Polymer bending

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
RickMc
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Polymer bending

Postby RickMc » Thu Jan 12, 2017 8:37 pm

Hello , I am installing some 5/16 UHMW on a fiber glass hull for the first time. I want to bend the polymer around the chines. They are about a 30 deg. bend . At about 7 1/2 feet forward, the bottom of the hull curves upward and tapers from 7ft. to 4ft. at the bow. I have started in the middle and have worked toward the stern with the center 2 rows of bolts. My question is, what is the best way to work thru the chines and the transition aria.
Thanks Rick
The glass is always half full....til I get a hold of it

terrible ted
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Re: Polymer bending

Postby terrible ted » Thu Jan 12, 2017 9:01 pm

uhmw gets bendable when hot, how pliable ?

bkmail
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Re: Polymer bending

Postby bkmail » Fri Jan 13, 2017 3:23 am

Force it to follow the contours of the hull with pressure. Use ratchet straps, prybars, and blocks to pry and force it then secure it. A warm hull and hot sun helps but its still work get it right.
Bk
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SWAMPHUNTER45
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Re: Polymer bending

Postby SWAMPHUNTER45 » Fri Jan 13, 2017 6:43 am

Hot sun and gentle help from hair dryer.

RickMc
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Re: Polymer bending

Postby RickMc » Fri Jan 13, 2017 8:55 am

Hot sun isn't an option here in Pa.haha. I do have my garage cranked up to 75. I also have a 1500 watt heat gun and a torch for torch down roofing.I'm pretty sure I can get it to bend around the chines on the strait sides of the hull. The problem I anticipate is where the hull bottom turns up and the taper starts. It seams I will have extra material at that point . What do you guys do at compound bends like that?
On another note I figured out a cheep effective countersink tool that works well. I bought a 1/2 in. countersink bit at Home Depot for $8. Chucked it tightly in my drill. Then cut a short piece of 1/2 in, EMT conduit and hold it over the bit to set depth. Just drill, move conduit like a pump shotgun to remove chips and drill again to clean up the hole . Working great so far.
Thanks for any tips or tricks Rick
The glass is always half full....til I get a hold of it

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nebraskaairboater
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Re: Polymer bending

Postby nebraskaairboater » Fri Jan 13, 2017 9:28 am

its my opinion that 75 degrees isn't going to be hot enough for install. When I did mine we had the garage at 100. You want it to be hotter than you ever expect it could possibly get after its on the boat. Poly expands quite a bit when it gets hot and will cause bulging between the bolts/rivets if you put it on too cold. The bulging will affect the ride of the boat and I have seen where it actually popped rivets out due to this.
Dan Porter, Jr.
Fremont, NE
16 x 8 1971 Flat Bottom Fiberglass Hull / 500 Cadillac/ 2.12:1 Rotator / 80" 3-Blade Sensenich S

bkmail
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Re: Polymer bending

Postby bkmail » Fri Jan 13, 2017 12:19 pm

Work outward in a radiating circle fastening it down. This will eliminate any bubbles or excess material.
Start where the bottom turns upward, in the center of the boat.
Your hair dryer, heat gun, or propane torch are a waste of time.
Trust me, I install this stuff on boats reguraly, just finished up a 15' Panther yesterday.

Be certain you have a flat bottom before laying uhmw. If you have a hook in the hull, get rid of it.
Bk
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502 BBC on a 18' Alumitech w/4 blade master blasters, Skip built

RickMc
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Location: North east PA.

Re: Polymer bending

Postby RickMc » Fri Jan 13, 2017 4:17 pm

Thanks for the replies . I've turned up the heater a bit and when I 'm not working on it I run My lift up .It's warmer higher up. i have also been warming it up with the torch . I'm trying to keep the polymer around 100 deg. while i"m working it.On the river I ride I can't imagine the water gets above 75 so I hope I'm good. I've worked 4 rows up the center and over to one side. Getting ready for the first cut and bend.Yes the bottom is flat .Its bellied if anything once I get the rigging back in . I'll Let you know what I learn . Thanks Rick
The glass is always half full....til I get a hold of it

Dr.Dan
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Re: Polymer bending

Postby Dr.Dan » Sat Jan 14, 2017 11:16 am

I applied poly in a relatively cold garage (direct hot sun would've been nice but I had no choice).

I was able to bend 3/8 poly around 4" radius chines with great contact. Bending up the bow was easy. I used lots of clamps, straps, and heat. I used a propane tiger torch to keep the poly hot. Very hot. The tiger torch is 500,000 btu and provides plenty of heat to wherever you need it. It worked well for me. I used buck rivets and everything laid down perfectly.

I don't think large compound curves are possible. You will need to make pie cuts.

dd

RickMc
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Re: Polymer bending

Postby RickMc » Wed Jan 18, 2017 4:59 pm

WE have been making some progress. My wonderful wife has been under my boat installing nuts and washers for 2 days. We found that using longer bolts, fender washers and a lot of heat the 5/16 UHMW bends pretty well.We did have to make a few relief cuts on the compound bends. Two so far on the one side but they stop short and don't extend onto the bottom.If someone can talk me thru it I have some pics on my I phone.
Have fun Rick
The glass is always half full....til I get a hold of it

bkmail
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Re: Polymer bending

Postby bkmail » Thu Jan 19, 2017 12:35 pm

Look at my website, lots of pics there of airboat and jetboat uhmw installs.
No relief cuts, no heat, compound bends. 3/8" uhmw, 8' wide x length of boat, all one sheet.
We install with weld washers or poly capped 1/4" x 20 bolts backed with bonded washers and locking nuts.

https://m.facebook.com/BKMarineServices

Bk
https://www.bkmarineservices.com
https://m.facebook.com/BKMarineServices

502 BBC on a 18' Alumitech w/4 blade master blasters, Skip built


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