Glen-L.com

Hi everyone:
I am a totally new boat builder , have done many fiberglass mayor hull repair. Decided to designe myself a 30' sport fishing planing hull , to build it frame and multi-diagonal planking method over frame . I designed the hull usin 3d Delfship , a lot of consulting and reading . I intend to use this boat in the South East coast of Florida . I haven't found a good refference about how thick the hull should be , I was thinking to use double planking with 3/8 marine ply , plus the glassing will be about an inche thick ; or could I go on 1/4 ply , if so shoul I go triple ?
I need guidense on it .

Thanks in advance.

Kiton

Hi Kiton,

The wisdom as suggested by all the material that I've read says that the plywood will be stronger (by weight) than the fiberglass. That said, you would probably be best served by going to three layers... probably of 1/4 inch ply strips, and then put a layer of 6# glass over it to seal and make it scratch resistant.

I'd recommend the books Boatbuilding with Plywood and How to Fiberglass a Boat, both available on the Glen-L site.

Of course, its I haven't actually built a boat yet... (since I was a kid, anyway), so perhaps some of the others here could offer the voice of experience.

_________________
Mike
http://mikesboats.blogspot.com/
Raleigh, NC

single ply hulls are very tough.

cold molded (like mine) is about 3/4 thick with 3 layers of 4MM ply covered with 1/8 veneer and glass (if you want). That is tough also

If you don't want to get into cold molding take a look at a build like the Double Eagle to give you and idea of what works very well

_________________
Dave

My Riviera build - the Midnight Cry Project

Video of Midnight in Action
Blog

Few things in the world measure up to the thrill and satisfaction of boating in a boat that you built.

seems if you are asking about the structure/method maybe it is better to select a proven Glen-L design to build

_________________
(insert witty phrase here)
Billy's Belle Isle website

My Tahoe 19 has 21" frame spacing. The bottom is 1/2" & sides are 3/8"

The 24' boat I'm looking at was designed for rough conditions. It has a 16" frame spacing. The bottom is 5/8" and the sides are 3/8".

I really doesn't matter what combinations of layer thickness that you use. More thinner layers will be easier to bend.

Bill

_________________
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

on the tornado and rampage...

30" frame spacings with 1/2" bottom and 3/8" sides.

Thunderbolt...(I dont have the plans but from what I can gather)

aprox 24" frame spacing with 3/8" bottom and 1/4" sides

Quote from Glen-L's boat building 101



These boats are sheet ply builds. Sheet ply builds are indeed very strong.

my jubilee calls for 36 inch frame spacing with plywood skin If I remeber right the skin is 1/2 inch

_________________
Don't be afraid to attempt anything. You might surprise your self in the attempt.
http://www.facebook.com/Home.Made.Boat.Building
Modified Jubilee-"Wild Flower" 40' house boat
14' Mr John-Wild Flower 2
32' Supper Huck- Wild flower 3

Rod H

Thanks so much everyone:
Most of you have experience , and I am impressed all of you had come to help. I am going to go deeply on your sugestions , as the carpenter said " measure twice to cut one's ". And yes, " Unico " is 30" space framing .


Thanks to all of You.

Kiton

Kiton,

I'm sure Oyster will chime in here with some answers,he's out of town till Sunday though I believe.

He's got lots of experience on these types of boats and should give you some good dependable insight

_________________
Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

A good reference book would be Dave Gerr's The Elements of Boat Strength For Builders, Designers, and Owners.

Here's an ebook preview .

Good luck with your project !
____________________
Paul Kane Chelsea, PQ

Building the Glen-L Hot Rod : http://www.boats.chelseacoachworks.com

Here is the 35' Glen-L Sea Angler
sports 3/4" topsides and 1" bottom
looks to be about double the planking thickness of the runabout boat designs posted above. Might be worth having a set of plans like these for further study before moving forward.


plans and Bill of Materials etc are here:
http://www.glen-l.com/designs/cruiser/seaangler.html

-Billy

_________________
(insert witty phrase here)
Billy's Belle Isle website

Billy C is right. You're looking at a harsh environmental boat. I'd rather see the boat a little heavy than broken.

Bill

_________________
Mini -Tug, KH Tahoe 19 & Bartender 24 - There can be no miracle recoveries without first screwing up.
Tahoe 19 Build

According to The Elements of Boat Strength For Builders, Designers, and Owners, a safe thickness for " Unico " hull's skin will be 0.870 in equal to 7/8 " running in rough sea conditions or up to 45 knots , which is far from my intended 30 max, 25 cruising speed .
Does this mean the entire shell should be 7/8 ? or, That's for the bottom planking and the sides planking could be thinner ? Like 11/16 for example ?

Thanks for inputs


" Learning is a never ending story "
A. Yakovlev

Thickness is only one part of the equation. You are indeed going way out on a limb and taking a big gamble and will be spending mega bucks and work when going on your own for a 30 foot hull.

The bottom design is as important as any other part of the proposed hull, not as much as the deadrise along the way but proportions along the way in the beam too.

There has been some good suggestions here in regards to books but one needs to be able to translate this into a boat. I think I am getting the feeling that you are attempting to come up with a carolina style runabout with the tumblehone and flared foward hull. There are already several one off guys with some proven ones running around and the plans can be purchased if you want to build your own boat.

In regards to thicknesses in those boats, you first need to determine if the plywood is just a mould and the glass is the structual part of the boat. Some of those boats are built using strip plank and skin glass which gives you the desired look with much less work and costs and some are laminated plywood layers and then biaxall cloth to achieve the look and strength which also has other advantages even though the costs jump up.


Many wooden runabouts here use the wood as the strength and the glass is for stabilizing the wood and by some measure the boat ends up weighing less.

The determining factor for me is to decide if you want a trailer boat and then design and or build around that using the motor also as part of your criteria. An inboard boat versus an outboard also changes many things. Many larger outboard runabouts in the 30 foot range and even beginning around 26 foot and running on open water includes brackets with a closed transom which also adds another deminision in your design and build.

The intregal components are just as important as the thickenesses of the bottom and sides and in many cases only keep the water from coming in the boat by comparision if the boat is a twisted and tortured plywood hull with a proper skeleton. Have I confused you yet?

Hi Oyster:
This design was originally 34' long and 13' beam semi displacement hull , I consulted with the original designer and He recommended to reduce the scale using the 3D software on all the elements at 75 %. Then we worked together to change it from semi displacement to a more planing hull using single I/O up to 320 hp / Bravo Two 2.0:1.
The choice of using single I/O comes from have better maneuverability at docking speed , and better for trailing too .
Using the software I have limitations , like structures / frame design , there are softwares that give the option , but from the point it is user driven allow you to make mistakes.
I surfed for a while looking for anything like this before attempt to design, and never found any , the Sea Angler feels like it , but it is to wide to trailer it . Florida trailer max beam 10 feet.
In the other hand , don't get me wrong , I prefer not too heavy because of power need to plane , but no too light either. My actual boat , factory SEA-FOX fiberglass construction is so light that a 2' wave make me jump in to the air.
If you could guide me to find this Carolina style runabout on this approximated sizes , Then as you said I could safe myself from many troubles.

Thanks so much.

Kiton