Laminated Bow info.

[bigbob]

I might answer the question about grinding lams. Most methods use a 'master taper' of the required taper rate as a backing to the lam being ground. It is passed through the fence and belt in stages , each time removing a little more excess until the full taper is achieved. With mine I grind full length lams as opposed to one limb lam and start from center on each. Some pencil squiggle marks radiating from centre tell when taper is approaching desired amount. Of course a digital set calipers are used in conjunction with the process.

[hunterguy1991]

Thanks for the explanation Bob, not 100% on it yet but I'm sure if I saw it done I'd understand fully.

Are you using a linisher like Daryl suggested or a spindle type sander?

[greybeard]

Colin, this was my first installation of the unit, the photo gives the details.

Grinder Details.JPG (143.56 KiB) Viewed 4014 times

The following photos are of the newer installation.

Multitool 3.JPG (40.52 KiB) Viewed 4014 times

Under Bench Mounting.JPG (129.29 KiB) Viewed 4014 times

At some time I will modify the fence setup so it has a worm drive adjustment.

I would recommend some method of dust extraction.

Daryl.

[bigbob]

Thanks for the explanation Bob, not 100% on it yet but I'm sure if I saw it done I'd understand fully.

Are you using a linisher like Daryl suggested or a spindle type sander?

I use a similar process to Daryl but different means. I do have a lengthy post on here from a couple years ago on constructing a lam grinder from a defunct belt sander and a spa pump motor.It is set up much the same a Daryl's, vertically mounted through a table. and incorporates a fence set at a true 90 Deg. to the face of belt.

[hunterguy1991]

Thanks Daryl, photos made it much clearer for me.

I think I will have to mock up a whole table to mount this as my bench that I use at the moment a) isn't mine to put holes in and b) is solid hardwood planks about 50mm thick.

Are you using the full width of the belt or just a portion of it? I figure there would have to be at the very least the width of a lamination (say 2") of belt above the table surface to ensure it is all ground off evenly.

The PVC piping is your dust extraction system Daryl? Is it all connected to a central shop vacuum or a smaller localised one?

How does one make/obtain a master taper? Are these just a tapered lam that is kept in perfect condition and taped to the back of another so as to replicate the taper of the master as its ground? I assume you would have several of these for doing different taper rates?

Cheers again!!

Colin

[greybeard]

Are you using the full width of the belt or just a portion of it? I figure there would have to be at the very least the width of a lamination (say 2") of belt above the table surface to ensure it is all ground off evenly.

At best I can get about 1 7/8" of true grinding width and that is why I use 1 3/4" glass in my recurve bows. In hindsight I should have bought the 3" model when it was available. If the need arose I would get the 4" model.

The PVC piping is your dust extraction system Daryl? Is it all connected to a central shop vacuum or a smaller localised one?

I run a 1hp dust extractor which services two band saws and the lamination grinder. Each machine is fitted with a blast gate so I can maximise the suction at each machine. Also I have a portable 1hp extractor to use with other machines.

How does one make/obtain a master taper? Are these just a tapered lam that is kept in perfect condition and taped to the back of another so as to replicate the taper of the master as its ground? I assume you would have several of these for doing different taper rates?

You can buy them or make your own, there are different taper rates available.

Daryl.

[hunterguy1991]

Thanks for thank Daryl.

I have come up with another question for you all, one that may raise some debate. I have seen on here that a lot of guys are curing their bows in a hot box or oven. My question is, is this necessary to produce a working bow? I know that the glues (particularly smooth on) is said to have better strength and bond when it is cured at elevated temperatures but surely the glues would still hold if cured at ambient temp?

I have only use Techni-glue so far along my bow making journey and have only cured it at air temp (sometimes upwards of 35 degrees through the day) and have not had a problem yet. I have even glue on risers late arvo and left them overnight in the cooler temps to set and not had a problem. I feel that as long as the glue is left its full specified curing time before stressing (techni-glue is 24 hours) there shouldn't be any issue.

Let me know your thoughts.

Colin

[Goatchaser]

I just prefer the oven as I have read somewhere that if epoxy is going to fail it will do so at higher temps than cured at, not sure if true but was a decider for me.

[bigbob]

It comes as a recommendation from Smooth -on for optimum performance, and when you think of it, its only the quality of the glue used that allows the bow to remain in one piece. For mine I like to have everything going for me that I can, to optimize reliability.

[greybeard]

Over the years I would have made or supervised workshops producing well over fifty bows glued up with Techniglue Ca that were cured at ambient temperature.
Although I have lost contact with the bows owners I have not received any complaints. I will point out that the bows were not put under tension for about three days.

In December 2010 I glued up my first longbow using Smooth-on and heat strips.

Putting durability and integrity to one side the heat strip system allows me to glue up in the morning and work on the bow after lunch.
Once temperature is reached cooking time is approximately 30 minutes for recurves and 45 minutes for longbows. If push came to shove I could glue up two, possibly three bows in a day and only require one form.

As with any product one should follow the manufacturers guidelines and recommendations.

What sold me on the heat strips was that I didn’t have a larger than coffin sized box taking up space in my workshop.

Re lamination grinders the following link is a longbow build a long by David Wallace from Miriam Vale. I put the link in so you could see the fence adjustment mechanism employed.

http://www.ozbow.net/phpBB3/viewtopic.php?f=34&t=10257

Daryl.

[GrahameA]

Afternoon.

... I have read somewhere that if epoxy is going to fail it will do so at higher temps than cured at ...

Hmmmmm...... If that was true Bows that had been cured at warmer temps would never fail under normal conditions which is cooler.

[Goatchaser]

Sorry Graeme, but as I have said before I am not here to argue, just stating that it is something I have read and as I said not sure if true but a decider all the same.

[hunterguy1991]

Daryl, I do see that advantages there, but I have no desire to knock up 2 or 3 bows in a single day. It will be a "one a month" type deal for me as a hobby. Even with Smooth-On one should not stress the bow for 24hrs even if heat cured and my use of Techni-glue suggests that it goes off enough to do the same as you propose, but not stress the limbs any while working on it.

I will always be giving at least a full 24 hours between glue up and first stress in the limbs (a good practise to adopt I think)

I have done a little research and come across some info that may interest you all. Techni-glue comes in different grades (R60, R15, R35 and R90) which have different characteristics. I would suggest looking at the label if anyone is using it to see which they have.

I have R60 grade which is a "Structural Grade" for use in Civil Engineering applications. Now I have experience with these type of magnitude loads and a glue that can withstand these will easily cope with the stresses in a bow...

I also came across this specification table.
http://www.atlcomposites.com.au/files2/ ... ca_r60.pdf

Please pay attention to the HDT (Heat Deflection Temperature) section. Depending on the Hardener used, various HDT values can be obtained. HDT is the temperature at which the glue starts to lose its strength.
I have the H60S Hardener which is the slow cure version (pot life is 30 mins) which has a HDT of 32 degrees after 24 hrs and 48 degrees after 2 weeks, Cured at 25 degrees.

Heat curing will elevate these temperatures further, however I don't see the need as 48 degrees is far higher that ambient temp in 90% of the country... Also not that curing at 35 degrees ambient would elevate these HDT temps somewhat as well.

I think this is all justification in my using Techni glue in my first bow build.

As far as what goat chaser has proposed, yes, they do fail at a temp higher than the HDT (but NOT the temp they're cured at)
which is more than ambient. Bows that fail tend to fail in the timber close to the glue rather than in the glue itself from what I have seen and read.

Colin

[Goatchaser]

As I am in the other 10% of the country I'll stick with my oven,

[hunterguy1991]

Go for it mate, whatever is working for you... as a beginner and not wanting to spend a ton on an "experiment" I'll be giving the other option a go.

[rodlonq]

Heat curing will elevate these temperatures further, however I don't see the need as 48 degrees is far higher that ambient temp in 90% of the country... Also not that curing at 35 degrees ambient would elevate these HDT temps somewhat as well.

Colin

Hi Colin,

I alway's heat cure to ensure temperature resistance. I was devastated when my first recurve delaminated because I left it in the boot of Dad's EH (30+ years ago). Even an unstrung bow has residual stresses in the fades which may be inclined to let go if HDT is reached. Just another thing to think about, I worry about my bows all the time when they are in a car.

Cheers………. Rod

[Goatchaser]

This is what was mentioned in the article I read about glue giving way at higher temps than cured, as general everyday conditions don't apply to every situation. Hot car, shed, etc, my bow shed is insulated lined and aircond all summer due to my bows and bow building components being housed in there.

[hunterguy1991]

G'day Rod

Thanks your thoughts. I had thought of that (leaving bows in cars) but for my first I think I'll cure it in ambient temp... will cut down on the build complexity and since the first will be an experiment should be ok. If it does eventually go, it will be lesson learned I guess.

I'm always careful with my bows I where I leave them but sometimes you cant help it. If I do heat cure my bows it will be using heat strips as these seem much easier than building a hot box, so I will have to ask Daryl more about them, where he gets them etc.

Colin

[rodlonq]

I reckon heat strips are excellent, however Greybeard has much more experience with them than I. I also keep the air connected with the regulator set to 65 psi so there is no risk of leakage and loosing pressure.

Bingham's heat strips are made for 110 V supply so you will need a step-down transformer = extra cost to be aware of. I think the 2" heat strips (a pair of 2" x 72") have maximum output of 375 W, but I would check on that.

I don't make a lot of bows, however spare time is limited. It is good to be able to glue up in the morning, start shaping in the afternoon and finish of by the end of the next day.

JessBowCookin.jpg (133.9 KiB) Viewed 3973 times

Cheers…. Rod

[Goatchaser]

do Binghams sell them anymore? , can't see them anywhere on their site.

[longbow steve]

From memory it is about 70 degrees that the fibre glass will start letting go so it would be fair to say the glue would be around that figure.
I am no chemical engineer but I would say the glue would continue to cure when it is exposed to higher and higher temperatures ie travell in cars etc.
Another concern is to know the relative humidity of your area and the day that you are working, it is good practice to heat the lams and glass to minimise the residual moisture content and get it as low as you can so glue absorbtion can occur to the best potential. In my climate I struggle to get timber to less than 16% rh for the majority of the year. Steve

[Goatchaser]

lams riser and glass all get pre heated in my oven for an hour before I start the lay up, as per Binghams instructions.

[GrahameA]

Hi Steve.

...I am no chemical engineer but I would say the glue would continue to cure when it is exposed to higher and higher temperatures ie travell in cars etc. ...

May I suggest that once the epoxy has cured going higher in temp will not cause it to cure more.

However, exposing Epoxies to elevated temperatures will decrease the bond strength. A practical example is heating arrow tips to un-glue them when the tips have been Araldited (Epoxy Glue) on.

[rodlonq]

do Binghams sell them anymore? , can't see them anywhere on their site.

I couldn't find them in the new catalog (No. 37) either.

Perhaps try HiHeat, a link is at this URL;

http://piratesofarchery.net/bb/viewtopi ... =27&t=4302

Cheers…… Rod

[Goatchaser]

cheers Rod.

[hunterguy1991]

Steve, you bring up a really good point about moisture content and humidity while gluing up a bow, something I had not considered yet so thanks for that one.

As far as the glue curing in cars at an elevated temp, unfortunately it doesn't work like that, GrahameA is bang on. Once a glue is cured the highest temp I can withstand before losing strength is its HDT. Using techniglue as an example, glue that is cured for 24 hrs at 25 degrees (standard room temp in chemistry) and the for a further 16 hrs at 80 degrees reaches a HDT of 68 degrees (i think from memory, check the link of specs i posted). However, even tho it was cured at 80 degrees if it reached 70 in an ambient environment it would start to lose strength because this is above the HDT...

Rod, thanks for the Heat strips link mate, will have a look into it for sure.

Colin

[bigbob]

another point to ponder is quite a few bowyers in US always use their lams within a day of them being ground. I assume this to reduce take up of ambient moisture. I try to adopt this practise where possible but pre heat my lams in any case before the glue up, allowing them to cool before applying epoxy.

[longbow steve]

Hi Steve.

...I am no chemical engineer but I would say the glue would continue to cure when it is exposed to higher and higher temperatures ie travell in cars etc. ...

May I suggest that once the epoxy has cured going higher in temp will not cause it to cure more.

However, exposing Epoxies to elevated temperatures will decrease the bond strength. A practical example is heating arrow tips to un-glue them when the tips have been Araldited (Epoxy Glue) on.

Thanks Grahame, good to have a good mind to clarify things. What causes the chrystalisation of the glue? Age or these temperature extremes? Steve

[longbow steve]

another point to ponder is quite a few bowyers in US always use their lams within a day of them being ground. I assume this to reduce take up of ambient moisture. I try to adopt this practise where possible but pre heat my lams in any case before the glue up, allowing them to cool before applying epoxy.

Yeah when I grind lams they are quite hot by the end of it and should be good to go straight away without re heating. The bamboo lams are hygroscopic, more so than most woods apparently so it is good to heat them or use straight after grinding the lams. Steve

[Goatchaser]

while we are on the subjects of "correct" glues and correct drying methods, I have always been worried about the idea of "which" glue is used to glue the vertical bamboo flooring together, ( different companies different glues??) as this process is out of the / any bowyers hands and intended for a totally different market and purpose?