Lofting woes
Lofting woes
Canoecraft's plans for the Ranger have the sheer listed as 0-11-5+ and profile as 2-00-6 which is a difference of 0-12-2+ (if my math is not mistaken) but the depth is listed as 13.5 in. This is over an inch variance. To further complicate, my drawn out plans have the difference at 13in. What am I not getting? First time builder.
Re: Lofting woes
Hi Kanu
Your math is a bit off, but your plan drawings sound like they are pretty close.
I like to convert the mold offsets to straight inches if I have to do math on them.
2-00-6 = 24 3/4"
0-11-5+ = 11 11/16"
the difference is 13 1/16"
Keep in mind this defines the depth to the INSIDE of the canoe. If you add 1/4" for the planking the depth becomes 13 5/16". With the tumblehome on this canoe, the outwales will tip up a bit at the outside edge. I would guess this might add another 3/16" or so to the depth.
I should also warn you that most of the stem measurements for the Ranger in Canoecraft are wrong. You can find the corrections here
https://www.bearmountainboats.ca/pages/faq
Keep us posted on your progress.
Stephen
Your math is a bit off, but your plan drawings sound like they are pretty close.
I like to convert the mold offsets to straight inches if I have to do math on them.
2-00-6 = 24 3/4"
0-11-5+ = 11 11/16"
the difference is 13 1/16"
Keep in mind this defines the depth to the INSIDE of the canoe. If you add 1/4" for the planking the depth becomes 13 5/16". With the tumblehome on this canoe, the outwales will tip up a bit at the outside edge. I would guess this might add another 3/16" or so to the depth.
I should also warn you that most of the stem measurements for the Ranger in Canoecraft are wrong. You can find the corrections here
https://www.bearmountainboats.ca/pages/faq
Keep us posted on your progress.
Stephen
Re: Lofting woes
Hello Stephen. Thanks so much for writing, I have asked this question in other places and got no reply and really Have no idea how else to find this all out. Yes, after I posted my question I saw that my math was off, but my actual measurements show the depth on the drawing to be 12 11/16 in and not 13.5. and that is from the top of the profile measurement down to the sheer line. And per many diagrams in books and online I have seen that the depth measurement is those two points measured inside the boat, rather than to the outside of the applied wood. As comparison, I also have Gil Gilpatrick's book as well as the plans that come with it and I measured those and they are spot on to what is given as the depth in the book. So either I am consistently off, I have drawn these out three time now, or there is something i just don't comprehend. Yes, i could just buy the plans but I am attempting to conserve funds.
Thank you, yes I am aware of the stem errors in the book.
Man, this is throwing me. I so want to get started on this boat but can't continue till I figure this out.
Radley
Thank you, yes I am aware of the stem errors in the book.
Man, this is throwing me. I so want to get started on this boat but can't continue till I figure this out.
Radley
Re: Lofting woes
Hi Radley
You are referring to other sources here for the definition of depth, but for the Ranger I would want to use the definition that Ted Moores uses. From Canoecraft page 31:
Stephen
You are referring to other sources here for the definition of depth, but for the Ranger I would want to use the definition that Ted Moores uses. From Canoecraft page 31:
As for your drawings, something does sound off, but without seeing them it's hard to figure out what from here. Are all your stations on the same sheet? Are you measuring Station 0?The depth of a canoe is measured amidships from the gunwales to the bottom of the hull.
Stephen
Re: Lofting woes
It took a little while to find it, but here's a thread on lofting the stations for a Freedom 17, created by forum member Cruiser : viewtopic.php?f=9&t=4658
He cut station molds from the lofted plans, and then compared them to a set of plans he bought from Bear Mountain and found they were a good match.
Maybe this can help you out.
Stephen
p.s. here is the Jason Eke video he refers to: https://www.youtube.com/watch?v=GKowlxVqJY0
He cut station molds from the lofted plans, and then compared them to a set of plans he bought from Bear Mountain and found they were a good match.
Maybe this can help you out.
Stephen
p.s. here is the Jason Eke video he refers to: https://www.youtube.com/watch?v=GKowlxVqJY0
Re: Lofting woes
Following ... will jump in if I can help
Brian
Brian
Re: Lofting woes
Hi again Stephen, and thanks. The thing you referenced on the Freedom 17 is something I found and read a while ago and then the author, Brian, suggested it to me on a FB group. And I have watched that Jason Eke video as well as others. I am educating myself as best I can. I am just still baffle by the depth thing. The other boats in CC seem to follow this weird pattern of not having the center station be the same as the stated depth for the boat (by that I mean what the offsets show for difference between profile and sheer vs what the boat specs are listed as). The Freedom for instance sys the sheer is 7 inches and the profile is 1 ft 8 in. That is a 13 in difference but the specs sheet says it has a depth of 13.5. I look at the center stations because by all definitions that is where depth is measured. This may be a case of me being way too obsessed with details and I would just figure it out once I started (which is almost always the case with me), I am just trying to be as smart and informed as i can since mistakes here can cost either money or maybe my sanity and I have so little left of both ;)
Yes, I am talking about station 0 here. And yes, I agree that the depth measurement is stated as for the inside of the canoe, but that is how I am measuring it for both what is given in the book as well as what I am showing on my graphs.
Eventually I will get this all, I promise.
Yes, I am talking about station 0 here. And yes, I agree that the depth measurement is stated as for the inside of the canoe, but that is how I am measuring it for both what is given in the book as well as what I am showing on my graphs.
Eventually I will get this all, I promise.
Re: Lofting woes
Hi Radley
I applaud your diligence in understanding the lofting process. It's the foundation of everything that comes after and you need to get it right. My concern is that you have gathered information from diverse sources and expect it all to agree. My guess is that there are at least two schools of thought on measuring the depth of the canoe. You need to limit yourself to the method used in Canoecraft for the duration of this project.
In order to make sure I was not blowing smoke earlier, I made a rough plot of Station 0 in Sketchup. If you open the attachment in another tab it's easier to refer back and forth. I omitted most of the grid lines so the station is easier to see. I added 1/4" planking at the profile and the sheer line, and a 3/4" x 7/8" outwale at right angles to the hull, as specified in Canoecraft. As you can see the vertical distance from the profile to the sheer line is 1' - 1 1/16", which is what I had quickly calculated earlier in the thread. My understanding is you believe this distance should equal the depth in the canoe specifications. I assert that is wrong, at least as far as Bear Mountain canoes are concerned.
On the other hand, if you look at the distance from the planking at the profile to the bottom corner of the outwale, as I described upthread, you will see it is 1' -1 1/2", which is the EXACT depth in the canoe specifications. I don't think that's a coincidence.
As a final thought, the specifications published by Bear Mountain in different locations for the same canoe sometimes have minor differences, as you can see if you compare Canoecraft with the Bear Mountain Boats Study Plans Catalogue. https://cdn.shopify.com/s/files/1/0525/ ... d.pdf?3170 I don't find this surprising for a company in business over 40 years. I doubt I could ever keep all this information 100% accurately up to date all the time.
That said, I think the offsets in the Tables of Heights and Half-Breadths, when taken with the corrections in the Bear Mountain FAQ are probably as close to perfect as you're going to get, considering how many builders have tested them over the years.
Keep on pluggin', and when you get building we do love pictures :)
Stephen
I applaud your diligence in understanding the lofting process. It's the foundation of everything that comes after and you need to get it right. My concern is that you have gathered information from diverse sources and expect it all to agree. My guess is that there are at least two schools of thought on measuring the depth of the canoe. You need to limit yourself to the method used in Canoecraft for the duration of this project.
In order to make sure I was not blowing smoke earlier, I made a rough plot of Station 0 in Sketchup. If you open the attachment in another tab it's easier to refer back and forth. I omitted most of the grid lines so the station is easier to see. I added 1/4" planking at the profile and the sheer line, and a 3/4" x 7/8" outwale at right angles to the hull, as specified in Canoecraft. As you can see the vertical distance from the profile to the sheer line is 1' - 1 1/16", which is what I had quickly calculated earlier in the thread. My understanding is you believe this distance should equal the depth in the canoe specifications. I assert that is wrong, at least as far as Bear Mountain canoes are concerned.
On the other hand, if you look at the distance from the planking at the profile to the bottom corner of the outwale, as I described upthread, you will see it is 1' -1 1/2", which is the EXACT depth in the canoe specifications. I don't think that's a coincidence.
As a final thought, the specifications published by Bear Mountain in different locations for the same canoe sometimes have minor differences, as you can see if you compare Canoecraft with the Bear Mountain Boats Study Plans Catalogue. https://cdn.shopify.com/s/files/1/0525/ ... d.pdf?3170 I don't find this surprising for a company in business over 40 years. I doubt I could ever keep all this information 100% accurately up to date all the time.
That said, I think the offsets in the Tables of Heights and Half-Breadths, when taken with the corrections in the Bear Mountain FAQ are probably as close to perfect as you're going to get, considering how many builders have tested them over the years.
Keep on pluggin', and when you get building we do love pictures :)
Stephen
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Re: Lofting woes
Wow, thanks so much for putting so much effort and thought into helping me. I cannot claim that I understand 100% of all you describe but it's over 50% so that's something. I agree that I am probably getting ifor from too many sources, I tend to do that when I find the available info does not answer my questions to the degree that I find satisfactory for my comprehension. I am buying some poster board today, as I have been just using large pieces of paper and those move and stretch too much which may account for my imperfect numbers. Also borrowing a straightedge from a friend which will likely be a bunch better than the thing I've been using. I am super low tech, and even my low tech is antique. If I don't end up making a duct tape canoe, I hope you will be impressed.
Here is a simple question for today- I cut out rectangles of wood a few weeks ago while visiting a friend who was building a garage and had some leftovers (free!). Was not yet sure what canoe I was building so asked around on forums and cut them to everybody's best guess. I think the width will be ok for the stations but not so sure about the height. The one I have for the center station (0), is 37 inches wide by 24 3/4 tall. Will that be tall enough for a 13? inch deep station with the mushroom stem beneath? Thanks, as always.
Radley
Here is a simple question for today- I cut out rectangles of wood a few weeks ago while visiting a friend who was building a garage and had some leftovers (free!). Was not yet sure what canoe I was building so asked around on forums and cut them to everybody's best guess. I think the width will be ok for the stations but not so sure about the height. The one I have for the center station (0), is 37 inches wide by 24 3/4 tall. Will that be tall enough for a 13? inch deep station with the mushroom stem beneath? Thanks, as always.
Radley
Re: Lofting woes
Radley, you may be getting caught up on one detail and it may become clearer as you start plotting the forms. The thing to realize is that lofting from the tables does work and it will match the purchased plans perfectly.
You can get poster board, but ruled 24 x 36 " paper is fairly inexpensive for 30-50 sheet pad, that will save you a lot of work. As far as it stretching, that can largely be eliminated by taping the edges once you start plotting.
As far as whether 24.75 will be tall enough, you will have to look at the sheer values at the ends to see what is required, those are the lowest points for the strongback ... the sheer line bends towards the strongback, that is your limiter as far as how high or low you can make the stations. When I do stations I like to add 2" to give me more clearance .... I will check my copy of canoecraft tomorrow.
Brian
You can get poster board, but ruled 24 x 36 " paper is fairly inexpensive for 30-50 sheet pad, that will save you a lot of work. As far as it stretching, that can largely be eliminated by taping the edges once you start plotting.
As far as whether 24.75 will be tall enough, you will have to look at the sheer values at the ends to see what is required, those are the lowest points for the strongback ... the sheer line bends towards the strongback, that is your limiter as far as how high or low you can make the stations. When I do stations I like to add 2" to give me more clearance .... I will check my copy of canoecraft tomorrow.
Brian
Re: Lofting woes
Here's Station 0 and the Stem Mold with a 2" grid. The station is obviously a half pattern but the stem is the full pattern.
To find the height of the tallest station for any canoe (at least in Canoecraft), go across the line of profile values and find the biggest number. For the Ranger that is Station 0 and the height is ... 24 3/4", so it's gonna be tight, especially if the sides of your pieces are at all irregular. The width looks like it will be all right.
edit: I see Brian posted while I was composing this. If you look at the stem mold you will see the sheer point he's talking about at the bottom of the curve. It is 1 1/2" above the baseline/ strongback as designed. If you do add an extra 2" to the height, you'd need to get bigger pieces. It might be worth it to keep your knuckles a little further from the strongback when shaping the stems, but it's up to you.
edit: I see Brian posted while I was composing this. If you look at the stem mold you will see the sheer point he's talking about at the bottom of the curve. It is 1 1/2" above the baseline/ strongback as designed. If you do add an extra 2" to the height, you'd need to get bigger pieces. It might be worth it to keep your knuckles a little further from the strongback when shaping the stems, but it's up to you.
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Re: Lofting woes
It's also good to remember that there is no rule that says the stations have to be 1 piece (although it is easier), if you have the "leftovers" from cutting those squares, you could always extend the the bottoms with a spacer and "lap" piece to give you more height.
Brian
Brian
Re: Lofting woes
Seriously, you guys are the best. I feel much more prepared and confident with your information and guidance. I am currently drawing out the grids and plotting the points on poster board. I could not find any poster board with grids printed on, but it's ok I am now much more deeply immersed into the process.
I don't know if this is a hard question to answer but I am wondering about the curve connecting the plot points. It seems that given the varying degree of bendiness in different materials that the curve might be open to interpretive differences. Is there a foolproof method? Can I use a strip if poster board? And if I bend the thing along the nails in the points, if the bender-thing is on the outside of the curve, I'd draw the curve on the inside of the bend, correct?
Thanks again.
I don't know if this is a hard question to answer but I am wondering about the curve connecting the plot points. It seems that given the varying degree of bendiness in different materials that the curve might be open to interpretive differences. Is there a foolproof method? Can I use a strip if poster board? And if I bend the thing along the nails in the points, if the bender-thing is on the outside of the curve, I'd draw the curve on the inside of the bend, correct?
Thanks again.
Re: Lofting woes
I'm gonna vote no on a poster board batten.
This video has a couple of ideas at the 4:10 mark. He's transferring plans rather than drawing them, but the battens should work either way. BTW that blending curve he's talking about is $50 Canadian! Rich actors, smh. https://www.youtube.com/watch?v=Q8cEZmO ... Bb&index=3
Will you be using the carbon paper method to transfer your patterns, and if so will the pencil pressure carry through the poster board and make a good impression? I ask because I honestly don't know. I'd hate to finally get a set of perfect plans and find out I couldn't transfer them. Maybe a quick experiment would be in order :)
This video has a couple of ideas at the 4:10 mark. He's transferring plans rather than drawing them, but the battens should work either way. BTW that blending curve he's talking about is $50 Canadian! Rich actors, smh. https://www.youtube.com/watch?v=Q8cEZmO ... Bb&index=3
Will you be using the carbon paper method to transfer your patterns, and if so will the pencil pressure carry through the poster board and make a good impression? I ask because I honestly don't know. I'd hate to finally get a set of perfect plans and find out I couldn't transfer them. Maybe a quick experiment would be in order :)
Re: Lofting woes
I traced plans onto poster board, using carbon paper with no problems. That saved the plans, and the poster board was easy to trace around onto plywood forms.
I agree using a poster board Batten would be too flexible, to mark. An 1/8" thick strip of Ash, would be fine.
Usually I just use my eye and a set of French curves, but nails and a batten are traditional.
Enjoy the process !
Jim
I agree using a poster board Batten would be too flexible, to mark. An 1/8" thick strip of Ash, would be fine.
Usually I just use my eye and a set of French curves, but nails and a batten are traditional.
Enjoy the process !
Jim
Keep your paddle wet and your seat dry!