Need advice on first glass bow!

[Apex Predator]

I have lams and glass on the way!  I built a simple form to build my first glass bow in the Hill style.  I tried to use a piece of 1/8" aluminum for the pressure strip, but it is too stiff.  I custom fit it to my riser, but still wasn't happy with how stiff it was.  If it shifted any, it would have given me problems.  I decided to go with a piece of PVC lattice.  It is 1 1/2" wide by 1/4" thick.  It is flexible enough to conform to the curve of my fade-outs.  My intuition tells me that the square corners will cause more pressure on the edges of the bows back, and may cause the center to bow.  Is this unfounded, or should I round the edges of my PVC pressure strips?  I will use innertube rubber for clamping pressure.  Any other tips you folks can give me on this type of form?  What kind of alignment system should I use to keep everything from sliding around while I am trying to clamp?  That is just a dummy riser, by the way.  I have my real one clamped to a board to protect the much thinner fadeouts.

 

 

 

[Apex Predator]

I guess I should have said that I'm worried about the bows belly from uneven pressure, since that is what will be face up in my form.

[elk ninja]

Apex,
I use a similar system in my clamp form.... I use the aluminum with cork glued on it and the form to even out the pressure... one of my recent lessons is the curve of the riser.  Yours looks real similar to mine in terms of the curve and how the pressure strip lies...
So here is my .02
I'd refigure the curve on the riser (I know it is a dummy, but I assume it's real close, radius wise, to what you'd use, otherwise a mock up would loose any value), I'd suspect you are going to have a tough time getting a good glue line in the area of your ring finger.  You could shorten the level area on the belly of the riser or lessen the total curve.  Let me know if that isn't clear.
As far as the pressure strip transmitting uneven pressure, it might, but I don't think it will change the final product.  Remember you'll thin the limbs.  In addition, you can use construction shims to even up the pressure, essentially a pressure plate for the pressure strip.
Mike

[Apex Predator]

Here is my actual riser.

 

 

 

[SteveD]

Looks good. I made a Hill style bow, I just used rubber inner tube. Used extra on the fade outs. It worked fine.

[PV]

A few bar clamps on the fade out could do the trick.If you are using the lattice it can be pre bent to conform to the fades with heat

[Apex Predator]

I think the lattice is a no-go.  I tested a piece in my kitchen oven on "warm", which is as low as it will go.  My hot box thermometer (meat thermometer) showed it at 185 deg.  When I took it out it was pretty soft.  I think under clamping tension it will deform.  My hot box will only be 165 deg, but I don't want to risk it.  I guess I'll pick up a piece of 1/16" aluminum that I saw at lowes.  This is getting expensive!

[wingnut]

"This is getting expensive!"  Welcome to the world of cheap do it yourself glass bows.  People can't figure out how a bow costs $450 when it only has $150 in parts.  Your beginning to learn the leason that all of us learned years ago.

Remember the first three bows probably will not be what you want and that's if your real smart.

LOL

Toss the PVC and use aluminum.  Use masking tape. . .lots of masking tape to hold your lams in place til you put the clamps to it.

Mike

[Swamp Pygmy]

No advice but I'm watching. Good luck.

[shantam]

you can make custom pressure strip by laminating 3
thin layers of wood into one bigger pressure strip.
use your form and riser,cover it with somethnig to protect it from glue nad you are done.this way you get a pressure strip that fits perfeclty into your bowform and riser.
shantam

[Apex Predator]

That's the best tip I've received all day!  I'll laminate a perfect set of pressure strips.  Thanks for the tip.

[shantam]

welcome body  :D
shantam

[onemississipp]

That was a great tip!

[NightHawk]

I see you have dowel rods sticking out the side of your form. Why are you using firehose as a clamping method? The dowels led me to believe you were going to use rubber bands(cut intertube)to clamp the bow to the form?

[Apex Predator]

I do plan to use rubber innertube for clamping.  I think someone else mentioned the fire hose method.

[Cupcake]

To keep everything lined up on my bow form from side-to-side I used several short stops screwed to the form on both sides.

 

Here you can see them in the photo.

I am going to make my next bow with a riser between the glass and had not considered there might be trouble clamping that area so this is a timely post for me.
Good luck, bow building is really fun.
Kevin

[Apex Predator]

I decided to go with 1/16" aluminum for a pressure strip after finding that the 1/8" was too thick to conform well to the fades and the PVC would soften in the heat.  I should have listened to Sam Harper!

I built a hot box using PVC for the frame and a roll of foil sided isulation.  It will take apart and fold flat when not in use.

 

 

 

[onemississipp]

Great idea on the heat box!!

Mine is huge and doesn't break down..

Way to go!! Keep it coming.

[7 Lakes]

The trouble with this type of form and strapping method is there is almost no pressure in the center of the lamination.  The bands are extremely tight on the edges and this often keeps the air in the center from being pressed out.  It's also a concern for gluelines in the center.  

Here is the best answer I found.  

Make your pressure strip out of several laminations glued together and pressed onto your form.  Make the final product thick enough so you can sand it so it's rounded.  That is, thiner at the edges and peaks at the center.  This will fit right back on your form and the rounded hump in the center will apply the pressure more evenly.  

You can also look for a rounded over piece of molding.  Imagine this picture rounded over. /^^\\