Remove hog from hull to improve turns?

-- Last Updated: Sep-16-13 1:17 PM EST --

I have an old woodstrip pro boat. I've enjoyed paddling it from time to time but I do notice that it is a PAIN to get it around the tight twisty corners of our tiny local river. Awhile ago I took a look down the keel-line and noticed that it has at least 1" of hog in it -- the ends are well lower than the middle of the hull. Ouch! That makes me think it would run straighter than straight. So I've unfastened all thwarts and seat-braces and have wedged the gunnels wider -- about 2.5" in the middle and 3" about 5' from the ends. Now the hull is pretty flat. The hull made some strained sounds as I wedged those gunnels wider but in general they seemed fairly flexy and nothing has cracked. I haven't permanently lengthened my alum-tube thwarts yet.

Now, given our twisty river I'm wondering if it might be nice to actually have a touch of rocker in this hull. It might be neat to be able to actually whip around my turns. Or maybe I should be happy with just getting it flat again.

Anyway, do you think I'll find that it turns a lot easier now that it's back to being flat rather than concave?

Like, a flat-keel boat tracks straight. Is it really possible that a hogged boat tracks "straighter than straight"? I suppose so because when leaned the ends won't come out of the water. Is that basically the main dynamic in turning? Not many people really lean a touring hull and they talk about "tracking" so maybe there's something else going on. Well, hogging can't be good.

Widening my tumblehome or whatever it's called might also increase my final stability, not that we need much of that. But we're not edgy racers anymore. I like a light fast boat still but the old pro boat might behave more kindly when it's loaded than it used to. Now I can be rewarded for tossing a cooler and duffles in it rather than getting scared!

I hope the hull won't mind the stresses of the wider thwarts. It's under new tension.

It was an old garage sale find so it won't be such a big deal of something odd happens. ...I wonder what I could do to relieve the tension or if it will eventually warp/adapt to it. It has a glassed exterior.

Read too fast. You think wider thwarts
would help your hog? By letting him roam wider?

Seriously, narrowing the thwarts in the hoggy area should help reduce it. But more relevant might be putting keel supports between the three thwarts and the bottom of the hull, to gently push the hull bottom back where it was meant to be. I would use minicell pillars and not try for a complete correction on the first attempt. Push the bottom down some, try the boat, and then consider what to do next.

A stripper can have considerable stiffness. It’s possible yours had some hog in it when it was first finished. A “glass” or composite boat can be pushed quite a bit, but a stripper, being stiffer, may not respond as fully to tweaking.

Is there such a thing as a warped hog in Africa?

Wider thwarts seems to reduce hog
I made a paper boat and when I spread the sides the ends went up. So I loosened my stripper thwarts then wedged them to spread the gunnels wider and the hog seems to have left the bottom of the hull.

It is weird, I agree. Do I even have the physics right?

I could see that locally that pinching the gunnels would tend to force the hull downward, give it more ‘belly.’ But since gunnels are 2 long single units apparently pinching them forces the ends DOWNWARD.

(Pinching them tries to lengthen them and make the boat longer but it can’t so it would push the ends down, eh? Spreading would exert a force that tends to shorten the hull but since it can’t it curls the ends upward. ? )

I kinda do like your idea of propping the thwarts. But my thwarts are light flexy alum tubing. Meant only to give connective tension, no vertical strength. I’d think that they’d tend to bow upward more easily than the hull would be forced downward but a little pressure might not hurt. :slight_smile:

Now, I do also have hull-bottom ribs in this boat, shaped like little arcs or slices. They’re glassed in. So the bottom of the hull probably hasn’t changed in shape. I really can’t tell how it got hogged. Maybe in the initial molding, as you suggest. Maybe being hung in a garage upside down by the ends for decades? :slight_smile:

Help, physics-people!

Agree with JeffOYB
In my experience working with Royalex canoes,…widening the center (installing a longer carry thwart) will actually increase rocker. I usually always shorten my thwart to narrow the gunwale beam to make solo paddling more enjoyable by creating slight tumblehome. This does however reduce rocker though so not so good for whitewater or manueverability.

partially correct

– Last Updated: Sep-17-13 12:38 PM EST –

The conventional wisdom is that widening the beam by pushing out the hull sides with wider thwarts will tend to increase rocker. But it also tends to reduce the arch or flatten the bottom of a shallow arch hull. I would guess that in some instances this second effect could outweigh the first and actually worsen the deformity of a hog-backed canoe.

I have adjusted the beam on a few boats by shortening the thwarts but only by up to maximally 2 inches. I can't say that I observed or measured any change in rocker in these boats, but then rocker is hard to define and quantitate.

As for the issue of whether reducing a modest degree of hogging will improve maneuverability, I can only guess but I suspect the change would be minimal. I have sometimes paddled Discovery model canoes by Old Town (3 layer poly) which were moderately hogged, which tends to occur with this material. In comparison with a new version of the same model I honestly didn't appreciate much difference.

I would be concerned that the flattening effect on the hull cross section would tend to have more effect, either good or bad, on handling than a small change in rocker.

small stream boat
Maybe the answer is a different boat. Canoes with a straight keel line are a pain in the butt on twisty rivers and streams. I love boats with lots of rocker even for lake paddling.

Widening the center thwart on a Tripper
increased flatness in the hull’s center, and might have led to hogging if I had gone further. I wedged a foam pedestal seat between that thwart and the canoe bottom, and ended up with a bit more rocker, and a wonderful center pivot zone that made my Tripper quite a bit better in whitewater than the rest.

Sorry if I misunderstand, but I can’t see how spreading thwarts would reduce hogging. I’ve seen enough OT Discovery rentals to doubt that theory.

Widen the thwarts and run a center board down the inside bracing down from the thwarts. This will help with the hog and make it turn better. Make sure to store the canoe right side up. Most canoes will hog if stored upside down for a long time. Good luck.

Bruce Barton

Normal storage is upside-down

– Last Updated: Sep-17-13 4:59 PM EST –

I would not agree that "most" canoes will hog if stored upside-down for an extended time. Upside-down storage has always been the normally-recommended method. As far as I can tell, the only canoes that ever get hogged in the first place are cheap plastic ones, like the Old Town Discovery (I've seen hundreds of them, and every single one was severely warped on the bottom), Coleman/Pelican, Rogue River, etc. I've yet to see a wood, Royalex or fiberglass/kevlar canoe get hogged at all, much less due to the method of storage (I have seen ONE Royalex boat get hogged at the two locations where the tie-down straps go, due to being habitually secured way too tightly to a roof rack in summer). In fact, storage rightside-up concentrates stress within the small areas of the hull which contact the substrate, while upside-down storage puts the stress over a large area of the hull instead (stress is much less that way).

Except for boats in dealer showrooms and museums, I've yet to see one that was stored rightside-up, so if your statement were true, almost 100-percent of the canoes in use would eventually become deformed, and that just isn't happening.

Hog, as in BBQ
Most hog is built into wood strippers on the form. There is a tendency to nor account for the strips bridging at the stems.

Lots of production boats exhibit hog too. Sometimes it’s a function of molds, particularly those with half splits, hogging. Successive hulls are hogged too.

Sometimes a solid, unscored or unheat-molded core will flatten the bottom and hog a hull. Sometimes un- preshaped aluminum rails force the stems downwards; hogging the boat. And too many beaver dams can hog paddlecraft over time.

So it goes, manufacturing is often an imprecise art.

Gee I have 17 canoes that range
from six to 100 years old. All are stored gunwale down. None are hogged. None are polyethlene or whatever crud Coleman uses.

So the notion that all canoes that are stored gunwale down will eventually hog is utter hogwash.

You might try…
replacing the center thwart with a sturdy wooden one that won’t bend before the hull does, and then put a brace from it down to the hull to try to force the hull downwards in that area and eliminate the hogging. I would think that might have more of an effect, and a more predictable effect, than spreading or pinching the gunwales at the thwarts.

Fight pork with porker. Carry a 500#
hog in the center of your boat.

negitive rocker?
Hog can be considered negitive rocker maybe? I have changed seat and thwart length on two royelex boats with great results. One was a Wenonna Sandpiper I widened to make it a more manoverable small creek boat. The bottom flattening a plus as it allowed it to float in shallower water. The second was an Esquiff Echo that I shortened seat ect to get a narrower paddling position. This reduced the rocker a little,but not enough to hurt it’s great handling.


I would stop short of causing a canoe
hull to “hog”, no matter what my goal. Some Royalex hulls are amenable to rocker adjustments, but if spread so hard that they hog, they’ll lose speed. Glad your Sandpiper experiment came out OK, but leaning or edging the boat is another way to extract maneuverability without losing speed.

Even my high rocker whitewater canoes need to be leaned at times, just to snake effectively down the river.

Talk to Tom
Jeff, have you talked to Tom Cannon about that stripper? He might recognize the hull & have some ideas.

Did your mods get it stable enough to pole on the Red Cedar?


report and pics of anti-hog project…
Thanks, everyone, for the ideas!

I spread the gunnels about 3" and got rid of the hog. We’ll see how it paddles now.

I see there’s one post where someone says ‘spreading the gunnels causes hog’ but maybe it’s just a typo – spreading reduces hog.

Maybe I’ll even try sanding down the bow and stern so it turns better. Or I’ll try wedging something under the center thwart.

One step at a time! :slight_smile:

I’ve always been able to pole and standup paddle my ol’ race boats. That’s where all the fun is! :slight_smile:

Yeah, Tom will have ideas if mine don’t work.