 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| HomeDiscussion GroupsBoatsPaddle BoatsSailingCruisingBuildingElectronics Related Topics CarsMotorcyclesMore Topics ... |
Boat Forum / Building / July 2006Teak on Steel
I'v been to look at my uncle's boat a De Ruyter 35' steel motor boat based on the Thames, I'm a trades man and he want me to fix his teak deck, some plank have become loose and warped from there fixing, It seem the the planks are 6mm thick (with a very thin pelet covering the screw)and screwed in to a 9mm ply which is fix to the steel. I can see that the ply is very decayed Question 1. How is the ply fix to the steel. Does any body have any experience of the type of system I would appreciate any help. Cheers Martin The subject is complex, because it stems around one unavaoidable problem, the difference in thermal expansion and contraction rates between steel and wood. The difference can be as much as a millimeter per foot of deck. So, if the wood is fastened directly to the steel, extreme pressures are created that can split the wood or visibly warp the deck in bright sunlight. If the deck is allowed to move over the steel, the abrasion will rub any corrosion protection from the steel and rust is the result. This rust becomes untreatable without removing the wood. I have tried many systems and all have their own unique difficulties. In your case, only the complete removal of the deck will reveal the method used. I could write a treatise on this subject, but it is safe to say that no method that I am aware of works well. Steve > I'v been to look at my uncle's boat a De Ruyter 35' steel motor boat > based on the Thames, I'm a trades man and he want me to fix his teak [quoted text clipped - 5 lines] > Does any body have any experience of the type of system > I would appreciate any help. Cheers Martin >The subject is complex, because it stems around one unavaoidable problem, >the difference in thermal expansion and contraction rates between steel and >wood. The difference can be as much as a millimeter per foot of deck. Yowza! 1 mm per ft run is 1 part in 305 thermal expansivity difference between wood and steel. That's not what it says in the data tables. What am I missing? What temperature range do you have in mind? Brian Whatcott Altus OK The problem with teak and steel, and even teak and fiberglass, is not so much thermal expansion but the teak changes in dimension dramatically with moisture content. It swells and shrinks like a cellulose sponge with sufficient force to crack or separate from non flexible adhesives like epoxy. Caulking or re-caulking should always be done when the teak is thoroughly dry - which can take a month or two in the sun. That way when it gets wet it will apply compression force to the caulking and help improve the seal. If you caulk to teak that has not been thoroughly dried, then when it does dry and shrink it pulls away from the caulking and creates a leak. If you can't wait until it is thoroughly dry, then your caulking grooves should be made wider - at least 1/4 inch - so the caulking material can flex far enough that it doesn't pull away from the teak. A narrow caulk can't stretch that much. Our decks are fastened from below with screws. The holes in the steel beams are over sized to allow the teak to "breathe". This is the best method I've found for securing a teak deck. The only problem we have is the 1.5" thick teak in 1960 is now 1.25 due to nincompoops sanding the deck and the tips of the screws are approaching the top surface of the teak. Where they reach the surface you have a leak and rot/rust starting. The same philosophy applies to gluing a thinner teak to a substrate - wood or fiberglass. Veneer teak is too thin to screw from below so choose an adhesive that has good flexibility, good adhesion to both surfaces and is laid thick enough to allow differential expansion with moisture content without breaking loose. My choice is regular silicone rubber cement. It handles CLEAN teak fairly well even if there is residual teak oil present, and is compatible with most other sub deck materials. > The problem with teak and steel, and even teak and fiberglass, is not > so much thermal expansion but the teak changes in dimension [quoted text clipped - 30 lines] > residual teak oil present, and is compatible with most other sub deck > materials. Pardon my lack of imagination, but I don't follow your description of screwing the teak decking to steel beams from below. In particular, how exactly do the screws fasten the wood to the beam, if the beam holes are over sized ? Thanks once again, Courtney > > The problem with teak and steel, and even teak and fiberglass, is not > > so much thermal expansion but the teak changes in dimension [quoted text clipped - 38 lines] > Thanks once again, > Courtney The heads of the screws hold the deck to the beams. the oversized holes allow the threaded part of the screw to move with the movement of the wood/steel interface. Brian, I really wish it ain't so, but it is. This isn't tables talking, it's personal experience. I see it every summer. My deck visibly buckles in the hot sun. Hose it down with water and it dissapears. Steve >>The subject is complex, because it stems around one unavaoidable problem, >>the difference in thermal expansion and contraction rates between steel [quoted text clipped - 7 lines] > > Brian Whatcott Altus OK >I'v been to look at my uncle's boat a De Ruyter 35' steel motor boat >based on the Thames, I'm a trades man and he want me to fix his teak [quoted text clipped - 5 lines] >Does any body have any experience of the type of system >I would appreciate any help. Cheers Martin If the rot isn't too extensive you might consider one of the Epoxy products like Git Rot or System 3's Fix Rot I've had good results with System 3. It might save you having to remove the under layment. Jim You could change to Flextek - the teak substitute that is plastic. I reckon a teak on ply deck lasts 10 years before it starts to really lift away. Rip it all off and paint the deck and use decking tiles where people want to sit around. You could change to Flextek - the teak substitute that is plastic. I reckon a teak on ply deck lasts 10 years before it starts to really lift away. Rip it all off and paint the deck and use decking tiles where people want to sit around. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.