seeking advise for rub strip layout

[Oyster]

I am bolting rub strips on the bottom of a freighter canoe and are down to the last two which are the most outboard ones. What I have done so far, is before I glassed I bored holes and epoxied filled the bores to drill out and bolt these strips to. How I got the layout is shot a laser line parallel with the center line of the boat and marked that as the center line of the epoxy plugs, then marked half of the strip width on either side of that ,plumb with the laser line. With that said the marks are wider than the width of the strips because of the curve of the hull. I have laid the strips up there centered between the lines and there is curve to it from some angles of view. My concern is bolting the strip on in this locate and having it drag heavily. Any thoughts?

[Oyster]

[Oyster]

[jsjpd1]

Since these last strips are pretty close to the turn of the bilge I'd be more inclined to let them follow the curve of the hull instead of parallel to the keel. I think I would also reduce the thickness of these ones some, the finished thickness of 1 3/4" with the plastic strips added on top of the wood strips seems a bit overkill. I would still want some sacrificial strip there though, you're intending for this boat to live a hard life.

Jim

[James McMullen]

Are you planning to sled this thing instead of paddle it? I think you've got plenty of strakes already and could leave off those outer strips.

[Oyster]

Since these last strips are pretty close to the turn of the bilge I'd be more inclined to let them follow the curve of the hull instead of parallel to the keel. I think I would also reduce the thickness of these ones some, the finished thickness of 1 3/4" with the plastic strips added on top of the wood strips seems a bit overkill. I would still want some sacrificial strip there though, you're intending for this boat to live a hard life.

Jim

jim, do you think that following the curve of the hull will cause less drag than parallel to the keel while going straight and turning?

[Oyster]

Are you planning to sled this thing instead of paddle it? I think you've got plenty of strakes already and could leave off those outer strips.

james,
i am not sure what you mean by sledding. there will be 2 forms of power, a outboard engine, or 2 rowing stations. my thought for the outer strips were for when in a hard turn in shallow water and the boat is leaning over it would still have protection from the gravel. do you see the outer strip as a big drag in a turn or any other problems with it?
thank you
royce

[Gib Etheridge]

My take is that they are definitely going to slow you down whichever way you orient them. Can you just add more cloth between the rub strips already installed?

[Oyster]

My take is that they are definitely going to slow you down whichever way you orient them. Can you just add more cloth between the rub strips already installed?

thanks gib,
the area that i feel needs protected is outside of the strips that are already installed. i think i agree that these are going to really drag the boat down, especially in a turn when you need it least. do you feel there would be any benefit to making them shorter to keep them out of the turn of the bilge? also make them shallower as jim suggested or just delete them all together?
royce

[Peerie Maa]

They will slow you down less parallel to the keel as you have planned than if following a natural lie.

[Tom Lathrop]

The main question is, why are the strips there in the first place. My guess is that the designer wants extra hull protection for scraping over the shingle you guys have in Alaskan rivers. They also offer a lot of strength and rigidity for cargo in a freighter canoe. The water that is trapped between the strips when running should have the same volume of space to flow aft for minimum resistance. That means that the strips should be the same distance apart which may not be a straight LASER shot but measured in equal increments from the keel. Unless someone has a more reasonable answer, that is what I would do..

[SMARTINSEN]

If, as Tom suggests above, the strips are to be parallel with the inside ones, they would look better if they were tapered on the outside. Perhaps thinner towards the ends, too.

[Tim Marchetti]

The main question is, why are the strips there in the first place. My guess is that the designer wants extra hull protection for scraping over the shingle you guys have in Alaskan rivers. They also offer a lot of strength and rigidity for cargo in a freighter canoe. The water that is trapped between the strips when running should have the same volume of space to flow aft for minimum resistance. That means that the strips should be the same distance apart which may not be a straight LASER shot but measured in equal increments from the keel. Unless someone has a more reasonable answer, that is what I would do..

The designer only calls for a single keel, but he wasn't thinking about skidding over beaver dams and gravel bars. Royce is doing a great job at modifying the design to meet his needs. It seems to me that the outside strips could be laid out as planed, but shorter. Maybe to the forward strap in the picture. It looks like the other strips will have you covered forward of there.

[James McMullen]

Seems like overkill to me. You are adding bucketsfull of wetted surface and drag already, not to mention extra points to snag and even trip on if you are working in running water. None of my whitewater canoes had any such thing. Are you sure you're solving a problem that actually exists? The three center ones will keep the boat upright when you're dragging it, I don't think you need any more.

[Bill Perkins]

As others have said ; I think the straight inner edge needs to be parallel with the other skids . I would make the skid shorter : placed to protect the turn of the bilge along about the middle third of the boat . The outside edge I would curve ; picking up the curve of the strip plank would make esthetic sense and be easy to lay out by taping some tracing paper to the boat. But the main point would be to follow and protect the turn of the bilge. I'm thinking you'll have an outboard onthe boat but won't be planeing .

The strake would be wider than the others at midpoint as I’m envisioning it ,tapering to a near point at either end and all edges faired a bit (the other strakes too) . The ends would be faired right into the hull and center on the turn of the bilge .The underside would need to be backed out (hollowed) to fit to the turn of the bilge . Shortening the strake would reduce the required width .I would try a few different lengths with some tracing paper on the boat .

[TerryLL]

Egad.
Just stumbled on to this thread. What I'm seeing here is a prime example of converting a slick and easily-driven hull into a slug. All that unnecessary wetted surface will drag horribly. Canoes get scratched and dinged, and this one will get a bunch of scars with or without all that extra timber hanging off the bottom. I'd opt for a smooth bottom and some planned repair and maintenance each Spring.

[Oyster]

They will slow you down less parallel to the keel as you have planned than if following a natural lie.

thank you nick
royce

[Gib Etheridge]

Even though speed's not an objective I think this last strip is not only too much resistance it's not the right approach to protecting the turn of the bilge. Rocks are often pointy jagged things and they will get up between the strips and do the damage anyway. The strips that you have applied so far are parallel enough to the keel that when dragging over some protrussion, whatever it is, it probably won't get wedged between the strips and the keel and necessitate lifting the boat to get freed up, but if you apply the bilge strips following the laminar flow, wherever that may be, you'll probably find yourself doing a lot of heavy lifting in slippery and otherwise awkward situations and positions. You could get hurt, it would ruin your day.

Still, the turn of the bilge is going to take a beating so something should be done to provide more wear resistance and strength. The easiest way to do that would be to lay on some more glass, or better yet one of the slippery tough fabrics. I don't know which would be the appropriate fabric for wear resistance but lots of people here do. Glass on the inside will add impact resistance, whatever fabric on the outside will provide wear resistance. It will be kevlar or aramid, something like that.

Now... If it were my boat I would cold mold a layer of fir in epoxy before laying on the wear resistant fabric. This will add considerable stiffness, which you will appreciate when the heavily laden hull comes down hard on a rock. I would add the wear resistant fabric on the outside of that as well. That's probably not what you want to hear, it would be nice to get it done, but it's an option worth considering.

That looks like a nice building job. Can we see more pictures?

[Oyster]

The main question is, why are the strips there in the first place. My guess is that the designer wants extra hull protection for scraping over the shingle you guys have in Alaskan rivers. They also offer a lot of strength and rigidity for cargo in a freighter canoe. The water that is trapped between the strips when running should have the same volume of space to flow aft for minimum resistance. That means that the strips should be the same distance apart which may not be a straight LASER shot but measured in equal increments from the keel. Unless someone has a more reasonable answer, that is what I would do..

thanks tom,
royce

[Oyster]

If, as Tom suggests above, the strips are to be parallel with the inside ones, they would look better if they were tapered on the outside. Perhaps thinner towards the ends, too.

thanks steve.
roger that on thinner at the ends
royce

[htom]

I would have glassed and filled the bottom and up to (say) six inches of the gunwales with graphite in epoxy before adding any of the strips, hoping that trials would show the strips weren't needed at all. Then I'd add the center, more trials, then the next two, more trials, and finally the out ones (all the while cursing that I must have chosen the wrong design to begin with.)

[Oyster]

The designer only calls for a single keel, but he wasn't thinking about skidding over beaver dams and gravel bars. Royce is doing a great job at modifying the design to meet his needs. It seems to me that the outside strips could be laid out as planed, but shorter. Maybe to the forward strap in the picture. It looks like the other strips will have you covered forward of there.

thanks again tim.
i am with you

[Oyster]

Seems like overkill to me. You are adding bucketsfull of wetted surface and drag already, not to mention extra points to snag and even trip on if you are working in running water. None of my whitewater canoes had any such thing. Are you sure you're solving a problem that actually exists? The three center ones will keep the boat upright when you're dragging it, I don't think you need any more.

james,
it may be that it is a little overkill, but i looked at a scott hudson bay freighter last week that had all of its keels worn thru the gel coat and deep into the cloth as well as most of the back of the bottom. so i believe the problem does exist. i think the application of a whitewater canoe and a 20' x 54" freighter with a couple thousand pounds of meat and gear is not very comparable. with that said i am pondering leaving the outside strips off. i hope this does not sound like i am arguing with you because i am not.
thank you for your input.
royce

[Oyster]

As others have said ; I think the straight inner edge needs to be parallel with the other skids . I would make the skid shorter : placed to protect the turn of the bilge along about the middle third of the boat . The outside edge I would curve ; picking up the curve of the strip plank would make esthetic sense and be easy to lay out by taping some tracing paper to the boat. But the main point would be to follow and protect the turn of the bilge. I'm thinking you'll have an outboard onthe boat but won't be planeing .

The strake would be wider than the others at midpoint as I’m envisioning it ,tapering to a near point at either end and all edges faired a bit (the other strakes too) . The ends would be faired right into the hull and center on the turn of the bilge .The underside would need to be backed out (hollowed) to fit to the turn of the bilge . Shortening the strake would reduce the required width .I would try a few different lengths with some tracing paper on the boat .

thanks bill,
this boat will have a outboard and if it performs like other freighters i am familiar with it should run around 20 mph lightly loaded so i guess you could call it semi planing. i will take your advise and tinker with some patterns.
thanks for your help
royce

[Oyster]

Egad.
Just stumbled on to this thread. What I'm seeing here is a prime example of converting a slick and easily-driven hull into a slug. All that unnecessary wetted surface will drag horribly. Canoes get scratched and dinged, and this one will get a bunch of scars with or without all that extra timber hanging off the bottom. I'd opt for a smooth bottom and some planned repair and maintenance each Spring.

thank you terry
royce

[Oyster]

Even though speed's not an objective I think this last strip is not only too much resistance it's not the right approach to protecting the turn of the bilge. Rocks are often pointy jagged things and they will get up between the strips and do the damage anyway. The strips that you have applied so far are parallel enough to the keel that when dragging over some protrussion, whatever it is, it probably won't get wedged between the strips and the keel and necessitate lifting the boat to get freed up, but if you apply the bilge strips following the laminar flow, wherever that may be, you'll probably find yourself doing a lot of heavy lifting in slippery and otherwise awkward situations and positions. You could get hurt, it would ruin your day.

Still, the turn of the bilge is going to take a beating so something should be done to provide more wear resistance and strength. The easiest way to do that would be to lay on some more glass, or better yet one of the slippery tough fabrics. I don't know which would be the appropriate fabric for wear resistance but lots of people here do. Glass on the inside will add impact resistance, whatever fabric on the outside will provide wear resistance. It will be kevlar or aramid, something like that.

Now... If it were my boat I would cold mold a layer of fir in epoxy before laying on the wear resistant fabric. This will add considerable stiffness, which you will appreciate when the heavily laden hull comes down hard on a rock. I would add the wear resistant fabric on the outside of that as well. That's probably not what you want to hear, it would be nice to get it done, but it's an option worth considering.

That looks like a nice building job. Can we see more pictures?

http://s1212.photobucket.com/albums/...ghter%20canoe/
gib,
thanks again for the replies.
here is a link to the build photos, also there is a build journal in the building and repair forum called 20ft freighter canoe build in alaska
royce

[Oyster]

I would have glassed and filled the bottom and up to (say) six inches of the gunwales with graphite in epoxy before adding any of the strips, hoping that trials would show the strips weren't needed at all. Then I'd add the center, more trials, then the next two, more trials, and finally the out ones (all the while cursing that I must have chosen the wrong design to begin with.)

htom,
i guess what i am doing is what you say in reverse some what. if i do not get the performance i need this way, i can always take these strips off. as far as this being the wrong design, what is the right design?
thank you
royce

[htom]

htom,
i guess what i am doing is what you say in reverse some what. if i do not get the performance i need this way, i can always take these strips off. as far as this being the wrong design, what is the right design?
thank you
royce

Actually, the design looks fine (not that I have enough Alaskan river time to be able to make such a judgement.) It's the idea that the rub strips are going to help that seems strange. They'll make a negligible contribution to buoyancy; the canoe will float only a couple of millimeters higher in the water because of them. That is enough to get it over some rocks without touching, of course. At the same time, the strips will be reaching down into the water an extra inch, or thereabout. So they will have collisions with the rocks than the hull would by itself would have floated over with 3/4" to spare. The rocks are not going to be aligned with the rub strips, so the part of the hull between them needs to be slick anyway.

Your boat, your choices.