Lifting roof XPStream - Almost Finished!

[OP827]

Guys,

I got a question about fairing the epoxy fiberglassed surface: what fairing filler to use best?

I was thinking about some options:

1. Usual Bondo resin mixed with microballs powder. I made a sample today, put the mix on scrap wood looks good and sands well..
Pros: Easy to make and use. Quick curing time. Cons: NOT sure if it will adhere properly to epoxy FG.

2. Bondo body filler. Pros and Cons are the same as above except could be a little more constly that above..

3. Other Vinyl Ester filler from specialty supplier? have no experience with that..

3. Last resort that I know will work for sure is epoxy with microballs. Pros: adhesion to epoxy FG is not questionable and strong. Cons: Higher cost, long curing time.


Please share your experience here. I may go for nice faired finish.

Thanks for all help! I may also publish this question on the board somewhere else to get more input.

[Bluebunny]

Hi OP,
I am no expert, but this is what I tried; single component automotive filler from a tube, and plastic wood filler. From my tests, these do NOT work well on a high wear surface like epoxy resin over plywood boat. I ended up using epoxy resin with talcum powder filling. I cannot comment on bondo or polyester.

I am struggling with primer/paint adhesion to the epoxy surface, even after sanding with 80 grit.

[OP827]

Thanks for sharing your experience here, BlueBunny. I found a few topics on this forum that discuss this subject and bondo polyester resin filler seems ok if it is thin application over the sanded epoxy. I just like the bondo filler for its curing speed, but still have my doubts..

On the other note, After a lot of thinking how to proceed with the lifting roof build, I have mocked up the roof line configuration. I am leaning towards simpler solution to the build, i.e. I will make large flat panel for the roof part, then put up flat side walls straight as the little foam piece in the photo, just to show the idea. I find this method will be quicker and provide for stronger roof part. I also plan to make the roof out of 16 panels located across. Each such panel will be laminated on the edge to create thin fiberglass C-channel and when they are glued together side-by-side, I will have fibeglass I-beams every foot on center. That should mitigate any potential issues with the foam de-lamination and make for a stronger and more rigid roof. After I made the flat panel and laminated it flat on one side, I will turn it over and lift one or both ends (front or back) to create needed curvature (similar to what you can see in the photo below) and laminate the interior side. After that lamination I will have a piece that I can then glue to the side walls.


Critique and sharing the experience with such work as described above are welcome!
I plan to work on the roof tomorrow.


Cheers and thanks!

[Bluebunny]

I like it. I have worried about the alternatives since our earlier discussions. This, near your original idea; Simple. Strong. Good on ya, mate!

[OP827]

I like it. I have worried about the alternatives since our earlier discussions. This, near your original idea; Simple. Strong. Good on ya, mate!

Thanks BB! I agree, earlier ideas required more labor and time (I do not have much of that!), and strength and rigidity could be less or not as easy to obtain as with this design. Also this simpler design is easier on the eye with other shapes on the trailer, right? Apple gadgets come to mind, why? ... no idea, I just like cleaner lines. I'll go for that then!

[OP827]

Hi OP,
I am no expert, but this is what I tried; single component automotive filler from a tube, and plastic wood filler. From my tests, these do NOT work well on a high wear surface like epoxy resin over plywood boat. I ended up using epoxy resin with talcum powder filling. I cannot comment on bondo or polyester.

I am struggling with primer/paint adhesion to the epoxy surface, even after sanding with 80 grit.

Thanks, I think I'll do microbaloons/epoxy mix. I only need thin layer fairing..
About painting, what paint are you using over epoxy?
I was considering some industrial or marine type that is designed to go over epoxy, I think it is polyurethane based.

I did prepare some foam for the roof this morning. That was the first time I tried to use a planer over XPS foam.. ... I know, it can be real messy, but I got my homemade dust collector and also made a dust hood for the planer. This system received a real workout today and held the test very well. The 25 gal barrel actually got overfilled with foam as you can see in the photos, but I did not notice any suction loss. It was a clean job, no mess, produced two big garbage bags of foam dust. Frankly I did not expect that much of the foam dust, as I was only taking about 0.5mm off each side to make the panel surface clean. The XPS foam as you probably know is inconsistent in thickness and has some slick thin coating that has to be removed so it can adhere to epoxy or other glue properly. Going forward I will use planer to prepare foam, sanding it is not so much fun as using good tools .

[noseoil]

Wonder if you can use the foam shavings to make a filler with the epoxy, sort of like a flow modifier or phenolic micro-balloons? Maybe mix it with glue & make "particle foam" or something?

[OP827]

Wonder if you can use the foam shavings to make a filler with the epoxy, sort of like a flow modifier or phenolic micro-balloons? Maybe mix it with glue & make "particle foam" or something?

I could if knew where to use it.. the shavings are not going to lay flat easily, they could pop up from the mix, similar to wood shavings. I have glass fiber filler which is much finer than the shavings and do not use it, as found it is not as easy to put down as with fumica or micro-balloons mix. Do you have an idea where the foam shavings can be used? Can only think of large holes or cavities to fill, but don't have those ..

[rebapuck]

I have no idea where you would use it... but suggest you hang onto the shavings until finished. Soon as you toss them, you'd think of some need for them. It's called Murphy's Law.

[OP827]

Hi OP,
... I am struggling with primer/paint adhesion to the epoxy surface, even after sanding with 80 grit.

Bluebunny, are you aware of amine blush you could get on your epoxy? Sanding does not remove the blush, but it is easy washable by water see here: http://www.epoxycraft.com/amine-blush-what-you-need-to-know/ . Hope it helps.

[mikeschn]

Very impressive, planing all that foam to size! Yea, I am fully aware that the foam is not a constant thickness all the way through, and rely on putty to fix that. I like your idea better. But how much does a 4x8 thickness planer cost?

Mike...

[WoodSmith]

Well Mike, what did you pay for your CNC unit? Will it do 4x8? It may take seven weeks of Sundays, but I have used (wasn't mine & my buddy moved sadly) a 4x8 shop bot to surface plane.

It did a great job on your front window cutout.

Woodsmith

[OP827]

Mike, I use 13" wide planer as you can see. But a large flat surface is required to assemble, that is why I still use the trailer floor, all panels are built and stacked on the shelves. Here is the photo of roof panel assembly today's work. I went with no spars - will see how it works with both sides laminated with 6oz epoxy for the roof. Need to add another three panels for the complete roof, it is quite large (6.5' x ~15.5ft), estimated the weight within 80 lbs for roof, total. Hope to make it light so it can be lifted by hand from one side at a time.

Waiting for the epoxy to set and then while it is still green I will start fiberglassing one side, maybe working late tonight...

Thanks for reading.

[OP827]

Well Mike, what did you pay for your CNC unit? Will it do 4x8? It may take seven weeks of Sundays, but I have used (wasn't mine & my buddy moved sadly) a 4x8 shop bot to surface plane.

It did a great job on your front window cutout.

Woodsmith

I think a vaccuum clamping will also be needed with that CNC to keep the foam flat, can be pricey too, when all factors are in..

[OP827]

Third of one side roof panel is laminated, good enough for today's work.