Hi everyone. I just bought a WS Tempest 170 (poly) and it's my first boat. To lug it around I bought some Yakima Hull Raisers (J-mounts) as well. I bought it from a store that specializes in kayaking and had them run me through getting it in the rack, tieing it down etc. They secured the straps and had them tight enough that it deflected the hull. I noticed that and mentioned it but they said it was OK (asked two different guys and the didn't even flinch when they saw it). I now have several dents in my new kayak.
I called the store up when I got home and they told me to leave it out in the sun for a few hours or to try using a hair dryer to heat up the hull (but not too close). I understand the platic used in these boats melts at 130°F. I used a Fluke IR thermometer (yeah, I'm a geek) and monitored the hull temperature (boy, it's starting to sound like a Star Trek episode... as I mentioned... geek). I got to 115 degrees for brief periods but I'm nervous about heating it up any more. I had my father help me out on the hair dryer side while I was on the other side pushing it out into shape. Unfortunately it had no effect. I suspect I didn't get it hot enough but I'd rather be safe than sorry. Wilderness Systems' website recommended using boiling water as a safe method to get the hull to return to its original shape as well (haven't tried that yet).
Some questions now. Is this a dent or is it "oil-canning" and what's the difference (or are they one in the same)??? Does this happen to everyone when they cartop their poly yaks or is this not normal?
This brings me to wheels underneath it. I have a Subaru WRX sedan. The boat at 17' is slightly longer than the car. Yakima recommends a front and rear spread on the bars of 25". I wish I could place them far enough apart so that the j-mounts were aligned with the hull reinforcements but that doesn't seem possible. Any suggestions? The store I bought it from adjusted the tie downs. I was thinking of not torquing it down so much and using a different strategy to making sure the boat goes nowhere. If I tie a line from the right back of the rack to the stern to the left back of the rack that should (if the line is tensioned properly and doesn't have a lot of spring (no bungees obviously) keep the boat from moving back under accelleration. It will also provide lateral stability and keep the stern from deflecting to the right (and the bow to the left) in gusty conditions (obviously the line must be tied off at the stern, it simply can't be passed through or no stability will be provided). Rigging the bow in a similar fashion should prevent the boat from moving forward under heavy braking. Of course in addition to the I would also have tie downs from the bow and stern to the bumper (to prevent lift at high speeds). If I rig it this way can I back off on the j-rack tie downs a bit?
One final thought (I know this is long). I was thinking about fabricating a thin fiberglass J-cradle to reinforce the hull. Here's the basic idea... I'd use the boat as the mold to create a custom fit. I'd have to do a bit of research to make sure I used a thin protective coating that the resin wouldn't eat through (I'd also have to do tests to see what temps the resin reaches when activated... I know they can get toasty) but... I'd get a rubber mat of some sort and cut it to shape and lay that over the middle of the hull. I'd then start laying fiberglass strips down and applying the resin. After everything cured... a little bit of sanding and cutting and I should end up with a nice skinny fiberglass J-cradle form fit to my boat. I'd just drill some hole into it and zip tie it to the j-rack. I'm thinking that this would distribute the weight a little better and it should provide some added rigidity so the hull doesn't deflect from the tie downs.
I've done a little bit of work (a little meaning once) with making a fiber glass mold and... it's messy as hell but it isn't too difficult.
Am I totally off my rocker or does this seem like it might not be such a bad idea?
Cheers, Joe
You have…
dents. Oil canning occurs on the water while paddling. Its kind of of popping in and out like the bottom of the old oil cans.
I would try to let the sun bring your dents out. This works with the memory of the plastic. You can use an inflatible beach ball or similar item to help achive a bit of internal pressure. Be very careful applying heat with a gun, you can alter the memory. The temps you mentioned aren’t really a problewm as they are easily reached in many parts of the country under the summer sun when the boat absorbs the solar radiance.
The folks simply strapped you down too tight. Snug works just fine. And don’t introduce a lot of tension to any bow/stern lines. This can induce additional problems. They’re a safety backup and can help reduce lateral wind wobbles.
Make some wooden molds for your custom cradles. Go to a craft store and get a contour ruler. Damned if I know what they’re really called, but its basically a square plastic ruler, flexible, and holds its shape. I found an inexpensive one in the craft department at… dare I say it?!.. Walmart. I believe its two feet long and will work nicely for your task. Buy a sheet of 1/8" luan plywood at Home Depot, etc. Inexpensive and easily molded for your needs. Get your boat’s contour with the flex rule and transfer the same to the luan ply. Wax it, contact paper it, whatever for a release surface and go to creating.
Hit a tire shop that services big rigs and scavange an old inner tube. Cut some appropriately sized sections and appy to the inner surface of your new custom cradles with solvent based contact cement. Grabs your boat nicely. Keep the rubber free of debris to avoid scratches and such.
da Vinci was a geek and fabricator extraordinaire. Go forth and emulate! A fine boat you have.
Pleasant waters to ya.
Holmes
too tight
and 'em R dents. Holmes is right about oilcanning vs dents.
sounds like you are over thinking this.
plastic won’t melt unless you REALLY heat it up, it won’t get rid of the dents unless you sortaheat it up. go slow w/ hair dryer and you’ll feel the material get soft then push it out and cool it off. wet towels or a hose/ cold water.
padded J cradles and less tension should be fine. if you have a secure bow/stern line the whole system can be rigged rather lose.
steve
i have pushed out the ‘dent’
with a piece of foam or anything to get the shape kind of right again…then poured boiling water on it…a couple of jetboils full (or kettles) and it will come back to close to where it was…then leave the inside stuff while the plastic cools…should be okay…never great as before though…
length of roof rack: you need the stretch kit from yakima…;it expands the bar spread on smaller roofed cars…works great…used one on my toyota tercel…i still have it if you need to get one-good deal-drop a line on email…
rob
Thanks for the feedback everyone
Sorry it took me so long to post back here, I just wanted to thank everyone for taking the time to respond. I got the big dent out using boiling water. It still has ripples but everyone seems to say that it shouldn’t make much of a difference. On calm waters I have no problems cruising at 4 MPH. When it gets choppy it goes down to around 3 to 3.5 MPH (I’d say really mild chop created from bazillions of power boats in Paugus Bay on Lake Winnepesaukee in NH). I’m assuming that’s OK for a novice and that the ripples aren’t really impacting the hull speed that much.
I’ve really been enjoying it so far. I need to take some more lessons so I can gain the chops to get out on the ocean. I have a feeling that Lake Winnepesaukee is going to get old REALLY fast (too congested).
Cheers, Joe
Try Squam Lake
Squam Lake in Holderness is much more kayak friendly. Only go to Winni in Fall and Spring except really out of way places of which there are very few.