Trouble with Polyester resin

[jackdaw]

We finished Thypod back in July last year, and had some great fun camping out in it. We didn't know when we built it, that polyester resin was porus , and noticed some cracking in the resin shortly after having it campable.It seemed worse on the top at the front of the trailer.
I gave the affected area a good coating of gel coat , thinking that would sort the problem out.

We covered the trailer over winter,but after it's first outing this year, I noticed more cracking, and some bubbling almost like blisters in the resin.

Further investigation showed a large area of the ply was damp under the resin, so I decided the best action would be to replace the ply , and cover the trailer with aluminium.

Here's the photos;

Cracking in the resin


The affected area;


On removing the ply, we found water on the insulation



We ended up removing the whole roof;



Here's Rosie gluing up for recovering



Heres thypod stripped , with its new roof, awaiting the ali skin.

I fixed a 3/4" batton along the bottom, and then a wider piece of timber under that to sit the ali on and make things a bit easier.With the batton removed I could dress the bottom edge of ali around the bottom edge of the trailer;



I bought a 35' long roll of 8' wide ali, there was a mix-up with the price, and I got it for £200. It's .032" or .8mm thick



It's not the easiest thing to work with;



Heres our 8' wide teardrop;



Perhaps we could have a built in porch;



The plasma cutter made light work of it ;



Removing the guide baton



We couldn't resist seeing what it's going to look like polished up;



Here's a view from the top, before we fitted the roof vent



Heres the rear hatch hinge refitted .I've still got a bit of finishing off by the number plate and the rear lights



The doors have new stainless steel hinges . The ali has been dressed around the doors , and into the returns;





It was dark by the time we finished for the day;



I'm planning on polishing the ali before fitting the trim and weather stripping.

I'm feeling confident the damp is going to stay out now

I think it should be done for our gathering later this month


I should have done it first time around, but we live and learn.

Dave

[S. Heisley]

Nice job, Dave. You'll get many more years of use out of that tear, now!

[NCrado]

Very nice! You did all that in a day?! You're my hero! I bet it will be a lot cooler now in the hot months if that was it in your signature

[jackdaw]

Thank you both,
I think it's probably a good 5 days work there : a couple of days to strip it all including removing all the lights, vents windows hinges and trim, and to get a couple of layers of masonite fitted and painted. Then it's been three days of working with the ali. At least one more to finish off the hatch and lights, refit the fenders and trim, but that can wait till we're polished up

As it happens we don't get hot weather often enough.

Cheers Dave

[kirkman]

[Miriam C.]

Wow what a great price and the look is fantastic.

I am bookmarking this so next time someone asks why not Poly resin I can show them.

[tonyj]

From what I have previously read, polyester resin merely "sits" on the surface of plywood and really doesn't sink into the pores. As the ply expands and contracts, small cracks appear, water gets in, and the real damage begins. Without fiberglass cloth, polyester resin on ply just really doesn't have a chance. I've had fiberglass resin with cloth separate from ply, and it is a reason I choose to work with epoxy.

Epoxy soaks into the pores of the ply, create a structural bond and helps create a waterproof barrier. With the addition of cloth, the marriage of ply and epoxy is complete.

Sorry about your damage, but your repair solution looks well worth the effort. Great job.

[kennyrayandersen]

I'm guessing you used just the polyester resin and no fabric? Still, seems like the epoxy is the material of choice and it wouldn't cost too much for a thin fiberglass mat (or it seems to me). So, word up if you don't go Al -- thanks for sharing your experience! and the new exterior looks great!

[starleen2]

Now before we go poking the finger at the polyester resins and touting the cure all epoxy solution, I would search for where the moisture came in. There are plenty of canoes and kayaks out there with polyester resins with and without cloth that are doing just fine – and they are in water more than a teardrop. I suspect that there was more going on than just the resin being porous. Polyester resins and epoxy have about the viscosity with the exception being CPES which is some what thinner and will soak into the plywood. Polyester resin thinned with ACETONE or styrene will do the same thing. However you solution looks great!

[kennyrayandersen]

Now before we go poking the finger at the polyester resins and touting the cure all epoxy solution, I would search for where the moisture came in. There are plenty of canoes and kayaks out there with polyester resins with and without cloth that are doing just fine – and they are in water more than a teardrop. I suspect that there was more going on than just the resin being porous. Polyester resins and epoxy have about the viscosity with the exception being CPES which is some what thinner and will soak into the plywood. Polyester resin thinned with ACETONE or styrene will do the same thing. However you solution looks great!

I've been doing quite a bit of reading about boats too because it's also on my want-to-build list. It seems most have made the switch to epoxy. I'm not a chemical engineer so there are probably reasons why, but I actually didn't see anyone that was still using the polyester resin, though it was mentioned in a historical context. It's entirely possible that I just didn't connect with a 'polyester' website. You are certainly right that a lot of boasts still use it (cost), but I think most of them are using some type of fabric or chopped fiber.

[planovet]

Now before we go poking the finger at the polyester resins and touting the cure all epoxy solution, I would search for where the moisture came in. There are plenty of canoes and kayaks out there with polyester resins with and without cloth that are doing just fine – and they are in water more than a teardrop. I suspect that there was more going on than just the resin being porous. Polyester resins and epoxy have about the viscosity with the exception being CPES which is some what thinner and will soak into the plywood. Polyester resin thinned with ACETONE or styrene will do the same thing. However you solution looks great!

I tend to agree. While an epoxy would be preferable to a poly resin, there may be some other factors in this case. The moisture on the insulation was around the roof vent. It's possible that moisture got in around the vent. Also, I noticed staining around the porthole in the front and where each roof spar was.

In any event, your solution really looks great and you did a nice job in getting it done in only 5 days.

[doug hodder]

Having built both boats and tears, the thing is...any moisture/water that gets in will penetrate the wood substrate and cause a finish to lift from the back side. On a boat, they typically get coated out on the interior with epoxy or poly resin as well. Tears typically don't have the interior water issue like a boat would, but a leaky vent or seam will cause it to happen. It just doesn't matter how good the exterior finish is, if water can get behind it somehow, over time it will show.

I've looked at old wooden boats that had cloudy exterior finishes on them and the clue is, they didn't coat out the interior completely and caused it to lift...it's a total strip and redo at that point. Boats will get lots of water in them however.

I think the real key is making sure that things are sealed up from the get go. Somehow, water got into this build and he's dealing with the results. The 3M 5200 sealer works well, made for underwater uses, like on transom sleeves on boats. I'm just not a fan of latex/silicone caulk or the butyl tapes, just me. I use the 5200 for vents and any joints/edges on my builds, especially it it's an aluminum top. Not cheap...but then redoing it all isn't either. Of course....how you store your build is paramount to keeping it looking and performing well. Others may have differing opinions. Doug

[Todah Tear]

Great job! Where did you get those windows? They look great!

Todah

[jackdaw]

Thaks for all your comments guys,
starleen2, It could be the canoes and kyaks have a good think protective gel coat, or flow coat on that was missing from my build I put a coat of gelcoat on the top, but that was after the cracking had started.

I'm sure your right about keeping it all sealed up from the off.
I think the original idea was to get a good smooth finish using the resin,and then paint it with automotive paint, but it was never realy as good as I had hoped for.........and I didn't paint over it.

Doug thanks for the tip on the m3 5200, I've found a suplier over here. It look expensive(5x the cost of silacone), but if it protects the trailer, I can see it's well worth the extra cost.

Todah, The round windows came from ebay. They must have been used in a counter somewhere, as they have SPEAK HERE marked around the top.
I'm going to leave the oval boat window out , and use it on the front of the trolley top that I'm building.

[mallymal]

Would this be any use Jackdaw?

Looks like a faster cure, but much better price....

http://cgi.ebay.co.uk/3M-4200FC-Marine- ... -Cartridge)_W0QQitemZ180347523115QQcmdZViewItem