The Core Project

[K.C. Walker]

I've decided to take on the project of putting a foam core in the bilge area of my DS 1. I know that it's a lot of work and probably more than what the boat is worth. However, with encouragement from Phill, who took on the task some 20 years ago and is still happy with the results, I thought I'd give it a go. Phill said that he has talked several people through this and that he would like to have a discussion on the forum for a more permanent record.

A good reason to do this is that it will make the hull stiffer and stronger than new without adding significant weight.

I came to this decision gradually by investigating some problems with my boat. I started out inquiring in August '08 on the forums here about what was a normal amount of flexibility for the fiberglass in the hull of this boat. I am not that familiar with Day Sailers so I wasn't sure if my hull was "tired" or whether the boats were generally built rather light and flimsy. Later I discovered the stringers on my boat were damaged and that the interior balsa wood core had rotted. I thought that would be the remedy. That is, I would just fix the stringers.

As is often the case with repair and restoration work, I found further problems after I got into the stringer repair. It turns out that the fiberglass in the hull had hydrolyzed from the continuous moisture in the stringer cavity. This problem most often manifests itself as gelcoat blisters. If you want to know more about this just Google gelcoat blisters and you'll find plenty of information. In the case of my boat, osmosis worked from within the stringers as well as from the boat having been on a mooring with the former owner. Basically what this does is breaks down the resin in the fiberglass matrix and leaves the laminate significantly weaker.

So, as I sanded down the area where the stringers were, I continued to discover deteriorated fiberglass. The fiberglass deterioration extended for about 2 inches each side of the stringer and where the stringer core was, a significant amount of the hull thickness. This appears as kind of milky white looking, rather than translucent looking fiberglass (you need to have the paint removed to be able to see this). And in my case which is rather advanced, there were also pockets of black stinky and gooey areas where the resin had broken down.

Fortunately, I was able to grind all of this out. And now I have about 10 hours of stringer removal + grinding time with 36 grit and I'm pretty close to ready to start re-laminating the inside of my boat. The hull is thin enough in areas that it's kind of scary, though. I drilled some holes through the hull to act as gauges so I wouldn't go all the way through.

I will first laminate some glass cloth as patches where most of the grinding happened then I will add the core and glass the top side of that.

KC

[K.C. Walker]

At the tail end of my thread regarding stringer repair http://forum.daysailer.org/forum/viewtopic.ph ... sc&start=0

Phill replied with this message.

Foam core, Great idea.

20 Years ago, I had a similar problem, altho my balsa wasnt totally wasted.

Since you have aleady removed the stringers (I left mine in place)......

I used Diviny-cell, Closed cell 2lb foam, prescored for easier shaping, 1/2" (wud use 5/8-3/4 if doin again), and foam cored the entire floor area of Lollipop, between the seats (seat removal would violate class rules, and make the hull perminately non-raceable). Under the cuddly I cored the floor to just above the waterline.
Complete old paint removed....miserable
40 grit sanding, to give good bonding tooth for resin.
Shaped 12x12 to 15/15" pieces of foam and "tiled" areas of the floor with the Divinycell. Used Polyester resin with fillers, micro ballons and wood dust to trowel on paste to fasten the tiles of foam to the floor.
After an area was tiled, one side bow to seat front edge for example, I then fiberglassed that area with chopped mat, 12oz i think. Then repeated above for other side of bow to front of seat tank.. Two layers of glass mat where crew would be stepping. Then repeated above for each side from seat front edge to CB rear edge. The rest of the floor to the stearn as one tiled area and glassed as a whole, again two layers of chopped mat whene stepping on would happen.

Took all winter in my tiny garage, Trailer tongue under my workbench, and transom 3" from garage door, starboard coaming against wall, and 15" of walk space on port side.

Hull properly stiff now.

Just one idea that takes awhile, but my DS was worth it.

phill

[K.C. Walker]

From a few PMs with Phill

If you want anymore info about my Coring project, I got the 'been there done that' blues, and would be happy to share my experiences. Just like explaining how to get a guitar neck angle set 'just right', It takes volumes of typing to address all the nuances.

He sent me some pictures of his core project that I have posted here. http://www.walkerguitars.com/photos/daysailer/index.htm

KC

[Baysailer]

I wonder if floorboards offer any flex fix? I know the floorboards play a role in the Rhodes 19 but there they are fixed in place with cross brace/ribs glassed into the hull. Oday used white oak for the ribs but newer jobs use glass/epoxy over closed cell foam. By the way I weighed my floorboards and they weighed 46#. I was surprised, I thought less. I've never sailed without the floorboards so I don't know how much my hull flexes. I don't have stringers so it may be a fair amount. I have stood in it on land snd there wasn't enough flex to worry me but I wasn't looking for it.

Fred

P.S. KC your guitars look like pieces of art but I'm sure form follows function. Excellent

[GreenLake]

This doesn't strictly belong here, but to answer Baysailer: I also don't have stringers and have not (yet) been bothered by the amount of flexing - could be because I've not been out in choppy conditions very much. Intrigued by the other thread, I've paid closer attention, and yes, I can feel some "give" - even with the floor boards in place. I
'm still trying to figure out whether this means I need some reinforcement or not, and if so, what. (Now back to K.C.'s core project).

[K.C. Walker]

I wonder if floorboards offer any flex fix? I know the floorboards play a role in the Rhodes 19 but there they are fixed in place with cross brace/ribs glassed into the hull. Oday used white oak for the ribs but newer jobs use glass/epoxy over closed cell foam. By the way I weighed my floorboards and they weighed 46#. I was surprised, I thought less. I've never sailed without the floorboards so I don't know how much my hull flexes. I don't have stringers so it may be a fair amount. I have stood in it on land snd there wasn't enough flex to worry me but I wasn't looking for it.

Fred

P.S. KC your guitars look like pieces of art but I'm sure form follows function. Excellent

Fred,

Interesting thoughts on the Rhodes 19. I would think that the glassed in ribs would certainly make a difference to the stiffness of the hull. I think that the floorboard in our DS1s only serve the purpose of keeping us from stepping on the hull and therefore spreading out the load. My hull was so flexible last summer that I could feel the hull bouncing my floorboards when I went over chop.

While walking around in my boat on the trailer, especially after I removed the stringers, it felt pretty spongy. Now that I have it ground down it feels scary spongy. It's scary enough that I've put down pieces of plywood to walk on. I really don't want to step through the hull!

Thanks for the kind words regarding my guitars!

KC

[Phill]

.KC Tks for starting this thread and posting my first pics. Great job.

Some random points.

I choose to use regular Polyester resin. Cost was the primary reason. I found a local fiberglass manufacturing company that would sell me fresh resin. Beware of hardware store resins, they may have surpassed thier best shelf life. In the end I think that the non-epoxy also may have kept the weight down also.

Because I used polyester resin, I was very concerned with getting a good bond, so read some of my processes with that in mind.

I found that the poly resin has the ability to somewhat soften the original poly layup from the factory. When wet sanding the bottom the following year, I had the grid pattern of the pre-scored foam, showing through the gelcoat on the outside of the hull. Very faint and only showed in a few small areas, but certianly caused by the resin curing and passing the square grid through the hull.

Another issue that I was careful of, when placing sandbags on the curing tiles of foam, I didnt use too much weight and cause a lump to pass through the hull.

If you choose to use Epoxy, most of the above issues will not affect your project.

With the above in mind, be very careful not to 'lock in' any mis-shappen hull areas that may be caused by trailer bunks or other aging. I used 4-5 2X4's cut to the approiate length and wedged them under the rub rail every few feet to take some of the weight off of the bunks. Be very carefull to keep the hull from twisting when doing this. The end product could very well keep the twist when the coreing locks in and stiffens the hull.

I left the stringers in mine, to also help maintain the original hull shape. ( this is a one-design )

After stripping out all the paint and sanding with 40 grit to give good 'tooth' for the resin to grip, I shaped each tile with a sanding block and about 100 grit paper to get a good fit with each edge.

When placing each tile permenatly, I followed the following process.
1. Cleaned the area with an acetone wipe ( use wisely anf follow good saftey practices )
2. Mixed a small batch of resin and pre-wet the area for the tile with just enough to get it covered, no exess.
3. Mixed trowling resin compound right after applying the pre-wet coat, adding the pre-wet excess to the mix. Compound contained West Systems 403 fibers and micro ballons. No real reciepe, just tried to get enough of the fibers to hold and carry the resin and maybe twice as much of the ballons to keep the compound as light as possible. Too much ballons, and you wont get a good bond. Too much fibers your project will come out a bit heavier. Tried to get the troweled resin paste to be thick enough to stand up and not sag too much before placing the foam piece on it.
4. Trowled the compound on the area to be tiled with a 1/4" V groved tileing trowel.
5 Placed the foam tile in place, weighted it with 10-15 pound sand or pea gravel bags.

Since I was doing this in a basiclly unheated garage in winter, I had a space heater under the current area helping to keep it slightly warm. I never aimed that heater directly at the area. The resin may have cured too fast, as it is thermothropic (sp), ie, it makes its own heat as the chemical process gels and sets.

Later after the cure or next day......repeat. ... ... ... ... ... ... ... ... ... ... ... ___ ...

This ends my first post of tips. More to follow. I dont want to make theese posts too long.

Please post any questions here, and I will answer them in the next post.

[K.C. Walker]

This doesn't strictly belong here, but to answer Baysailer: I also don't have stringers and have not (yet) been bothered by the amount of flexing - could be because I've not been out in choppy conditions very much. Intrigued by the other thread, I've paid closer attention, and yes, I can feel some "give" - even with the floor boards in place. I
'm still trying to figure out whether this means I need some reinforcement or not, and if so, what. (Now back to K.C.'s core project).

GreenLake,

I don't consider this off-topic. I'm still trying to figure out what the best of the DS1 hulls would've been like when they were new. I suppose I could take a trip to Cape Cod and go push on the bottom of a few new ones. I think the idea of glassed in ribs as Fred mentioned the Rhodes 19 have and also we discussed in the other thread, could work well for stiffening up the hull. It seems it would be a lot easier and less expensive to do, especially if you don't have stringers. I know that my other boat, a Lockley Newport Whitecap that's 19 feet long weighs in at about 725 pounds (when new), including its 125 pound centerboard, has a very stiff planing hull when compared to my DS.

In my situation, I am already into it pretty deep as a repair. Yes, the core will be somewhat expensive to do but I figure I'm already into the repair I might as well get an improvement out of my effort, which I believe the core will do. Theoretically, aside from getting more stiffness in the hull, a core helps a great deal with torsional strength. This counteracts the twisting of the hull when the mast is loaded in one direction and you are hiking out in the other direction, making the boat more efficient.

KC

[K.C. Walker]

Hey Phill, don't worry about being too wordy on this subject! I am lapping it up!

Although I only have about 10 hours of working time on the project so far, I'm not going to speculate how much time I've spent researching on the web (hey, it's better than TV). I think Google must be pretty worn out, though.

Here are some links to videos of people working on core composites. The 2 videos are on vastly different scales, though. http://www.youtube.com/watch?v=tODrifW6LQQ & http://www.wenonah.com/video/index.php

Thanks again for your thoughts and experience!

KC

[GreenLake]

I'm still trying to figure out what the best of the DS1 hulls would've been like when they were new.

This is getting me curious about the stringers. My DS is supposedly a '71. Were the stringers added because they changed something about the hull, or because the original hull had proven deficient?

..., the core will be somewhat expensive to do but I figure I'm already into the repair I might as well get an improvement out of my effort, which I believe the core will do. Theoretically, aside from getting more stiffness in the hull, a core helps a great deal with torsional strength. This counteracts the twisting of the hull when the mast is loaded in one direction and you are hiking out in the other direction, making the boat more efficient.

Given what you found (and removed) under your stringers, I can see your rationale for wanting to try a core. Looking foward to more of your write-up as the work's progressing, and, eventually, your "confessional" about your experiences with the "new" hull.

Can't wait.

[K.C. Walker]

GreenLake,

I find it interesting that some of the DS1 boats don't have stringers. I think that the Phill's boat is earlier than yours and mine is later and we both have stringers with the balsa core.

Yeah, I can't wait myself. I just hope I'm sailing by the end of June!

KC

[GreenLake]

According to the state registration '71 is the year with hull# 1404. Incidentally, there's no trace of a hull number or builder's plaque anywhere, that I can find). The floor's been painted, so it's not easy to get a clear picture, of whether there have been modifications.

What I can see, is that there's a single layer of fiberglass cloth that's been applied in a somewhat sloply manner on part of the floor and along the centerboard trunk. I'm thinking that this could be a repair attempt by a previous owner. If so, it would hide most/all traces of any stringers - if those had existed and were removed later at any point.

Can you confirm that the builders of these early hulls used mat and not cloth?

[K.C. Walker]

GreenLake,

I'm not sure what to make of your date and hull number information. Phill's boat is a '66 with a hull number of 2543 and mine is a 74 with a hull number of 7002. I think that the hull layup on all the boats is suppose to be the same, as that is part of the one design. They are laid up of both cloth and mat, roughly alternating. On the inside in the bilge area when I started to grind it down I saw more mat. I think that's because the top of the stringers and tabbing were mat. The hull forward of the seats is cloth on the inside lamination.

I added some more pictures to the gallery of Phill's boat. You can see pretty clearly the construction before he started coring. Mine is pretty similar. I do see some variations, though. I would say that the original work was reasonable, not sloppy.

In the pictures that Phill provided I can see that his stringers did not go to the transom. On my boat someone apparently decided that a floor area was weak and put in plywood stringers down the middle and continued the other 2 stringers on to the transom with plywood. They obviously installed these with the boats sitting on a trailer with bunks, because they were depressions from the outside in that area. When I removed those stringers the hull shape returned to normal.

Just as a point of interest as far as precision or sloppiness goes in construction of these boats. I was sighting my boat from the transom forward making sure I didn't have a twist in the hull before I start re-laminating. I noticed that the centerboard trunk and the mast don't line up. I thought this was a little strange so I started measuring. The mast opening in the deck is a half-inch to port and the centerboard is a half-inch to starboard. One thwart is an inch longer than the other one! And yes, I think this is all original. I didn't have any trouble balancing the boat last year, its sails fine. I guess it's just a little personality quirk. I understand that J-24s have some asymmetrical quirks, as well.

KC

[GreenLake]

I'll post infos on the date in a separate thread.

I double checked: there's a cloth layer innermost (topmost) in the front as you describe. In the back, it does not extend all the way to the tabs for the seats; in fact, it's about as wide as the area between and including the stringers.

There's a cloth draped around the lower back half of the centerboard trunk. That could be a repair, because its edges are very sloppy.

The inverted U channel for the mast support is missing the drainage holes visible in Phill's pictures, but looks otherwise the same (there's some reinforcement under the tabs for that channel as in his photos).

If that inner cloth is original, then there were no stringers. The floor boards are resting on supports that, while raised in the middle, would not have cleared any stringer profile of any substance.

[Phill]

Kim, very very nice work with the pics, Thank-you ! http://www.walkerguitars.com/photos/daysailer/index.htm
Wish I had known that removing the stringers in the aft area would reduce/remove the hollow hull shape in that area. Mine were 3/8" deep spanning about 3.5' forward from the transom. Sure would have saved me a bunch of filler and fairing.

Next installment of steps.

Forgotten tip..... Where I needed a bit of extra filler, spackling, I used Red Devil Ultra light spackling paste. Water based, mostly microballon (i think). Got this from friends when I was building RC Sailplanes. Obsure RC tip that I use in sailing. "Simplify, and ADD lightness."

I foam tiled the port side under the cuddy first, as shown in the first 4 photos. Thinking ahead, I didnt want to have to crawl around on the foam before glassing it. Keeping one side non-foam, resolved that problem under the cuddy.

After getting the foam laid from bow tank to front edge of seat, I stopped tileing, and glassed the port forward side:
I first used my foam shaping sanding block and rounded the top edges to get a softer shape for the glass mat to follow. I cant remember for sure, but I think I used 12 oz chopped mat. Appeared to be about 1/16" to 3/32"' before resin was applied. My thinking was that I wanted 'all direction' strength and I didnt like the idea of multiple layers of woven glass at counter posed layers. Too much work! When I glassed I tried to get as much of the mat as possible on the 'lips' of the bow tank, seats and keelson. I felt that may be where I would have delaminating trouble, if anywhere. And, I wanted to tie the coreing into the seat tanks for a complete unit of stiffness and not leave area to 'hinge' if stressed.

When I laid the glass I did it in smaller than whole areas. I planned the areas so that the next overlappling course would align with an area that I wanted the extra stiffness of an athwartship rib. If you study the pics, you can see where there is an extra dark yellow 3-4" striped running sideways. You can also find them in the white paint final pics.

I tried to use the least amout of resin to wet out the mat layup. A laminating bubble roller made especially for fiberglassing is necessary here. http://www.fiberglasssupply.com/Product ... tools.html
These may be found at high end auto paint supply locally. Lots of other good products on that site if you dont have a local fiberglass suppler.
With one of the above rollers you will be suprised how much you can spread the resin, if you are quick.

I used only one layer of the mat from the bow tank to the front of the CB trunk, except for the overlap/rib at the mast step. From about the CB front edge to about 18" aft of the CB trunk, I used two layers of mat. My thinking was lighter in the non-traffic areas, and extra where we stepped and dropped things. If to do over, I would do two layers everywhere aft of the cuddy edge. I've found that a dropped large bow hook or other metal object, bruises the glass, and probably compromises the layer.

After glassing the port forward side and getting a thin finish resin layer on it. Again, thinking to leave as much of the mat texture for non-skid texture... I started the whole process over on the starboard forward area. Only this time I had 1/2" less head room when working under the cuddy See pics for most questions..

Next installment....... how I added some extra stiffening at the keelson and CB trunk.

This may be worth about 2 bits.
phill