Pressure strip

[buckeyebowhunter]

Anybody use anything other than metal for pressure strip? Mine is pretty beat up and I ordered a new strip but it's too wide for my form. It gets caught on the washers I have bolted to the form for alignment purposes.

Thought about trying a strip of 1/16 phenolic instead. Thoughts?

[Crooked Stic]

I use industrial base board the kind you would see in offices (not rubber but kind of a flexible plastic) and bandsaw to what width you need. 

[Kirkll]

Anybody use anything other than metal for pressure strip? Mine is pretty beat up and I ordered a new strip but it's too wide for my form. It gets caught on the washers I have bolted to the form for alignment purposes.

Thought about trying a strip of 1/16 phenolic instead. Thoughts?

I would advise getting rid of those edge washers, and just use Zip Ties. Just drill 5-16" to 3/8'' holes in your form about 3/4" below the edge. Once you you start using zip ties you will wish you had tried it sooner. It just takes all the fight out of laying these up in the form...

I use 22 gage #304 stainless steel strips myself.  I've used regular steel, and formica in the past before i started using heat strips. Regular metal bends to easily, and formica doesn't hold up long. i never tried linen phenolic though... kinda soft...  Kirk

[Crooked Stic]

Here is the thing I see about pressure stripes about anything .030 will work. But the main thing is having the correct spacing between top and bottom of your form so it's dog bone shaped when the hose is inflated. Then there are lots of guys using topless forms and to me that's where the zip ties would work well over the pressure strip.

[buckeyebowhunter]

Kirk, i always use zip ties to get everything taped down but then left the washers on to keep things from sliding. You think it'd be cool to take off washers after taping? I was always afraid stuff might try to slide still.

[BO-R]

Mine is similiar to Kirks, since I use the voltage regulator setup my pressure strip serves dual purpose.
I tie wrap over top of upper pressure strip thru form and holds material quite nicely .
I use about 5 tie wraps for entire form. If all your material is same width should have minimal movement.

[Kirkll]

Kirk, i always use zip ties to get everything taped down but then left the washers on to keep things from sliding. You think it'd be cool to take off washers after taping? I was always afraid stuff might try to slide still.

First of all you really should use the heavy duty zip ties. They have different weight heavy duty ones that hold 100#. Those allow you to really cinch them down tight.

Secondly is the space between your forms make a big difference on things sliding around when you air up your hose. Mike mentioned previously that you want a dog bone shape when your form is buttoned up, or have that hose as flat as possible and centered up perfectly. Getting the hose off center just a wee bit can shift the lams sideways.  But…. With heavy zip ties, and taking care to center up your hose. You won’t get any shifting sideways.

When you first start your air up… just give it 15-25 pounds and look at the hose. If it isn’t centered correctly, drop the pressure and adjust it.  Don’t air up all at once. Give it a moment and go up to 30# and let it set for 30 seconds, then go up to about 50- 55 pounds. 60 at most… you do not need more pressure than that. That 30 second wait time allows the excess epoxy to bleed out the sides without the lams moving.

I haven’t used side washers on my forms for 15 years now and a lot of those years I built 50-60 bows per year or more.    Kirk


On a side note… You want to avoid letting down the air pressure from full 50-55# to make an adjustment because it can suck air back into the limb edges. It’s really noticeable on clear glass over veneers. If for some reason you do need to release the pressure to adjust something, when you reinflate the hose, go a bit higher than you had it prior. That’s another good reason not to use too much pressure.  Food for thought.    Kirk

[Buemaker]

I believe that the hose when pumped up should not have the cross section looking like a dog bone, but as a flat oval.

[Kirkll]

I believe that the hose when pumped up should not have the cross section looking like a dog bone, but as a flat oval.

When pumped up that is correct... but with the air completely out of the hose before air up it somewhat looks like a dog bone.

[buckeyebowhunter]

I've had pretty good luck airing up to around 40psi. Once the form has sat in the heat for a while the pressure increases anywhere from 5 to 10 psi.

When I first started I was actually cracking some limbs, airing anywhere from 60-70psi. The old binghams kit recommended 60. In my opinion this is too much.

[Crooked Stic]

I have been using 70 psi for as long as I can remember. With no problems.
The one time I screwed up and had removed my air regulator from the line. And aired one up with about 120-30 psi all at once. My hose got stuck and could not get it off quick enough. That one split a veneer.

[Kirkll]

I did a lay up one time where i had just bumped the pressure to 25# and was giving it a moment before i aired it up to 50-55#. i had turned on my heat strips too....

and then my phone rang and i started bucket mouthing with my bro and forgot about it. Once i realized what i had done, the epoxy had already started curing and it was too late.

So what i did was lay up the second limb at 25# too and figured i'd give it a go..... Absolutely zero issues with that lay up and those limbs are still going after 10 years.   

Bottom line is excess pressure is not needed if your forms fit well or you are using a top less form with strapping tape.  btw... those topless forms using mule tape look pretty slick. i may give that a go in the future.    Kirk

[buckeyebowhunter]

What is supplying the clamping pressure with the topless forms? Or are they just taping the air hose down?

[Crooked Stic]

Mule tape and .500 steel rods thru the form to wrap the mule tape around.

[kennym]

9/16 osage squares will drive in a 3/4 hole on a topless form and take 60# with the topless form, just sayin...

Test bow and test mule tape...

[kennym]

Oh, and on the air pressure, I use the zip tys , put in 10 lbs , cut tys and pull out to finish air up.

I've noticed there isn't much more glue squeeze out after the initial 10 lbs so I prob use more than needed at 60...

[Kirkll]

Kenny has a good point on the use of zip ties….. I think the type of pressure strip you use could make a difference.

 personally…… I do not remove mine, but…I’m using 22 gage stainless steel strips, and the zip ties dose not effect the glass or make dimples.  You do NOT want those zip ties right on the glass.

I’ve done that by accident a couple times and it leaves a beautiful indentation of a Zip tie on your glass…    Ruined the limb.

I know a lot of guys who like to remove the zip ties prior to full pressure on their hose. But…..I think it’s peace of mind rather than necessity…..  I’ve never removed them or had issues.    Kirk