Stringer repair ?'s

Hello all,
I am new to the forum but, I have been reading for a while. I have a couple of questions that I hope you guys with your infinite knowledge could help with. I am replacing the stringers in a 29' Scarab sport. I have the deck off and the old stringers out. I have refabed the new stringer out of 3/4 marine grade plywood and I laminated 2 boards together to make the new ones 1 1/2" thick. I am ready to put them back in. My questions start here.

1. I have read about encapsulating them in glass and epoxy. Is this something I do prior to installation? Should I cover in epoxy let dry and then glass the new one in place? What is the best epoxy to use for this?

2. I plan to use some sort of glue/epoxy to put between the hull and stringer to help keep them from moving before I start to glass in place. What is recommended for this? Can I use 3m 5200? Or do I even need to "glue" in place?

3. I plan to use a couple of layers of biaxle to glass the new stringers in place. Is there something better to use or is this cloth sufficent?

I have worked on a few boats and I know how to lay fiberglass pretty well. I have used glass to make a bunch of interior stuff for lowriders and speaker enclosures. This is by far my biggest project and I just want to make sure I do not miss anything that should be done. Any advice would be greatly appreiciated!
Thanks in advance!!

 

Scarab Freak , Dont feel alone I am in the middle of the same job on a 30' Scarab, Mine all started with an engin bulkhead and is winding up a complete Restring also, I'm looking into composites but as of yet I am undecided, the one thing I can tell you for sure ,...do not mix epoxy's and resins the resin does not like the epoxy, do your homework and dont mix systems... I to am pretty good at glassing and am thinking about a possible profession change as there are a lot of "rotting go fast boats out here " E mail me if you want. Ill give you any info I can , best of luck will keep you posted ....JT

 

found the information

I was reading you post and I am new to this site but I was doing some research and ran across the information you are speaking of. I was researching using the west system and Boaters World sales a book 2.99 that addresses replacing and repairing the stringers with wwest system product and i read most of it at the store and it recomended laminating up your stringers and then you can use the epoxy to attach the stringers and then wet them in. I hope this was some help I have yet to get any here, but for 2.99 I would head to boaters world and pick up the book and I would imagine that that their web site has the booklet in pdf.

 

Stringers cont'd

Scarab freak, I have a few questions, comments.. in mix and match fashion.... 1st were your stringers originally 1 1/2 wide (as the ones in my scarab were only 3/4'') what did you use to laminate them together with , ? glass? epoxy ? wood glue? gorrilla glue? how much of a lap or offset did you use? I havent begun building mine as Im not sure whether I'm using wood or composites yet, I had thought of laminating with 4' offset but joints , trying to use as many 8' sections as possible . While still in the tear down mode on mine I noticed that the stringers originally were covered first in a fine cloth(where engine stringers butted the bulkhead the cloth on the bulkhead was not wetted between the joints which leaves me to believe originally the stringers/bulkheads were wrapped in this cloth prior to installation ) then the engine bay stringers were covered, then installed , then the whole assembly was fiberglassed in with a heavy woven roving , the quality seems to have been absent as I have open wood at the secondary stringer fronts ,the woven had sagged at my front gas tank/cabin entrance bulkhead and at numerous spots throughout the hull ,nothing was real "tight as far as corners nooks etc ,Im sure we will both do a better job when we reinstall , I believe you should make a few "jigs" throughout the hull to keep the stringers properly aligned, one other thought,/ question "from a marine surveyors websight"any time you notch or cut out or change height along a stringer you diminish the strength/and create a stress riser. are you notching the stringers like original, where the transverse bulkheads/partitions go ,or are you making the bulkheads /partitions (other than the engine bulkhead) in seperate pieces???

 

I have a suggestion you guys...

86 the wood all together (for installation that is). Rather, use the wood stringer system you have in mind to build a complete stringer mold. Lay up over the mold, release and then glass into the hull. Leave injection holes in key areas to inject PVC foam. Then fill your holes. That will give you a completely composite stringer system and extra bouancy. You can them bond your new deck to that. Document and photograph your work. That should increase longevity and resale value if you're ever in a pinch.

Any comments to my suggestion are encouraged )

 

what is a stringer

 

I have been a fiberglass hobbiest for many years and in 1976 worked for 4 months in a fiberglass shop making master molds for sinks, tubs and shower walls from woven roven and epoxy resin. I have owned several I/O boats with rotten mounts and fixed them all the same way. If you pound a boat with bad mounts, the engine will crush the mounting floor and sink the boat. I felt if I had to go to all the trouble of removing the engine to fix the mount, I might as well sell the boat for junk, therefore I came up with a creative repair method.
I've seen repair shops rip out and splice in a new wood stringer and then glass it up. Well that's great but a lot of unecessary hassle and expense.
1. Take the motor mount off but dont remove the engine. This allows you room to work. If you repair the mounts one at a time you probably don't need to support the motor. Take a wood bit about 1.5 inches or larger depending on the boat size and drill one or more holes in the mount as deep as possible without going through the boat bottom.
2. Get a one gallon bucket a mix a thick but semi pore-able slurry of shredded woven roven and polyester resin. Pour it into the hole you drilled while using a stick to stuff the hole until it wont take any more of the slurry. On my under 20 ft boats I fixed, they took from 1/2 to 3/4 gallon per mount.
Let it set up over night and drill new motor mount holes the next day. Use a good grade of stainless or the original screws and drill the hole smaller then major diameter, but not smaller then the minor diameter of the screw. If the hole is too small you will crack the glass. On a 140 hp Volvo Pinta I used a 5/8 screw and torqued it to about 125 ft lbs, I was amazed it did not strip. Whatever you do make sure that the mixture does not cure at a higher rate then recommended. If done correctly this will be stronger than the original. Assuming you have room to work you should have about 4 hours into the job four four mounts.
Fiberglass is nasty to work with, so buy a gallon of acetone for cleaning up and a particle mask to avoid inhaling the glass fibers as you shred them. The fiber glass itches so minimize contact with the cloth, especially on your forearms.
If you want to check to see if your motor mouunts have any integrity, check the wood screws that penitrate the stringer with a wrench. Just remember they are very easy to strip in an old boat, so don't use hardly any force at all. In fact, if you see that the screw at not screwed all the way down, this is a sure sign that your stringer screws are stripped.
When I fixed the Volvo Pinta, I had already crushed the rear motor mounts in a wave jumping storm and did not know it until I got the boat home. Another five minutes of pounding would have sank the boat because every time I jumped a wave the motor would lift out of the rear mount about six inches and slam down crusing the floor.

 

Stringer Motor Mount

I have been a fiberglass hobbiest for many years and in 1976 worked for 4 months in a fiberglass shop making master molds for sinks, tubs and shower walls from woven roven and epoxy resin. I have owned several I/O boats with rotten mounts and fixed them all the same way. If you pound a boat with bad mounts, the engine will crush the mounting floor and sink the boat. I felt if I had to go to all the trouble of removing the engine to fix the mount, I might as well sell the boat for junk, therefore I came up with a creative repair method.
I've seen repair shops rip out and splice in a new wood stringer and then glass it up. Well that's great but a lot of unecessary hassle and expense.
1. Take the motor mount off but dont remove the engine. This allows you room to work. If you repair the mounts one at a time you probably don't need to support the motor. Take a wood bit about 1.5 inches or larger depending on the boat size and drill one or more holes in the mount as deep as possible without going through the boat bottom.
2. Get a one gallon bucket a mix a thick but semi pore-able slurry of shredded woven roven and polyester resin. Pour it into the hole you drilled while using a stick to stuff the hole until it wont take any more of the slurry. On my under 20 ft boats I fixed, they took from 1/2 to 3/4 gallon per mount.
Let it set up over night and drill new motor mount holes the next day. Use a good grade of stainless or the original screws and drill the hole smaller then major diameter, but not smaller then the minor diameter of the screw. If the hole is too small you will crack the glass. On a 140 hp Volvo Pinta I used a 5/8 screw and torqued it to about 125 ft lbs, I was amazed it did not strip. Whatever you do make sure that the mixture does not cure at a higher rate then recommended. If done correctly this will be stronger than the original. Assuming you have room to work you should have about 4 hours into the job four four mounts.
Fiberglass is nasty to work with, so buy a gallon of acetone for cleaning up and a particle mask to avoid inhaling the glass fibers as you shred them. The fiber glass itches so minimize contact with the cloth, especially on your forearms.
If you want to check to see if your motor mouunts have any integrity, check the wood screws that penitrate the stringer with a wrench. Just remember they are very easy to strip in an old boat, so don't use hardly any force at all. In fact, if you see that the screw at not screwed all the way down, this is a sure sign that your stringer screws are stripped.
When I fixed the Volvo Pinta, I had already crushed the rear motor mounts in a wave jumping storm and did not know it until I got the boat home. Another five minutes of pounding would have sank the boat because every time I jumped a wave the motor would lift out of the rear mount about six inches and slam down crusing the floor.

 

DON,T let the stringers touch the bottom of the hull. You will set up local stress points that will crack the hull. Search the site for stringer replacement and you will find all the info needed. Your question is the most common one this site.

 

Not to be contrary, but "repair" and "fixed" don't belong here. This is referred to as "rigged". The engines are usually mounted to stringers and the stringers are there to strengthen the hull, not neccessarily to mount the engine. If the mounts are rotten the stringers are compromised. It seems to me what you are doing is creating a bunch of piledriving plugs that have as much or more chance of sinking a boat as rotten mounts. Sam

 

stringer repair

I have a 36 ft motorsailer, that has a lot of rot damage, the stringers are mahogoney and most of them are rotten, the fiberglass surrounding them is about 1/4 in thick on top, are there any fillers I can use such as Seacast or something to repair them in place, I would hate to have to tear the deck off and gut the interior, are there any options? the hull is solid glass and is quite thick, the deck is wood and also the cabin area

Mark

 

An easier way to do this, and time saving as well, would be to use a product like Space Age Synthetics Thermo-Lite board (available in many densities) or Penske board. They are glass reinforced PU foam panels available from 1/2" to 2" thick, with either woven roving or CFM as the skins of the panel and come in standard 4'x8' sheet sizes. Build the stringer system, tag it into the boat (I like to use about a 1/4" space between the stringer itself and the bottom, to avoid point loading) and then encapsulate them in glass. The 20lb density SAS material is 54% lighter than plywood (XL marine board) and is 96% closed cell foam content. Just be sure to pre-wet it out first for the best bond.

good luck

 

Go to the Miami International Boat Showand check out the new Scarab 30 Sport. She's beautiful! I'm sure she,ll be posted on line soon.

 

Well said. Please keep the cheap fixes to the other sites. A job well done takes time and money.

 

who says that repairing a stringer with epoxy filled materials is a cheap fix, if the stringer is wood that is encased in mat and roven woven but not touching the hull, and the wood rots out and you replace the wood with another material, how do you say this is a cheap fix, fixing the stringers in place would be more expensive, I thought you boys knew what you were talking about