The Re-core: materials

Figment · Post by **Figment** » Thu Jun 03, 2004 4:15 pm

As much as I would like to put the deck recore job off for another year, I really know I shouldn't.

I'm starting to put together a rough budget to do this over the coming winter. I'm coming up with a material cost of around $1200, which includes:

3gal, 3qts epoxy resin and hardener.
1gal silica
1gal microballoons
14 yards 55" dynel cloth
25 yards 6"x17oz biaxial tape
Misc. abrasives
1gallon primer
1gallon paint
6 4x8 sheets core material

gloves, mixing cups, sticks, spatulas, brushes, etc. are not included because I seem to have a lot of leftovers kicking around.

Have I omitted anything obvious from this list?
Are any of my quantities way off base?

I haven't decided on a core material yet, but I didn't find any huge cost swings between foam, balsa, or ply. I'd love to hear comments on this.

Indoor storage for the winter is an expense yet to be determined.

Post by **Tim** » Thu Jun 03, 2004 5:42 pm

If I were you, I would plan on buying your epoxy by the 5-gallon kit from the getgo. The unit cost is less, and you typically get more convenient containers and dispensing arrangements (at least with the 2:1 type like System Three or MAS). Even if by some miraculous chance you don't use it all immediately, it will always come in handy to have around. It's been so long since I did mine that I don't remember how much I actually used--and my project records weren't itemized (now I itemize every expense...). All I know is I kept buying more, gallon by gallon, thinking it would be enough...only to run out shortly thereafter. Stupid, that way.

Anyone with more recent experience--and detailed records--care to chime in with their epoxy usage?

From your list (specifically the 14 yards of 55" cloth), it looks as if you're planning on laminating a new top skin, rather than re-using the old skins? It takes plenty of resin to wet out this much material.

I understand from those who have used it that Nida-Core requires substantial amounts of resin to wet out the attached mat for bonding. Otherwise, it seems to be well-liked, and I would probably choose it myself the next time. Otherwise, I would use balsa, which I maintain is an excellent core material--IF properly installed.

With either product, it takes copious amounts of thickened resin to properly bed the core top and bottom (or bottom only, if you're laminating new over the top). Fairing a raw laminate smoothly also will require a fair amount of resin and thickeners...not to mention the inevitable waste when pots kick off before you're done, etc. These are the factors that make determining how much you need very difficult, but you need to allow for them regardless.

Other than the resin (and possibly filler) amounts, the list looks appropriate to me, give or take.

Dave, 397 · Post by **Dave, 397** » Thu Jun 03, 2004 7:22 pm

Using Nida core, and adding the miscellaneous solid glass reinforcements, I have consumed about 10 gallons to do the recore per se. 12 gallons to date, and just bought another 5. Hopefully the last 5 will get me thru most everything, I will also have used about 7 gallons of poly resin on the here-and-theres where I really needed the manipulability of poly and/or for laying up custom parts and the like.

Three sheets of Nida will probably do the boat if you think it out VERY carefully, but it's so cheap (I think I paid about 38.00 a sheet including tax) that it pays to get 4.

The big trick is just as Jeff describes from #30...wet out the skin, wet out the scrim on the Nida core, then use a notched spreader to apply a very-silica-thickened mixture to the skin, then slap core to skin or skin to core.

I guess Jeff did the whole shot at once, skin back down and all...but I am a bit chicken about that, had enough trouble with stuff wanting to gel putting down the foredeck skins. I ended up putting the core in, then the skin on in a second operation. Nida is not particularly flexible--definitely not like netback balsa or double-scored foam--so the placement of weight is very helpful (read essential) in clamping stuff down. Jeff had a bunch of brick, so he used that and I think if a guy had all those bricks it would be super ideal. Failing that, I used 12x12 blocking timbers from the yard in the places that I could (hard to use large stuff as the decks are one continuous curve) and then used 3 dozen plastic gallon milk jugs full of wet sand as well as a bunch of empty gallon bottompaint cans out of the dumpster that were also filled with sand and water. I'm not sure whether Nida is available double-scored or not, but if it is it would be well worth getting!

Best,
Dave

Post by **dasein668** » Thu Jun 03, 2004 9:08 pm

Dave et. al.

I requested a sample from Nida about a year ago or so. The sent me a whole stack of samples, including Nida laminated between Meranti, 18 oz glass, and formica.

Among those samples was a scored piece. Squares are 2" on a side. See below.

Figment · Post by **Figment** » Fri Jun 04, 2004 9:57 am

I'm going to TRY to reuse the top skins. I think that by the end of this season they'll be in pretty rough shape, though. I already had to quick-patch a 10" long fracture on the port side deck a couple of weeks ago.

The dynel is about cosmetics. I just love the look. My plan (vague and theoretic at the moment) is to reuse the existing topskins to the extent possible, fair as necessary, and then lay the dynel as a nonskid topcoat.

OK, so I drastically underbudgeted the epoxy. Figures, as I made the same mistake on the bulkhead project. I dig the idea of using the nida-core, but if it's such a sponge for resin.... I may go the plywood route. I gotta go back and read your recore writeup, Tim, you used plywood, right? Any challenges involved with getting it to take the camber of the deck?

Figment · Post by **Figment** » Fri Jun 04, 2004 2:33 pm

(Stupid question, but the $1500 price tag says I gotta ask it)

Would it be completely impractical to tackle this work without storing the boat indoors for the winter?

Thanks guys.

Post by **Tim** » Fri Jun 04, 2004 4:48 pm

Figment wrote:Would it be completely impractical to tackle this work without storing the boat indoors for the winter?

Impractical--yes. Absolutely.

But is it impossible? Well, no...if you're dedicated, work efficiently, and have some sort of shelter. You simply cannot do this job in a timely manner when at the mercy of all manner of inclement weather. If you can throw together a moderate A-frame thing, or whatever, you might have a chance. Haul out early, get to work in October. With luck, you can finish. I did mine starting in October and had it roughed out before winter. Final fairing and such only took place in the spring.

The way I see it, under these circumstances you pretty much have to blitz it--that is, start working, and don't stop till the job is basically done. If you do a weekend here, a weekend there, with all the associated delays caused by weather, temperature, other plans, etc...well, then we'll see you back in the water in 2006. You can't count on enough good, warm (epoxy temp) weather. The weather can turn cold early, or might not until Christmas.

Simply put: you cannot underestimate the time involved. This project cannot be banged out in a weekend or two (not that you thought it would be, but I must reinforce). Extra help for some of the work is OK, if you trust the workers. But this is not a project for no-nothings.

You'll be a lot happier indoors, and that might also give an opportunity to take care of some other things, too. Just because. Granted, the price is stiff.

Alternatively, you could move to the country and spend 2 months building a boat barn!

Post by **Tim** » Fri Jun 04, 2004 5:00 pm

Figment wrote:I dig the idea of using the nida-core, but if it's such a sponge for resin.... I may go the plywood route. I gotta go back and read your recore writeup, Tim, you used plywood, right? Any challenges involved with getting it to take the camber of the deck?

The plywood I used was free, and an ample supply came with the boat. This, along with the fact that the P.O. had recored one sidedeck with the stuff already, more or less forced the decision for plywood. I would not have used it otherwise. The material I used was 3/16" in thickness, so I used two layers; it was easy to conform to the deck curves as necessary.

Although I'm pleased with it to date, if I were doing the same project over again, knowing what I know now, I would choose balsa or Nida-Core. I really like balsa, frankly, and think that the problems so many people associate with it can be easily dealt with.

That is:

1. Bed the core in heavy layers of thickened epoxy. Original balsa cores in boats like ours were set in polyester-wetted mat--an absolute joke of a way to install it. No one knew better. It's the whole wood/epoxy-as-an-adhesive thing. Balsa, set in thickened epoxy, will stay put. It's easy to fill the kerfs in the scored core in this manner, also. Then, any replacement of topskins (or lamination of new) must also be done in epoxy, to ensure that wood-adhesive bond and secondary bonding strength. Done in this manner, that fiberglass will never debond from the core.

2. Eliminate core at all hardware penetrations. We all know how to do this. When recoring, you have the unique opportunity to really leave yourself nice buffers around each bolt, stanchion, etc. If the stuff that you remove is going back in the same place, then it's a cinch to leave the core out of these areas, and replace it with solid glass. If you're moving anything, it's worth it to carefully plan ahead. And, of course, there's always the overdrill-fill-redrill method if you miss a spot, or decide after the fact to change one location or another.

If you do these two things, the balsa will last beautifully, with all its benefits. High-end builders use balsa because of its excellent structural qualities. Doing things right take time; this equals cost, which most builders are unwilling to foot since the customer, not knowing any better, doesn't want to foot the cost either. So builders take shortcuts. You, with your free/negative labor, don't have this issue, so the only cost is time.

I refuse to join the "balsa is bad" crowd. It's actually excellent...but it does require careful and meticulous installation. That said, I'm also interested in the Nida-Core, but have not used it personally. Eventually I'll get around to a test panel or something.

The Good Goose · Post by **The Good Goose** » Mon Jun 07, 2004 7:43 pm

I believe I used about 13 gallons of epoxy for my recore including the cabin top. I used Nida core and would definately use it again. I faired with micro balloons and have had no problems. I would reccomend Mas epoxy It was what I used and I was very happy with it. I probably used 40 or fifty mixing containers I used paper food containers Clam chowder as I recall alot cheaper then paint containers. I used five gallon buckets filled with water to weight my skin down. Lots of them maybe 20 or so. where the skin was too skinny to set a bucket on I would set a block and a bucket on top of that. sand would be better then water in the buckets for sure. Make sure you have enough weight. It takes alot.

Hope this helps.
Brock Richardson

Figment · Post by **Figment** » Tue Jun 08, 2004 12:15 pm

13 Gallons!!! Yowza. Most of my cabintop is sound, so I hope I won't need that much. On the other hand.... if I'm going to be modifying my cockpit seats and stiffening the cockpit sole..... Curse that Other Hand!!

I think that the nida vs. balsa will come down to simple economics. I haven't yet found a really compelling reason to favor one over the other in terms of performance or workability.

Dave, you bought scored nidacore for $38/sheet? Thats a LOT less than the prices I'm finding. Care to share your source?

Dave, 397 · Post by **Dave, 397** » Tue Jun 08, 2004 12:54 pm

I bought PLAIN (unscored) Nida, which worked just fine, for about 38.00 a sheet from my local composites wholesaler. The company is a nationwide one, called Composites One...there might be an outlet near you. If not, the setup I worked will probably work for you, too.

Part one is that they didn't stock the material in the 10mm thickness, so they were ordering it in for me...I think that helped with the price.

Part two--and here is the big one...this place sells to huge boatbuilding and aircraft accounts, mainly, and do not actually have a retail or "walk-in" pricing structure. The price (which is the industrial user price) is the price with these guys, pretty much.

I found them by contacting the makers of the Nida core for a distributor near me, which was a lucky stroke as I have gained a good working relationship and much savings with these people over time.

One last word, though---most of the sales reps for these places are familiar with part numbers and prices, and expediting your order. Product knowlege is not usually a strong suit, and it doesn't need to be for that type business...so you need to go to the Mfrs. as needed for info, etc...and then have the part number of the materials, etc. that you want ready to go when you call up the wholesaler. Also helps to let 'em know, like when you walk in, that you have plenty of time and understand that the phone comes first.

Best,
Dave

The Good Goose · Post by **The Good Goose** » Tue Jun 08, 2004 9:14 pm

Composites one in Bristol R.I. was where I got my nida core.

Brock Richardson

Figment · Post by **Figment** » Wed Dec 08, 2004 9:40 pm

Now that I'm actually buying materials, I'm reading back into my materials list above.

At the moment, it occurs to me that 17oz. biax is probably overkill, and might even create a big hassle at fairing time. Would ordinary glass tape (generally lighter weight) be more appropriate?

Post by **Tim** » Thu Dec 09, 2004 7:36 am

I used 2 or 3 overlapping layers (I forget) of 10 oz. glass tape on the seams when I recored. The thickness buildup is much less than with biax. You'd have to grind out some pretty substantial areas to allow more than one layer of typical 17" oz. biax to remain flush. Some overlap--and ultimate removal during the fairing process--is inevitable.

More recently, I've had good luck working with the Gougeon Episize 15 oz. biax tape, which is quite smooth, wets out easily, and isn't overly thick since there's no mat on the back.

Figment · Post by **Figment** » Mon May 16, 2005 4:55 pm

(cross-posted from another thread. Seems relevant to future searches.)

jhenson wrote: Can you recommend the quantity of 2' X 4' balsa sheets one would need to do the lower decks. For that matter, any other comments on supply quantities for this job would also be appreciated.

hmmmmm. I can't seem to find my receipt from the core order, so I can't say for certain how many sheets I had when I started, but based on the space left in the box, I'd guess it at 6 2x4 sheets.

Other supply quantities....
40 yards of 4" biax tape. I have 5 yards or so left over.
Easily 8 gallons of epoxy.
Two 5quart tubs of silica thickener, three tubs of microballoons.
Two rolls of longboard paper.
Three 50-count boxes of 80grit discs

Adjust all of the above downward 10% or so if you're only doing the main deck. Also adjust as necessary to reflect the condition of your deck. Mine was in remarkably poor shape, and I had to do some "reconstructive" work to the bottom skins.

Figment · Post by **Figment** » Mon May 30, 2005 6:55 pm

Lesson learned: when ordering materials in advance, no matter how far in advance, always open the packages completely to see that the materials are as ordered. Little time-saver.

The big roll of dynel cloth that's been sitting on the floor in my office since December was opened today. It's carbon fiber.

GRRRRRRRR!!!!

Post by **Tim** » Mon May 30, 2005 7:05 pm

Gee, that sounds like kind of a costly error for the company that shipped it! Carbon must cost a lot more than dynel.

Figment · Post by **Figment** » Mon May 30, 2005 7:20 pm

eh, it all worked out for the best, I think.
It was a beautiful sunny day, which made for stifling heat in the shed, but that same weather also persuaded us to take a borrowed-dinghy ride down the river.
A much-needed day of waterborne relaxation.