Lots of knowledge lurking on this site,
if you where making a tiller or a laminated beam to suite a curve in the deck head and me being a complete novice with timber how do you go about measuring and laying out a pattern for your job ?
is there a system to make it accurate or is it just by eye? thanks in advance some links might be useful.
Select to expand quoteMAGNESIUM said..
Lots of knowledge lurking on this site,
if you where making a tiller or a laminated beam to suite a curve in the deck head and me being a complete novice with timber how do you go about measuring and laying out a pattern for your job ?
is there a system to make it accurate or is it just by eye? thanks in advance some links might be useful.
according to all the you tube I have watched you would make a template/pattern out of ply or cardboard or similar
As it happens I've just been doing exactly that ie, laminating some deck beams, well Bimini roof beams but same thing. 1st up do a table of off sets, set up a straight edge or string line and record distance from straight line to the curve of the beam, it's easier if you make the measurements at a equal stations
Transfer the measurements to a flat area. Hammer nails in at the cross points, then spring a batten around the nails & scribe the line. Now screw some gluing blocks along the scribed line
Then all you have to do is bend your 1st stick around your jig & glue the next one to it. To make life easier it's best to screw the 1st laminate to the blocks ( if you can ) otherwise you can end up with a springy epoxy mess
If the tiller is to have a curve, it's best to first steam bend the wood pieces you're going to laminate. Otherwise you're relying on the epoxy to permanently bond the strips under stress.
I built a new laminated tiller for a dinghy a while ago. It needed to be straight, then curve through about 25 degrees towards the aft end, then be straight again for a short section where it attaches to the rudder cheeks.
As the timber strips were only about a metre long, I simply softened the strips at the point where I needed the bend (towards the rudder end of the tiller), by steaming them on the stove using a couple of oven trays - the one on the bottom full of boiling water and the other as a lid on top. This worked fine even though there was a gap between the two due to the strips sitting across the bottom tray and sticking out both sides of the trays. As the wood strips were only about 30mm by 5mm thick, softening was a matter of 10 minutes or so over the steam. Then I put them in a simple jig that held them in the desired bend until they cooled. I did them in two batches as that was what would fit. I used two different woods, one light, one dark, alternating for the appearance. As it happened one was a bit softer than the other, but this didn't matter in terms of bending them. I then epoxied the pieces together. I have seen where some put a fine layer of fibreglass tape in the epoxy between the layers to further strengthen a tiller, but I didn't bother with that.
If you're looking to steam bend longer pieces, you can make up a steaming box out of 12mm marine ply which is long enough to fit all or a batch of your pieces, and connect it up to an old pressure cooker full of water on a gas stove, Run a hose (that won't get too soft due to the steam) from the outlet on top of the pressure cooker lid to a cap on the end of the box, and then have a hole as a vent at the far end of the box. That way the steam has to travel the length of the box and the pieces in it. If you're putting multiple pieces in at once make sure you keep the pieces apart from each other and the sides of the box so they get steamed equally on all sides. A jig (or set of clamping points such as shown in the earlier post) will enable you to clamp the hot pieces into the form you want until they cool. Best to build a jig so that the pieces are held in the correct curve, but apart from each other so they cool evenly and more quickly than if you clamp them together,
Once cooled they'll hold the bend and you can just layer them with epoxy in between and lightly clamp then to hold them while the epoxy sets. Its likely a matter of opinion, but I think epoxy glue (such as araldite) sets a bit stronger than just straight epoxy.
If you haven't got or cant get an old pressure cooker, then a large pot with a lid will do, and you can drill a hole in the lid and fit an outlet to attach the hose.
Steam bending has no doubt a bit of magic about it, there's no chance I could have bent this merbu cover strip on this project cold
The holding strength of epoxy when thickened with fumed silica if your joinery is neat or chopped cotton if it's a bit not so tight will be stronger than the wood. When tested to destruction the wood always gives 1st. Of course by using the off sets you can make a pattern then saw the beam out of a single piece of timber, or glue several pieces together and saw it out of that. So many ways to have fun
Amazing stuff Woko - the old and the new. When I first read your stuff on steam bending I was dubious but it seems like a good way of increasing the allowable thickness of the laminations. I had to do some tight radii and had to reduce the laminate thickness way down. I might have a go one day.
Oh and one thing - if you use thicker laminations that take a fair bit to clamp down then you will get some spring back. It's hard to work out how much but it pays to put a few mm of extra bend into the jig if the laminations require significant pulling into the jig.
Select to expand quoteKankama said..
Amazing stuff Woko - the old and the new. When I first read your stuff on steam bending I was dubious but it seems like a good way of increasing the allowable thickness of the laminations. I had to do some tight radii and had to reduce the laminate thickness way down. I might have a go one day.
Oh and one thing - if you use thicker laminations that take a fair bit to clamp down then you will get some spring back. It's hard to work out how much but it pays to put a few mm of extra bend into the jig if the laminations require significant pulling into the jig.
To be fair Quixotic gave the rap on steam bending. I just boiled that bit of merbu. And yes it's a neat way to reduce the thickness of laminations. the beams I'm making at present do spring a little off the jig but the design has support and I'm concerned with head room & overall height, if I didn't have these constraints I would add another laminate
Obviously the above has answered it - but if you need more the joggle stick / tick stick method for bulkheads can be used for bulkhead tops to the deckhead fit as well.
Ah the joy of joggling. One of the best kept secrets ( wasn't sure if i was allowed to mention it ! ) a bit indulgent for a simple curve though. How many ways can we make a curved beam ? While this one's not strictly a beam. It's a lovely curve in a 6x2 or 140x45, in this case the off set was drawn on the plank, the radius cut out and two straight sides glued together.
Thanks for replies guys.
R13 that was a interesting video shame the channel has ceased
