2001 Suburban Pop Top Conversion

sallf

Member
Laid the first 2 layers of glass this week. I definitely have some spots to sand down, but overall think we did pretty good! The only thing I would have done differently might have been to have some mylar wrapped pieces of plywood ready to help compress the edges. There were a few spots where the fabric kept wanting to peel away which was an inconvenience. You'll notice a couple spots that I've clamped. I might even recommend cutting enough to cover all the edges. We'll see what it looks like when it actually gets out of the mold.

Threw a quick timelapse together as I thought it might be a good way to see what was and was not working:

More info on the process:
- We mixed 15 cc's per pint of polyester resin which seemed to work well (about 65 degrees outside).
- Disposable brushes to blot, paint rollers to spread and steel rollers to compress.
- Laid 2 layers of 1.5 oz fiberglass mat. Plan on doing another 3 after I add internal reinforcements.

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I've spent most of my day today thinking about how to add reinforcements/stringers, mount my rack, add a lifting mechanism and attach the canvas sides. Ultimately I keep drawing up designs that look like @boll_rig 's setup except I'm thinking I might do a manual lift with pneumatic struts. I know @rayra has mentioned using conduit. I like the idea of being able to use threaded connectors but bolting and wrapping the circular conduit seems challenging.

This is where I currently am in my thought process and would love any feedback!

Step 1: 1/2" or 3/4" Plywood (or maybe deck composite since it won't rot)
- Lay two verticals and a few cross supports.
- Reinforce corners with dowels.
- Wood is definitely easier for me to work with. My only concern is a lot of people have been talking about wood rot in fiberglass, but that's mostly on boat forms and I guess I'm not too worried out here in dry Colorado.

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Step 2: Lay final 3 layers of glass to seal that in

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Step 3: Square tube or "c" channel frame.
- This will not be glassed in.
- Canvas can screw to inner edges.
- Pneumatic lift can attach to bottom edge (I hope)

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Step 4: Add a couple more supports since the frame will be lifting the top

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Step 5: Pull from mold, flip, add two strips of stainless steel to to the top to reinforce where the rack will sit, and glass that in
- Rack would either:
1. Bolt all the way through (this makes me nervous because of having to seal it)
2. Attach weld nuts to the top and use them to bolt to the rack (would still run some carriage bolts all the way through the stainless steel strips to make sure they are secure, but would glass over them to seal it in)

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I'm hoping to do pneumatic struts similar to the build @DAlgozine posted. Anyone know where to get some like this? I'm hoping to lift about 4 feet and am guessing that means I need some that are about 5 feet extended?

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Any other thoughts or advice would be greatly appreciated! Biggest concerns right now are:

1. Wood rot.
2. Sealing any holes I drill through.
3. Finding struts that will lift the top ~4 feet.

TL;DR It's moving forward :).
 

Attachments

rayra

Expedition Leader
McMaster-Carr will have all the pneumatic struts you could want, or at least help you identify what you are after. Their prices are all over the map, so shop around

My idea for the EMT was the strength of a round tube. And I'd just drill thru-holes where you-d want to attach your struts and / or lockdown clamps / attachments. Put hardened bolts thru the holes to act as your pivot pins. Glass the rest of the EMT into place.

But any sort of suqare or round tube or even angle iron will work, anything with any lateral rigidity.

I'd suggest a frame as in your Step3, but also put a perimeter frame at what would be the top of the pop top. THink of it like an inverted roof top basket.
 

Factoid

Three criminal heroes
And don’t go take a leak without removing your gloves first! A tidbit of information I wish I didn’t possess...

I like the epoxy West Sytems best. You can get a thickener for it that will allow you to build up the sides without it pooling on the bottom of the mold. Also, it is far superior for bonding wood to itself without needing to use additional mat to hold it in place.
 

sallf

Member
I'd suggest a frame as in your Step3, but also put a perimeter frame at what would be the top of the pop top. THink of it like an inverted roof top basket.
@rayra thanks as always for the ideas! I found some struts on mcmaster. You're right, their prices are all over the place so I'll keep looking around to see if I can find them cheaper.

For "Step 3" were you talking about something like this? Basically a second perimeter reinforcement for the top edges. I think that's a good idea. Will definitely make me feel better about lifting from the frame.

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sallf

Member
And don’t go take a leak without removing your gloves first! A tidbit of information I wish I didn’t possess...

I like the epoxy West Sytems best. You can get a thickener for it that will allow you to build up the sides without it pooling on the bottom of the mold. Also, it is far superior for bonding wood to itself without needing to use additional mat to hold it in place.
@Factoid thanks for the tip! Sorry you had to learn the hard way, that sounds...unpleasant to say the least.

Are you saying that I might be able to just coat the wood in resin and not cover it with mat?

I've heard of people using sawdust to thicken resin. Was considering that to fill in the cracks that'll inevitably exist when I add the plywood. Have you every tried that?
 

sallf

Member
Knocked out the internal wooden frame this weekend. Decided to use adhesive to get the plywood to stay in place and plan to glass over all of it soon. First thing I did was a quick adhesive test. Liquid Nails multi purpose, Loctite PL Marine and JB Weld Plastic Bonder. I believe they all listed "fiberglass" as a recommended material (though that seems a little vague).

Loctite PL Marine adhesive was the clear winner. I don't have a picture, but I put a thin bead on the front edge of each test piece, let it sit for 24 hours, and then used the back of the piece of plywood as a lever. The other two pulled off pretty easily (JB weld was really easy and would absolutely not recommend that for this application) but the Loctite made me find a screwdriver for additional leverage and ended up breaking the plywood and never actually gave way.

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Ended up lining up the cross supports with where the holes for my rack would be drilled.

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Found some heavy things around the garage.

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I think it's looking pretty good. I originally thought I would add some stringers to reinforce the vertical edges (was going with wooden dowels with chamfered ends) but ultimately decided they were going to get in the way of the metal frame.

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Lifting
I had decided to go with gas springs for an assisted lifting mechanism, but have struggled to find any that are long enough. To get 3-4 feet of headroom I need some that are around 4 - 5 feet (48 - 60in). Mcmaster maxes out around 36" on their basic springs. The closest I have found are these at 45", but am worried that 4 of them would give me too much lifting force.

If I can't find any, I'm thinking I could got back to a scissor lift design (maybe use a horizontal screw drive to drive the lift or some smaller gas springs like this design) or build something like this bed lift (I'd end up with 4 of them and would need to put the ends in a slot so they could slide). These all seem like good solutions but am trying to keep the metal work to a minimum just because I don't have enough metal working tools.

Anyone have thoughts here?
 

rayra

Expedition Leader
yes that last blue wire frame is what I was trying to convey.

Talk to boll_rig about his scissor lift layout, IIRC he ended up wanting more end support, Also IIRC when I was discussing that with him back then I was suggesting some sort of hinged stiffener bars at the corners, like fold-down table legs. The middle scissor frame gets it up and down in a controlled manner and the corner legs could act as jack legs / stiffeners when the pop-top is up.

You should talk to him also about his evolving plans for dressing up the hole you will be cutting in the roof. Too, how big he made the hole and where the internal bracing frames are, see if he thinks he should have made the roof hole larger or smaller, rigidity etc.

Too, before you finish framing and glassing, consider the placement of any lights or wire runs (external and internal), think about any spacing or arrangement conflicts.

You're making fast progress. I can't seem to get any project done that fast, I tend to work on too many things at the same time.
 

sallf

Member
You're making fast progress. I can't seem to get any project done that fast, I tend to work on too many things at the same time.
I haven't seen my friends in weeks, lol. I've been manically working on this with all my spare time, would love to have it done for summer trips.

boll_rig was nice enough to show me his setup the other weekend. His scissor lift is so stout that he ended up not needing any additional supports. I still haven't locked down a design that I'm happy with for the lifting mechanism, but if I do use gas springs I'll definitely need something to help with lateral support.

Finished up the fiberglass this weekend. For the last layer I went with cloth just to give the interior a nice finish.

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Since the first lay, I've been clamping the sides to ensure they all stay compressed.

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Used some plastic putty knives, pulled the few screws that were holding it together and gave it some well placed smacks and it basically came right out of the mold....basically.

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Threw it on top of the truck and am pretty pleased with how it turned out. Actually for never having fiberglassed before I would say it came out REALLY well. Sides feel really solid, top feels like it would support a few hundred pounds and there are only a few dry spots where I think I'll add a little more resin.

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I ordered a couple gallons of primer and roll on truck bed liner from Monstaliner. I really wanted to go with black, but all the boat builders yell at people who ask if they should paint their fiberglass boat black, so I went with white. I considered an off white, but with options like "yank my doodle" ...decided to just play it safe.

Next steps:
Now that the hat is done, I'll start working on the internal frame this week. The plan is to pick up some aluminum square channel, build the frame and attach the pieces with plates and hardware, and then maybe take it to a metal shop if I think it needs to be welded.

I've also heard brazing aluminum can work. Anyone know if that might add sufficient strength?

Still thinking through lifting mechanisms...
 

boll_rig

Adventurer
Dude! Killer work on this so far. Only thing I would advise on the underside is if you have any air bubbles after laying cloth over the wood, you should cut them out and fill them again with resin. Even the smallest ones will continually expand and shrink in different climates and start to break down the integrity of the mold.

Excited to see where this goes.
 

sallf

Member
Dude! Killer work on this so far. Only thing I would advise on the underside is if you have any air bubbles after laying cloth over the wood, you should cut them out and fill them again with resin. Even the smallest ones will continually expand and shrink in different climates and start to break down the integrity of the mold.

Excited to see where this goes.
Thanks for the tip @boll_rig. There are a couple dry spots from the first lay that need a little more resin, so I'll be sure to get at an bubbles as well.

No real progress to report except that the Monstaliner paint arrived. I still need to pick up square tubing for my inner frame (am thinking I'll use hardware reinforced with JB Weld to hold it all together...which should be strong enough without having to find a welder). I'm being held up a little bit because the 45" gas struts from GoWesty sold out and I'm waiting on them to get back in stock (was told it would be by the end of this week). My most recent final decision is to use 4 of those struts to give me an assisted lift at the corners and then work in two scissor supports on the long sides for lateral support and to keep the top level as it goes up and down. At that point if I think I'll need additional stability I'm confident I'll be able to figure something out.

The gas struts lock which is good, and I might add a locking mechanism (probably a twist knob to add friction to the system) to the scissor supports. Find a super detailed drawing below.

I did email Colorado Camper to see if they'd be interested in building me a scissor lift with an actuator, but didn't hear back and it sounds like they aren't really taking on small projects like this anymore.

Hope to have an update by the middle of next week!

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rayra

Expedition Leader
only advice at this point on the exterior is correct any voids or imperfections BEFORE you monsterline it. The coating will accentuate more defects than it will conceal. Get it as pretty as you can make it.
 

sallf

Member
Made some more progress over the weekend, which is exciting, but have started to shoot from the hip a little more and got a little sloppy on a couple things. I think it'll still keep out the rain and I don't think I've made any irreversible mistakes, but this really keeps my brain working. Okay, what have I done.

First, re @rayra and @boll_rig advice I sanded down some of my major bubbles and imperfections and ended up laying a thin layer of resin on both sides to reseal and saturate a couple dry spots.

Once that cured started the process to apply the Monstaliner. For fiberglass they recommended starting with a two part epoxy primer. I believe they sent me one quart of the paint and one quart of the catalyst. Two thin coats left me with about 1/4 quart of each left (it's a 1 to 1 mixture). Let that dry for about an hour and then did two thick coats of the white Monstaliner. The directions said to roll on generously...so I did, and it used up most of the gallon.

Overall, I'm pretty happy with it. Definitely far from perfect (you'll notice some waves on top of the part from where I guess I didn't get the mylar liner to sit flat in the mold), but hopefully the geometry in the front makes up for it!

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I originally taped the bottom edge after the primer in fear that if it was too thick my bulb seal might not fit correctly, but in a last second decision, was worried that the gray might show, and put a thin Monstaliner coat. Just enough to get it white.

Before

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After.

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Next up I positioned my rack and drilled those holes. After trying to buy a handheld drill guide at HD and not finding one, I built this simple jig to help me get level holes. I was really concerned about this since I was going to eventually have to line up square 1x1 tube, but think I'm diverging from that plan a little.

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Had to cut down the crossbars, but seems to be pretty solid. Only planning on mounting a solar panel at the moment, but like that I could throw something up there if I really needed to.

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No picture here, but after drilling the holes, I mixed up the rest of that epoxy primer and let it drip down into my drill holes. I plan on putting silicone in there as well, but my thought was if any moisture does get down there, this will hopefully keep it from absorbing into the wood...hopefully.

Then since it was mixed up, I rolled the rest of the epoxy to the inside (what will be the) top...which failed to coat the whole interior. Doesn't look great, but I plan on covering it all up anyways and I'm 95% sure it won't hurt anything.

I'm currently trying to finish up the internal framing which is where I've really started making it up as I go along. I started enthusiastically slicing up my square tubing to get the corners...which might have been easier if I had just cut pieces to the angles, but I was worried about my draft angle making that hard to line up.

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Front and back are both cut-up bent pieces and I plan to connect them with thicker square tubing along the sides. This tubing on the side is what I'll mount my gas struts to (which finally came in today!)

I'm no longer going to run anything across the wooden horizontals, the whole thing is pretty stiff as it is, but will have 10 or so elbow brackets that will run from the square tube on the side, down and across the holes that I drilled for the rack.

Biggest concern right now is that x4 90lb gas struts might have been a little much. If I did my math right, when the topper is fully lifted, each strut should be pushing up with about 55lbs. Assuming the topper is going to be about 100lbs (hopefully a little more) that obviously means I'm looking at about 120lbs to get the lowering process started. My plan right now is to build like this is going to work, attach it to a piece of plywood and figure it out from there. I figure the worst case scenario is the force is too much and I'll have to redesign, but the existing work to the topper shouldn't have to change.

Anyone have experience mounting one of these struts when you need to mount it not fully extended?
 

rayra

Expedition Leader
on strut mounting just make damned sure the distance between your mounting locations exceeds the fully compressed length of the strut. Then if desired you can make that distance greater as a means of limiting how high your top goes. Small exercise in geometry. And you have to make sure your front pair and rear pair use the same distances so your pop top goes up level (presuming your vehicle-end mounts are level with each other / the ground in the first place. And that said if they are not, you could deliberately alter where either the front or rear pairs attach to the pop top if you need it canted fore or aft.

The waves in the glass are partly why I'd use an interior mold, so you can see your final / exterior surface as you make it and catch / correct such things on the fly. It's that or finicky precision constructing an exterior mold.

Looks good so far, great progress and I like the way you sliced the tubign to make the radius bends in the corners.

And another tip too late, if you want a cheap jig for making straight / perpendicular holes thru a surface, a door knob installation kit / jig is a cheap easy way. Has a puck-shaped plastic alignment jig meant to socket over the edge of a door. But it has a flat even bottom and would work to align a hole thru any flat surface. As long as you want a hole >1/4"dia. And best tip is drill a much smaller diameter and shallow pilot hole, so the bigger bit doesn't just wander all over the place at the start.
 

sallf

Member
Thanks for the tips @rayra! Bit of an overdue update but I'm still making progress when I'm not out of town.

I diverged a little bit from my original plan, I'm pretty happy with the stiffness of the part, so I didn't feel the need to run square aluminum tube across the width. I ended up bending some aluminum pieces and gluing them (with the same Loctite PL Marine adhesive) along the sides, if for nothing else, to have my bolts pull on metal instead of fiberglass.

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Then I got a stronger steel bar and ran it along the long sides. Also just Glued in with Loctite and JB weld for the metal on metal. Got real close to buying a welder for this job, but I think the JB weld should do fine.

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The plan is (was) to mount my gas struts to the ends of the steel tube, so to provide a little extra vertical and torsional support for it, I cut these weird pieces and JB welded them in. Seems pretty sturdy, but I figure worst case, if some of those attachment points start popping loose, I'll just drill some carriage bolts through the side. Don't think it'll be an issue, but good to know I can fix it if I need to.

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It looks a little improvised and homemade...but that's because it is. Fortunately I plan on covering everything when I get to the interior design.

Next up I mounted my gas struts and attached them to a piece of plywood so I could try and close it and see how everything holds up. To my surprise, 360 lbs of lifting was a bit much :LOL:. I don't have a picture but after we flipped it over my friend and I couldn't even get it starting to close. Also, those gas struts give almost no lateral support, so it was constantly kicking left and right. Needless to say, my lifting mech needs some work.

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(failed)

New Design
SO, after trying multiple times to call and email Colorado Camper Van and getting no response, I drew up a modified scissor lift (similar to the Westfalia-type design below) that seems like it might work. I wanted to do a normal scissor lift, but I had a hard time finding some stock metal I could use to make a track and lock in wheels for the ends the slide.

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The benefits of what I'm calling the "modified" lift is that I won't have any sliding parts, thus can make everything a pivot point (easier construction), the down side is the math for those lifts is really complex! For my situation I need the top and bottom to be parallel when the top is down. As the lift opens it tends to create an angle and at its simplest form, there are 6 variables you can mess with.

I spent a few days trying to wrap my head around it and ultimately built a scale model. It's actually a pretty cool mechanism once it's all put together, seems a lot more solid than I might have thought.

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