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Copy an existng boat only longer

oldbuffpilot

Well-Known Member
May 13, 2014
553
22
79
Central Kansas and Central Texas
Hopefully this post will start a discussion and I’ll learn some more about our little boats.Below are pictures and specs of a boat that I built by copying a 9’6’ Water Moccasin.The boat turned out much like the original, except much lighter, which was the idea. I like and use this boat a lot. Of course we are always looking for better. I’m thinking of making another about 11’ long.
Current Pirogue
Length 9’ 8”
Beam 35 ½” (5” aft of center)
Cockpit 5’ 10”
Side height 8 ½”
Flare 30 degrees
Rocker stern 1 ½”
Rocker bow 2 ¼”
Weight 19.6 lbs.





New Pirogue changes
  • about 11’
  • Rocker ½” stern,1”bow
  • Flare >30 degrees
  • On the current pirogue the tumble homes require an extreme bend to fit with the side panels, this increases the difficulty of building, I’d like to decrease that bend if possible.
I am soliciting ideas and comments on these changes, objective of the build is more capacity, more stability, and gain experience.
I am assuming that rocker and flare are determined mostly by the shape of the side panel and the shape of the forms. For the Changes I would:
  • increase the side panel length to about 11’ 7”;
  • increase the cutback of the rainbow to about 61/2”,
  • leave the end angle at about 50 degrees.
  • Change the side panel height to about 5” at the beam and 7” at the ends, to decrease the tumble home bend. Would this work??
I plan to make the changes by cutting the side panels a little oversized and ‘work down” to the desired shape of the pirogue. As Beekeeper put it “sneak up on it a half inch at a time." I am looking for suggestions from you old timers.
That’s a lot of typing just to stimulate some response on the forum, BUT I am stuck in a recliner with a knee on ice, a small casualty from getting out of the boat. :)
 

beekeeper

Well-Known Member
Mar 4, 2009
1,824
50
You have dipped up quite a plate full. Some thoughts to get started. I may have to call you.
Increasing the side panel to 11' 7" will put you close to your 11' overall length. It will also help with tumblehome bend.
Increasing the flair will increase, not lesson the rocker. I don't know if increasing the cutback of the rainbow to 61/2" will give you the exact rocker you want. Making the panel longer may change the ratio of cutback to rocker.

To help with the tumblehome bend consider leaving off the little reverse angle of the stems and run the strips all the way to the stems. I don't think it will increase the wind signature. Having the strips go all the way will narrow the panel at the stems and decrease the bend overall.
I 'm not sure lowering the sides will help with the tumblehome bend if you keep the depth of the cockpit the same. The bend in the side would be less but you would have to increase the width/height of the tumblehome to maintain the depth.
 
Last edited:

oldbuffpilot

Well-Known Member
May 13, 2014
553
22
79
Central Kansas and Central Texas
You have dipped up quite a plate full. Some thoughts to get started. I may have to call you.
Increasing the side panel to 11' 7" will put you close to your 11' overall length. It will also help with tumblehome bend.
Increasing the flair will increase, not lesson the rocker. I don't know if increasing the cutback of the rainbow to 61/2" will give you the exact rocker you want. Making the panel longer may change the ratio of cutback to rocker.

To help with the tumblehome bend consider leaving off the little reverse angle of the stems and run the strips all the way to the stems. I don't think it will increase the wind foot print. Having the strips go all the way will narrow the panel at the stems and decrease the bend overall.
I 'm not sure lowering the sides will help with the tumblehome bend if you keep the depth of the cockpit the same. The bend in the side would be less but you would have to increase the width/height of the tumblehome to maintain the depth.
Thanks, some more to think about. I got out my side luan patterns for this boat stitched the ends together to review how things work. Didn't make a tumble home pattern, now wish I had. It became obvious that increasing the height of the sides towards the end would make the tumble home strips bend more. I maybe barking up the wrong tree, maybe I could put up with hard bend in the tumble home by using 1/2
'" wide strips..I'm not sure I understand canging the reverse angle of the stems and strips to the to the stems. I'm not in a hurry to start yet, so I'll think some more and maybe draw a picture and call you. We'll be leaving for texas next week.
Thanks again for the reply.
 

jdupre'

Well-Known Member
Sep 9, 2007
2,301
40
South Louisiana
Re: cutback height. If I recall, seedtick and keith used to cut back almost 8" on 12 ft pirogues with approx. 30 degrees of flair. 6 1/2" may not be enough, but you can always cut it a bit higher if needed. The rest of the stuff I'll leave to beekeeper as he would be my go-to if I ever built a boat with tumblehomes.
 

beekeeper

Well-Known Member
Mar 4, 2009
1,824
50
Don't know if I can write this well enough to keep from confusing us anymore. "Reverse angle" of the stem was in reference to the area where you tumblehome panels meet. The strips appear to not meet in a point on the stem. They meet the corresponding strips from the other side.
If the strip closest to the cockpit ended at the stem in conventional/traditional manner the panel would be more pointed and would not be bend as much.
The panel does not have to have nearly parallel sides. The strips can come to a point.
I have not built a tumblehome panel on the table, but the 3/4" strips I bend on the boat bend easy enough.
These pictures may help. Not tying to say my way is best, just trying to clarify.
https://www.southernpaddler.com/community/threads/a-plank-pirogue.10721/page-2
 

oldbuffpilot

Well-Known Member
May 13, 2014
553
22
79
Central Kansas and Central Texas
Don't know if I can write this well enough to keep from confusing us anymore. "Reverse angle" of the stem was in reference to the area where you tumblehome panels meet. The strips appear to not meet in a point on the stem. They meet the corresponding strips from the other side.
If the strip closest to the cockpit ended at the stem in conventional/traditional manner the panel would be more pointed and would not be bend as much.
The panel does not have to have nearly parallel sides. The strips can come to a point.
I have not built a tumblehome panel on the table, but the 3/4" strips I bend on the boat bend easy enough.
These pictures may help. Not tying to say my way is best, just trying to clarify.
https://www.southernpaddler.com/community/threads/a-plank-pirogue.10721/page-2
Flash the light came on ! We are going to make our annual trip to Texas next week , I hope to start this project about 2 weeks from now . Bee, your your pictures and explanation are very helpful thanks
 

beekeeper

Well-Known Member
Mar 4, 2009
1,824
50
Re: cutback height. If I recall, seedtick and keith used to cut back almost 8" on 12 ft pirogues with approx. 30 degrees of flair. 6 1/2" may not be enough, but you can always cut it a bit higher if needed. The rest of the stuff I'll leave to beekeeper as he would be my go-to if I ever built a boat with tumblehomes.
I think Keith and seedtick' boats have about a 24" wide floor. Oldbufpilot' floor probably closer to 30". Do you think that would make a difference? Wider floor requires more cutout, or less for the same amount of rocker?
 

jdupre'

Well-Known Member
Sep 9, 2007
2,301
40
South Louisiana
Bee, I would say a wider floor would need more cutout. The sides have a longer route to take to get to the stems......rising all the way. My go-to is always a 1/4 scale model. That will tell you all you need to know.
 

jdupre'

Well-Known Member
Sep 9, 2007
2,301
40
South Louisiana
No flower boxes here , Jack. I sell the boats before they get to that point. I did sell my aluminum pirogue experiment to a guy who said his wife wanted it for a flower box. I got my money and she got her flower box. Fair enough.
 

Kayak Jack

Well-Known Member
Aug 26, 2003
13,976
168
84
Okemos / East Lansing Michigan
Just kidding you. ;-)

Years ago, my granddaughter and I were invited to visit with an old college buddy. Later there was a second visit. We were treated very well. In recognition of their generous hospitality, I gave them my Royalex canoe so their grandchildren could paddle and play on the adjacent channels and lagoon of the Huron River on the S’ly shore of Lake Erie.

Time has passed; grand kids are now adults, and the canoe has become a flower box.
 

oldsparkey

Well-Known Member
Aug 25, 2003
10,431
113
78
Central , Florida
www.southernpaddler.com
Just kidding you. ;-)

Years ago, my granddaughter and I were invited to visit with an old college buddy. Later there was a second visit. We were treated very well. In recognition of their generous hospitality, I gave them my Royalex canoe so their grandchildren could paddle and play on the adjacent channels and lagoon of the Huron River on the S’ly shore of Lake Erie.

Time has passed; grand kids are now adults, and the canoe has become a flower box.

Where did we go wrong in this section ?

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