphua” TARGET="_new">http://outdoors.webshots.com/album/187342804Ftphua</a>]
when dealing with hard tracking it’s more a function of stern depth and grip than bow grip. while the bow will have some effect on initiation it’s the keeline and stern that directs the bow in a turn.
In designing and prototyping the Tempest 180 we used the 170 platform and had to tweak both stern and bow. what a royal PITA. can’t even imagine the Frankenstien you will end up with! We nicknamed the T-180 ‘ol Cut and Paste’
hows your edging skills?
I would build another boat and keep that one as a ‘tracker’.
Looking at that long straight keel line
I just cant’ imagine what you could do to that boat to make it less tracky. Sounds like you need a shorter boat for exploring those marshes and winding creeks. And one with more rocker throughout, not just at the ends.
I would be very reluctant
to touch the bow keeline because it could cause the kayak to leecock which is not a good characteristic.
If it’s tracking that you would like to adjust, the stern keeline is the place to work. I have removed and added to the stern keeline on my wood kayaks with very good results. Take off about a 1/2" at the stern keeline and taper it up the keeline a couple feet for a smooth transition. A belt sander works great. This is one of the nice things about wood kayaks, you can make them handle just the way you like a kayak to handle for your weight. If you make it too maneuverable you might have to add some type of a skeg to help reduce weathercocking in strong rear winds. Go for it. You’ll be glad you did.
You could just round off the ends, but then you’d start to create a blunt, flat face. How much depends on how slended the bow slice is. If it’s skinny enough, you won’t notice much. But if it’s not as sharp entry then you’d need to trim along the keel line to get a clean fit.
Just out of curiosity how did you make it? When you say inwale do you mean pre-glued sheerclamps when stitched up or inwales/sheerclamps added after hull was glued and before deck went on?
The regular QC is a maneuverable kayak.
sheer clamps/inwales were added
to side panels before the panels were sprung around bulkheads to help maintain fair curves. since i narrowed the side panels i could’nt use the measured deck of the qc plans so i decided to build using the ‘skiff-build technique’ by bending panels around moulds instead of using s & g precut panels. its built somewhat like a clc boat. i’ve built several skiffs so i am familiar with that technique.
got any pics of that school bus?
i am going nomadic : ) since i just retired. ooh yeahhh!
maybe youre right steve
yes my edging skills are improving every time i go out. part of the reason i chose to do a greenland style boat was to improve my skills. my other yaks are very ‘turny’ so this one has been a challenge.
reason why I ask
Just out of curiosity how thick is it?
The pre-glued sheerclamps limit the possible curve near the ends to a wider radius than the midsection. Imagine holding a bendy stick by the ends, it curves in the center then straightens out near the ends. I made a Ch18 where the sheer was absolutely straight for 3’ with the other side a bit curved simply because of the density/flexibility difference in the wood.
With a four panel hull that makes the ends a bit narrower and pushes the bottom panels into a tighter v than if it was made only with 4mm.
I saw this all in one month after building a Ch18,Merganser16 and my own design trying to figure out what’s wrong with the CLCNorthbay,NBXL(broaching,weathercocking,lack of response on a lean). On my design what developed on the computer was NOT what developed in construction because the side panel could not bend as expected on the 'puter with the 3/4" cypress glued on.
The plain 4mm hull or one with temporary forms near the ends are less likely to be extremely pinched as the bottom panels have less tension pushing them together than a side panel with pre-glued sheerclamp.
The CLC Arctic Hawk has two strips of 4mm ply added AFTER the hull is stitched up and glued. It’s got a couple curves in the sheer as a result of the forming bulkheads, although it’s nearly straight keeled it can lean on a turn because the side panels have lots of flare. I don’t think you could get the same ends if it had a thick sheerclamp glued on.
Anywho, roundabout way of saying that more maneuverability will come from more rocker and different ends,in other words a different hull, especially given the rest of the hull is glued solid.
i’ve done it
I’ve done that on my self-designed homebuilt franken-S&G kayak aka “sharkie”. i did it both in stern and bow…Yeah the stern seems to be more of the factor in trackiness of a hull, but take too much trackiness off the stern and you’ll move the pivot point way forward and have a wickedly weathercocking boat, at least that’s how i imagine it.
build another boat - ditto
after looking at the pygmy site and yr yak, this is not the yak to make extensive mods on - no matter how much you like to tinker.
the lowest panels define the keelrocker and yet terminate relatively low at the ends. way too much hassle to redo. possible, but the best way would be to reintroduce another partial ‘dart’ panel betw the 2 existing and redo a large part of the lowest to reshape - too much dicking around for minor benefit.
build a different boat. and do not put sheerclamps in unless part of the original design - as lee says, it predefines shapes that you often don’t want right at the bow and stern, as well it just adds wt for no good reason.