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Lumpy plywood
I have been restoring a plywood boat approx 20yrs old & have noticed a
ridge in one sheet of ply running accross the sheet in a uniform manner. I have removed paint down to the wood & everything seems OK, no sign of damp or delaminating. Is this quite normal for ply to do this or could there be an underlying fault? If so is it best to just ignore it as it just seems cosmetic to me. By the way its nowhere near the end of the sheet or any other obvious weak point. Thanx, Graeme |
Lumpy plywood
Hi
"Graaeme" skrev i en meddelelse om... I have been restoring a plywood boat approx 20yrs old & have noticed a ridge in one sheet of ply running accross the sheet in a uniform manner. I have removed paint down to the wood & everything seems OK, no sign of damp or delaminating. Is this quite normal for ply to do this or could there be an underlying fault? If so is it best to just ignore it as it just seems cosmetic to me. By the way its nowhere near the end of the sheet or any other obvious weak point. Thanx, Graeme You shuld not vorry, ------- this one you can se, acturly nomatter ply or wood, a boatbuilder know af a few "repairs" that made it possible to use a plank making it even better than one with no foults from the start, and if you check how you fit veners together , you will know what your "foult" is. With tradisional wood, you drill out knots and repair cracks, with Ply you shuld be glad that this efford is done, producing an even better enginered wood product, it's just a prove about quality you notised. ----------- Check how you make two pieces of veneer fit edge by edge. P.C. http://groups.yahoo.com/group/Cyber-Boat/ |
<:_)>: Lumpy plywood
Backyard Renegade wrote:
....snip... Ahhh, your guess makes more sense based on his origional discription... Not a 'guess' ... :-) Several years in the Doug Fir plywood indy ... QC function ... MS in Wood Tech too ... I was thinking the wood was more swolen there because of a void behind it, I did not think about overlapping. :-) Core "Voids" are yet another consideration ... Still all in all sounds cosmetic. - Core Laps - Sorry ... not 'so', at all. In a sanded panel ... it seriously degrades the bending modulus along(with) the face_ply grain... 'Fresh' out of the hot press ... hard to visually see In sanded panels , a bit easier to 'see' ... *if* you're familiar with samded face_ply wood 'grain' patterns . Some core-laps in sanded 3/4" cause the face-ply to be sanded =entirely= thru ... primarily due to the 'construction' ... face/back = 1/8" ven 2 cross plies, 1 center ply = all of 3/16" ven ttl = 5 plies ; 13/16" +\- Envision a laped 3/16" cross ply going thru a sander . Most scarfed panels are =rigorously= inspected along the panel edge for just such 'defect' ... panels are rejected =prior= to scarfing ... Perhaps an 'exception' mite be un_sanded sheathing grades ... Floor underlayment is not an exception ... esp "PTS" grades HTH |
<:_)>: Lumpy plywood
0_Qed wrote in message ...
Backyard Renegade wrote: ...snip... Ahhh, your guess makes more sense based on his origional discription... Not a 'guess' ... :-) Several years in the Doug Fir plywood indy ... QC function ... MS in Wood Tech too ... I was thinking the wood was more swolen there because of a void behind it, I did not think about overlapping. :-) Core "Voids" are yet another consideration ... Yes, core voids is what I was referring to... Still all in all sounds cosmetic. - Core Laps - Sorry ... not 'so', at all. In a sanded panel ... it seriously degrades the bending modulus along(with) the face_ply grain... When I suggested it was only cosmetic, I was taking into consideration the idea that it had been in service for nearly 20 years with no considerable degradation of the vessel... I am also assuming that the builder was aware of the defect and as many of us do now (with the ****ty plywood available today) carefully place these defects in areas where they are not going to effect the strength of the boat or the integerity of the structure itself.. Scotty from SmallBoats.com 'Fresh' out of the hot press ... hard to visually see In sanded panels , a bit easier to 'see' ... *if* you're familiar with samded face_ply wood 'grain' patterns . Some core-laps in sanded 3/4" cause the face-ply to be sanded =entirely= thru ... primarily due to the 'construction' ... face/back = 1/8" ven 2 cross plies, 1 center ply = all of 3/16" ven ttl = 5 plies ; 13/16" +\- Envision a laped 3/16" cross ply going thru a sander . Most scarfed panels are =rigorously= inspected along the panel edge for just such 'defect' ... panels are rejected =prior= to scarfing ... Perhaps an 'exception' mite be un_sanded sheathing grades ... Floor underlayment is not an exception ... esp "PTS" grades HTH |
<:_)>: Lumpy plywood
Backyard Renegade wrote:
....snip... Core "Voids" are yet another consideration ... Yes, core voids is what I was referring to... 'All things considered' ... :-) voids arent as detremental as laps BUT ... in a 3_ply panel I'd not use it if the void( edgewize panel view ) was more than 0.75" x "panel_width", in a sanded 1/4" panel ... Maybe make 'that' 0.50" ... :-) When I suggested it was only cosmetic, I was taking into consideration the idea that it had been in service for nearly 20 years with no considerable degradation of the vessel... On a larger hull ... 20' + ... assuming UN_glassed exterior ... just painted plywood. With out 'jigging' up the hull , torqueing it ... :-) to see how the panel with the lap in it performed ... I'd be leary of not repairing what I'd just discovered ... a lap. Epoxy 'in' a backer panel, in side the hull ... 6" overlap, both sides of the core_lap , panel face 'grains in same direction ... "AC" ext grade in same panel thickness I am also assuming that the builder was aware of the defect Not many folk inspect every edge, of every panel, going into a boat hull. and as many of us do now (with the ****ty plywood available today) carefully place these defects in areas where they are not going to effect the strength of the boat or the integerity of the structure itself.. Stick with Doug Fir(DF) plywood , exterior( marine grade ? ) ... and mills that make 'scarfed' panels ... Improves your chances of getting 'quality' panels ... I'd even go so far as to locate an 'inland' DF mill source ... as opposed to a coastal mill ... "nicer" wood. :-) Off -shore 'stuff' I dunno ... I'd want to sample, & boil-test, the glue lines before I 'purchased' for a boat hull . |
<:_)>: Lumpy plywood
I'd even go so far as to locate an 'inland' DF mill source ...
as opposed to a coastal mill ... "nicer" wood. :-) how much of a difference does the coast/inland factor affect the quality of timber? A timber supplier here in the UK supplies US Doug Fir but specifies whether it is coastal or inland which made me curious about their relative qualities particularly with regard to a boat building application. |
<:_)>: Lumpy plywood
Ric C wrote: Is Doug Fir acceptable as substitute for okume? What about MDO? Once you have used a sheet of 1088 or even the cheaper 6566 grade okoume or meranti you will wonder how the US plants can sell what they call "marine grade fir" with a straight face. Even worse, after the local retailer puts his mark up on it, marine grade fir cost more than a sheet of imported 6566 okoume. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com |
<:_)>: Lumpy plywood
It's for a hard chine, flat panel catamaran. I won't use endangered imported
wood. I think we have plenty in this country and we manage to make it sustainable, which is actually cool. Weight is important, so is durability. DF is plenty strong. I can use core cell but I don't really want to have to glass the interior. I will though if I don't find an alternative. Plans call for 9 mm Okume w/ 9 oz glass outside. 9mm MDO w/glass? or 6 mm DF inside and 3 mm coremat/core cell and 18 oz glass outside? Thank you Ric "0_Qed" wrote in message ... Ric C wrote: Is Doug Fir acceptable as substitute for okume? Lumber or plywood ? Depends on the comparative strengths ... & the glue_line if plywood. What about MDO? MDO is a resin impreg paper overlay ... cures hard & brittle ... typically on/over a DF plywood panel ... Suspect on curved applications . |
Lumpy plywood
As you know, plywood is a "layered up" substrate that is produced under tons
of pressure utilizing a variety of glue and temps for various applications. Many times I have taken back to the shop a sheet of Plywood with just such a laminating flaw in it. Didn't do anything negative to my project, just ticks me off cause, I don't see it in the dim lights of the Lumberyard. From my experience , I'd say, it's a crease that got caught in the press and sneaked passed Q.C. "Graaeme" wrote in message om... I have been restoring a plywood boat approx 20yrs old & have noticed a ridge in one sheet of ply running accross the sheet in a uniform manner. I have removed paint down to the wood & everything seems OK, no sign of damp or delaminating. Is this quite normal for ply to do this or could there be an underlying fault? If so is it best to just ignore it as it just seems cosmetic to me. By the way its nowhere near the end of the sheet or any other obvious weak point. Thanx, Graeme |
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