# design question (brett)



## marshman (Feb 9, 2007)

question....right up your alley brett...

side panels...im just piddling with a scale model right now..

seems im coming up with a rocker in my bottom at the rear...cant have that for sure...  my memory is fuzzy...seems that we have discussed this before somewhere..do i need to concave my bottom edge to eliminate the rocker, or just strongback it??  i know on the fs 18 drawings the bottom edge is concave, but i thought that was because of the vee...

maybe im crazy...maybe its just the crappy material im working with??  lets discuss this...i know youve been playing with shapes and whatnot very thoroughly....


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## Brett (Jul 16, 2008)

Rocker can be caused by curvature in the chine.
I keep the aft sections of the chine straight and parallel to each other.
From about where the plane is aft, the bottom panels restrain the chine.
And the sides restrain the bottom. That eliminates the rocker.


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## Brett (Jul 16, 2008)

What looks like a curved chine in this image,
is simply a reveal caused by allowing the panel to hang
down past where the chine really is. Hold a straight edge
to your monitor and line up the rear of the chine
with the screw heads along and above the chine.
All in the same line, not curved as the image would make you think.










Here's the reveal, I figured to use this difference
between the bottom of the hull and the side panel
to create a splash rail to deflect spray by filling the gap
with microballons to the shape of that small triangular area under the plane.


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## marshman (Feb 9, 2007)

ok...i kept everything straight for my 8 footer...didnt get any rocker...but this one is gonna be 18 feet....so i figured maybe thats where it came from...
[smiley=1-mmm.gif] [smiley=1-mmm.gif] [smiley=1-mmm.gif]


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## Brett (Jul 16, 2008)

Are you using laths to frame your shape, or just flat panels?

This is what I started with, laths at the chine and shear.
All curves, only the keelson and transom are straight.










The bottom panel edges are parallel with the keelson
and when the chine strips are fastened to the panel edges
are forced to stay straight up to where i wanted the curve to begin.
About the second clamp from the transom.


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## marshman (Feb 9, 2007)

> Are you using laths to frame your shape, or just flat panels?



huh??  just flat panels...when i build with ply, ill be using a frame near the front(deck support), one in the middle(tankseat like a jonboat) and a frame in the rear(deck support)...and 2 longitudinal stringers...and then a couple ribs/side supports to support the gunnels....


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## Brett (Jul 16, 2008)

I'd like to see a pic to understand where the rocker is coming from...


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## firecat1981 (Nov 27, 2007)

I think I know what you are talking about, it's a issue with my design as well since it is mostly flat bottomed. The panels will have a natural tendency to not want to lay flat once any type of curve is made in them, usually the bow, for me it's a bulge right behind my second frame that I will need to work out. 
Putting on the side pannels makes it worse because you now have an unnatural force pushing down on the hull bottom. A strong back will help, and adding stringers if done well can correct the issue.


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## marshman (Feb 9, 2007)

ha.. too late..i tore it apart...my pieces (cardboard cut with scissors) were a little off from eachother...  like i said, crappy material...i feel sure that once i start building ill work it out...im just bored and getting antsy..

just for some reason an old convo stuck out in my mind about concave....cant reember where i got that from...hell, may not have even been on here...

as you can tell, im not building to any plans or anything...i have a picture in my brain of what i want...im just gonna start building and with a little trial and error, we will see what i come up with...the only constants i have are some dimensions that i want... long(18), skinny(36 bottom, 48 beam), low sides(14 inches), as light as i can possibly achieve( i will be dragging this boat over dams), high transom for a 25 on a jack.....NO vee...all flat...pointed bow, or jonboat style...havent decided..


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## Brett (Jul 16, 2008)

Sounds like a cypress skiff.
A kind of flat bottom dugout canoe...sort of...I think


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## marshman (Feb 9, 2007)

yeah, it would look similar to that if i do the pointed bow... a squareback pirogue on steroids...

im working on uploading an album of pics ive saved over the years that pertain to what im wanting to build...while, none of the skiffs in the album are what im building, each one has something that i like...


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## marshman (Feb 9, 2007)

except without that rocker!! rocker is the devil!!


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## Brett (Jul 16, 2008)

I think the original bow rocker was to help slide over logs
when roaming around back in the bayou. An all flat bottom
would impact the log instead of sliding up and over.
Old deadfall cypress don't float do they?


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## marshman (Feb 9, 2007)

yes, bow rocker for sure...thats what its for...to slide over logs, dams...i was talking about the rocker in the rear...the skiff you posted could never plane with an outboard...

if youve ever seen an aluminum crawfish skiff (in louisiana there are thousands of them) they have a really pronounced "upswept" bow...thats the reason, to slide over stuff...and the steering wheels are all the way forward to be able to see better while navigating flooded woods...


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## marshman (Feb 9, 2007)

and theres no such thing as "floating" cypress deadfall around here in these parts....if its floating, somebodys gonna grab it and bring it to the mill to sell, or bring it home...

but yes old cypress logs are stuck down on the bottoms of the swamps, lakes....they call these sinkers...there are some people around manchac louisiana that make a killer living going to find these sinkers and raise them up with cranes on barges, and big float bags and bring them to the mill....thats some of the most beautiful wood ive ever seen in my life...always been my dream to have a room in my house done in sinker cypress...its very very very expensive...


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## marshman (Feb 9, 2007)

take a look thru here...they are in no particular order...like i said, none of them are what im building, but each one has some feature that i like or am considering trying...

http://s294.photobucket.com/albums/mm116/mikebro72/my%20marshskiff%20ideas/?start=all


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## Frank_Sebastian (Oct 15, 2007)

In regard to the bottom edge of the FS18 being concave, what drawing are you looking at?

Knowing Jacques, that sounds unusual.

Best regards,
Frank_S


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## firecat1981 (Nov 27, 2007)

I'm thinking he meant concave in relation to the bottom, like the upward curve or rocker in the front of most boats? :-/

I dig your design meathod cause obviously it's the same one I use, and most of us do some sort of major adjusting in every build. I would encourage you to get most of the planning done before the build as it will save you a ton of time and money. My current build is moving along much faster then the last one even though I only have 1/8th the amount of time to work on it. Planning and figures on paper are easier to go back and reference when you need them too.


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## marshman (Feb 9, 2007)

> In regard to the bottom edge of the FS18 being concave, what drawing are you looking at?
> 
> Knowing Jacques, that sounds unusual.
> 
> ...



page 4...side panel..theres a 1" to 1 1/4" to 1" concave....


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## firecat1981 (Nov 27, 2007)

Ok I got what you are saying. Are you asking how do you determine the full scale curvature of the side panels so they don't distort the bottom panles and follow the flair correctly?


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## Frank_Sebastian (Oct 15, 2007)

Yes what Firecat said. The boat has taper toward the transom, but when the side meets the bottom you end up with a straight line. It is a good idea to use a pair of straight stiffeners to temporarily hold the bottom flat during assembly.

Frank_S


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## marshman (Feb 9, 2007)

> Yes what Firecat said. The boat has taper toward the transom, but when the side meets the bottom you end up with a straight line. It is a good idea to use a pair of straight stiffeners to temporarily hold the bottom flat during assembly.
> 
> Frank_S



ah...yes!!!   thats what the concave is for...to squench the buttcheeks together....that was the big turnoff for me with the fs18......i was so hott and heavy waithing on them drawings to come out...i was one of  the first to order them...then when i saw, i was somewhat disappointed....no disrespect to mr jaques...it just wasnt for me....still isnt...

i feel confident i can achieve why im shooting for...i have built several boats from aluminum with no plans...i just build to what i see in my mind...


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## JaxLaxFish (Aug 23, 2010)

NO vee...all flat...pointed bow, or jonboat style...havent decided..

I'd suggest skipping the johnboat style and going for the pointed bow if you plan on fishing in any type of wind. I have a fiberglass skiff similar to a johnboat and like many carolina skiff owners my only complaint is hull slap and difficulty in poling because it won't track well. Just my 2 cents


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## WhiteDog70810 (May 6, 2008)

18' long, 3' wide across the bottom and 4' across the gunnels with sides that run straight from the middle station to the transom?  Will you use stringers or chine logs?  Why so narrow?  I like to hear the "whys" behind designs.

Corrugated cardboard ticked me off pretty quickly.  For your modeling purposes, try masonite and zip ties.  All of your curves will be very developable, so the masonite shouldn't give you bad information.  On more complex builds, the masonite can make contortions that ply can't mimic in real life.  

You compiled a lot of flat back pirogue pictures. I really like that flat back pirogue plan that Gator Boat Co sells. If I had sense, which I don't, I would have built a 14 footer from their plans just to get my feet wet. I look forward to seeing what you cook up. 

Nate


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## nmcphail (Jul 17, 2009)

I was taking a look at your album, lots of good hulls... what can you tell us about the skiff in pics 69-80? Are there any details somewhere?


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