bending plywood

[Alan Peck]

I am getting ready to install the plywood on my plywood over sawn frames runabout.

I know that the forward end of the bottom panel is going to be difficult to bend.

I read that placing rags soaked in hot water will help in the bending process. I decided to experiement a little before trying the actual bottom panel. I took a scrap of Meranti plywood (marked BS 10888) and placed a towel over it. I then poured boiling water over the panel every five minutes for a total of twenty minutes.

The panel bent farily easily, but to my dismay, about a hour later I noticed that the plywood was delaminating!!! I was able to strip a couple of plys away with just my hands. Its pretty scary to think what would have happened if I had done that to the actual panel.

I assume that I must have done something wrong. Perhaps it was the use of boiling water (which I didn't think would be worse than steam) Should I have used hot water, i.e., not boiling? If so how hot can the water be so that the plywood does not delaminate?

Any advice would be most appreciated.

[NormMessinger]

Whoa! Somewhere in this forum has been posted a URL to the 1088 specifications. I think you got plywood that was falsely stamped 1088. If you confirm this would you care to tell us from whom you purchased it?

--Norm

[Alan Peck]

Norm, I am not sure of the origin of this particular plywood. I'll try to find out and will post the information.

Thinking some more about the problem, the test piece I used was only four inches wide. This meant that the edges of the plywood were exposed to the boiling water, not just the surface. I don't know if that makes a difference or not. I really don't think that should matter.

[Ian McColgin]

I think endgrain exposure is a huge problem. Where I've had nasty bending problems, I've been able to go to thinner plywood and a couple of layers. Even so, if there's an undetected void in the inside lams, it may fail as you bend. It's the way of life.

G'luck

[Keith Wilson]

Yikes!! Now that's a scary one. What kind of "BS 1088" plywood was it? It sure doesn't seem like it's genuine. NO decent plywood, even scruffy ACX fir from Home Depot, should delaminate with a little boiling water. I've been using Malaysian BS1088 6mm Meranti myself, lovely stuff and not too expensive, but I'm going to go home and boil a few scraps (OTOH, maybe I don't really want to know http://www.contrabandent.com/pez1/cwm/cwm/uhoh3.gif )

[Nicholas Carey]

Originally posted by Alan Peck:
[B]I took a scrap of Meranti plywood (marked BS 10888) and placed a towel over it. I then poured boiling water over the panel every five minutes for a total of twenty minutes. [tale of Woe and Intrigure regarding plywood reverting to a stack of veneer followed][B]

Well...if it was actually BS1088 certified, it shouldn't have. BS 1088 plywood must pass a stringent 72-hour boil test.

You might want to see this recent posting in this forum:

http://media5.hypernet.com/~dick/ubb/Forum4/HTML/000816.html

regarding Lloyds type approval for marine plywood, especially since BS 1088 is supposed to be (or is already) withdrawn.

[George Roberts]

Pouring boiling water over a panel is not identical to the boiling test. I don't know what the actual test is, but you need to follow the actual directions before making a claim that the material is not BS 1088.

[gert]

I microwaved in boiling water a piece of Accume 1088 3/8 ply for a full 20 min. There was no change whatsoever to the plywood.

[G. Schollmeier]

Alan,
Was the Meranti you had trouble with from the samples I sent you. My tests(boil,soak overnight, freeze, and left in the sun for a week) show no sign of delam. Maybe not from same sheet but from same lot. http://media5.hypernet.com/~dick/ubb/eek.gif
Gary

[Alan Peck]

Gary, yes it was. The material looked excellent and you had no trouble. So I am really confused. I think I'll do some more experiments and see what, if anything, I can figure out. I'll keep you posted.

[Eb]

Someone correct me if I'm wrong but I understand that there is a very limited number of plywood factories worldwide that are certified by Lloyds to produce BS1088 plywood, and those that do sell it at a very high price.

I have in my garage sheets of $30 plywood that have red ink stamps claiming BS1088 certification. I'll try and scan the stamping which looks homemade, very crude. I know this plywood cannot be the "real stuff" at $30 per sheet. However, I have boiled small pieces, 2" x 3" for several hours then left them out in the CA sun for months without any delamination, checking, shrinking or swelling, so I use it.

Does anyone know what a Lloyds BS1088 stamp looks like?

Eb

[Nicholas Carey]

Originally posted by Eb:
Someone correct me if I'm wrong but I understand that there is a very limited number of plywood factories worldwide that are certified by Lloyds to produce BS1088 plywood, and those that do sell it at a very high price.

Right you are. But Lloyds doesn't grant the right to manufacture BS1088. BS1088 is [was] a Standard issued by the British Standards Institute (BSI -- http://www.bsi-global.org ). Anybody can pony up the cash for a copy of the Standard[1] and manufacture product that satisifies it. Certification is another matter. If you want to display the BSI Kitemark

http://www.bsi-global.com//Kitemark/images/kitemark.gif

which is a hallmark of quality and standards compliance (All applicable standard numbers -- #### -- should be in "close proximity" to the kitemark) as BSI is rather, er, aggressive about defending it.

You can be pretty well assured that anything bearing the kitemark meets or exceeds the standards it claims to meet. BSI Certification is part of the process[2] you have to go through to get the right to use the Kitemark. BSI conducts follow-up audits (ISO 9000 is a part of the mix) to ensure that quality is on-going. They will pull the kitemark licence for failed quality audits.

Of course, there is a small chance that the manufacturer is simply using it w/o authority and BSI just hasn't gotten around quite yet to dragging them into court for misuse/dilution of the trademark http://media5.hypernet.com/~dick/ubb/wink.gif

Lloyds Register, on the other hand, issues [B]type approval certificates for lots of different marine items -- plywood is just one of them.

"Lloyds type approved" means that Lloyds Register has certified it as meeting the applicable Lloyds Register's Rules and Regulations. You can buy them online too at http://www.lr.org/publications/index.html

The link I posted earlier will give you (just enter 'plywood' into the search engine) a list of Lloyds type-approved plywood manufacturers, with some information on what standards it meets.

[1] You can too. Go to the BSI catalog web site at http://bsonline.techindex.co.uk and search for BS 1088. Here's the information you get:

Standard Number: BS 1088 & 4079:1966
Title: Specifications for plywood for marine craft
Abstract: Comprising 1088: Marine plywood manufactured from selected untreated tropical hardwoods. Species of timber, quality of veneers, jointing, lay-up of plies, bonding, defects and marking; gives illustrations of the various bond qualities of plywood. 4079: Plywood made for marine use and treated against attack by fungi or marine borers. Covers cases where the risk of attack by fungi or marine borers is more severe than untreated timbers will withstand; gives a range of appropriate preservatives.
Availability: Electronic (text only when in subscription) and Hardcopy (includes text and materials that cannot be delivered electronically)
Subscription Modules: GBM29 (Shipbuilding & Marine Structures), GBM42 (Wood Technology), GBM55 (Trading Standards)
Status: Current, Work In Hand, Confirmed
Publication Date: 30 November 1966
Confirmed On: 15 December 1988

UKP 33.00 (BSI members)
UKP 66.00 (non-members)

It's expensive because that's how standards organizations like ANSI, ISO, BSI, etc. fund themselves.

[2] The Process:
http://www.bsi-global.com//Kitemark/images/kitemk_apply.gif

[ken mcclure]

Ok. Here's a followup question, then. Does BSI provide a written certification in addition to allowing the manufacturer to use the kite?

If so, would it not be prudent to ask a manufacturer about whom you are unsure to produce a copy of that written certification?

Part 2 of this question is, would BSI maintain a list of manufacturers who are certified, and can the public ask BSI if a given manufacturer is on that list?

I have seen more than a couple plywood manufacturers make claims that their products "meet or exceed the BS1088 standard" and, having lived part of my life in Missouri, would like to have the proof.

[G. Schollmeier]

The stock involved here is 9 mm, 7 ply, Meranti, with a 1088 stamp on it. The stamp was on one of the pieces that I sent to Alan. It had good color and grain and I found no voids in it. The shade tree tests I did showed no delam. I have never tried to bend this stuff when it's still hot. I have some scraps I think are from the same sheet and will do more tests today. Most of that sheet is the bottom of a boat right now and this concerns me. The supplier I use has been
around for years, they specialize in wood sheet stock, I will be talking to them
also. Thanks for bringing this up Alan.
Gary

[Alan Peck]

Gary: Don't get too concerned about the Meranti you sent me. I ran another test last night. I boiled a sample for twenty minutes and found no signs of delamination or other problems.

I re-examined the piece that I had tested with hot water just on the surface and I think that perhaps it did not actually delaminate.
A careful examination seems to indicate that the wood actually pulled apart between the seams and that the glue line did not fail.
I am beginning to think that I simply overstressed the plywood by trying to bend it too much and too quickly. I'll try another test with the hot water and towel method and this time I'll be sure not to try to bend it in too tight a radius. I'll let you know how it goes.

Sorry for any confusion.

[Nicholas Carey]

kwmcclure said, in essence:
I'm from Missouri; you've got to show me.

If you go to the BSI web site and rummage around there is an online list of license holders as well as a search engine for it.

I'm sure there is documentation regarding all this certification, but good luck trying to see a copy of it (unless you're going to be buying plywood by the container load.)

[jeff pierce]

Just thought you might want to hear from someone who used the method on a similar boat.

I used the boiling water over the towel method to bend the bottom forward planks on my 16' runabout. I used marine fir ply, 3/8 thick. I had no delam problems, but you are right about being difficult to bend.

The hot water does help, but I found I had to make the bends gradually. A tremendous amount of force was required, and had to be maintained.

I ended up using through screws to attach a temporary wooden block to the inside of the forward end of the planking piece. I attached an eyebolt through the wooden block. I then used a come-along between the eyebolt and part of the building form on the floor. My process was to apply the hot water treatment, then after 15 minutes or so, winch the plank down some, then let sit overnight. Next day I would repeat. Took about 4 days to draw the plank down to the chines all the way forward. Once it was fully bent and sat for a day, I removed the plank in order to apply epoxy. The plank kept a good deal of its bend when removed. I then applied the epoxy, reattached the plank at the aft end, cranked it back down (this time all in one shot) and screwed it to the frame all around.

Not saying I'm any kind of expert, but hope you find this useful.

For what its worth, if you decide it really did delaminate, there's something wrong with it and you'd better buy a new batch.

[ken mcclure]

Thanx, nicholasc. Exactly what I needed!

Ken

[Alan Peck]

Jeff: Thanks for the suggestion on a bending method. Sounds like a great way to proceed. I used a similar method to bend the chine and shear battens.

Alan

[Keith Wilson]

Well, I boiled a scrap of my BS1088 Meranti for an hour or so, then left it in the water overnight. Sure was soggy, but it didn't delaminate. I guess the boat won't fall apart for a while yet. Great relief!

[G. Schollmeier]

More tests and same results. Boil, soak, freeze, and left to dry in the sun. No delam after 5 cycles. Of some interest is that I also put a strip of 1/2" BCX pine in the pot. It has some nice bends and twists but no delam. The meranti stayed straight except for some that I bent. Once dried the bend held without to much spring back. When forced into a tight bend the meranti fractured very easy.
The meranti remained stable thru a wide range of abuse. That is what makes it a great boat building plywood. If protected from rot a boat made from it should last a long time.
Gary http://media5.hypernet.com/~dick/ubb/smile.gif