Stringers???, composite, fir, spruce, other ??

BillD

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Hello ALL,

Dreary day outside today. Not much to do but boat dream. ;)
In my mind's eye I'm reviewing the "new virtual DE build" list of options.
Todays topic is "in" the solid glass hull layup,,,,,,,,,,

What are your opinions on "stringer material".
I think most builders use fiberglass encapsulated wood stringers in hull layup but I was reviewing John's (Blitzen) 36 Flowers build on noreast.com from a few years back and he mentioned the use of "composite stringers".

I've also read that some builders off "double up" stringers in the engine area of the hull.

And some hulls have 2 full length stringers only flanking the keel and other hulls have 2 shorter stringers flanking the 2 full length inside stringers.

De-mystify hull stringers, wood or composite, number of them etc.

Appreciated,

Bill D
 

petrel

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My BHM had a stringer that looked like half a fence post and some cardboard tubing- pretty. It has been replaced w/ some laminated scraps of Coosa.
 

Helen L

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My Dixon (1987) has foam cored stringers and ribs, solid glass hull. Pretty cool considering its age. Too bad they had built everything topside with spruce.
 

F/V First Team

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Everybody does it differently, I personally have used no fewer than four different styles and materials. They all do the same thing, to a certain point. It all depends on how the vessel is going to be constructed and used.

Chances are, if you're going to have a Down East boat constructed, unless otherwise specified, you're going to have some fir glassed over.
 

Raider Ronnie

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tunamojo

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hmscapecod

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Mine are a couple layers of coosa glassed over. Don't use spruce, (2 x 10's, .. 12's) I did work on one a few years back and drilled a couple 3" holes to run stuff and the glass layers fell right off the wood.
 

wiggy

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stringer material

I just had Compsys make a set of Prisma 10" foam composite stringers for my Seaway. When I compared the cost of using the Prisma foam to Coosa, the Prisma was way cheaper, especially when you consider that the Prisma stringers already have the glass on them. They should make for an easier install since all I have to do is wet out the glass. I'm installing them in a week or two. I'll post how it goes.
 

BillD

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To funny. I often look at fishing threads and think to myself can't there be any "tricks of the trade" anymore. Never thought of it from a boat builders perspective especially on this site.

My BHM had a stringer that looked like half a fence post and some cardboard tubing- pretty. It has been replaced w/ some laminated scraps of Coosa.

My Dixon (1987) has foam cored stringers and ribs, solid glass hull. Pretty cool considering its age. Too bad they had built everything topside with spruce.

Everybody does it differently, I personally have used no fewer than four different styles and materials. They all do the same thing, to a certain point. It all depends on how the vessel is going to be constructed and used.

Chances are, if you're going to have a Down East boat constructed, unless otherwise specified, you're going to have some fir glassed over.

My sisu was laid up with foam board encapsulated in glass, stringers !
When I saw them I just smiled !!!!
They are so light and unbelievably strong.

My BHM has 4 full lenght 2X douglas fir stringers glassed in.
I plan to extend the height with additional doug fir glassed on top of the existing ones & up to the new deck height.

Here is a photo.... they are not as thick as they look they have an l shape at the top for the decks to be fastened to they are very thin
photo-3.jpg

Mine are a couple layers of coosa glassed over. Don't use spruce, (2 x 10's, .. 12's) I did work on one a few years back and drilled a couple 3" holes to run stuff and the glass layers fell right off the wood.

Thanks for all the replies. We are all here to "learn" ? Correct ?:p
 

BillD

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Can't you leave us builders some secrets?

Travis,

IMO it if a "boat builder" is going to participate as a member on this forum then he or she has a "duty" to respond and answer a question if they have knowledge to share on the subject.:D

And, I don't believe they'll be that many of us attempting to lay up their own hulls !!!!!:D

btw, I'm only joshing with yah. You've got a business to run and some tricks of the trade are proprietary.

OK, so what is good or better about composites stringers over plain old Maine grown wood?;)
 

F/V First Team

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The first use of stringers is popping the hull from the mold(s) and therefore the fir glassed over will probably be the best and easiest method. The strength of the wood lends itself well to this cause, letting the stresses go along the length without relying solely on the fiberglass to keep everything intact. Usually there are chains tossed through the holes and this has a habit of tearing the outside layers of a composite set up, being a balsa core stringer system with fiberglass on each side. Not the end of the world, the affected areas can be ground away, or more times than not, just cleaned up with a somewhat larger hole saw that cuts everything away. Or just glassed over and everyone pretends that it doesn't exist (not in my shop, but hey it happens). Solid fiberglass stringers suffer from the same damage but not as severely. Tossing a length of pipe through the holes gives a more even distribution of the force as well as a non-marring surface to which chains can be either slid through the pipe, or fastened around it to pull the product.

When using stringers to fasten engine mounts, I would not suggest balsa cored stringers. The entire premise of fastening engine mounts to something suggests that there will be forces exerted upon that area, not only from the weight of the engine on a cantilevered plane, but also the stresses involved with compression from the fasteners. Balsa core does not like being compressed, and even less when there are sudden shifts in the weight of the supported surface. Namely the vessel going through and over waves with a large chunk of iron bouncing around under the deck.

Fir seems to take this compression fairly well, although I would strongly suggest backing plates for all through fasteners. The solid glass stringers don't have to worry about compression all that much, however loose bolts will damage the laminate over time due to the shifting compression loads. Backing plates are suggested for this method as well. Backing plates are our friends after all, there is enough stress in the life of a boater.

When attaching something directly to the stringer the fir gives something for the fastener to "bite" into and generally it is thick enough to drive the screw in blindly and not have to worry about sharp points poking through the other side. Balsa cored stringers also have this ability, although the only area for the screw to grab onto is the fiberglass sheathing the balsa. Foam coring is no different. Solid glass stringers need to be through-bolted with fender washers preferred and maybe some barrel nuts (personal preference since I really don't like being torn up while playing bilge rat).

If the stringer is only going to be for supporting the work platform (deck) then there really isn't any difference between the various choices and methods, it's when you start poking holes and fasteners into the stringers that it might be prudent to take a step back and think about what's going on and how you are going to use them.

Water happens on a boat, be it fresh, salty or from sources unknown. Over a period of time that water will find its way into the nooks and crannies available and screw holes and bolt holes are just fantastic for migration, not to mention limber holes and oopses that happen along the way. This will rot your balsa core and given enough time your fir as well. The water will sit and start adding up, freezing every winter and silently delaminating your bonds as well, every winter getting ever increasingly worse. Foam core, while immune to rot, will still delaminate the same way. Best to glass any penetrations in the stringers when dealing with a core material, be it balsa, foam or solid wood and caulk all fasteners to prevent errant moisture from crashing the party.

Fun times below the deck. Hope this has answered more questions than it has produced.
 

BillD

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The first use of stringers is popping the hull from the mold(s) and therefore the fir glassed over will probably be the best and easiest method. The strength of the wood lends itself well to this cause, letting the stresses go along the length without relying solely on the fiberglass to keep everything intact. Usually there are chains tossed through the holes and this has a habit of tearing the outside layers of a composite set up, being a balsa core stringer system with fiberglass on each side. Not the end of the world, the affected areas can be ground away, or more times than not, just cleaned up with a somewhat larger hole saw that cuts everything away. Or just glassed over and everyone pretends that it doesn't exist (not in my shop, but hey it happens). Solid fiberglass stringers suffer from the same damage but not as severely. Tossing a length of pipe through the holes gives a more even distribution of the force as well as a non-marring surface to which chains can be either slid through the pipe, or fastened around it to pull the product.

When using stringers to fasten engine mounts, I would not suggest balsa cored stringers. The entire premise of fastening engine mounts to something suggests that there will be forces exerted upon that area, not only from the weight of the engine on a cantilevered plane, but also the stresses involved with compression from the fasteners. Balsa core does not like being compressed, and even less when there are sudden shifts in the weight of the supported surface. Namely the vessel going through and over waves with a large chunk of iron bouncing around under the deck.

Fir seems to take this compression fairly well, although I would strongly suggest backing plates for all through fasteners. The solid glass stringers don't have to worry about compression all that much, however loose bolts will damage the laminate over time due to the shifting compression loads. Backing plates are suggested for this method as well. Backing plates are our friends after all, there is enough stress in the life of a boater.

When attaching something directly to the stringer the fir gives something for the fastener to "bite" into and generally it is thick enough to drive the screw in blindly and not have to worry about sharp points poking through the other side. Balsa cored stringers also have this ability, although the only area for the screw to grab onto is the fiberglass sheathing the balsa. Foam coring is no different. Solid glass stringers need to be through-bolted with fender washers preferred and maybe some barrel nuts (personal preference since I really don't like being torn up while playing bilge rat).

If the stringer is only going to be for supporting the work platform (deck) then there really isn't any difference between the various choices and methods, it's when you start poking holes and fasteners into the stringers that it might be prudent to take a step back and think about what's going on and how you are going to use them.

Water happens on a boat, be it fresh, salty or from sources unknown. Over a period of time that water will find its way into the nooks and crannies available and screw holes and bolt holes are just fantastic for migration, not to mention limber holes and oopses that happen along the way. This will rot your balsa core and given enough time your fir as well. The water will sit and start adding up, freezing every winter and silently delaminating your bonds as well, every winter getting ever increasingly worse. Foam core, while immune to rot, will still delaminate the same way. Best to glass any penetrations in the stringers when dealing with a core material, be it balsa, foam or solid wood and caulk all fasteners to prevent errant moisture from crashing the party.

Fun times below the deck. Hope this has answered more questions than it has produced.
Appreciated!
 

Kaiser

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I am not a boat builder but do know a thing or two about wood.

The Black spruce found in Maine now has little strength and 0 decay resistance. The spruce from 150 years ago, different story.

If you must use spruce soak it in Jasco copper brown then let it dry out

Fir, well the devil is in the details

Balsam fir from Maine has low strength and 0 decay resistance.

Hem Fir, put your best sneakers on and run from that one.

Douglas fir (DF) from home depot is second, third or even fourth harvest that has very course annual ring count, is much stronger that the east coat fir but little decay Resistance. Would not use in a boat.

Dense grained DF (either old growth or inland) has a higher strength to weight ratio than A-36 structural steel. With the density it is quite decay resistant.

Some Douglas fir sold is actually Larch. This stuff is super strong and wicked decay resistant. If you can find it use it! It has a more brown color than the pink of DF. often the grade stamp will read DF/L

The Rolls Royce of North american softwood for boat building is Alaskan yellow cedar(actually a cypress). Almost as strong as DF fantastic decay resistance, Light, straight, works like plastic. You can get long lengths or better yet buy it as a glu laminated product. Cypress International with North east distribution from Hood in MA

White cedar from Maine is great too. If one were to finger joint it and laminate it into large sections to ANSI A-190 standards,that would be a great product. Cant find a good supply of it.
 

BillD

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I am not a boat builder but do know a thing or two about wood.

The Black spruce found in Maine now has little strength and 0 decay resistance. The spruce from 150 years ago, different story.

If you must use spruce soak it in Jasco copper brown then let it dry out

Fir, well the devil is in the details

Balsam fir from Maine has low strength and 0 decay resistance.

Hem Fir, put your best sneakers on and run from that one.

Douglas fir (DF) from home depot is second, third or even fourth harvest that has very course annual ring count, is much stronger that the east coat fir but little decay Resistance. Would not use in a boat.

Dense grained DF (either old growth or inland) has a higher strength to weight ratio than A-36 structural steel. With the density it is quite decay resistant.

Some Douglas fir sold is actually Larch. This stuff is super strong and wicked decay resistant. If you can find it use it! It has a more brown color than the pink of DF. often the grade stamp will read DF/L

The Rolls Royce of North american softwood for boat building is Alaskan yellow cedar(actually a cypress). Almost as strong as DF fantastic decay resistance, Light, straight, works like plastic. You can get long lengths or better yet buy it as a glu laminated product. Cypress International with North east distribution from Hood in MA

White cedar from Maine is great too. If one were to finger joint it and laminate it into large sections to ANSI A-190 standards,that would be a great product. Cant find a good supply of it.

Takes all kinds of specialists to get good information on this forum !!
Thanks:D
 

eyschulman

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Not a boat builder but I am thinking the wood -foam etc may be most important as a form for glass shape. Provided the glass shape and specs are adequate for the job it may matter little whats inside. Hollow beam of proper spec. might be best nothing to decay. On smaller projects I have seen cardboard shipping tubes cut down center used as forms for stringer like support. In my present 48ft boat epoxy- plywood-glass hollow stringer boxes support twin JDs
 
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