Cheap bastards attempt at DIY fiberglass structural panels .One person in tool shed

[high-and-dry]

For a truly professional job, lower weight and better physicals, add a sheet of plastic, some tape and a vacuum pump for a couple of hundred dollars.
Cheers,
Peter
OKA196 motorhome

I used melamen coated mdf as my table, gave it a coat of car spray on wax, the epoxy did not stick to it. My vacuum pump was 75 bucks off craigslist, but you can get em for 50 from amazon. My vac bag was a pvc pond liner, epoxy wont stick to pvc and it cost 50 bucks.

 

[opp1]

After Scott's input I've decided to go with the bonding all the way around with an inner and outer bond beam. When looking at the stress diagrams it shows a weak point about 6 inches below the bond beam because the bond beam is a hard spot. with all the holes drizzl up with resin on a 4 to 6 '' grid you have bonded the inside to the outside skin so that hard spot doesn't mean anything.
To make it easier to build if you mistakenly cut the panels the wrong size or not square . You don't have to fight all the different angles. To make putting the top panels on easier. And making it so you can just match the bottom inside and then fill with foam and backfill with fiberglass on the top . A K BONDING beam. Side wall dam to push foam into any spaces. Foam trimmed ready for bound beam. Panels riveter on first foam fill

 

[opp1]

Today finish the last large panel that goes up on the roof
Because of the way they're made out of polyester with wovening that will shrink as it cures putting down the outside layer first adding foam and then another inside layer it causes the panel to get a bowl shape
So when floor walls and roof are tied together they put them under load not rigid, under load. Increasing resistance to vertical and horizontal movement. that's about 45 minutes of work installing that and most of that was grinding it back to feather out the exterior Bond beam .
Even the interior bond beam puts it under load
Had to add 75 lbs on the roof to to push out for side and front panels to line up .
in one of the pictures where you see the bow where the clamp runs across the top . what nice about just tossing the panel up there with a gap that will be back filled with foam. Did not have to guess Or cut any angles.
Out side bond 2 layers 6 oz woven . That will shrink pull panels tighter.

 

[opp1]

Got home tonight so though go out installed the back part . under 30 minutes
Need to start the doors. As this to be a low cost build. I think the cheapest way to do it will be go to the walls and move about a half an inch of foam where the where the door was cut out . Then use a Dye grinder so I can bond to fiberglass to not foam. then back fill with woven and 1/4'' chop strand. Then make 2 inch strips to bond in place for the the door seal. if not going for the cheapest route I made some door jambs for the trailtops would use them. But going for a low cost build.
What do you think

 

[opp1]

walls installed just need to tape and feather out. install doors vent and shelves on the Shelf trailtop components for the flip up

 

[opp1]

STOP ,ARRÊTER Haltu !!!!!!!!!!
As this was meant to be a low cost build . So easy if you have trouble scratching your ear you can still build one of these.
I have been spoiled building Trailtop trailers that are actually designed to take an impact.
SO here the ARRÊTER. on the outside bound beam. if your Feathering something back that means you have to remove material you've already paid for and work on it. Then pant. if you were to use 2 in angle aluminum the cost would get expensive real quick going around the outer edge .As the inside Bond beam made out of fiberglass why not you the outside. The thing that makes this way a building so strong is the bow in the panels. of the same material you can't stand on a flat roof where a little bit of bow you can stand on it .
So new plan is a 1'' cap /bound beam with a semi-flexible angled fiberglass around the edge. Stills keep cost down . if you have trouble scratching your ear you can still build one of these. .you can use fully coated structural panels. does away with most of the mess from the ground back and no painting

 

[DzlToy]

Isn't polyiso even weaker than XPS foam typically? How good is your bond between the panel and the resin?

Polyisocyanurate will crumble in your hand quite easily and should NEVER be used to make sandwich panels; neither should EPS/Styrofoam for the same reason. Yes, I know people have done it, but I have also seen people eat fast food and type three paragraph-long posts with little to no punctuation too. That doesn't make either OK.

The bond between the XPS and the resin isn't as big of a deal as many people think when you are using XPS. Of course, you want to do the best you can, but the next fraction of an inch down into the foam, where there isn't any resin, has whatever tensile or shear strength the foam has. This foam simply pulls away from the other foam around it. DIY sandwich panels often fail due to either delamination, thin/weak skins or weak core material that shears/crumbles. Making the core thicker is a cheap and easy way to make a somewhat stronger panel, without adding much weight. This does not make XPS into Nomex honeycomb, however.

 

[rruff]

The bond between the XPS and the resin isn't as big of a deal as many people think when you are using XPS. Of course, you want to do the best you can, but the next fraction of an inch down into the foam, where there isn't any resin, has whatever tensile or shear strength the foam has.

One way to improve that is to use a wallpaper perforator to make a bunch of small cone shaped indentations, then work the epoxy into them so you have a much greater surface area. It's still weak though... at least the 25psi stuff is.

 

[high-and-dry]

I used dow 25 psi blue foam, I have 2 skins made of fiber glass sheet. Its plenty strong, people have been using this style to build things for 60 or so years.

Styromax builds 30 foot campers from 25 psi foam, mine and Jess's are both 25 psi foam. My trailer has about 5k miles with no issues. I would not use polyiso, and would have loved to be able to afford polyurethane foam. There are refer trucks driving around this country made with foam panels skined with fiberglass that probably have a million miles on em.

Once something is built, its not some much the bonding of the skins to the foam, it is the compressibility of the foam. The way the skins and foam get put under compression and tension does not need a super bond. it spread out over the whole panel. A 4x8 panel has 4608 square inches, so even if 1/2 the panel is not seeing any stress it can still support a ton and only have a 1 psi load.

I guess all those boats with balsa wood and foam cores that sail around the world for the 50 years are going to fail any day now.

 

[rruff]

I guess all those boats with balsa wood and foam cores that sail around the world for the 50 years are going to fail any day now.

I don't disagree with most of what you said... I think the stress on a camper can be mild if you do it right. If you avoid induced stress from a flexible chassis... or from attaching heavy things to the skin... the likely weak point is impact resistance. But people build serviceable campers with canvas and Titebond skins, and epoxy/glass is a big step up from that! I'm amazed at what Styromax gets away with. Edges just butted and glued, with no reinforcements. But... if it works...

Regarding boats, balsa is a lot stronger than foam, and when foam is used on a boat it's typically high density PVC or PU.

 

[opp1]

''Polyisocyanurate will crumble in your hand quite easily and should NEVER be used to make sandwich panels ''
They are used in buildings that do quite a bit of swaying and expansion never have a problem again they are structural foam panels

We had rentals rear end stop on the freeway. 2 flip over and Drag . NO breakage of the foam.
If you leave it out in the sun yeah it will crumble other than that it's just fine. All though they were Trailtops trailers and Trail tops are designed to take an impact. They all have Polyisocyanurate foam.
Polyisocyanurate is the only foam you can get that is a structural the other stuff is not considered structural Had panels set out side for years maybe a inch in will go bad along the edge where the Sun hits . As long as you keep the sun off it it is great.
The skins are tied together with a 6-inch grid of angled holes that let a little bit of the resin drizzle down. Tying the two skin together. Not relying on the strength of the foam.
As the skins are layer with woven . are way stronger .that's why they can't be rolled up
The way panels are laid up and actually have a bowl shape .So when tied together is constantly under load which makes it extremely strong think of a ball. See all those holes in the foam. As the holes are angle it keeps the skin from moving up and down or sideways

This a low cost build. I'd sure put this up to any other slip panel way of building that I have seen. Building this way is by the straw that saved the camel's back numerous ways to keep making it stronger and stronger as you proceed with the build ,and not using a 5 gallon bucket to fill up a teacup
For years I would have swore that the trailstop was the strongest way you could go .Got into an argument with an engineer from Lawrence Livermore labs . Did a load and stress analysis.. Because of the bowl shape of the skin makes it consistently strong. and because the way the Skins are tied together they can't slip Beyond each other
I like the look of the trailtop a lot better because of the infill recessed panels and raise skeleton. Infill which can be anything from Burl Walnut to carbon fiber

 

[opp1]

f I did not changed my mind about going with a smooth Bond beam. I'd be done now.
I have to fill what I ground out for that Bond beam. the reason I changed my mind is that smooth Bond beam look so damn boring after building trailtop style pods. not counting the time it takes to make structural panels .You could do a base shell in probably 15 to 20 hours out side the rain may slow you down but there's nothing to warp.
For the bond cap I used aluminum angle as a mold .I like it better than steel because it's straight
The cap is 3'' on top 2'' on the side

 

[opp1]

Had a bit trouble putting top cap on because of the bowl shape of the roof . Added 20 concrete stepping stones to the top which are about 15 lb each. To each plain to try to flatten the roof out did not move a bit. over rear storage area 300 lb in an area 57 in by 48 in it did not move a bit .have not even added the bulkhead or the rear shelf in yet that will make it much more stronger . At this time.
So glued and rivet the side first . Then add 3 stepping stones on top of rail and work down running two rows of rivets on top one on the side

 

[opp1]

Door if you buy premade one they can at least get you a nice motel room and a box of chocolates and dinner.
The most important part is the door jamb and seal.
By the way those drop down horse trailer windows the most sell as doors they're $175 each on a skid of 60
The pod I'm building will probably last well over two hundred years and most door companies we'll be long gone
The door jam that I'm doing you just need two pieces of angle and some type of seal.
Made fiberglass angle that will expand with the pod.
install the outside angle than trim to the inside
on the inside angle trim down one side for your bulb seal to set on and door to reset on.
I like a big deeper channel that way I can put in dust brush & bulb seal

 

[jwiereng]

please provide cross sectional diagram of the door seal detail. Do you mitre and glue the bulb seal?