Author Topic: Vacuum bagging  (Read 1060 times)

Online Flem

  • Trad Bowhunter
  • **
  • Posts: 993
Vacuum bagging
« on: March 19, 2019, 11:20:30 PM »

Online Flem

  • Trad Bowhunter
  • **
  • Posts: 993
Re: Vacuum bagging
« Reply #1 on: March 19, 2019, 11:46:17 PM »
Speaking of tubing. I started with reinforced vinyl, no good, it doesn't like heat. The green stuff is heat tolerant reinforced rubber (250F). I put a quick disconnect and a check valve in the line, because it nice to be able to pull the vacuum on your bench before going in the hot box. Originally I used the little brass connector to attach the vac line to the bag, but found that it got too hot and weakened the interface with the bag. I replaced it with a nylon bung for a plastic barrel (250F).



Online Roy from Pa

  • Administrator
  • Trad Bowhunter
  • ****
  • Posts: 15897
Re: Vacuum bagging
« Reply #2 on: March 20, 2019, 04:21:39 AM »
Pretty high tech there, Flem.

Looks cool.

Online Forwardhandle

  • Trad Bowhunter
  • **
  • Posts: 1653
Re: Vacuum bagging
« Reply #3 on: March 20, 2019, 09:41:23 AM »
Thanks Flem I have been waiting on this one with great interest I have multipal uses for a vac press , that Joe wood workers page is very good I have been looking for a decent vac pump fo the right $$$ but a little skeptical of some I see for cheap & re builts I know you got lucky on the E box store but I'm not much of a gambler looking for some thing new !
If you fear failure, you will never try ! But never except it!!


Online skeaterbait

  • Contributing Member
  • Trad Bowhunter
  • ***
  • Posts: 1062
Re: Vacuum bagging
« Reply #5 on: March 20, 2019, 10:50:49 AM »
Can you reuse the bags? Would you mind showing some pics of how your hose connects to the bag?
There is no shortcut for experience.

Online Flem

  • Trad Bowhunter
  • **
  • Posts: 993
Re: Vacuum bagging
« Reply #6 on: March 20, 2019, 12:51:33 PM »
Ritchie, I don't blame you for wanting to buy new. I will say my used pump is probably 10yrs old. Guess I got lucky!
Skeater, I have tried to reuse the bags, but it seems like they always get compromised somehow. It really sucks to try to find pinholes! Might have a better chance for reuse if you used a heaver plastic than 4mil.
 
Stupid bag won't work if you don't seal the ends and get a port in it!

I sharpened a piece of copper pipe to cut the port. Its nice when it just  barely stretches over the fitting

 
The bung adapter has a shallow seat on the inside and I replaced the hard rubber washer with 2 nestled O rings, for more grip on the bag, the outside is a soft rubber washer, hard washer and nut.



To seal the ends, there are a few options. Some people use a roll closure, didn't work for me. The setting compound tape works good, but the best closure and cheapest/no waste solution is the impulse sealer.
$15 cheap Chinese POS, but its lasted a long time

Online skeaterbait

  • Contributing Member
  • Trad Bowhunter
  • ***
  • Posts: 1062
Re: Vacuum bagging
« Reply #7 on: March 20, 2019, 02:01:03 PM »
Thanks
There is no shortcut for experience.

Online Shredd

  • Trad Bowhunter
  • **
  • Posts: 999
Re: Vacuum bagging
« Reply #8 on: March 20, 2019, 05:58:39 PM »
Cool Rig you have there Flem...  Love to see someone else using vacuum bagging...  It is so useful in many applications...   I glue up my forms using a vacuum bag...  No screws to worry about being in the wrong spots...  A lot of guys would cringe at the fact that you only got 12 psi going at 25 hg...  Just goes to show you that you don't need a lot of pressure to make a good bond with epoxy...

Online Flem

  • Trad Bowhunter
  • **
  • Posts: 993
Re: Vacuum bagging
« Reply #9 on: March 20, 2019, 07:02:02 PM »
Thanks Shredd. I concur with everything you stated. I'm always looking for stuff to squeeze, cause it works so well.
12psi sounds so wimpy! I prefer to brag that it generates 1750lbs per Sq. ft :goldtooth:

Online Crooked Stic

  • Trad Bowhunter
  • **
  • Posts: 3406
Re: Vacuum bagging
« Reply #10 on: March 20, 2019, 07:55:57 PM »
I think epoxy will bond without pressure.
High on Archery.

Online Shredd

  • Trad Bowhunter
  • **
  • Posts: 999
Re: Vacuum bagging
« Reply #11 on: March 21, 2019, 12:33:27 PM »
   That's about 1,100 lb on a 60" bow...  Seems enough to me...   :thumbsup:

   Stic...   Don't think it...  Know it...  Matter of fact the more epoxy you squeeze out the weaker the bond...   Talk to any boat builder about that or just look up info on epoxy...  I think that there is only so much that you can learn from other craftsman and hearsay and then there is the reality of the situation...

Offline ztontonz

  • Trad Bowhunter
  • **
  • Posts: 62
Re: Vacuum bagging
« Reply #12 on: March 21, 2019, 02:38:29 PM »
Really interesting setup. Thanks for sharing !

Online Crooked Stic

  • Trad Bowhunter
  • **
  • Posts: 3406
Re: Vacuum bagging
« Reply #13 on: March 21, 2019, 03:47:20 PM »
Ok so you got a tire on your Jeep 17 X 10 X 33. It carries 35 psi. air pressure. What is the overall PSF press. ??? :bigsmyl: :bigsmyl:
High on Archery.

Online Shredd

  • Trad Bowhunter
  • **
  • Posts: 999
Re: Vacuum bagging
« Reply #14 on: March 21, 2019, 03:58:36 PM »
  144 x 35 =  5,040 lbs.

Online Shredd

  • Trad Bowhunter
  • **
  • Posts: 999
Re: Vacuum bagging
« Reply #15 on: March 21, 2019, 04:01:14 PM »
  A 60" x 1 1/2" bow with 60 psi on it is 5,400 lbs...

Online Bvas

  • Trad Bowhunter
  • **
  • Posts: 1938
Re: Vacuum bagging
« Reply #16 on: March 21, 2019, 05:21:16 PM »
  A 60" x 1 1/2" bow with 60 psi on it is 5,400 lbs...
Shredd if you are talking hose forms, then I don’t believe this is completely true. :dunno: Just because the hose has 60psi, doesn’t mean all that pressure is being transferred to the bow. Some of that pressure is used to fill the gap in the form. If it takes say 5-10psi to expand the hose to the form, then you are only applying 50-55psi.
Some hunt to survive; some survive to hunt

Online Roy from Pa

  • Administrator
  • Trad Bowhunter
  • ****
  • Posts: 15897
Re: Vacuum bagging
« Reply #17 on: March 21, 2019, 05:41:59 PM »
Fugger this weight out for me, Shreddy..


Online Flem

  • Trad Bowhunter
  • **
  • Posts: 993
Re: Vacuum bagging
« Reply #18 on: March 21, 2019, 05:58:15 PM »
This thread sucks! I need to wrap this up. Get it in the bag. I already got enough baggage in my life.
OK, thats all the cliche's I got.
 So I'm not going bore anybody with a glue up. I'll get right to the baggage.
I don't go to much trouble pre-bag. I do use some disposable cauls on the sweeps, just to make sure to get good pressure on the one area that the bag stretches most. Also no need for any tape or strapping to keep things in place, except on the ends to keep things from sliding down.



Once that done, its into the bag. Helps to cut the port hole first, not much room after the blank is in.


Heat seal the ends and its time to suck, which can be done one of two ways. You can close the ball valve, pre-charge the tanks and then get a fast draw down. Or what I prefer, the slow draw down. Turn the pump on and while its pulling, make sure everything stays lined up.



The green material is breather fabric, allows the vacuum to pull along the entire length of the blank. It also sucks up any excess resin. You can buy fancy breather/bleeder fabric, I just use whatever I have laying around that fits the bill.This stuff was some furnace filter material.


I'll say it again, this method is not superior to any other, I like it because its easy and I'm lazy.
I do think it has two advantages over other methods
1)no need to strap or tape the crap out of the blank, the vacuum pulls the blank together from all sides.
    makes it real easy to keep things lined up.
2) For the style of Bows I make, no form needed. For other styles, bottom only. No form= less mass to bring to heat. I preheat to 160deg, after the blank goes in the box it takes about 5min to get back to temp.
« Last Edit: March 21, 2019, 06:10:22 PM by Flem »


Users currently browsing this topic:

0 Members and 1 Guest are viewing this topic.
 

Contact Us | Trad Gang.com © | User Agreement

Copyright 2003 thru 2019 ~ Trad Gang.com ©