Only 2 9ft stringers on the whole boat? Need to add more?

[Serf27]

My enough mount stringers were bad so I cleared the area last year and I just cut new ones last weekend.

I cut a section of the floor out to see how long they went and the more I cut, the more bad flooring and stringers I found.

My question is, it looks like there is only 2 factory stringers on the hull.

The original engine stringer was 2 2x6s sandwiched together. 1 2x6 was the length of the bilge box and the other stringers was a longer 2x6 that ran to around under the dash/steering wheel area.

I now have the whole floor taken off and I still don’t see signs of any other stringers.
There looks to be like a random 1x2 or 2x4 on the sides that someone just wedged in there.

The new engine stringers I cut are from a 4x6. I cut the 4x6 to match the 2 original 2x6s.

My question is, do I just add the new engine stringers and glass them over with new plywood?

Do I have to add ribs?
A second set of stringers on the outsides?

I used the boat like this like 6 times and it didn’t break, and I don’t see where more stringers would have been installed at the factory.

I still need to remove the foam.
The center red lines represent the engine stringer and the outer lines represent where I think someone else put a 1x2.

Thanks.

 

[matt167]

What kind of OMC drive do you have? Many boats only have 2 stringers, most have some bulkheads too

 

[dubs283]

Is the engine/drive package still in the boat?

I like the pics cuz everything has been removed from the interior save for the fire extinguisher, an empty beer can and one stereo speaker. Gotta have fun tunes with a reasonable amount of safety available

 

[88 Capri (2022 SOTY)]

This is how my setup was, albeit my boat may be smaller because my stringers were 3/4" plywood. As you can see how stringers, bulkheads and engine mounts are ties together to form the spine "structural part" of your boat.

 

[Scott Danforth]

Just an FYI ....laminated plywood will be 5x as strong as a cut-down 4x6

I would have just laminated 3/4" plywood to 1-1/2" myself

 

[dubs283]

A proper constructed boat should contain white oak and at least one big block engine

 

[cyclops222]

Solid lengths of wood can be very erratic in strength. Due to many changes in the grain patterns. But plywood is difficult to use as wood for engine mounting beams. Some boats just screw in bolts with wood screws on 1 end. And Machine bolt threads on the other end

 

[Serf27]

What kind of OMC drive do you have? Many boats only have 2 stringers, most have some bulkheads too

I’m not sure, an omc 3.8 stringer, 1986.
I see where the 2 stringers were and looks like one bulk head at the top, near the driver and passenger.

Can I glass in my new engines stringers and add bulk heads and call it done?
The new stringers I cut at 7ft.
Thanks.

 

[Serf27]

Just an FYI ....laminated plywood will be 5x as strong as a cut-down 4x6

I would have just laminated 3/4" plywood to 1-1/2" myself

The plywood for the floor? Or where does the plywood go that you’re talking about?
Thanks.

My plan was to install the new 7ft stringers and put fiberglass over them and then put 3/4” plywood side to side for the floor, screw the plywood to the new stringers and then put fiberglass over the plywood and overlap the new fiberglass onto the sides of the boat.

 

[Scott Danforth]

You pulled out a 9 foot long "bone" and want to replace it with a 7 foot long "bone"?

 

[Serf27]

Solid lengths of wood can be very erratic in strength. Due to many changes in the grain patterns. But plywood is difficult to use as wood for engine mounting beams. Some boats just screw in bolts with wood screws on 1 end. And Machine bolt threads on the other end

Is it better to cut up the 2x6 into sections and then install with fiberglass?

I don’t want the boat to bend or crack while I use. I used it before as is and maybe the strength isn’t needed or maybe I didn’t go over any crazy waves, but the floor is out now and it needs new engine stringers, so might as well make it solid.

Thanks.

 

[Scott Danforth]

Laminate the stringers. Make them 9' long or longer

 

[Serf27]

You pulled out a 9 foot long "bone" and want to replace it with a 7 foot long "bone"?

No, I’m not sure exactly how long it was,it was all crumbling. One side did still have some wood intact and I was able to see that it was 2 pieces of 2x6 because they had straight edges.

 

[Serf27]

Laminate the stringers. Make them 9' long or longer

That’s what I’m going to do.

I’m also going to add some bulk heads like the ones in this photo and put fiberglass over them too. For the plywood floor, I just screw it into the stringers and laminate it all the way to the sides of the hull so it is bonded to the hull?

 

[Serf27]

This is how my setup was, albeit my boat may be smaller because my stringers were 3/4" plywood. As you can see how stringers, bulkheads and engine mounts are ties together to form the spine "structural part" of your boat.

That looks good.
I’m going to add bulkheads like your boat.

 

[Scott Danforth]

Read links 14, 15, and 18 in their entirety.... All your answers are in the stickies

How To's and Other Great Information

Disclaimer iBoats has no control over external links contained in stickies and to be aware that links are fluid and may or may not work. 1. Coast Guard Safety Standards for Backyard Boat Builders Verified 2. Fiberglass Information Verified 3. Pouring Foam in's and out's Verified 4A. Basic...

forums.iboats.com

 

[cyclops222]

Whatever pieces of plywood you cut to a final shape. To be installed in the boat. COAT ALL surfaces with a thin coating of just liquid glass mixture.
All surfaces out of sight WILL get wet from water as it get into each compartment. Remember to cut a BIG DRAIN hole on the very bottom of each bulk head to allow POSITIVE draining for each bulkhead compartment into the bilge pump compartment.
Glassing the long stringers ? That is up for discussion. Reason ? Depending how much flexing ........they will do ? Big hard impact wave flexes the bow section areas ? Migh be next to no flexing with enough....THIN PLYWOOD ...... bulkheads. They do not need to go from keel to top deck. 3" to 6" wide RIBS would be over kill but provide plenty of resistance to bottom and side flexing.
We have made strong lightweight plywood ribs by overlapping 4 separate pieces of 1/8" to 3/16" thick plywood. WE we made the over lap areas about 3" to 6" areas. We screwed them together in the hull with about 4 screws. S S is not needed. The 4 screws are used as relocating screws.
We dry fitted ALL the ribs in the hull with the screws. Them removed all the ribs. Unscrewed all the rib sections. Coated all the surfaces & edges. Reassembled all the rib sections with the 4 screws. Let them harden for several days. Notched the ribs to slide down the stringers. ? Small strips of glass cloth wedged into the corners. Or small pieces of triangular blocks with glass as glue. Locked the ribs to the stringers. NEATNESS is NEVER required below the deck areas !!
Do a dry fitting of the completed ribs to cut off any excess top height to clear the top deck. 2" to 4" below the deck is fine.

Think out the steps several times. Fiberglass glue demands that if possible.
The hull survived all the years without additional bulkheads or ribs.
Your call on any extra reinforcing. Make the repairs enjoyable.
I would coat the long stringers completely after they have a good dry fit.
WE had to cut to shape and scarf 3 or 4 pieces of boards to fit them to the upward hull curve. Yes it can become tedious to do some repairs. But if you like the hull ? Do the steps with a feeling of accomplishment.

 

[cyclops222]

We all forgot to ask what HP was the maximum rating ? What are you putting back in ? HP engine

 

[matt167]

We all forgot to ask what HP was the maximum rating ? What are you putting back in ? HP engine

Inboard boats do not have a hp rating. Some boats list a max engine weight in the specification for said boat. Like old StarCrafts if you look at the brochures, list the I/O hulls without engine/drive and then list how much weight to add for the various optional engines.

 

[cyclops222]

You are so right matt167. I looked up USCG rule started in 1972. Anything is allowed as you stated. Insanity for safety of inboard engine powered boats ?
Insurance companies accept 800 hp crate engines ?