Reuse or replace outer skin after recoring

[crufone]

Some folks have told me to remove the entire foredeck skin in one piece prior to removing and replacing the rotten core material. The idea being that you can perserve the non-skid and can save on materials. The boat is a Typhoon and the entire foredeck is about 35 sq.ft.
If I can get the skin off in one piece how easy is it to readhear to the new core without getting any voids between the two? If there are some buckles in the original skin can they be flattened with heat and weights? My thoughts are that while it might be a cleaver time/materials saver to reuse the original skin better adhesion would be achieved with a new lay up of matt and cloth............but I don't know having never done this before.
I certainly can use the intact original skin as a pattern for the new non-skid if I don't reuse the skin.
From those who have done much of this work please respond. Thank you,
Michael #161

[Case]

I've never recored myself. But I've been reading for a long time. A very long time...

Apparently, you don't really save time (or money) reusing the old skins. Often, it takes more time to reuse the old skins and getting a good result compared to doing a brand new layup. I'll let others with actual experience chime in.

- Case

[jeffwagnpete]

This is what happend to me when I was taking off the top skin on deck. Don't laugh at this photo people, this was when I had no clue of what I was doing. Most of my deck was rotted; however, in a few spots there was no rot and look what happend, ripped off the bottom skin, so, I decided to work from inside the galley, I decided to tear off the entire bottom skin to remove the rotted balsa core, had to ripp out the old bulkheads, alot of people told me that is was a difficult procedure, but I still made it through with determination, I cut away the entire bottom skin with an angle grinder and a universal cutting wheel and removed the entire balsa core with a heavy hammer and a heavy chizzle, I now have a beautiful top deck with some pretty expensive core material, and my new deck looks really good, I used floor jacks and shims to get back to shape, the core material I used was stuff that when heat was applied to it, it would conform to the shape, so I know there aren't any voids, its sealed up pretty tight now. I used sheets of paper to outline from the top deck before I actually was cutting the shapes of the expensive core material, I applied the matting on top of the new core material and put into place and floorjacked it up. Sounds pretty confusing, but there are alot of ways to skin a cat. My motto is, just do it. I was unfamiliar with this territory as well, but after doing this, I feel like a veteran now. I also had the help of a 30 year boat builder veteran who gave me tips on this, and would come out to check on my work, good man he is.

[jeffwagnpete]

Oh, forgot to add, make sure you are fully covered, I mean fully covered, head to toe, use rubber bands around the neck to secure the sock on the head, so no glass particals get in the neck area, I hate fine glass particals. I did this in 90 degree heat and and humidity, I lost about 15 pounds of weight, so, buy yourself mass 1000 powder shakes and drink alot of those, cause your going to need the energy to do this, definately not an easy task this was. If you want to know how I created the layers of glass to cover that large hole in the above photo, just let me know and I'll tell you, cause that's a different area of art. But there are products out there to add the layers of thickness needed. Fiberglass is amazing stuff. But you can do it!! I have confidence in you!

[Tim]

I've done it both ways. In multiple recoring efforts, I have only reused skins once and will never do so again. It's a false economy and can lead to issues throughout the process as well. Use all epoxy resin and plan on new skins. (Or don't, but that's my suggestion.)

Things to consider about re-using old skins:

• It's time-consuming to prepare the old skins for re-use;
  
  Removing the old skins in sound, re-usable pieces is often harder than easier, and can be time-consuming at best and impossible at worst;
  
  You still have to grind, taper, and tab all the cut seams, plenty of work in and of itself;
  
  You still need a lot of epoxy to secure the old top skin in place over the new core. Not using enough epoxy to secure the old top skin will lead to voids and poor adhesion and you'll be right back where you started. At best, it's an inexact process.
  
  "Saving" the old nonskid pattern on the old skins is often not feasible given the destructive nature of skin removal and the requirement to grind, taper, and tab all the seams, unless you don't mind the obvious appearance of a patch (I mind very much, but not everyone cares about appearance);
  
  Despite best efforts, even using the same thickness of core beneath an old skin often causes the old skin, when reapplied, to stand proud of the adjacent areas.

Laminating new skins over a deck recore is a fairly straightforward fiberglass project and ought to be within the realm of anyone undertaking a recore job in the first place (which really isn't a beginner's job). The new skins cost money in terms of fiberglass and epoxy, but that's the way it is, and you need these materials to reuse the old skins anyway. I don't know what the net difference in cost might be, but it's not a backbreaker in any case and represents the cost of doing the project. The worst mistake one can make is anticipating that doing jobs oneself is necessarily inexpensive. Doing a good job at any task is almost never inexpensive.

[crufone]

Tim,
I was hoping that you might chime in. I believe that the non-skid on the Typhoon is just built up of layers of paint, it definately does not have any pattern. Surrounding the non-skid area is a border of flat surface about 3" wide. In the middle of this flat area is where I was planning to make the cut through the outer skin. This would provide me with a 3" wide space to make the joint repair for the replaced skin or a new lay up WITHOUT affecting any of the non-skid area. If I shore up from underneath I feel that I can remove the entire foredeck, about 35 sq ft. at one time.
I have salvaged from a closed down boat yard some sheets of what I believe to be coring material. They measure 32" by 65-1/2" and look to be polyurethane foam. Which coring material is better Balsa or Urethane Foam? The foam sheets are not serated and have no scrim backing.The West system booklet on "Fiberglass Boat Repair and Maintenance" does not suggest an alternate matt/cloth lay up for skin repair. Tim what is your take on this? I have heard that the best results are achieved from alternating glass matt and woven cloth. I assume that the matt should be the first new layer over the new core and then the cloth on top?
Michael

[Tim]

Mat and roving is old technology. It works, but don't bother. it's labor-intensive, creates a rough surface, and a very resin-rich laminate (i.e. weak for its weight).

Today, we have stitched fabrics that incorporate the mat right into the backing, such as 1708 biaxial cloth (45°x45°), 1808 biaxial (0°x90°), and numerous weights and variations thereunto. It's easy to use, though harder to wet out than woven cloth. 45° biax, like 1708, is a good choice for repair because both sets of fibers will span the seam for good strength; a 90° fabric will tend to have one set of fibers paralleling the joint, thereby adding no strength to such a bonding situation. This is why this material is so widely used for the sorts of repairs you read about here and elsewhere.

1708 biax is widely available, relatively inexpensive, and a good all-around choice for many boat repairs. One layer of 1708 biax set in epoxy resin equals about 3/32" thickness, so use that to figure how many layers you might need to approximate the existing thickness of your top skin laminate. Probably 2-3 layers only. When properly wet out, these materials tend to provide a much more favorable fiber-resin ratio,

I stand firmly by my earlier recommendation to laminate a new top skin. Either way, it might be possible to incorporate your new seam into an area that can be easily repainted/patched, though depending on the situation it might require you to "cheat" down the width of your bonding taper between the new and old material to ensure the overlap remains within the area you hope. You'll have to determine whether this is something you want to do or not. But I consider anything other than the smallest, isolated recore job to be a call for new deck paint, given the generally invasive and extensive nature of the repairs, so keep this in mind as you prepare your repair plan. It may not be feasible--nor desirable--to avoid a more significant repainting project.

[crufone]

Thanks for the reference to the #1708 biaxial cloth. What are your thoughts about the use of foam coring vs balsa. I may have some foam coring to use for this job. If I am to recore only portions of the deck should I not mix different coring materials on the same deck section? Perhaps it really doesn't matter if all is resined properly together.
I don't have the boat apart yet but tapped with a hammer and only about 30% of the foredeck sounds bad. I assume this will grow to about 50%, and if that is the case perhaps I shouldn't make more work and rip the entire foredeck off to inspect the core. It looks like most on this list only recore the bad areas piecemeal.
Your comments have been very enlightening. No sense of me to reinvent the wheel here and make the same mistakes others have in doing this work.
If I don't bother to reuse the original deck skin then I can put the non-skid back on where I think it makes the most sense. I plan to more the forward mooring cleat forward a bit to allow the installation of an opening hatch for ventilation in the future. Although the poor installation of a 4" round port forward of the cuddy has caused it's share of rotten deck coring!!
Anyway I would really like to hear some comments on using foam sheet coring versus balsa coring.
Michael #161

[bigd14]

I did this project last summer. I was surprised at how much core was wet, but still firmly attached to top and bottom skin. I think there was an area about the size of my hand that was dry. There was no way to preserve the top skin, so I just left a bit on the center line to serve as a reference point and rebuilt it. Not too bad all in all, although bubbles due to rising temps were my nemesis. I was happy with the balsa core. I imagine it would be a real pain to score the foam you have. With the balsa it draped nicely over the curves. One thing I would do differently is add a little milled fiberglass into my thickened epoxy mix along the middle of the foredeck, since there were a few ominous cracks when I first set foot on it. In fact, if I were doing it all over again, I would add a touch of milled fiberglass into a lot of my thickened epoxy mixes to avoid it being too brittle.

Good luck and keep us posted on your progress.

Doug

[Tim]

You can use unscored core for deck areas, but be aware that the sheets won't conform as naturally to the curvature of the deck mold, and you may require additional efforts to ensure that the core is thoroughly and well bonded in all areas.

Balsa is a good core material--it has some of the best physical properties of any core material, and is inexpensive and easy to use It has received an undeserved bad rap because of poor installation practice over the years, but it's not the core's fault. Foam is not a magic bullet to end future core problems, but there are several foam products that make good core. Before you use the foam you say you have available, find out what kind of foam it is.

[Quetzalsailor]

I did my little, but miserable, cockpit floor recore from underneath, and with a new skin. Lying on my back, under the cockpit, wearing contractor's trash bags. New core and skin pre-prepared, bonded with filled epoxy, and of course, tabbed in.

A friend of mine, who was then professionally employed, reused his dad's skin, from underneath, and vacuum-bagged in place. This was a whole cruising boat foredeck. Must have been awful!

I'll do my work on Q from above and will be supplying new skin and non-skid. It won't be a recore, but a localized series of repairs.

[Rachel]

A friend of mine, who was then professionally employed, reused his dad's skin, from underneath, and vacuum-bagged in place.... Must have been awful!

Especially for the dad.

[Quetzalsailor]

Not his dad's whole skin, just his foredeck skin.