Weakened Deck Beam

[The Froon]

Hello forum! I have a Sea Sprite 23 that I am restoring, and am now turning my attention to the deck beam that has weakened over the years. This Sea Sprite is a 1968, and the previous owner created a solution for the weak deck beam / mast step. One of the deck beams (there are two spanning the underside of the deck, and both attach to knees tabbed to the hull) has been sandwiched between two 2x4s. The "fix" has in fact made the deck very solid, but it is kind of unsightly and unfinished. I am looking for some direction on how to go about repairing, and in such a way that will not take away from a finished cabin. The deck is not cored - at least from what I can tell thus far (I have not drilled any test holes). Here are a few picks of what I am dealing with; you can see the hair-line crack in the deck beam (white) in one of the pics:







Thanks,

Brian

[Tim]

Well, you could simply replace those nasty 2x4s with shaped wooden beams of a more attractive nature--either laminated beams (strongest) or solid wood.

Or, you could concentrate your efforts on repairing and reinforcing the original encapsulated beam in such a way as to eliminate the need for the additional wooden supports.

Which direction appeals to you?

[The Froon]

Tim, the method I employ for the repair is most likely going to depend on what is involved. I am learning how to restore a fiberglass boat through the assistance of the forum, tons of reading, and hands-on work. I would be interested in hearing your thoughts on both options. I am kind of a purist...which is leading me to recreate this Sea Sprite as she would have been off the showroom floor.
Also, as an aside, can you suggest a sanding tool for the deck? I have been using a Dewalt variable speed 5" random orbital, but it is very slow-going and I have to tilt the machine up to apply a little more direct pressure onto one area of the sanding pad for better results. I feel that there is a tool out there better suited for paint removal.

As always....much thanks,

Brian

[Quetzalsailor]

Some few questions: Is there any way water could have gotten/got into the encapsulated beam? Or was it simply not strong enough? You could investigate by drilling a few small holes into the bottom of the beam; if rotten, as opposed to broken, you have a different repair problem.

If you think of that beam in the same way as steel I beams are made: The deck is the top flange, the vertical sides of fiberglass and the wood core is the web, and the bottom of fiberglass is the bottom flange. It's not nearly as black and white as that; the bottom portion of the sides and the bottom portion of the wood core act as part of the bottom flange, too. My point is that the bottom-most, 'extreme fiber', portion of that beam is going to do the most work.

Thus adding useful material to the bottom of that beam will be the most effective way (particularly weight-for-weight) to re-create the beam. Bonding a strip of decent quality wood would do it and, if varnished and all, would look fine. Bonding a strip of fiberglass would do the same. In both materials, it's the longitudinal fiber, the wood cells or the glass fibers, that's important.

My guess is that a 2" wide by 3/4" strip of wood or a 2" wide by 3/8" strip of glass would do it. The guess is based on your reported adequacy of the two sections of 1 1/2" x 1 1/2" poor-looking SPF that were added to the sides of the old beam; the 3 1/2" x 1 1/2" widths of wood on either side of the middle add nothing to the strength of the repaired member at the site of the break. (The two radial knots at the port end of the aft sister's notch, and the center pith is the reason I say 'poor'.)

Given my age, flexibility, and size, I'd want to roll the 23' boat over and work downhand; possible?

[Quetzalsailor]

Please don't razz me about the relative sizes of the repair strips. If you used longitudinally oriented glass, like batten or structural fiberglass stock, the comparison would be far more favorable than 2:1.

[Tim]

I have been using a Dewalt variable speed 5" random orbital, but it is very slow-going

Do you mean something like this?



Or like this?



If the first (the vertical-axis finishing sander), then you are using the wrong tool for major sanding/paint removal/etc (though it's a good general finish sander for other purposes).

If the second (the right-angle DA sander), then you have a good tool for the job already and just need to learn to use it effectively (though I've never used the DeWalt version).

My workhorse, as frequently noted on this forum, is the Porter Cable 7335 right angle random orbit sander (5"), which is similar to the DeWalt right angle shown just above. This is the tool, when combined with the proper sanding discs and proper grit.

The right angle DA-type sander like the PC 7335 has abundant power and paint/FRP removal capacity for what you are doing. If you can't do it with this, you're either using too-fine paper, or not using the tool effectively.

If you have a lot of paint to remove, try a scraper first, though these bring their own cautions with their use.

Do not use a right angle grinder. Please.

[Tim]

...the method I employ for the repair is most likely going to depend on what is involved...

What's the core problem that the existing 2x4s are attempting to correct? Is it damage to the original encapsulated beams, or simply unwanted flexing of the deck in the area that the 2x4s are stiffening?

Does the deck flex without the 2x4s in place? Do other problems exist? Are they just an overcautious attempt by some previous owner to stop something that was thought to maybe exist, but may not?

Knowing how or why to repair something relies on knowing what the real problem is to start with.

[The Froon]

I have not taken the 2x4s off as of yet, and have yet to raise the mast since I purchased the boat. I imagine that the deck began to flex, resulting in the cracking of the original deck support. (sorry if I am not using the correct terminology). I am almost positive there is no core material on the boat - there isn't any in the cockpit, hull, and deck toward the stern. I did however see a couple Sea Sprites that did have fired decks on a website belonging to a boat yard in RI - I believe they are called "Guck", if you search on "Sea Sprite Repairs" it will come up.

Are you suggesting that if I layer several sheets of cloth to the underside of the deck, then this will adequately strenghen the deck?

I have been using the palm-oriented sander, finish sander. I need to get the right angle sander.

[Tim]

Are you suggesting that if I layer several sheets of cloth to the underside of the deck, then this will adequately strenghen the deck?

No.

What I am suggesting, though, is that you need to know why you are repairing what you intend to repair before you repair it. What appears to be, and what actually is, can often be different things. Not that you don't have a problem, necessarily, but you do need to assess the "why" first before knowing the "how".

To that end: remove those 2x pieces. Inspect the original stiffeners. Determine whether, or why not, they are adequate. If not, then decide whether to cut them out and replace them with adequate supports, or whether to sister them with new wooden beams similar to the 2x4s, or some third option.

I am unfortunately not intimately familiar with Sea Sprite 23s and can't offer any specific information at this time, but in the most general terms this is how you should begin the project. It will help make the way forward clear if you know these answers.

Also, when I said "what is the core problem you are trying to correct", I should have said "what is the root problem", or "what is the essence of the problem". I didn't mean to confuse the issue with anything related to deck core: I understand that you think you do not have a core in this part of the deck (which is one reason why it may flex , by the way.) Those encapsulated support beams were originally intended to stiffen the area; are they not doing their job? Are they damaged? Or was the 2x4 support put in "just because"? You first need to determine the real need for strengthening before you strengthen.

[The Froon]

Tim, thanks for the depth of explanation. You are right, I need to remove the 2xs to really determine what is going on. It is documented that the Sea Sprites built prior to 1969 had issues with the deck flexing - I suspect also that this was due to the decks not being coded.

Last question for now... How do I know where the boat would sit in the water in order to strike a new line? Also, should I make the cabin top level and then strike the water line parallel to that?

[Tim]

How do I know where the boat would sit in the water in order to strike a new line? Also, should I make the cabin top level and then strike the water line parallel to that?

You don't. And you don't want to guess without having some better information either.

Do you have reason to believe the current location is wrong? If not, you can use it as a reference point. All you need to strike a new and better line, whatever its location, are two accurate points: at the stem and the centerline of the stern waterplane.

[Case]

Remove the 2 x 4s and drill into the beam. There is wood in that beam under the 2 x 4s. It may be rotten and if this is the case, it needs to be replaced. The solution is to cut the entire beam out and grind away any remnants then glass in a new beam.

I'm not 100% certain but I think your Sea Sprite 23 is not a 1968 - more likely built before 1964. Pre 1964s have no coring in the decks like yours. But on the other hand, yours may have been custom built with no coring. There were lots of variations in the 1960s for Sea Sprite 23s so my information might be wrong...

- Case

[LazyGuy]

Froon,

One of the things that is consistent among Sea Sprites is that they are all different. My "guess" is that the reason for the two 2X4s is because the deck sagged when they tensioned the mast. Tim is right (as usual), the best way to fix it is to figure out what is wrong. Test drill into the bottom edge of both beams, before drilling into that aft beam (the one that is sistered) I would put on a rain hat. If it does rain, consider cutting the glass around the edges of the entire beam so that you can pull the entire beam down and out in one piece. If the stars are aligned and gods are smiling, the beam will come down with enough of its original shape to make a copy of the top edge. They are great boats that sail like a dream.

Silly as it may sound, you may not have a problem since you have solid decks. These things were club raced all over RI and Sea Sprites were known to have bad decks. Silly as it may sound, since even a little deflection in the mast step significantly affects speed and ability to point so it may have been installed as a preventative measure for a known design issue that you may have never had.

[The Froon]

Dennis, thanks for the comments. I fully believe the deck is not cored, but I will drill into the beam to make sure. Can you advise me on how deck flex / deflection can affect speed and/or the boat's ability to point?

Brian

[bhartley]

Looks like a pretty good repair to me... I would cut the ends off of the bolts and paint the support if they bother you -- and go sailing. This is a very standard repair on a Seasprite 23. The support beams are VERY structural and I can only assume based on the sistering that the old beam had split.

It is June. Go sailing!!!

The beam serves two purposes - the main one is to support the mast step and the second is to give you something to smash your head into when getting into the v-berth. Go sailing.

There are manly SS23's with a similar repair. It looks like they did a very functional job. Is your rigging short? It the deck concave? Since only one appears to be sistered, it looks like a precaution. The "lump" they have cut around is what really matters as this is the reinforcement for the mast step. If this is punky, you have a real problem. Otherwise, step the mast and go sailing.

The Seasprite 23 is an amazing boat to sail. They are beautiful to look at. Noone will ever care about getting in the v-berth and seeing this repair. Go sail.

I repeat. Go sail. If you have a need to make a change, do it in the fall. Go sail.

Bly
Another SS23 owner.

[The Froon]

Bhartley, thanks for the comments. I really wish that I could go sailing right now; however, I am determined to fully restore this Sea Sprite. I have a goal of being in the water this time next year. Plus, in FL you can sail year-round!

Would you have any pics that you could send me of your Sea Sprite? I would love to see your boat and get ideas fir mine. I need pics of the engine well especially. Jaxsurf@gmail.com

Thanks,

Brian

[bhartley]

Brian,

Pictures of Ariel

Here's a link to lots of pictures of Ariel. She is currently in the yard on her trailer awaiting the arrival of her six new chain plates. She's a 1973 Wickford-built hull so she may look a bit different than the earlier models. There's also a link to an assortment of random Sea Sprite cabin pictures (including one "don't let this happen to your mast step" photo).

Assorted pictures of Sea Sprite 23 Cabins...

It seems a 15 minute job to unbolt the existing sistered pieces and see what the problem is. If you do replace the original beam (each one on ours is two pieces sandwiched together), be darn good and sure you don't have rot in the wood under the mast step - and there IS wood under the mast step! You can easily drill a few test holes through the top skin. Once filled the mast step will cover them up. Ditto from below. The support beams are spreading the load of that one roughly 6" x 10" block of wood under the mast step. If the step is comprimised, the time to replace it is when the beams are off!

If you need a picture of something in particular, let me know and I can take one for you -- at least for a few more weeks before she gets wet.

Bly

[Figment]

Do not use a right angle grinder. Please.

Party pooper.

[The Froon]

Bly:

Thanks for the pics, and suggestions. I can't wait to finally put in her in the water!

Brian

[LazyGuy]

The affect of a soft mast step on sailing performance is simple. If the mast step sinks straight into the boat 3/8 " you effectively lengthen all the rigging 3/8" so the rig is no longer properly adjusted. Your mast is falling off to leeward, your jib luff is no longer properly tensioned and will fall off to leeward more than you want, and since your backstay is loose, if the jumper on the mast is adjusted properly, the top 3' of the mast is now bent forward (slightly). Everything I pointed out (except maybe the jumper) will hurt the pointing angle. Yes you can still sail that way but it would be tough to win a race.

Even if you properly adjust the rigging on the mooring, as sail pressure increases, the stresses on the rig will increase and the mast will be driven further into the mast step.

To quote Figment - "Damned because it is all connected"