Formula 27PC Transom Work

[alldodge]

Start looking for plywood the other day and came up with exterior BC plywood. In WOG's thread it mentions Aruaco Plywood and MDO. The Aruaco comes out to be ACX exterior plywood. The ACX tells me it has one side which is grade A, one side grade C, and the middle being grade X. MDO is exterior grade and is the first choice of sign painters, but it does need the edges sealed to keep from water penetrating.

That said all the plywood I use will have edges sealed with resin. The BC looks to be a better option then the ACX because it is grade B on both sides, and grade C on the inside layers. Did I miss something in the translation?

 

[Arawak]

Number of plies is also an important consideration. More plies the better. I have had good luck with the fir G1S (ACX) at Home Depot here in Canada, but I look through the stacks. Last boat project I did, I found a stack that had a run of several sheets with very few void on the edges.

Here's two layers of 3/4" from that batch:

 

[Woodonglass]

Yup you missed the fact that standard ACX Will have more interior VOIDs in the laminates where as the Arauco brand has almost none. The X also means that the plywood uses Exterior rated 100% waterproof glue for it's laminations. ACX uses a Better Grade of Veneer wood than the BCX does. Not by much but a little. Plywood Lams are graded with A being the best and then B, C, and D. The aruaco also has 7 veneers whereas a lot of the others only have 5. All Plywood require their edges to be sealed in the marine environment and ALL plywood should be encapsulated with resin. Even the most exotic High Dollar Marine plywoods will rot over time with long term exposure to the elements if left unsealed.

 

[alldodge]

Yup you missed the fact that standard ACX Will have more interior VOIDs in the laminates where as the Arauco brand has almost none. The X also means that the plywood uses Exterior rated 100% waterproof glue for it's laminations. ACX uses a Better Grade of Veneer wood than the BCX does. Not by much but a little. Plywood Lams are graded with A being the best and then B, C, and D. The aruaco also has 7 veneers whereas a lot of the others only have 5. All Plywood require their edges to be sealed in the marine environment and ALL plywood should be encapsulated with resin. Even the most exotic High Dollar Marine plywoods will rot over time with long term exposure to the elements if left unsealed.

Ah Nope didn't miss that part. I read up on plywood and their rating system. Googled arauco plywood and found it being listed as ACX, which told me the interior plys of the wood is X rated and has more voids. So BC exterior exposure 1 plywood is the face is grade B and the other side as well as the interior is grade C. BCX is grade X on the inside layers which has more voids
Arauco ACX Plywood
http://www.magers.org/handy/plywood_grades.html
Plywood Grade

 

[Arawak]

AllDodge, the X means it uses exterior glue. Don't think there is such a thing as grade X ply.

 

[alldodge]

AllDodge, the X means it uses exterior glue. Don't think there is such a thing as grade X ply.

Not from what I have found, click on my link above.

 

[Arawak]

You may be right, but I don't see it in the link you posted. In fact every reference I can find states that ACX is A/C plywood with an exterior rating. For example.

But in any case, with regards to MDO, lots of people have used it with good success. It's also used in concrete forming due to high strength and the finish. I think weight is the only drawback.

 

[Woodonglass]

Not sure where you got your info but...I've been working wood for 40 years...

Plywood 101.

A,B,C.& D refers to the Quality of the veneers. "A"- being the Best "D"- being the worst. X refers to Exterior or EXPOSURE rated. This means the glues used are rated for Exposure to the elements and it also means the types of wood used have a better rating for exposure i.e. douglas fir etc.. Pressure Treated is really good for exterior use but it creates all sorts of issues for the boat builder due to the chemicals and the "Wetness" of the wood.

Here's the link to the APA (American Plywood Association) Plywood Rating site...

http://www.globalwood.org/tech/tech_...wood_grade.htm

What does the "X" in Plywood Rating really mean...



These two links will clear it up for you!!!

 

[alldodge]

Well kind-of sort-of maybe kind of thing. I have read though those links some time ago along with the ones I posted (in my previous post) and others. Agree I want exterior grade plywood and not exposer 1 or 2. I sent an email to APA for clarification and I'm sure your correct having all the years involved in this issue, but I have to verify,no offence, it's just my nature. What ever I find out I'll post

 

[Woodonglass]

Yup, the "X" rated Plywood sold @ HD and Lowe's means that it's using 100% waterproof glue and it's the stuff you want to use. I Really think you're "Overthinking" this whole thing. This topic has been dicussed and exorcised hundreds of times here on the forum and the Aruaco and the ACX plywoods from Home Depot and Lowe's have been successfully used in Hundreds of restorations. I had a major discussion with a member a couple of years ago on the MDO plywood and he called the APA and spoke with them for an hour to verify that it indeed was A-OK for using in boats. I have some PDF file info on that if you want it.

 

[alldodge]

You were right WOG, got an email from APA is morning and X is exterior as you said. So looks like Wikipedia and a couple other sights are in error. They sent me the plywood spec and it list marine grade as A-A, A-B, B-B, HDO and MDO made from Douglas Fir and Western Larch.

As you saw I'm sure I can get by with ACX due to sealing all sides with resin and glass.

I'm leaning away from using high density foam because I'm nervous enough using wood, but tpenfield has brought up some good info on it. Wouldn't use it for the transom, but stringers and other surfaces may be doable.

 

[Arawak]

Another thing to note is that there is a common misconception that a property of marine plywood is rot resistance. In fact, except for marine grade fir plywood (and treated panels like Greenwood's XL fir ply) tropical marine plywoods often have rather poor rot resistance. Point being that no matter what grade of untreated plywood you use, it needs sealing.

High density foam will be very pricey, and not really bring you any value for the kinds of boats we are rebuilding. Check out Joel Shine's rebuild using foam - it's pretty cool.

My recommendation is a good sheet of whatever exterior plywood is accessible to you, with as few voids as possible. The approach is proven and well supported by the folks here and elsewhere you have done it. Your rebuild will be far superior to the original.

 

[alldodge]

Anyone know the shelf life of VE resin? The VE is said to be close to epoxy and epoxy has a 5 year shelf life. Polyester has only a year

Been working on a list of stuff I need to get. Already picked up the safety equipment, and also have paddles, mixing bowls and cups. Figuring I'll have 3 sheets of plywood and will install at least half. It would be easier to get precut 4 and 8 inch mat but could also just cut it my self.

50 inch x 25 yards1.5 oz CSM
50 inch x 25 yards 2.0 oz CSM

10 gal VE Resin includes 12 oz MEPK
16 oz extra MEPK
5 gal Acetone
10 lb bag 1/4 inch chopped strand
4 lb talc

3/8 corner roller
3/8 x 4 roller
20 roller heads
Several brushes

8 cu ft 4 lb density foam (2 each 16 lb kits)

 

[Arawak]

Anyone know the shelf life of VE resin? The VE is said to be close to epoxy and epoxy has a 5 year shelf life. Polyester has only a year

VE has the shortest shelf life of the three.

 

[Woodonglass]

Uhmm this^^^ is not actually the case. If you research all the MFG;s of resin you'll find that VE is about the same as Poly. Most MFG's state that it's shelf life is 90 days but...if stored in cool dry conditions it usually will keep for up to a year or more. MEKP is usually the thing that goes bad first but even it can keep for up to a year. Poly is just about the same. Epoxy DOES usually have the longest shelf life of ALL.

 

[Arawak]

All of the promoted VE resins I've seen have very short shelf lives. Is unpromoted VE resin generally available to consumers?

 

[Woodonglass]

FiberGlast, Tap Plastics, USComposites and Most all the Other Major Retailers of VE advertise the shelf life @ 3 months. And as I stated they do so to be on the "Safe"side. If kept cool and dry it WILL last much longer.

 

[tpenfield]

Get the VE resin, shelf life won't matter, since you will be using it pretty much right away.

Seems like a lot of CSM and no 1708 or 1808 cloth. :noidea: I would think that you will need a fair amount of 1708. 25 yards of 2 types of cloth seems like way too much.

I'd be ordering about:

8-10 yds of 1708
6-8 yds of 2.0 oz CSM

You won't really need much, if any 1/4" chopped strand or talc, since you probably should not bed the stringers to the hull, as Formula does not. Match the existing construction as much as possible. (I used a small amount of peanut butter to fill the mating edges of the repair work. So, I just cut up some CSM for the amount needed)

I used on my bulkhead and mid-cabin floor repair on my Formula 330 the cloth that I had left over from my F-242 repair and building my 8 foot pram boat (2 projects)

It was approx:

3 yds 50" wide 1708
2 yds 24 oz WR
5 yds 2 oz CSM

4 gallons VE (bought new)

Your project would be a bit more than mine . . . maybe 50% more or double.

Probably used 1 gallon of acetone.

The CSM cloth is useful in encasing the plywood, but the 1708 does the job of holding things together. I coated both sides and lower edges of the plywood pieces for the bulkhead, the mid-cabin ribs and the floor, so they would not want to collect moisture.

Just my thoughts, based on my F-330 repairs.

 

[rickryder]

AllDodge This is the plywood I used for my rebuild.... Underlayment plywood....has almost no voids in the core and very strong

http://www.roseburg.com/Product/ridg...-underlayment/

specs

• Lengths: 8?, 9', 10'
• Widths: 4?, 5'
• Thicknesses: 11/32??- 1-1/8"
• Grades: APA ? PS 1 standards
• Face: Western softwood (typically Douglas fir) veneer that has been touch sanded. It has limited pitch pockets, open splits and other open characteristics but these do not compromise the strength and durability of the panel.
• Core substrate: Multi-layers of thin wood (veneer) in alternating wood grain directions, which increases the strength and stiffness of this finished panel.
• Back: Douglas fir or white wood veneer that provides excellent strength and durability and balances the panel to reduce warping.
• Adhesive: NAUF exterior, fully water resistant phenolic glue

 

[tpenfield]

my boat uses the Roseburg plywood too . . . Here is a picture of the Starboard stringer showing the Roseburg imprint.