Stringers is the subject !!

[Krazymaan]

Some first times are better off forgotten.

[GregAdams]

Hi Greg,

A little slower than I would like to be , my health isn't the best, but purchasing materials now, and getting ready to start reassembling the boat. Hull is gutted and ground out, deck is off.

I got samples from Corelite and Coosa. Both are really nice products. I spoke to people from both companies asking questions, both have great people working with them. Very helpful and informed, and polite. Both products made HERE IN THE USA !!

I glassed together some small test panels with polyester resin and CSM ( However I am using Epoxy on my boat...didn't have any for testing ), and then compressed them to cure.

Then later after curing for 24 hours under pressure tried to separate them at the bonds with a chisel. Both were really tough to bust up, however for ME and MY test I liked the Corelite products better.

Corelite Board is about 1/2 the cost of Coosa.
Corelite is formed under compression. It's really lite and strong. Easy to cut and shape. The glass bond in my testing could not be broken at the bond. Forcing the bond to separate cause it to pull a chunk out of the piece it was bonded to.

So for my project I am using Corelite Board 1/2" thick stringers in 28lb. density.

https://www.corelitecomposites.com/corelite-board.html

You thoughts Greg?

I hope you had a great spring/summer and now your going into fall.

Are you bonding two 1/2" layers together to get your thickness? With a layer of glass between? That will work.
It might be called Core"lite" but it is a high density foam at 450 kg/cubic metre. In other words it is heavy. Very heavy. Lighter than plywood, but plywood is not a good choice for stringers because of its density and fibre orientation. Corelite is heavier than Western Red Cedar for example, which is a good choice if one is going down the wood path. The glass layer in the middle only adds more weight and provides no benefit. Any fasteners in the top edge of the stringer will need to be drilled off centre. The layer of glass, which is three times the density of the foam, will be thinner than any fasteners you try to screw into it.
It is still warm here. Plenty of skiing at the moment

[W2F a V-King]

I used to think I was a good skier 35 years ago or so, but I have seen how you guys ski in Aussie..Amazing. My little ski boat back then could pull a slalom skier at a little over 60 or so and thought that was something...But Not compared to you guys.

A single piece of 13mm thick and 16cm tall piece of the Corelite board is what I am using for my stringers, and not planning attaching anything to the stringers. Bed, filet then covered in glass. 4 stringers are just over 3 meters long, and the two center ones are 2.25 meters, with a seat box built into the front of those. 6 in total.

I will be glassing two pieces together to get the 4 stringers to the 3+ meter length, with that knife edge splice method though.

My understanding the Corelite Board is PVC based. The Corelite Pet is a high density foam. ( Comparable to Divinicell H80) Not using it for the stringers. My core will be out of the Corelite Pet in 13mm thick, contour-able. Maybe I misunderstood ? I Need to double check that.

I did try a drill and screw test on the Corelite Board, and it held better than I thought it would. Although, unless the plan changes, there won't be any screws used for permanent holding. Maybe to stitch something in place while it gets glassed. The stringers at the rear will be glassed to the transom and motor well.

Glad you still have warm weather....still wet and cold here. Well on and off anyway...really weird winter here in TN. Looking forward to spring.

[tunnels]

where's the calc to determine more glass in the floor/stiffer material and no stringer or stringer(s) and lighter layup?

By what I see no one really knows ! its all guess work !!To build a competition boat you'd have to build it in one mold and there should be a given laminate of a particular weight and all boats should be very close to being identical!
And each boat should have a identification number !!

[powerabout]

Tons of one design racing dinghys/beach cats done like that.
All get weighed after building as its critical.
2lbs over and nobody will buy it

[tunnels]

Tons of one design racing dinghys/beach cats done like that.
All get weighed after building as its critical.
2lbs over and nobody will buy it

That's the one ,heavy decks on light hulls of sail boats !class racing !! nothing like that here that's for sure !it free for all !

[tunnels]

Tons of one design racing dinghys/beach cats done like that.
All get weighed after building as its critical.
2lbs over and nobody will buy it

After reading all the thing guys are doing to make stringers what are your views on the thing of stringers ??
Personally id be right into hollow shape and get the strength and stiffness 100% from the glass structure only !! I am 100% sure it would be much lighter and far stronger and only joined at each end !! That's all !! in big boats been doing it for 40 years and never had any kind of a problem !!

[powerabout]

I see large trapazoid shapes on racing yachts so no core just laminate with large surface area where they meet the hull.
You would need to mold them over something but definately looks the way to go rather than doing what looks like engine bearers running through the hull from front to back

[tunnels]

I see large trapazoid shapes on racing yachts so no core just laminate with large surface area where they meet the hull.
You would need to mold them over something but definately looks the way to go rather than doing what looks like engine bearers running through the hull from front to back

It really is quite primitive whats being done in the name of making hulls stiff ! a hollow shape made with the right types of glass used continuously from end to end would be virtually indestructible and distribute the loads applied to the hull bottom much more evenly and over a much !wider area!!

[powerabout]

As a powerboat has a nice big transom to distribute the point loading of the engine i would think that they could well do with a stronger layup and no stringers not to mention decks fully glassed on and not the scene of the next failure due to a severe stress raiser that causes

[tunnels]

As a powerboat has a nice big transom to distribute the point loading of the engine i would think that they could well do with a stronger layup and no stringers not to mention decks fully glassed on and not the scene of the next failure due to a severe stress raiser that causes

But with a wide open cockpit these small boats must have a element of twist specially if there is no floors fitted and glassed in place ! no matter how many stringers get fitted twist is there for sure !

[W2F a V-King]

But with a wide open cockpit these small boats must have a element of twist specially if there is no floors fitted and glassed in place ! no matter how many stringers get fitted twist is there for sure !

Not so, for sure!
Yes, maybe so if the boat had no deck. Or any other kind of structure for support.

The deck on the HydroStream V-King is solidly bonded to the hull.

The sides of the hull flare out horizontal to make a flat 1-1/2" or so area from bow to stern, where the deck and hull meet together, with the deck flaring out horizontal the same amount. It makes this same 1-1/2" or so area the bonding surface between the two parts of the boat. Deck and Hull.

All around the perimeter of this, is a belt of CSM is used to bond the two together, with a bedding compound filling in any voids in the transom area, where the deck covers the top of the transom.

Then the hull has a riveted ( from up under the lip ) aluminum rub rail about every 6" or so that is crimped around and over the top of the deck after it has been bonded in place to the hull, covering the now bonded deck to hull seam.

Then inside the boat where the deck meets the hull it has a belt of heavy CSM maybe 4 to 6 inches wide again from bow to stern, making the bond between the two complete. This double glassed bond forms a sideways T or triangle of bonded glass. Kind of like an I beam that wraps around the boats complete perimeter.

The transom motor well also part of the deck is bonded solidly to the transom. Actually imo the strongest bond in the boat. It was the toughest to separate from the hull/transom area.

So no twist, no flex.
No floor necessary with 6 stringers.

Guess you would have to see one up close to understand.

The only reason I know this is because I have completely dismantled my boat down to it's last components, and can see first hand just how it was designed. Another member here actually brought the triangle beam to my attention. You have to cut through it to get the deck to separate from the hull.

A real PITB.

[tunnels]

to demonstrate twist take a rectangular plastic box any deepth but first without a lid ! hold one end in each hand and it twists !!
Now fit the clip on lid and no twist !!
Ok now cut a square hole in the lid leaving a small amount of lid all round still clipped to the base !! what happens ??
It Twists !!
A little harder but it will twist if the hole in the lid is a bit smaller then you get a rippling effect in parts of the lid that's left!!
Same principle applies to boat decks those ripples are not as visable because of the coamings But the corners are stressed places that crack the gel coat normally because of the Twisting action BUT if a good floor and grid system is fitted then you wont get any twist what so ever!! you should try working with tunnels and cats the twist can be a major problem and the securing of internal floors !!

I can see im going to have to take some close up pictures of this simple demonstration!!

[W2F a V-King]

No worries Tunnels...

No pictures needed.

[tunnels]

No worries Tunnels...

No pictures needed.

Some guys don't believe it ! even when you show them they shake there heads and mutter a lot !!