Starting 87 SN Floor/Stinger Repair

Here is the shopping list posted by Bill (SkiBum) on March 15. It is from a thread started by Jon4Pres regarding the stringer floor replacement in his 82. BKH

To replace the stringers this is a pretty good list of materials:

quan      item
5 gal     Epoxy resin 635 thin 3:1 ratio
1 roll    50 yds 2" E-glass tape
1 roll    50 yds 4" E-glass tape
1 roll    50 yds 8" E-glass tape
5yds      Epoxy mat
5qts      West 404 filler (fine glass)
5qts      Aerosil-Cabosil thickening agent
5qts      Fairing compound
25 ea     2" wood paintbrushes
25 ea     stir sticks
5 ea      1qt mixing containers
2ea       2"x10"x16'
2ea       1"x6"x12'

Each stringer consumes about one gallon of epoxy resin from start to finish. Use the epoxy mat to laminate both sides of the stringers. Seat the stringers with 2 layers of epoxy mat and clamp until cured. Fill gaps with 404 filler and epoxy. Then use 2", 4", 8" strips along the joint. Use 404 and epoxy to make a bead 1" above and below the joint 1/4" to 1/2" thick.

That is all it takes to laminate and install the stringers.

I'm starting my stringer replacement this week. Can you tell me how much resin and cloth to order for the stringers and floor.

Thanks Pgaski

copcraft wrote: Bill For some reason the way you just explained putting the mat under the stringer just made sense to me. I wish I would have understood to do that. It sounds like that would work good. I didn't put anything but epoxy between the hull and stringer. Oh well. David

What is important is to maintain a 50/50 mix of resin and glass. The glass adds strength to the resin. The two layers of epoxy mat below the stringer help maintain that ratio of glass to resin as well as compensating for inconsistencies in depth. Subsequent filling of gaps should be done with some sort of fine or chopped strand glass mixed with the resin to keep that ratio.

I have certainly gone out of ratio several times on my project. Gravity pulls the resin down the sides of the stringers into the bilge and on the other side it pools. That's when I learned to use aerosil-cabosil as a thickening agent.

Yak3 wrote: I'm taking a break cause I don't want to rush it and screw it up, but i'm afraid of sanding the stringer down to far...How much of a gap can i have?

I am assuming you are talking about the gap between the hull and the stringer when you set the stringer in place? If that is the case then you should have most of the stringer touching but as much as 1/4" gap is not bad in limited spans.

When you apply the new stringer first use clean water and a green scratch pad to clean the area. Then wipe with paper towels and let dry. Now, apply epoxy resin to the hull. Add a layer of epoxy mat just as wide as the stringer. Saturate the mat with epoxy. Add another layer of epoxy mat. Saturate this mat with resin and roll out the bubbles. Apply epoxy to the bottom of the stringer. Set the stringer in place and apply weights to hold it down.

The weight of the stringer and weight will force the stringer onto the mat. The mat will compress in deep spots and expand to fill low spots.

When it is cured go back with West 404 filler and epoxy to fill the gaps. This gives a rock solid bond to the hull.

Follow by using consecutive layers 2", 4", and 8" wide along the joint. Then use the 404 filler to make a bead 1" up the stringer and 1" down the hull. Make the bead at least 1/4" thick to 1/2" total.

Take your time. Do it right the first time.

I have a lot of respect for you Bill, doing this day in and day out for almost 3 months now. I spent about two hours grinding tonight, and it's tough work - particularly for a guy like me who spends his days in a suit behind a desk. Hands, back and arms are spent.

I'm enjoying it, but can't imagine putting in the hours you have in such a short period of time.

Keep the pics coming. Your thread is one of my main reference guides. BKH

Eric

That is exactly what I kept telling myself when I was talking myself out of putting more layers on. Our phone conversation also made sense regarding the lack of strength in a rotten stringer. Like you said, anything ne would be stronger.

David

Brian

I had the same deal when I took out the stringer. There was about 1/4" of resin the length of both sides of the old stringer. My new stringer was probably not as tight and form fitting as it should have been. I grinded quite a bit of the old fiberglass out, but still had a "groove" where the old stringer was. I poured a bead of resin in the groove, placed the new stringer in, then epoxyed a 4" strip of 7 1/2oz cloth (2" up the side and 2" on the floor) on the downhill side of the stringer. When that was dry the next day I sanded, cleaned w/acetone and then poured epoxy into the voids on the uphill side. I then did the 4" cloth on the uphill side. I then started going from the floor up the side, over the top, down the side, and onto the floor. I staggered the width on the floor with every layer. I now have about five coats like that on the stringer.
     I don't know if it's right or not, but it seems pretty strong. Good Luck.

David

I'm definitely with you Bum. You have me rethinking the process.

Question: I pulled two stringers out yesterday. It looks almost like the floor was laid, wet and thick, and the stringers were pushed down into it 1/4 to 1/2 inch. So, my question is, how far down did you grind? I though I remember reading that you put down two layers of mat and set the stringers down into that. If so, my assumption is that you ground down abut 1/16 of an inch below where the stringers were sitting when removed.

Thanks,

BKH

Gangster, you may of had saturated foam adding alot of weight to the boat, the foam is very dense when wet.
it is a touch easier glassing over the foam and my presonal preference is using wood, it lets you screw everything together and Im use to doing glass work on flimsey fountains and other paperthin hulled boats and with wood you can build a skelton and make the repairs much more rigid, unlike a correct craft hull which is very well reinforced due to the way it's manufactured its a matter of personal preference, there are pro's and con's of both methods, i guess it comes down to whatever you would be more comfortable doing.

SkiBum, I hope this doesn't sound like I'm trying to start a debate, but what about weight? Do you think all that glass & resin weighs more than glassed wood? My boat porpoised very bad before and I think/hope it was because of the weight.

SkiBum wrote:    I learned it is more labor intensive to laminate both sides of a piece of wood then install the wood as apposed to simply layering glass over the foam.

Interesting perspective. I've been staring at mine a lot trying to determine in my head how to do it. I would have thought the wood would be easier because you could coat it out of the boat where you have more room to work, and the pieces would fill up large spaces at a time when installed into the boat. Thinking about your statement however, has me thinking it through, yet again.

Took out two stringer today, so I better make up my mind soon. BKH

I guess I was leaning towards the glassed wood because I haven't much experience with fiberglass so far. Maybe after I get into it I'll gain the nerve. As for the burried sled, there's no shortage of riding. I get 2 months of nice boating, and about 4 months of sledding.

Gangster,

There is one floor section on the 87SN that is supposed to be wood. CC used 3/4" thick by 3" wide planks stapled to the stringers then covered with glass. The rest is glass over foam.

Before I knew the floor was primarily glass over foam I planned to use the 3ply laminated top and bottom with glass. I did that in a small area in the bow. It worked just fine. The idea was that I would save in materials cost because I could laminate a thin layer of glass on the bottom of the 3ply and two thin layers on top but still have a solid floor.

I opted to finish the boat using glass over foam. It really did not consume a significant amount of additional materials. I put down biaxial mat, epoxy mat, cloth, and epoxy mat to get a 3/8" to 1/4" thick layup. It was easy to level with fairing compound. I say it is the way to go.

The glass comes in several variations. I don't want to use the word "woven" because it may spark a huge debate, but basically cloth is interweaved glass that is very strong. It comes in a variety of thickness measured in ounces. I used primarily 10oz. It is thin. You can get it as thick as 28oz.

The mat is glass that is not "woven" but rather consists of loose strands of glass that are connected together by either a special glue or is stitched together. The kind that is stitched together is called epoxy resin. Polyester resins actually dissolve the glue in the mat where epoxy resin does not. Now you can use epoxy resin on mat that is not epoxy mat, but it will significantly slow your work because you must physically work the resin through the glass. Not the preferred method.

Biaxial is a special fabric that consists of epoxy mat sandwhiched between two layers of cloth and stitched together. It combines strength and thickness. Very good stuff, but very stiff and difficult to work on 90 deg angles.

Well the company sells wholesale, but I can buy it through the company I work for. So I guess that's why they only sell such large quantities. I was able to buy 50 yd rolls of 2", 4" & 6" (no 8"). Can I ask a stupid question? Is mat = chopped strand? I am also curious - Skibum you started out to use fiberglass over plywood for the floor, then ended up going just fiberglass. If you had to do it again would you do the same?
By the way, here's something that might cheer up any Southerners... This was taken around March 1st, my snowmobile's buried!! I've got some time on this project...

Plus you will need various thicknesses for the project. You will never be able to make the 90 degree bends with just biaxial or mat. Like skibum said, you will need some 10oz cloth, biaxial, and mat to make all the necessary bends and buildups.