stringers

[AcctTwrs]

Those of you building boats over 24 ft+. I'm useing 3X3/8 flat bar about one foot apart on a 3/16 sheet bottom..
Should I make stringers perfectly verticle or 90% to the bottom sheet.. and why... boat will be about 28ft and 10ft6in.
wide when finished. Thank you Tom

[AcctTwrs]

Really.... I was hoping for a little response but I guess not...

[Chaps]

Heck, I don't know, I've seen it done both ways. Maybe one of the builders will see this and respond.

[S L Dave]

Hey Tom,
I am not qualified to offer any thoughts on this, but there are some insanely knowledgeable people on here that probably just missed your post.

Dave

[CTMD]

Bearing in mind that the answers are worth what you have paid for them....

I can't comment on whether your stringer size is right as I'd need to know you frame spacing, bracketing details and weld schedule to do so, deadrise, local deadrise, chine width, LCG, material grade etc etc..

Stringers at about 12" centres sound a little far apart, but may be ok depending on frame spacing. Go with smaller stringers closer together and you'll get a better end product.

if possible make the stringers 90 degrees to the plate. If using a flat bar stringer a vertical stringer will need to be approx. 10% deeper where the local deadrise is 20 degrees and even more where you have steeper deadrise. This rough calculation only takes into account basic section modulus, however, you also need to consider toppling as with vertical stiffeners the force applied to the stringer doesn't pass through its centroid so the stiffener will also have to be thicker or have a flange to avoid buckling.

Download a demo copy of hullscant and have a play around, this may help you get a better feel for the trade offs you need to make when specifying your boat's scantlings.

[AcctTwrs]

WOW... Now that's some response... guys I thank you much for the response...
Chris... especially your input... I have more 3/8x3 flat bar i can put in more stringers closer together. On 3/16th plate I'm thinking frames 18 inches apart of 1/4in. floor to hull if you will as if it where a bulkhead...
With stringers @ 90degrees to the hull presents a puzzle like assembly problem... have you ever put one like that together,,..?? This is why i suggested vertical stringers to make installation easier... Any thoughts...
Never heard the word centroid... in boat building principals.. It's going to be a beech to get all the bulging out of the bottom of the hull as it is....And keeping the boat as straight as possible...
Again thanks for your time...
are you near Craigyburn???

[welder]

Have you already bought the plate for the hull ?
Most hulls that size are using 1/4" [.250] and of course , marine grade alloy.

WE WANT PICTURES of the build process.

[CTMD]

This 23' boat is designed to the ISO standard for boats up to 12m (40') it has 5mm (3/16) 5083 bottoms, frames on 600mm (2') centers and 60x5mm (2.4" x 3/16") stringers on 175mm (7") centers.

"Centroid" is the centre of area of the stringer and from a simplified point of view the point it wants to rotate around if forces are applied to it. When you have vertical stringers the force applied by pressure on the bottom doesn't pass through this point so your stringeris always trying to twist. As a result you put a much higher load on all the welds, particularly the ones on the inside edge of the stringers.

[pjay9]

Check that trailer! Capt PJ OH! Yeah...nice boat!

[AcctTwrs]

Chris... I clearly understand the principal pertaining to the term centroid now. I have seen examples of too much pounding
on a hull bottom with the stringers in the vertical position...it made much more sense when you explained it... as a light bulb
went off in my head.. Seems like the stringers will go in at a 90 degree to the hull then... nightmarish to think about it though.. Given the hull plate is 3/16th thick do you have a recommendation for station and stringer spacing. The hull has
10ft. 5in. beam so 5ft from CL to chine..
Welder... yes I have already bought the hull plate. 3/16th I need to find a host site for pictures .

Thanks guys...

[CTMD]

what sort of deadrise are you looking at? And do you have a target displacement?

[AcctTwrs]

Chris.. thanks for your inn site. The stringer centers a 7"OC. and frames @ 24"OC. is likely the way to go..
At this point I'm re cutting the shear as i changed my mind. As what the hell was I thinking . Looking for more of the backwater look. You can get a look at the work I do at my website. http://www.AccurateTowers@aol.com.
I have to find the tutorial picture posting... just need a host site.

[AcctTwrs]

Welder... You speak of 1/4in plate like it was the only thing to use... Are there any builders using 3/16" thickness hull
material.. ?? I'm probably going to make my bulkheads as frames from bottom to deck underside.. giving the boat more
longitudinal strength overall... I finished forming the nose section and the boat will turn out 27' LOA.
I'd hate to hear a big crunch coming off a wave in 5ft. seas...I think it best to set up a dual transom mounting with a single
300 Yamaha 4 stroke. Giving the buyer a choice of 1 or 2 OBs. As I build my own T-Tops. No console, A T-Top/ control box
my vision of the future. I've built a few of them already. If you sent me your phone # I'd send you a picture...

[welder]

Here is a link on how to use Photo Bucket.
viewtopic.php?p=255#p255

and if you go to your USER CONTROL PANEL [ top left under Martys boat] you can start a Album here .

Most builders use 1/4" plate for the hull and 3/16's above that, the 1/4" 5086 is almost bullet proof.

What grade of alloy plate and filler rod are you using ?

Hope you get the picture thing going as we would really like to follow this build.

[CTMD]

[quote="AcctTwrs"]Welder... You speak of 1/4in plate like it was the only thing to use... Are there any builders using 3/16" thickness hull material.. ?? quote]

Lots of builder's use 5mm (3/16) plate for boats this size in Australia and Kiwiland. Heck we used to use 8mm on the bottoms of 120' 40 knot ferries when I was in that industry. Unless Austal have made major changes to their scantlings the bottoms of your navy's new 400' tris will probably have 1/2" plate. Like styling a lot of it comes down to what the client demands. Going to 1/4" plates on a 27' boat will only add about 60 lbs to the weight of the boat and $200 to the material cost but it allows them to use fewer stringers saving labour and produce a fairer hull due to a reduction in heat distortion. Ironically a boat designed to be built out of 1/4" plate and engineered to the limits of the materials will be no stronger than a 3/16" boat with the exception of it's resistance the plate piercing if you beach it on a rock.

[AcctTwrs]

Welder... Chris... I'm dying to post my pictures but i can't find a way to transfer them from my cell phone to photobucket
or cellphone to Alloy boats. Did the photobucket account as you suggested... I have to get my pictures in my puter first... there in lies the problem...

[gandrfab]

Might try E-mailing from cell to computer?

[AcctTwrs]

G and Rflab Welder... Got my pictures down loaded to my puter.. and a new photobucket act. I'm looking at this evening
before I can post any pictures here... simply put your url between the img brackets and post ...????? As PB will do the rest..?
Then you guys can howl away...
Catch ya latr..

[gandrfab]

G and Rflab Welder... Got my pictures down loaded to my puter.. and a new photobucket act. I'm looking at this evening
before I can post any pictures here... simply put your url between the img brackets and post ...????? As PB will do the rest..?
Then you guys can howl away...
Catch ya latr..

We are not close enough together to really be completion to each other, good luck and I look forward to seeing the pix.

[AcctTwrs]

[img]

These are current pictures... you can see why im concerned about stringers with such a large area to cover..
Id really like this to be strong..

[AcctTwrs]

GandRfab... You posted it... so I got to ask... What is " completion " sorry had to ask... just screwin wit ya

So there are some pictures for you to absorb... damn thing wouldn't take them at first. they had to be a certain size
got a lesson on resizing on photobucko... what a pain...got some mo pictures too...

For those of you wondering why the sides so low..???? It's going to be the biggest flats boat (backwater) you ever saw..

[AcctTwrs]

Can someone tell me I want to change my password... went to user control panel as prompted... Nadda nothing
is this a joke or what...

[welder]

Who told you to change your password, We do have a password quality checker for your safety , it tells you how good/safe it is. It may be promting you to make a better password. On the pictures, if you set your phone or camera to take a picture 800 by600 in size you dont have to reside them later and the picture will look pretty big on the forum.

[welder]

Dang phone keeps spelling for me. LOL

[pjay9]

GandRfab... You posted it... so I got to ask... What is " completion " sorry had to ask... just screwin wit ya

So there are some pictures for you to absorb... damn thing wouldn't take them at first. they had to be a certain size
got a lesson on resizing on photobucko... what a pain...got some mo pictures too...

For those of you wondering why the sides so low..???? It's going to be the biggest flats boat (backwater) you ever saw..

Try setting the camera image size to be smaller if planning for the net and posting...makes it so much simpler no messing with PB or a picture editor program! Capt PJ

OPPS! just saw that Les said the same thing...I should have read it ot the end before responding! OH WELL!!! The rsain is coming this afternoon, it will wash it all away again! (this is a PACNW comment!)