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Thread: wax to stop glue sticking?
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3rd October 2010, 06:27 PM #31Intermediate Member
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Update
Hey guys,
Thanks for all your help so far! Pictures below as promised... with a little more success and progress than this time last week.
IMG_0465.jpg - the form
IMG_0464.jpg
IMG_0466.jpg
- Above - This is the form which i am bending the wood over. Last week i attempted to bend approx 9 x 2.5mm cedar strips, which i used boiling water on at the sharpest radius point - to get it all the way there.
IMG_0467.jpg - failed bend using WRC
IMG_0468.jpg
- Above - After gluing with bondcrete, leaving for 24 hours and unclamping, there was no movement (bounce back) in the radius or bend, however one week later, you can see form this picture what happened. Completely changed shape and opening an arch on what was supposed to be a flat base. Major spring back on the upper side also.
I have since used this piece to practice my edge cleanup methods and finishing up... which i'm happy to do on the router with the infeed fence set to .2mm
IMG_0456.jpg - 50.8mm flush cut bit
IMG_0457.jpg - .2mm offset in-feed fence
IMG_04601.jpg - blade (upside down)
IMG_0454.jpg - Finished surface (upside down)
IMG_0458.jpg - Finished surface
- above - This weekend i got a new carbide tipped bandsaw blade, tuned her up and started ripping 2mm strips off a nice block of Oak and Jarrah, making sure i cleaned up the previously cut surface on a router table - setup as a planer - before cutting the next strip. This proved to be effortless and i'm stoked with the results. I then cleaned the remaining faces with the same setup (router table setup as plane) but using a backing block behind the 2mm strips for support.
Im now ready to start bending the Oak and Jarrah around the form, but found that the 1.5mm (net dimension after planing) lams still need some slight steaming to get them the rest of the way without splitting - but i didn't want to go any further with glue up until i found out if the steam/heat bending is what got me in to trouble with the previous attempt - the timber springing back and completely out of shape.
IMG_0455.jpg
IMG_0465.jpg
-above- this is a picture of the Oak going around the form. This is as far as it went before the lams were about to split/snap. So I steamed the lams very slightly and managed to get them around and dry clamped without any drama. I have also provided a picture of the lams and where they naturally spring back to once un-clamped (in the background). There is a lot of force required to get them tot he form, so my concern is that once glued, and un-clamped after 24+ hours... ill end up with a badly shaped bend...
Can anyone shed light on that? sorry, probably a stupid question!
For those who haven't seen it, this is the chair which i am trying to make (below), and the form i've made is to replicate the 2 legs...
Bouncer21980Lg.jpg
Thanks to everyone who has offered assistance to date, you've been a great help... it has been many years since i've touched tools and timber and i think i've chosen one of the harder projects to get back into it ) why do things in halves.
T
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3rd October 2010 06:27 PM # ADSGoogle Adsense Advertisement
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3rd October 2010, 06:50 PM #32
I don't think you will get much springback if you use Techniglue epoxy to glue the laminations, although I must admit that I have not tried glueing nearly as tight a curve as yours. However, it is not going to work if you have to steam the wood. You may perhaps find, though, that the laminations are less liable to splinter once the epoxy is on them and has soaked in a bit. I think the job would be easier if you made a second former, so that the laminations are sqeezed between the two formers.
I still think the easiest way to stop your laminations sticking to the former is to line the former with brown packaging tape. I suspect that wax would just soak into MDF, so you would have to use a lot of it. It only takes a couple of minutes to stick the tape on, and the job is done.
Rocker
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3rd October 2010, 07:33 PM #33Intermediate Member
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Hey Rocker,
Thanks for the advice, i have actually gotten some brown packing tape to try on the next glue up. It sounds far easier than anything else!
Your advice, if i need to steam the 1.5mm lams then it isn't going to work? - im not sure how thinner i could go... ill try get them to 1mm or under and see how i go. What is the downside of steaming lightly, the lams, to complete the bend? also, you suggest i might get the bend after coating in glue... i know this is a hard one to answer, but is the additional bend or flex you get once glues substantial? - ill give it a go either way.
I've also ordered a few glues to try out, one of them being Techniglue epoxy - hopefully arrives during the week so next weekend i can try it out!
Ill keep you posted!
thanks again
T
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3rd October 2010, 07:58 PM #34Banned
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T , how about trying the bend with solid timber
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3rd October 2010, 09:05 PM #35Intermediate Member
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MJ - funny enough, i haven't. It all started because lams where supposed to give me minimal spring back, and for consistency (2 individual legs) it was the best option.
I also decided not to go steam bent solid wood because i wasn't equipped for it. strangely enough, i think i've spent more time and money going the lam route, that i could have become 'equipped' for steam bending twice over.
is there good math i could use to understand the spring back in solid bent - so the legs are parallel? trial and error?
T
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3rd October 2010, 10:12 PM #36
Ecks,
The downside of steaming with epoxy is that water is not compatible with the glue. I can't really quantify how much extra bending you will get when the glue is on , but I think a minor amount of splintering will not matter too much, so long as it doesn't affect all the laminations. Possibly, if steaming is essential to achieve the bend, it might be better to go with a poly glue, which is compatible with moisture; but I have never used poly glue for bent laminations myself, and I am not sure if its working time would be adequate.
Rocker
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3rd October 2010, 10:15 PM #37Banned
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3rd October 2010, 10:49 PM #38Intermediate Member
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Thanks Rocker.
I don't actually glue up while the wood is still damp, i steam to get the bend once, then leave the clamped lams till they dry... steaming and bending once gives it enough flex that i can come back a week later and bend the lams a second time without stressing or splintering. So in this case, moisture shouldn't be a problem?
I was more concerned that, since i require so much steam and force to get the lams around the form... that the glue was not holding that shape over the week after the clamps had dried, and therefore flexing out of shape.
If the lams are dry, and having been bent once, allow me to bend again when ready for glue up - would this pose the problem i just mentioned?
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3rd October 2010, 10:50 PM #39Intermediate Member
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3rd October 2010, 11:29 PM #40
I think once you get the lams bent and dried close to the correct bend you'll find that gluing them with the Techniglue will give very little springback. It's a very hard epoxy with virtually zero creep and for the bend to spring to any degree, the glue must creep.
You may also try overbending the lams and drying on a tighter form and hot pipe bending would certainly be worth investigating to do these lam bends. I have hot pipe bent 3mm lams to a 13mm radius so your radius is doable.
Cheers
Michael
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4th October 2010, 08:02 AM #41Intermediate Member
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Hey thanks Michael... appreciate the feedback. Ill give that a go, sounds like it will be my best bet, as well the Techniglue sounds like a much better glue to work with
Cheers
T
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