Giving it a shot... My First Laminated Glass Bow Build

[Roy from Pa]

Very nice work..

[Skyhigh315]

Great stuff!  I wish I had access to a shop like that...

[Major Boothroyd]

Thanks guys, and thank you Trux and bigbob, for the tips on the overlays.

One other question I have... do you recommend cutting string nocks on the tips and tillering before gluing on the reinforcement layers, and then continuing cutting the string nocks trough the new pieces after shaping/sanding, or is it better to wait to begin tillering until after gluing the reinforcements on from the get go?

[bigbob2]

I usually cut in small nock grooves first to determine bottom and top limbs, measuring at fades and then glue on nock overlays, shaping them during tillering process.

[bowhntineverythingnh03743]

x2 what bob said as well. I always get my limbs bending correctly and get the nocks cut in to almost exactly where they will be after the tips are glued on. Then it is as easy as shaping them up.

[Major Boothroyd]

Just a quick update for today.  I went to the shop to work on the tip reinforcement pieces and the riser accent pieces.

I cut the pieces out of Micarta and Bolivian Rosewood.  I spent some time shaping the wood accent pieces for the belly of the riser, since I felt that those pieces will be just slightly too thick to bend properly to the contours of the riser.

I finished up the session by roughing up all mating surfaces with 800 grit sand paper.

I am just waiting for some more EA 40 Smooth On Epoxy to arrive any day now, and then I'll glue up these pieces.  Next, I'll start to build my tillering tree.  I have most of the hardware already, but I'm planning to make mine easily portable, so I can bring to the community woodshop to use there.  I think I'll try to construct it so I can clamp it to a beam or something when using it.  I'll have to work out how to have a detachable section that will have rulers & a grid.

[mikkekeswick]

It is going well for you  
Did you mean 80 grit to roughen up your mating surfaces?

2nd that... 800 is too fine...  Use 60- 80 grit...Some guys even score things with a hacksaw blade...

[kennym]

No 800!! But if feathering g out to glass , 40 will make the transition less smooth. I'm gonna start using 120....

[Major Boothroyd]

Sorry, I meant 80 grit.  I posted last night right before hitting the hay, and I guess I was tired!

[Major Boothroyd]

since we're on the subject of sandpaper, what do you guys like to sand to prior to spraying a finish on your bows?  I'm wondering what it will take to get a nice clear "polish" to the glass, and smoothness to the wood.  

I think I read some posts somewhere saying that to get a really nice finish, some wood types need to have the pores filled with something prior to spraying the finish on.  I'll have to search, but I can't remember what the recommended filler material is.

Obviously I am a ways off from being ready to start working on any of the finishing stages, but I thought I'd start to ask the questions.

[mikkekeswick]

Sand glass to 320 before spraying. Wood to the same.
Anything finer and the surface doesn't havew the correct 'tooth' for the varnish to adhere properly.
Yes you do need to fill the pores if you want a mirror finish. If you are happy with a matt finish then you can leave 'open' and it won't look bad visually. It you want matt and flat then yes fill.
I use a shellac based filler but others are available. Make sure what you use will be compatable with your chosen finish. Shellac works with everything  

[mikkekeswick]

I'm interested in what others use for grain fillers as well!

[bigbob2]

I just use C.A glue for filling pores etc.don't like the stuff but it does a good job. Some times need multiple coats.

[Major Boothroyd]

Okay, today's update...

Thank you guys for the tips on sanding prior to applying the finish!

I went in to the shop, and started fabricating my tillering tree.  I got a few ideas from various members here, and largely I am copying the one in Roy's video here...

         

Thank you, Roy!  That is a very helpful video, since I shoot 3 under, and had been wondering how, exactly, I should tiller my bow.

Anyway, the drill press at the shop was down, but should be back up by early next week, they said.  A part broke and they're just waiting for the new part to arrive.  So, I'll have to wait until next week to finish the tree, but I don't have a lot left to do on it before it's done.

In other news, my EA 40 Smooth On arrived today, so I will be gluing up the tip reinforcements in the next day or two.  I also received my UBR 10 rasp (Dean Torges design).

After a lot of deliberating, I ordered some Thunderbird satin finish, along with their filler product, so we'll see how that does.

I can see light at the end of the tunnel!

I am going from memory because its been a while...

I used some Aqua Coat to fill wenge grain that was used for accents... Wenge has pretty big pores... From what I heard I thought that Aqua Coat would be the trick... It took 3 coats and still did not fill all of the grain and if you did not sand it totally off it left a dull pale haze under the finish... In my book, that really sucks...

   I used the same urethane finish that I used to spray up my bows... A couple of quick passes with a fine artist brush did the job and because it is the same finish that you use to spray there are no discolorations...

[Major Boothroyd]

I got a few things done on the bow since last week.  I epoxied the tip reinforcements, shaped the tips and filed in my string nocks to about 85% - 90% of the depth of the bow I am trying to emulate, which is a McCullough Griffin, BTW.

I strung it up for the first time today, and took some measurements and photos, and compared it to my Griffin.

The limbs are clearly going to need some tillering work, and I'looking forward to hearing what you guys think.  The first thing I should probably mention is that the Griffin is asymmetrical, as in the length of the string nocks is not equi-distant to the fulcrum of the grip.  For better or worse, I chose to duplicate the distances on the Griffin, since I really like how it shoots and feels.  So, for comparison, here are some measurements:

Both bows have identical limb measurements (measured along the belly of the bows):

Fulcrum of grip to bottom limb string nock = 32 1/2"
Fulcrum of grip to top limb string nock = 31 3/8"

Both bows when strung with the same string have a brace height of 8".  I normally prefer it around 7  1/2", but this is the string I have at the moment, and since it's just for comparison purposes, I think it's fine.

Here is a photograph of my Griffin, strung up.  The limbs look like they show a fairly symmetrical bend, or arc, and the measurements I took confirm that.  The blue tape was just mark precise places to take measurements (12" and 24" from each string nock).  The top limb is on the right side of the photo:

       

As you can see on my build, the limbs are not bending symmetrically (top limb on right side of photo):

     

The tiller measurements for both bows are as follows (measuring points from string to belly of bow):

Griffin:
12" from bottom limb string nock = 3  1/4"
24" from bottom limb string nock = 7"
24" from top limb string nock = 7"
12" from bottom limb string nock = 3 5/8"

My bow build"
12" from bottom limb string nock = 4  1/2"
24" from bottom limb string nock = 7  3/8"
24" from top limb string nock = 6  3/4"
12" from bottom limb string nock = 3  1/4"
 

My biggest concern is that it seems like the top limb is closer to showing the proper bend or arc, with reflex, and the lower limb may be too weak from the get go, since it isn't exhibiting much reflex compared to the Griffin.

I'm not sure if I'm coming to the right conclusion, so I look forward to hearing what you guys think, and what you recommend my process to tiller this bow should be.

Anyway, here are some photos of my rough shaped/sanded tips and my string nocks, which are not cut to the full depth just yet...

Bottom tip:
               

Top tip:
       
               

[mikkekeswick]

Do you have an I-beam in the riser? If not flip the designated limbs. Aim to get the differences in the strength of the limbs down to 1/4 inch. Lower stronger.

[Mark R]

It looks like the riser into the fade is much thicker towards the right side of of picture (the top),also are the limbs different lengths from the riser fades to the tips. Not sure what your riser design thoughts were, you cant add to the bottom limb so you might have to shorten the top to get tiller to work, lots of questions, good luck.

[Major Boothroyd]

mikkekeswick, there's no I-beam in the riser, however, because of the asymmetrical design of the limbs (length wise) and riser (shape wise), I don't know if flipping the designated limbs would work well.

Mark R, yes, the design is based on the bow pictured above mine in my last post (a McCullough Griffin), and the riser follows the shape of the riser in the original bow pretty faithfully.  Also, the limbs are different lengths, apparently by design.  Before starting this project, I compared my Griffin to two others that are owned by friends of mine, and they all bear the same asymmetrical limb (and riser) design.

Also, the top limb is already shorter than the bottom limb, by 1  1/8".  Again, this matches the bow mine is based on.

I probably should have started with a symmetrical design for my first bow build, but oh well... it's too late for that now.  Worst case scenario, if I can't get this one tillered properly, I'll consider it a learning experience and try to do better on the next one.