extending 8' pram plans to 10'

[starrfish1968]

any advice on extending plans for a stitch & Glue 8' pram to a 10' pram
Is this extending this boat too much?

I have the plans, and the build looks simple enough, but I would really like to add the extra few feet to length.

current dimensions are:

8' length
stern is 33" wide at chine 41" wide at sheer
bow is 24" wide at chine 23 3/4" wide at sheer
boat sides are 15"

Should I scale all measurements Up 125% (8' to 10' = 125% when increasing length

I guess scarfing will be needed for the sides and bottom.

Build calls for all parts in 1/4" ply, but since I will need to do a scarfing joint on the bottom would you upgrade to 1/2" for the bottom? and keep 1/4" everywhere else or just continue on with 1/4" all around to help keep weight down.

Thanks in advance for the advice.

[Noah's]

You can lengthen or shorten most boat designs by about 10% without causing problems but this is 25% so you are stretchhhhing things a bit. The other problem with expanding stitch and glue designs is that the panel curves are usually drawn by boat design software to produce a specific shape when stitched together. If you try to lengthen the panels you change curve and therefore the boat shape. I once stretched an 11’ skiff to 11’ 10”, it took a lot of fiddling and the bow came out a little higher, but overall it worked pretty well.

[starrfish1968]

Thanks!

I kind of thought stretching 25% might be a bit much.

But, if I scaled "all" the measurements up, wouldn't the panels stay in the same curve, since everything is scaled up at same %? Or is this one of those weird "higher math" things where 25% isn't really 25%

I'm still considering giving it a go since it is a pram style. if it where any other style I would be a bit more skeptical of extending design that much.

Where do you recommend finding plans. I might not build pram if I could find a simple 10'-11' stitch & glue skiff or a 10' pram already to scale.

thanks again for the advice.

[starrfish1968]

emailed the prams designer. he feels extending this design to 10' shouldn't be a problem, but suggested beefing the transom to 1/2 ply instead of spec'd 1/4. and using a scarf joint to lengthen ply. I do plan on checking a local "real" lumber yard for 10' ply and save myself the extra step of scarfing the joints.

will post progress when build begins. at the moment scouting materials.

[Noah's]

Thanks!

I kind of thought stretching 25% might be a bit much.

But, if I scaled "all" the measurements up, wouldn't the panels stay in the same curve, since everything is scaled up at same %? Or is this one of those weird "higher math" things where 25% isn't really 25%

I'm still considering giving it a go since it is a pram style. if it where any other style I would be a bit more skeptical of extending design that much.

Where do you recommend finding plans. I might not build pram if I could find a simple 10'-11' stitch & glue skiff or a 10' pram already to scale.

thanks again for the advice.

Glen L has a couple of nice designs in stitch and glue in the 10 to 11' range. The model Bullseye comes to mind.

Jason @ Noah's

[starrfish1968]

who is glen l and how can i get his bullseye plans? skiff? pram? looking into local 10' plywood. save myself the scarf joint.
email me at
onevizcaya@yahoo.com

with details i appreciate it. almost bought a 10' aluminum jon boat but deal fell through. I'm being called to build my own plywood boat... I can hear it! felt the urge for several years! got another line on another jon boat... would really like to say I built this boat myself... caught this fish on a rod I built myself.... on a lure/fly I tied myself...
2 out of three ain't bad but 3/3 is a home run!

thnks again.

will search site for glen an his bullseye but feel free to email me direct...

[starrfish1968]

did a search of your site... no glen l or bullseye... any help would be great!

[lewisboats]

http://www.glen-l.com/