Making your own fiberglass lams for bowbuilding

[dfrois]

Hello to all,

This is my first post, and it seems only fair to start by thanking evryone here for all that I have learned by lurking here for the past few months. I have taken up archery, and began bowbuilding recently (I`m finishing my second bow). the first question  i would like to put to all the knowledgeable bowyers out there is this:

Someone asked recently why buy ready-made fiberglass lams instead of just laying fiberglass fabric on top of the wood lams. I know why: all the types of publicly available fiberglass mats or weaves are either isotropic (meaning the fibers are in all directions at random) or ortothropic (I think that is the correct term- it means that the fibers are at 90º to each other, as on a weaved fabric). For bow limbs, we need the fibers to be (almost) all longitudinally aligned with the direction of the limb; there is no point in having fibers at 90º to the limb plane. But I have no ready acces to fiber lams for bowbuilding, and the only supplier that I have used only has one thickness...so, it got me thinking...
I have some fiber fabric leftovers, from other endeavours, and it seems easy to cut a few strips, paralel to one direction, and then remove the transverse fibers by hand. Do this in 3 or 4 layers, then lay it on a form like the one for bow limbs, with bow-making epoxy, to remove the excess. After curing, ther should be a (fairly) homogeneous lam, with longitudinal fibers, with a thickness determined by the numbers of fiber fabric layers...

Does anyone see any obvious reason why this shouldn`t work? I know it`s a lot of work, lams are cheap, etc....but remeber, I don`t have anywhere to buy them, and especially I don`t have a choice of thickness...or a drum sander to thin them!

Just wondering...

And thanks again for all that you taught me!

DF

[Living_waters]

I actually know someone that makes some really fine bows using the the e-glass or unidirectional tape on their osage R&D bows. And I have seen a web site showing someone making clear lams by applying release agent (vasoline I believe) to a sheet of glass and laying unidirectional glass and epoxy resin on it. They sanded the back after it was done and I believe they said they vacuumed the lay up to help with air bubbles.

The concept of commercial and hand laid is the same, just commercial has the resources to have better tolerances and access to better materials.I am all about innovation and being resourceful, and I have found what some people say cant be done is done easily by others many times.

[dfrois]

Thanks for your reply. So, there are those out there who are doing something similar? Great! That means I`m not completely foolish in thinking about it. Yes, the air bubbles would probably be the hardest issue to solve...that and maybe get a small enough variation in thickness, over the length and width of the lam. I am definitely going to try this after I finish my bow. If anyone is interested, I may post some pics and results...but, as with bows, I don`t expect great things with my first tries. We`ll see.

[fujimo]

i have had a fair amount of time with glass, and resins. (- problem with car wax's, Pam, vaseline etc is that they are not designed to be used with resins- and can create undesirable effects)

in my mind this is how i would do it:
 two thick glass sheet/panes.  use some of that heavy gauge vapour barrier plastic( avoid the creases). lay plastic on one glass sheet. tape the edges down- so it is nice and smooth. do the same with the other.
lay the fiberglass down on the one plastic covered glass sheet, wet it out with the resin, lay the other plastic covered glass sheet on top.
place some spacers around the perimeter, to control the desired thickness.- DONE!!
 you will have to experiment with how much glass to resin- remember you want the highest possible ratio of glass to resin, yet still maintaining a fully wetted out matrix- no white starry dry areas.
when it is cured lift the top glass off, peel the plastic off- do the same for the bottom.
the thicker the glass the better- less prone to flexing.
 the plastic takes the place of release agents- and allows for flexibility in the release yet still retaining regidity in the "mould"
cheers
wayne

[inksoup]

well,

as far as i know if you apply glass strands with polyester it makes perfect limbs. does not matter if it is isotropic or whatever. fiberglass boats are with glass strands and polyester since it is elastic and strong enough.

mostly, ready made fiber bows are made of glass strands and polyester mixtures with high temperature and pressure.

best.

[dfrois]

Thanks both for your input. Fujimo, I too have had some time with fiberglass and resins, etc. , and I coudn`t agree more regarding waxes and such. I much prefer a solid barrier, and barrier plastic is perfect. Using glass panes seems indeed the best strategy, one of the reasons being that it allows you to see what is happening with the layup. I will probably try your idea, and use long spacers close to the fibers, with holes in them to allow excess resin to pour out. Should be fun.

Inksoup, I have wondered if the unidirectional orientation of the fibers is indeed required, and if it is just an optimization or really necessary. I may try to build 2 limbs for a takedown, one with unidirectional glass and the other with plain fabric weave (cloth-like), to see if there is a measurable difference. My guess is that there will be a difference, but maybe it is not as big as one might expect. For the record, what I want to make are lams to use with wood cores and veneers, not solid glass limbs. The epoxy resin I use can cure at room temperature, in 8 to 24 hours, so it should be good for these experiments.

[dfrois]

Also, forgot to mention that I have a pair of solid fiberglass limbs, bought as part of a new, cheap takedown, and those limbs are relatively thick, and very heavy for their poundage. My wife`s Samick Vision limbs, with the same poundage, weight nearly half...and the first pair of limbs that I made, and use today, are also a little over half their weight, despite being 50% stronger in poundage. So, all-glass limbs do work, and have some advantages for hunting (insensitive to moisture, harder to break in a fall, etc.) but I prefer to make laminate limbs with wood in the middle and fiber front and back.

[fujimo]

good luck- we will be watching. plenty of pics,eh!

[BenBow]

There is a guy from Australia that makes his own carbon lams. He used to have a build along on the ozbow site but that's a few years ago so I don't know if it's still there.

[BenBow]

Here's a quote on what he said about making fiberglass lams.
 

It is easy to make your own glass laminations, here's how.

You need the following:
Uni-directional glass fabric, not woven and not chopped strand mat.
A good laminating EPOXY, not polyester, not vinylester and not an epoxy adhesive.
A mould, about 180cm long, with a recess about 0.8mm deep and 35 to 50mm wide; 35mm for a longbow and 50mm for a recurve.
A lid for the mould.
About 24 G cramps to clamp the lid to the bottom section of the mould.
Some means of tensioning the fabric in the mould while the epoxy sets.

You cut the fabric into strip/s, depending on its thickness.
For a lam 180cm long you will need at least 25cm of waste, ie 205cm of fabric.
Coat all surfaces which will come into contact with the epoxy with a release agent. Allow to dry thoroughly.
Clamp one end of the fabric in the mould.
Thoroughly saturate the fabric with epoxy.
Tension the fabric.
Work the epoxy into the tensioned fabric.
Clamp the lid to the mould.
Wait 24 hours.
Place the mould complete with clamps in a hotbox and cure at an elevated temperature according to the manufacturer's specifications.
Disconnect the heat and allow the mould to cool in the hotbox.
Remove the clamps.
Remove the laminate from the mould.
Remove waste fabric and epoxy from the sides of the laminate with a sharp Stanley knife.
Cut the waste ends off the laminate.
Sand one surface with 60 grit paper to form a surface which will bond to epoxy adhesive.

Then make another laminate.

Now you are ready to make your bow.

 

[johnny girardi]

Cant you buy epoyx impregnated glass strands just like carbon strands.I think they come in ribbons. the smaller the ribbon the tighter the layup.you may need high heat with these.

[dfrois]

Sorry for the delay, was out shooting in the weekend.

Wow, great info there! BenBow, that description on how to build them sort of matches what I have been considering. I don`t have access to unidirectional fibers, but the weaves that I do have, if cut in 5cm strips or so, will allow manual removal of transverse fiber, leaving only the continuous, longitudinal ones. I had considered the need to keep them stretched during the layup and cure, but thought that it might not be needed, if they were initially aligned and then compressed from above.The depth of the recess would ensure that the lam would always have a consistent thickness, but it is also a trap, because the ratio of fiber to epoxy would vary according to how little or how much fiber was used. I think I should try to get as much fiber in there as possible, for a given volume/depth/width. Too much resin would not be good...The other problem is: how does the excess resin exits the mould? There could be areas where the excess resin would stay trapped inside the mould, or move the fibers out of alignment while pushing through a tortuous path to get out when squeezed. Perhaps small holes, on either side of the mould, placed every few inches, would sort that.

johnny girardi, that would indeed be a good step, if only I could find them. I think that kind of products are called "prepegs", short for "previously impregnated", or something. I don`t have an oven, however, and the resin I use cures at room temperature.  

I`ll try to find the time this week to make some experiments, and see if I can learn something useful. I will take pictures and post them. It´s the least I can do for all the help that all of you have given me.

Thanks.

DF

[BenBow]

If I remember correctly the guy who makes his own carbon lams has used some of the weaves as well and I think he indicated it helped keep limbs from twisting. His forum name is gilnockie on the ozbow forum so you could do a search for more info there. I've thought about building lams but don't have enough time to do what I'm doing. I have epoxied 10-12 layers of the fiberglass cloth in my riser to strengthen it.

[fujimo]

one can get continious roving on a roll- kinda like they use for chopper guns- cheapest way to go- but for your first experiments , the manual way would work great too.
the stretching i would say would be imperative- keep everything nice and in place and pre tensioned.
 the continious roving would also allow you to use a setup like one does for a continious bow string- and keep it all tensioned.
and you will get a formula worked out as you go along- how much resin to glass- weigh and measure everything as you start- those records will be invaluable- as you develop your product.
in another life i used to build hi-end vac bagged and pressure moulded competition kayaks and equipment ( slalom and white water) and weight to strength ratio is critical in other words glass to resin ratio.
i just know that without the accurate records, i could never have maintained any consistancy, and it  would never have worked.
kinda like keeping stack layups for bows.
good luck- i wanna see more!!!

[dfrois]

Well, it took longer than I thought, but I finally managed to put my, and yours, ideas to the test. I have made my first fiberglass lam...with mixed results. The good news is that it does work. I have obtained a 0.8mm lam, fairly constant in thickness, with a lot of fibers in it. Not very good, but I think it is useable for low poundage bows (20 to 40#), which was my idea to begin with. The bad news is that:
a) It is a lot of work
b) The lam is not fully transparent (mostly my fault)
c) There is a lot of wasted resin (partly my fault).

I took pictures as I went along, and will post a more detailed description briefly (as soon as I can get my "#!$$%&$&#$ card reader to behave!!!).

DF

[milehi101]

Do NOT USE polyester for the glass Lams Epoxy does not like it and will not bond with it very well use epoxy resins for the job.  Also go to a fiberglass supply store and buy a product called mold release and some mold release.  The suggestion of 2 layers of glass will work but not as well as a vacuum bag.  Coat the glass on the contact sides with several coats of mold release wax and wipe it off each time.  After a few coats apply the mold release A soft brush will work I use the product from West systems and it can be applied with a soft brush. (it cleans up with water)after it dries you are ready to lay up the glass and put the top piece over the layer of glass and let it dry for at least 24 hours.  The glass will release from the layer of fiberglass and you will have a nice piece of flat glass that is ready to cut into strips and sand to a final thickness.

[milehi101]

I forgot the word wax at the end or the line that says mold release. It should be mold release wax.  Their are 2 products mold release and the mold release wax.  It takes several coats of wax the first time or two you make a layup before you apply the mold release.  after a couple of lay ups it only takes one between lay ups.

[fujimo]

the mold release liquid is a PVA liquid- it is best sprayed un with a spray gun, or the very least i have used a high quality  squirty bottle- it can work too. but brushing does work- but can leave brush stroke marks on the final part.
but the soft brush would be the ticket.
 the glass is suggested as an economical, yet practical alternative to vac bagging- in fact it would be synonomous with "pressure bagging" a viable technique.  as the costs of, vac pump, residue trap and all the plumbing, peel plys and membranes etc would be quite costly- especially for an experiment.
my only concern with vac bagging, would be that it would be difficult to obtain an absolutely smooth and uniform top surface, especially when dealing with individual strands of fibres..
but there is heaps of good advice and opinions on here- so forge ahead- and remember to keep us posted

[fujimo]

why didnt you get clarity- was it air bubbles. or moisture?
air bubbles would best be eliminated by the vacuume bagging process.
i still wouldnt wax the glass- it will be really hard to get the two panes apart, especially if you are using thick enough glass, you wont be getting the flex in it , in order to "peel" off the top layer of glass, ( go on... ask me how i know this!!    )thats why i suggested the plastic film- i geuss you could wax the bottom pane and then use plastic fim under the top pane- that might be the best of both worlds.
lets see the pics, when you are ready
wayne

[dfrois]

Sorry for taking so long to respond - I am having some weird problems with creating an account with photobucket, so that I can post pictures.
 milehi101, thanks for your sound advice. I did not use polyester resin, but rather the epoxy resin that I also use for my laminated bows. I do not have the stuff needed to use vacuum bags. I have quite some experience with making fiberglass-related stuff, i n a previous life, and never liked wax of any sort. It seems to only work well for me when using rigid molds for large pieces, where exact thickness is not important. Maybe it`s just me...but I do prefer plastic wrap, at least for what I do now.
~Fujimo, I don`t really KNOW, but I very strongly suspect it was the way I wetted the fibers. I layed them down on the mold, only trapped at one end, and then poured resin from above, working with a spatula and a small roller to wook the resin downwards into and around the fibers. After doinf this for a few minutes, the fibers were reasonably wet, but the resin on top was getting a milky look, like there was millions of microscopic air bubbles trapped in it...which they probably were. Squeezing the fibers betwwen the planks got rid of most of it, but not all...hence the fuzzy look. The next time, I will pour a coat of resin on the bottom of the form, before laying the stretched fibers on top and pressing them down. That will also help getting the fibers better aligned...my working the resin down disrupted the already imperfect alignement quite a bit. That in itself does not bother me, but the possibility of having wildly varying thickness, due to having too much fibers in one spot and not enough on another one, close by, does bother me.

Let me see if I can get this photobucket stuff sorted, so that I can post pics.

DF