Ubolts to attach the floor to trailer?

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Ubolts to attach the floor to trailer?

Postby Vesselhead » Sun Jun 11, 2017 12:39 am

Hi Everyone,

I've been worried about drilling holes into my trailer frame and I want to use ubolts instead. Any concerns with this approach? I'm thinking 4-6 of these:

https://m.lowes.com/pd/Stanley-National ... lt/3428588

They are long enough to go through the 3/4" ply floor and around the 1.5"X1.5" steel tubes frame.

Thanks,
Becky
Last edited by Vesselhead on Sun Jun 11, 2017 11:28 am, edited 1 time in total.
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Re: Ubolts to attach the floor too trailer?

Postby KennethW » Sun Jun 11, 2017 6:22 am

Why not use t nuts in the plywood with a strap(like the u bolts) under the frame and two bolts. Then you will not have to deal with a lump on the floor.
https://encrypted-tbn0.gstatic.com/imag ... ZzeWnPly-A
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Re: Ubolts to attach the floor too trailer?

Postby Dale M. » Sun Jun 11, 2017 7:53 am

If you have worries about holes in trailer frame, you have wrong frame.... If drilling 8 or so 9/16 inch holes for clearance of 3/8 bolts weakens frame to point of failure you have wrong frame....

Also you might consider having some tabs welded on frame for bolting purposes...

I think U-bolts would be ugly and awkward as the will have issues of bending frame and cause physical interference for floor being smooth....

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Re: Ubolts to attach the floor too trailer?

Postby Vesselhead » Sun Jun 11, 2017 11:34 am

KennethW wrote:Why not use t nuts in the plywood with a strap(like the u bolts) under the frame and two bolts. Then you will not have to deal with a lump on the floor.
https://encrypted-tbn0.gstatic.com/imag ... ZzeWnPly-A


That's another option. Then I just need to find the right size plate.

The ubolts will be hidden inside. I'm going to have an insulated floor. So there won't be a lump. They will be hidden inside the 1.5" subfloor space.

Your idea is a good one in that I could get things more snug to the frame.
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Re: Ubolts to attach the floor too trailer?

Postby Vesselhead » Sun Jun 11, 2017 11:42 am

Dale M. wrote:If you have worries about holes in trailer frame, you have wrong frame.... If drilling 8 or so 9/16 inch holes for clearance of 3/8 bolts weakens frame to point of failure you have wrong frame....

Also you might consider having some tabs welded on frame for bolting purposes...

I think U-bolts would be ugly and awkward as the will have issues of bending frame and cause physical interference for floor being smooth....

Hi Dale,
You would do 8 bolts? That seems like a lot. I do have a sizeable build, a bit less than 5x10 at this point. I wonder what the math is for deciding how many is needed.

Why would a plate bend the frame? The square U I plan to put onto the plywood side. No lump will be exposed because it is in the sub floor. Planning on insulation. Hoping we can take it skiing eventually.

Becky
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Re: Ubolts to attach the floor to trailer?

Postby KennethW » Sun Jun 11, 2017 1:08 pm

What is the subfloor for? Just lie the insulation on the frame.

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Re: Ubolts to attach the floor to trailer?

Postby Dale M. » Mon Jun 12, 2017 7:55 am

My build is 5x9 and I used 8 bolts mostly becasue of spacing to spread out connection points equally around parameter of frame so there was support equally around floor (frame outside dimensions is 5x9 with tabs welded to inside of frame rails)...

Number and size of bolts is a personal thing for what ever one feels appropriate for build strength...

You could use something like elevator bolts or carriage bolts and drop a bolt on each side of frame rail and use a plate to sandwich frame rail between plate and floor... There is probably 20 different way to do this, use amount of bolts and bolt size you are comfortable with...

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Re: Ubolts to attach the floor to trailer?

Postby aggie79 » Mon Jun 12, 2017 8:46 am

Did I read right that your floor will be insulated and the bottom plywood will be 3/4" thick? If so, the 3/4" plywood is overkill. You really don't need much in the way of fasteners to attach the teardrop shell to the frame. I used self-tapping trailer deck screws that go directly into the 2" tube steel frame.
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Re: Ubolts to attach the floor to trailer?

Postby KennethW » Mon Jun 12, 2017 9:34 am

aggie79 wrote:Did I read right that your floor will be insulated and the bottom plywood will be 3/4" thick? If so, the 3/4" plywood is overkill. You really don't need much in the way of fasteners to attach the teardrop shell to the frame. I used self-tapping trailer deck screws that go directly into the 2" tube steel frame.

Self-taping trailer deck screws sound like a good way to do it.
I agree 3/4 in the floor is just extra weight. Unless it is a standy. All you will be doing is kneeling on the floor that is supported on 4 side. 3/8 is enough. Unless you plan on a lot of off roading you don't need anything under the insulation. I would drop the insulation on the frame with a 3/4 border of wood for mounting the walls and 3/8 ply wood on top. That is just me. I like to build light.
My teardrop has 2" foam with FRP on top so I know 3/8 plywood would be plenty thick.
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Re: Ubolts to attach the floor to trailer?

Postby working on it » Mon Jun 12, 2017 11:44 am

aggie79 wrote:Did I read right that your floor will be insulated and the bottom plywood will be 3/4" thick? If so, the 3/4" plywood is overkill. You really don't need much in the way of fasteners to attach the teardrop shell to the frame. I used self-tapping trailer deck screws that go directly into the 2" tube steel frame.
  • I didn't insulate, but installed my floor in two stages, with two types of fasteners, making a 3/4" floor from two different plywood sheets.
  • 1)The base, a 4'x 8' sheet of 1/2" birch plywood (it sat unused in my wood storage shed for 10-5 years, very dry and hard), was centered on my 50" wide x 97" frame (original was 50" x 60", rectangular tubing added), with 1" frame showing on the sides, and 1" on the rear (the front was set flush with the frame). I used eight 3/8" carriage bolts to the original frame tubing, at the old front and rear tube, slightly countersunk to not have the bolt heads protrude too much above the plywood.
  • 2)Then, I applied a full, thick coat of Titebond 2 adhesive to cover the birch base, and placed a sheet of 1/4" Lauan over it, using Tek screws to secure it to the perimeter of the frame. I started at the back, working forward, pressing out the glue with a roller as I went. I used around 36-38 screws, if I remember correctly. I sat some feed bags in the center, to hold it flat, and let it dry for a week or so.
  • I probably didn't need to do the double-layer floor, but, after countersinking the carriage bolts, I needed to cover the heads anyway, so the Lauan was an afterthought, which brought the floor thickness to 3/4" (nominal), to match the plywood thicknessI was going to use for the remainder of the build. I used the birch, just to use it up, and had planned to use linoleum to finish the floor, but I liked the grain of the Lauan, so it became my floor surface. I had always intended to screw down the perimeter, so that served the double purpose of securing the top sheet, also. Looking back, I would've just used the perimeter screws, but I was in overkill mode, so why not use two methods of fastening down the floor?
  • 86939 1/2" birch plywood base, with carriage bolts
  • 86940 top sheet screwed and glued on; drying out
  • 86942 finished floor, stained, polyurethaned
  • 2013 HHRv,"squareback/simple" TTT, semi-offroad? 4x8, 2000+ lbs travel weight
  • featuring: 3500 lb Dexter axle w/brakes & HD leaf spring system > riding on General Grabber 27x8.5-14LT tires, LED lighting inside, A/C & heat, AGM battery 12vdc, 110vac from extended run generator onboard or park power, Coleman dual-fuel stove & Northstar lantern
  • 147697148333
  • 148599125895148106
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Re: Ubolts to attach the floor to trailer?

Postby Vesselhead » Wed Jun 21, 2017 12:33 am

I love the color your floor came out.
Thank you for the advice.

Did you do any rubber tape between your wood and the frame?
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Re: Ubolts to attach the floor to trailer?

Postby Vesselhead » Wed Jun 21, 2017 12:37 am

Dale M. wrote:My build is 5x9 and I used 8 bolts mostly becasue of spacing to spread out connection points equally around parameter of frame so there was support equally around floor (frame outside dimensions is 5x9 with tabs welded to inside of frame rails)...

Number and size of bolts is a personal thing for what ever one feels appropriate for build strength...

You could use something like elevator bolts or carriage bolts and drop a bolt on each side of frame rail and use a plate to sandwich frame rail between plate and floor... There is probably 20 different way to do this, use amount of bolts and bolt size you are comfortable with...

Dale


Thanks Dale. That is how I felt. You can do it multiple ways. I finally decided to go with grade 8 bolts with a locking nut to the frame. I'm going for 6 3/8" bolts and if my arm holds out I may do 9, but that feels like serious overkill. Unless I do decide to attach water pipes to the bottom which is currently my intention and the reason for the 3/4" floor.
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Re: Ubolts to attach the floor to trailer?

Postby Vesselhead » Wed Jun 21, 2017 12:43 am

aggie79 wrote:Did I read right that your floor will be insulated and the bottom plywood will be 3/4" thick? If so, the 3/4" plywood is overkill. You really don't need much in the way of fasteners to attach the teardrop shell to the frame. I used self-tapping trailer deck screws that go directly into the 2" tube steel frame.


I love your build. Read through it a couple times. Thanks for the feedback. I'm planning on mounting potable water grade plastic pipes about to the bottom for grey and clean water so I wanted something sturdy to attach to.

Some decisions are made. The frame plywood is cut as well as floor insulation and I already have asphalt emulsion on the bottom so I'm not planning on changing my structure.
Also my side walls are routereded to fit over the wood frame.
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Re: Ubolts to attach the floor to trailer?

Postby aggie79 » Wed Jun 21, 2017 9:48 am

Vesselhead wrote:
aggie79 wrote:Did I read right that your floor will be insulated and the bottom plywood will be 3/4" thick? If so, the 3/4" plywood is overkill. You really don't need much in the way of fasteners to attach the teardrop shell to the frame. I used self-tapping trailer deck screws that go directly into the 2" tube steel frame.


I love your build. Read through it a couple times. Thanks for the feedback. I'm planning on mounting potable water grade plastic pipes about to the bottom for grey and clean water so I wanted something sturdy to attach to.

Some decisions are made. The frame plywood is cut as well as floor insulation and I already have asphalt emulsion on the bottom so I'm not planning on changing my structure.
Also my side walls are routereded to fit over the wood frame.


:thumbsup: I understand your design decision on the 3/4" plywood.
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Re: Ubolts to attach the floor too trailer?

Postby Vesselhead » Wed Jun 21, 2017 10:31 pm

Dale M. wrote:If you have worries about holes in trailer frame, you have wrong frame.... If drilling 8 or so 9/16 inch holes for clearance of 3/8 bolts weakens frame to point of failure you have wrong frame....

Also you might consider having some tabs welded on frame for bolting purposes...

I think U-bolts would be ugly and awkward as the will have issues of bending frame and cause physical interference for floor being smooth....

Dale


Yeah. My frame is industrial. Got it from the guys at iron eagle in Portland. I was worried about the wire harness the put inside for me. I'm convinced. I'm doing grade 8, 3/8" bolts with huge washers on the ply and locking nuts. It's a really nice solution. I am still not sure why folks were worried about the ubolt. I guess the vibration from a fire road is legit and we fully intend to be on unfriendly roads some day.
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