laminating help

[johnnyb]

hi laminating up a pair of curved arms. I've sawn a chunk of pine along the radius. cut some strips. I'm laminating them together so they are identical. I've got some epoxy to use. any other tips. something stop it sticking maybe a way to line them up?

never really tried this technique.

 

[johnnyb]

like this

 

[baldkev]

I haven't tried this, but from what i understand, you could do a dry run with your former and put a pencil line across the sections to get a visual that it lines up while clamping.
One of the members here ( dr bob i think ) said he pencil lines his timber before cutting the strips, which ensures the best possible grain match when he laminates it
Put plastic sheeting over your work areas, plenty of clamps and some offcuts. You can clamp offcuts on the sides to keep it aligned
Edit to add you could cover the formers in parcel tape to stop it sticking to the formers

 

[johnnyb]

one huge blunder is I've not accounted for the thickness of the thing. it will be a smaller radius on the inside doh! love the packing tape.

 

[baldkev]

As in your former is too tight a radius? Thatd be good because you usually get some springback

 

[johnnyb]

the actual radius doesn't matter. but the inner radius former needs to be smaller than the outer radius former by the width of the part( in my head it didn't matter but I think it does. I can draw it using a compass set to the thickness as I used a pre made rad template

 

[Yojevol]

If you are going to glue them in one go between male and female formers you are going to need an enormous amount of force. It may be better to glue one lamina at a time. In this case you won't need to worry about the radius of the female former.
Male sure you have a good amount of extra length over and above your design length because it's often a problem to get the lamina ends to lie down properly. You have a fairly gentle curve here so that shouldn't be great problem. It's also easier to manage if gluing individual laminae.
Glue from the centre outwards
Have a dry run and have everything laid out ready for the real thing.
Good Luck
Brian

 

[recipio]

I've done a bit of laminating on a smaller scale. Those slips look to be about 6 mm thick so a dry run is advisable. I'd screw the convex former to a baseboard to prevent it moving around and drill holes in it to enable the use of G- clamps - you are going to need a lot of clamping pressure. You can never have enough clamps - keep them around 5 cms apart or gaps might appear in the lamination. Some slippage is inevitable but you can clamp the laminations vertically with a non stick block.
I have never found it necessary to use epoxy, being messy and expensive. Any PVA glue will work as long as the ambient temperature is above 6 C. Lastly a gentle curve like this will go through a thicknesser to clean up but I have found a little sideway's pressure will get curved laminations through the machine. ! . My old Scheppach has rubber rollers which may be a factor so ideally the laminations should be a little wider than needed to allow for this.

 

[johnnyb]

I don't have large amounts of clamps so one at a time would be great. I always thought pva was a no no. if I do them one at a time do i use both formers?

 

[recipio]

I don't have large amounts of clamps so one at a time would be great. I always thought pva was a no no. if I do them one at a time do i use both formers?

Laminating is not an exact science. As long as all the components are equal you should be able to incorporate them into the design. Incidentally you can compensate for unequal radii by cutting a router template with a bit that is the thickness of the finished component, using a router with a trammel bar. So if your finished component is 20 mm thick, use a 20 mm cutter to make convex / concave templates in one pass. This will only work up to the limits of the router bit dimensions of course. Use the template to create the convex/ concave formers with a bearing guided pattern bit.. I've found PVA to be perfect for laminating as long as you leave it overnight to cure. There is an article in 'Fine Woodworking ' a few years back which found PVA to be stronger than Polyurethane glue . I'd glue the laminations in one go, starting with a clamp in the middle and working left and right. G clamps are invaluable for this - you might struggle with sliding bar clamps.

 

[MARK.B.]

I may be stating the obvious and not in any way trying to teach you how to suck eggs, but make sure that before you start that you have enough glue on hand to complete the job,you will be slapping it on at a fairly rapid pace so will use more than doing a job where you can take a little more time applying the glue. I got caught out once when thinking i had enough, and too be fair i did except the second bottle of glue i reached for had gone off .

 

[Yojevol]

If you don't have many clamps you can make your own using threaded rod. See the sketches in my post in thisThread
Brian

 

[baldkev]

What do you have available? G clamps, sash clamps, even ratchet straps might help.....
Or are there any members nearby?

 

[baldkev]

Here's another thought..... could you make a wider former, say 2" wider, clamp the middle up tight as, put screws down from female to male ( on the outside of the workpiece each side ) then clamp the next section either side of centre, screw, etc until you use all the clamps, then take off centre clamps and move them to the next position, clamping and screwing until you laminations are secured in a fully screwed former

Itd definitely need a dry run

Edit to add, if that doesnt make sense I'll draw a pik.... ive got 6x 180 screws that should cope with that, especially with an impact

 

[Orraloon]

Never laminated on that scale. Only Archery bows. Looking at the layout I think you will have trouble doing both side by side. Wet epoxy and wood strips will want to slide around like oiled snakes. You will also need twice the clamping force. Way I see it if both are done on the same form they should be pretty close to the same. When I did the bows the form was the same width as the work with a few uprights screwed to the sides to prevent sideways slippage. I would ditch the top half of the form and just have a sacfricial bending strip on top thats not glued. Plenty clamps and some helping hands would be useful too. Tape up everything you dont want to stick. Its a messy process. Rubber gloves, ventilation, acetone for clean up. As others have said do a dry run first to see how it goes as to clamping pressure required and to avoid surprises with the real thing.
Regards
John

 

[okeydokey]

Other than steaming some mahogany many years ago I have never bent wood.
So I know nothing, but some thoughts follow
You mention you are going to carve the finished wood to make arms (for a chair?) would you have to have each lamination so tight and flat to each other that when you carve there wont be any gaps, or maybe some kind of filler will conceal them before whatever finish is applied?
What timber?
Why the laminating technique rather than simply carve a solid piece of wood.
Good luck

 

[Jones]

Fixing the form to a base board will help a lot with alignment of the strips, if you can't use a full board some pieces screwed on will do. Parcel tape is much better than plastic sheet ,it will stay where you put it and won't get rucked up or caught in the laminations.

 

[BEE13]

You'll find it easier to ensure that the epoxy doesn't have air holes between laminations if you use a filler in the epoxy mixture. Google epoxy filler. West do several for different purposes. Prime the bare wood with standard epoxy mix then add filler to the rest of the mixture to about the consistency of cream and use that as the glue.

 

[Hornbeam]

Doing a dry run is good but when your laminations are covered with glue everything moves about a lot.
Parcel tape to stop everything sticking to the mould
Screw on some pieces to the side of your former to stop everything moving sideways
It looks like your laminations are quite thick (OK) make sure you have them ordered so you keep the grain match
For thicker laminations, I only use a female former as if using a male and female, you have to be very accurate to allow for the thickness of the laminations
I use the Tage Frid method for clamping using threaded rods and home made blocks. See attached you will have to open the image of teh book to get a better view Barter Books : Frid, Tage : Tage Frid Teaches Woodworking. Book 2: Shaping, Veneering, Finishing
Use a scrap laminate or pice of thin ply to prevent any pressure marks
Apply clamping pressure from the centre of teh curve working outwards
I use aerolite for teh adhesive
Ian

 

[Hornbeam]

Gluing individual laminates may be easier but you may introduce springback between esch glue up. Better to do iyt in one go and get someone to help if needed (my wife loves this part )