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Main Boards => The Bowyer's Bench => Topic started by: Bryan Adolphe on May 15, 2024, 02:36:44 PM

Title: Limb deflection on pads.
Post by: Bryan Adolphe on May 15, 2024, 02:36:44 PM

What’s your thoughts? I’m a bit concerned when The limbs are braced. There’s deflection at the wedge that sits onto the limb pad i’m wondering if I Should add a Substantial underlay I guess you’d call it on the limb To stiffen it.  There’s a lot of pressure down into that limb butt.  I think you can see the light and the actual arc in the wedge from the end of the riser to the bolt.  :o
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Title: Re: Limb deflection on pads.
Post by: buckeyebowhunter on May 16, 2024, 09:07:04 AM

Several of my early bows had daylight shining between the pin and limb bolt. I think that my riser pads weren't perfectly flat. I never had any issues with those bows. Your wedge looks plenty thick enough to me. But if it worries you might glue a 1/16 piece of phenolic on the belly side of the limb pad and re drill holes.

Title: Re: Limb deflection on pads.
Post by: Bryan Adolphe on May 16, 2024, 09:36:15 AM

Quote from: buckeyebowhunter on May 16, 2024, 09:07:04 AM

Several of my early bows had daylight shining between the pin and limb bolt. I think that my riser pads weren't perfectly flat. I never had any issues with those bows. Your wedge looks plenty thick enough to me. But if it worries you might glue a 1/16 piece of phenolic on the belly side of the limb pad and re drill holes.

  I went back to check another riser that I just pattern sanded the back profile  and my limb pads are perfect but  I think my problem is when I go to put my overlays on I didn’t recheck those limb pads and now I see they’re not perfect...  A bit of hand sanding and doublechecking prior to finishing should do it. I do install those back overlays with an air hose method but It could easily be in the milling of the overlays  :banghead:

Title: Re: Limb deflection on pads.
Post by: kennym on May 16, 2024, 12:58:36 PM

Check the limbs where they lay on riser too , I’ve had a couple that weren’t perfectly flat …

Title: Re: Limb deflection on pads.
Post by: Kirkll on May 16, 2024, 01:19:54 PM

Another thing you can do is to move those limb bolts out about a 1/2" or so. So they are not so close to the limb butts. I still get that now and then on perfectly flat risers if i use more flexible wedge stock.  I kind of like to match my wedges to the riser wood on some bows, but curly maple isn't stiff enough and i'll get some daylight now and then... Purely cosmetic as far as strength goes until you start getting over 80#... You can put a piece of mole skin or thin rubber pad under it for looks.

 The 80-100+ pound bows, i use a piece G-10 on the limb butts that overhang the riser a bit to get rid of that high compression on the glass right at the end of the riser. I did have a 90# bow limb break right at the riser once.

Here is a bow that has seriously heavy limbs that you can see the extra limb but protection on the limb butts in a few of these photos.... 

 https://photos.app.goo.gl/MbpkpzAXqq6y3VB28

Title: Re: Limb deflection on pads.
Post by: Bryan Adolphe on May 16, 2024, 01:20:21 PM

Right, you are Kenny I did check the limbs And yes, they’re not perfectly flat.

Title: Re: Limb deflection on pads.
Post by: Bryan Adolphe on May 16, 2024, 01:39:04 PM

Thanks, Kirk my thoughts are to move that limb bolt down a bit on the next ones.     that was my concern the pressure right at the end of the riser on the glass. All of my bows so far are under 55 pounds. Good to know thank you..

Title: Re: Limb deflection on pads.
Post by: Jon Lipovac on May 16, 2024, 02:47:55 PM

I've also had this happen before and did what Kirk suggest and moved my limb bolts out a little.
I've done this before. As long as your overlays for the riser and the underlay for the limb are ground perfectly flat. I'll drill the pin holes and bolt holes in them ahead of time. Then use a release like Johnsons Paste Wax or something similar on the pins, tape the overlays and underlays where they contact each other, glue them up and install the limbs, tighten the bolt and string it to brace. That way when the glue dries it will fit perfectly. I've never had the overlays look like they were not tight.

Title: Re: Limb deflection on pads.
Post by: Kirkll on May 22, 2024, 10:42:58 PM

Actually what i found best was building in a wee bit of reflex in my wedge, and once the string is on she flattens out.... here is a good example with and without a string...  Click on the photos to enlarge them.

https://photos.app.goo.gl/kFmVNJBRpHKy1PnB8

This particular bow has 75# limbs and i have a G-10 limb butt overlay to protect the glass. i haven't found this necessary on bows up to 65#, but i do this on my heavy limbs to insure the compression point at the end of the riser doesn't fracture the glass... don't ask how i know this...just trust me on this one.

Title: Re: Limb deflection on pads.
Post by: Bryan Adolphe on May 22, 2024, 11:16:59 PM

Jon i like that idea of glueing up the limb pad overlays and bolting on the limbs… should be a great fit. Right now the risers I have , the overlay Is the full back of the riser, I built a form and use an air hose at glue up , there’s also 4-5 laminations in the overlay and it seems they’re ending up, not perfectly flat. Something else to figure out & work on  :biglaugh: [ You are not allowed to view attachments ]

Title: Re: Limb deflection on pads.
Post by: Kirkll on May 23, 2024, 12:49:55 PM

Quote from: Bryan Adolphe on May 22, 2024, 11:16:59 PM

Jon i like that idea of glueing up the limb pad overlays and bolting on the limbs… should be a great fit. Right now the risers I have , the overlay Is the full back of the riser, I built a form and use an air hose at glue up , there’s also 4-5 laminations in the overlay and it seems they’re ending up, not perfectly flat. Something else to figure out & work on  :biglaugh:

What type of material are you using for overlays, and how are they prepped before lay up?  And .....are you using a stainless steel pressure strip, or very stiff pressure strip on these? 

Even using a milling machine, and prepping my phenolic before application of the overlays, i still  use a sanding block to make sure the limb pad areas are flat once they are installed. But....I use super glue to apply my limb pad overlays on the riser and do not use an air hose. I have better control doing this using a flat block of wood and clamps.     just a thought....   Kirk

Title: Re: Limb deflection on pads.
Post by: Bryan Adolphe on May 23, 2024, 03:36:24 PM

Kirk i have usually used all wood overlays milled to thickness on the drum sander , this one in the picture is 2 laminations of bamboo one lam of wenge and one of Jatoba on higher poundage bows I have added a 1/16” of phenolic , I don’t think I could lay up full overlays Like this with superglue …. with just lim pads To deal with i could see that working well , I do use a metal strip, same as my limb layups.
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Title: Re: Limb deflection on pads.
Post by: Kirkll on May 24, 2024, 02:16:25 PM

I can see using EA 40 for full length radius overlays. You'd just have to have the outer layer thick enough to adjust the limb pads for square and flat again before installing your hardware. Typically it should be close enough to adjust the limb pad surface using a long block with sand paper for fine tuning.   Looking good!  :thumbsup:

I'm not sure whether i like the idea of gluing limb pad overlays on the limb butts using the bolts and a string to apply the glue pressure. As that wedge area in the limb flexes on the limb pad. the limb butt overly would be trying to hold that slight flex.  I believe these may pop loose when shooting the bow, or even unstringing it,  if it has enough flex to it...

I think you are better off building a slight reflex into the wedge area that flattens out on the limb pad when strung. You are actually getting some extra preload on your limbs doing this too.    Food for thought...   Kirk