LVL- Laminated veneer Plywood Beam for Stringer?

yorklyn · Post by **yorklyn** » Fri Mar 07, 2008 10:43 pm

Hello,
I Was wondering if anyone knows any reason why I shouldn't use a LVL (Structal building beam) to replace the stringers in my 10 meter. I'm a contractor by trade and have used laminated plywood beams in structal applications. I can purchase a 1-3/4 inch X 24 inch beam and rip it down to 19 inches to use for the main stringers. These beams are glued and compressed under extreame pressure which virtually elimanates voids. It comes with a water resistant coating sprayed on the outside but I believe I can sand the coating off to promote adhesion with the epoxy. I spoke with a engineer at the manufacture and he said he didn't know of anyone using a lvl for a stringer, he said it should be fine under load however he said the beam was only rated for interior applications. I plan on using west system epoxy to fully encapsulate the stringer and Glass it in. I'm doing all the work myself and feel it would be much quicker and stronger using this beam instead of splicing together 8 ft sheets of marine plywood.
I think I'll be ok doing it this way. What do you guys think???

Thanks

jimini · Post by **jimini** » Sat Mar 08, 2008 1:06 am

Why not use what was in it before? We're talking one of the main components here probably the third most important part of the boat next to the keel and transom... Its a terrible amount of work to replace the stringers again if the water would somehow enter the wood and start destroying the interior glue...why take a chance?

prowlersfish · Post by **prowlersfish** » Sat Mar 08, 2008 7:30 am

I think you will be asking for troulble . use a "marine grade" wood .

Mac32 · Post by **Mac32** » Sat Mar 08, 2008 9:37 am

I looked at using laminate beam to replace my stringers and there were two main reasons I didnt.

First was I could not get a straight awnser on if the actual glue used to laminate was 100% water proof and would not start to break down if there was a chance for water to get in contact with it for a prolonged period. This would mean a huge amount of work scrapped if I had delam issues down the road. And chances are water will come in contact somehow......

The second was the cost when compared to the scrap usage of cutting and optimizing my own marine plywood layup out of 4x8 sheets.
(marine ply is glued with adhesive not affeced by moisture like std grade plywood)
So I went with the 4x8 sheet layup using west system epoxy to bond and coat the stringers. I used (2) 1/2" and (2)3/4" sheets to make up a 2-1/2" thick stringer.

I cant remember how many sheets of ply I used but I think it was only 4 or 6 fro this job at around $65 per sheet for 3/4 and $45 for the 1/2 marine plywood.

Here are a few pictures......Remember these are only opinions not expertise.....Just an amateur here.

yorklyn · Post by **yorklyn** » Sat Mar 08, 2008 9:40 pm

I don't know Mac, those pictures sure don't look like a amateur did it! Nice work.
I spoke with Paulw from this site today. He is thinking of buying a 10 meter that has the same type of issues as my boat. He has a fiberglass guy that he spoke with for me. His guy confirmed what you guys said about the glue. I guess my biggest issue now is finding good plywood locally.
I removed the cabin floor today and confirmed the starboard stringer is bad up to the bow, The port seems OK , its alittle wet but not rotted. Since it looks like I'm replacing most of the other stringers I'll problably replace all of them.
I really appreciate everyones input. It is a great resource to be able to get help from a site like this! Thanks again guys!
I took alot of pics today and will post them soon so you guys can appreciate your "non tore a-part" boats more!!!

Mac32 · Post by **Mac32** » Sun Mar 09, 2008 10:19 am

yorklyn,
Call the local lumber stores, the family owned kind. I found two by me locally that have marine grade plywood and two more than can get it in a few days. The big box stores just looked at me crooked and told me the only difference between theirs and marine ply was the amount of layups.....not true, what about the glue???? they also told me to use pressure treated exterior grade, fortunatly my anal retentive engineering personality kicked in and did research, this would create a huge issue due to moisture content ratings of their wood more then the bond issues (still not sure if there would be bond issues?) not to mention the sheets all looked like potatoe chips.

So all in all it was only $15 or 20$ more per sheet than the pressure treated box store potatoe chips. Maybe a total of $100 more to the whole project......this was worth the peace of mind especially on a job that will be at least $1800 in materials when the job is done. Now if I can only figure out how to get paid for the

labor........

yorklyn · Post by **yorklyn** » Sun Mar 09, 2008 3:08 pm

Mac32,
Thanks for all the help! I think I have a lead on some good marine plywood locally, I'll find out this week.
I had another question, What weight fiberglass (how many ounce) woven roving did you use? I read that I should alternate layers of the heavy woven roving and fiberglass mat. I'm trying to figure out how heavy a material to use as well as how many layers to install. I think once I decide on the material weight, I can measure the old fiberglass and look at a chart to see how many layers would be needed for the required thickness.

Thanks again

jimini · Post by **jimini** » Sun Mar 09, 2008 4:13 pm

I can honestly say I don't know.... sorry... anyone else know?

yorklyn · Post by **yorklyn** » Sun Mar 09, 2008 4:34 pm

Danny Bailey · Post by **Danny Bailey** » Mon Mar 10, 2008 9:47 am

Has anyone ever thought of adding fiberglass to the exterior of the stringer to eliminate the need for the piece of wood inside? I heard that Hatteras stringers had foam inside only as a filler and that the laminate around the foam carried all the structural load. Sure would be nice to have no wood at all to ever rot out again.

jimini · Post by **jimini** » Mon Mar 10, 2008 4:11 pm

I would have been inclined to go with plastic lumber... made for marine applications; outdoor benches; comes in sizes of board feet or plywood... worth checking into and it can't be much more expensive as marine grade wood products...

yorklyn · Post by **yorklyn** » Mon Mar 10, 2008 5:52 pm

Danny,
"Has anyone ever thought of adding fiberglass to the exterior of the stringer to eliminate the need for the piece of wood inside?" That thought crossed my mind. I just Don't have enough engineering knowledge to take a big risk
RJCRESS:
I have the boat on $2400 worth of rolling boat dollies (I'll have to post a picture, their pretty cool). These Dollies support the boat from the outer stringers about 16 inches in from the sides. The dollies leave the keel suspended. I took 2ft lengths of 6x6 timbers and cribbed up under the keel in 4 places. I think I'm going to attempt to support the keel in as many places as I can as well as place a few boat jack stands along the gunnels. I hope that will be enough as I need to complete these repairs in my warehouse before putting it back in the water. I know It would be less of a risk doing it in the water so I'll have to be careful and see.
JIMINI:
I believe the big issue with the composite lumber is its lack of structual strength. I will be using it alot of other non structal places instead of wood. I don't know if epoxy will adhere to it?
Thanks Guys! [/quote]

jimini · Post by **jimini** » Mon Mar 10, 2008 8:04 pm

There is a Fiber Force Plastic Lumber made with fiberglass strands which is structurally stronger than wood

yorklyn · Post by **yorklyn** » Mon Mar 10, 2008 8:31 pm

Jimini,
Never heard of that brand. I checked out their website. The 2inch stuff will span 24inchs, not bad. I sent them a email to get some further info. Thanks.