Power lam question

[talkingcabbage]

I've built a few of the glass bows now, but I've read a lot about people using power lams and tip wedges.  What are the advantages of these, and the disadvantages?  I've never used them or really paid attention to bows with them.  How long are they, usually?  How do they fit into the stack?  Etc?

Thanks in advance guys,

Joe

[Furtaker]

Power lams help to move the bend further away from the fades making more of the limb do more work. On some bows at full draw,  with out a p- lam, it looks like a hinge at the end of the riser fades. Throw in a p-lam and the hinge goes away and you get a nice even bend in the limbs.
Tip wedges help cure weak tips. Maybe some tips are too soft and bending too much or string angle at full draw may be too close to 90* causing the bow to stack  
Basically they both help distribute the work load through out the whole limb.
The only disadvantage of using them is if your design doesn't  need them.

[Dmaxshawn]

P-Lams add about 5-6 pounds.

[kennym]

Great answers! All I could add is tips if using seperate p-lams or t wedges.  You can pin the p-lam to keep it where you like it, and on the tip wedge, figure where you want the tip wedge, cut it and the lam next to it same length(1"extra long) and use a pc of tape on the end of em to hold in place. Just fold the t wedge out, apply glue and fold over on other lam, then proceed as usual.  Clear as mud?

[md126]

would a longer riser/fade be the same as a power lam?  also, is the power lam/tip wedge only feasable in longbows, 3pc or 1pc?

thanks

[kennym]

If you made the fades really long, the riser would make the power lam OK, but with the cost of riser wood, I'd rather use a power lam...

I use both in my 1 pc and 3 pc longbows sometimes, seems to work well.

[JamesV]

I don't know how this fits into the equation but this what I do. When I grind my lams I start the taper 2 1/2 - 3 inches past the end of the fades to the tips. This moves the bend further down the limb away from the fades. This works really good with the limb profile and taper rate I use.

[Crooked Stic]

Power lams will also take some stress off the fades. A longer riser will do the same thing sorta. By this I mean if your longer riser fades work some then the result can be the same. So a power lam will work and make the bend more gradual. They seem to be easier to layup when put on the belly ramps.
Tip wedges stiffen the tips for better string angle and aid in the draw weight coming in earlier in the draw. When all of this done right and tweaked makes a better performing bow.

[talkingcabbage]

Thanks for the responses guys!  I don't think my design needs them right now, but maybe I'll play around with them in the future.

If I add tip wedges and don't necessarily need them (to compensate for weak tips), will it add considerable hand shock?

Also, if my design doesn't really hinge off the fades, will adding a power lam be detrimental to the tiller causing a less-than-desirable feel when shot, or will it just add poundage and fps?

[talkingcabbage]

'Nother question, what's the usual dimensions of a power lam?  As in, how long, rate of taper, etc?

Joe

[Crooked Stic]

No set demensions. That is something you find out by trial and error and see what works best for your design. Taper rates also will vary depending on design. A lot of the time most guys want to cure hard bending right off the fades to get a more gradual bend and unload the stress. And again trial and error. My one piece design has a .008 taper power lam and is 11 in. About four in. past the fade. I tried to equal the length of my takedown riser plus wedges with power lams using the same limb profile as the takedown.