Large Resin Hull Warp Fix

[Devin]

I saw the post below about 1/700 resin hulls with warps and how to fix them. I've fixed 1/350th scale resin DD hulls before. Now I have a 1/350th scale cruiser hull, about 20" long, that I need to take some "banana" out of. Too big to be putting in the sink full of boiling water, I don't trust the oven trick on something this big. Has anyone ever had any luck with clamping a hull straight and then using a hair dryer to heat it? The warp is very minimal -- the bow and stern only sit 1/8" off of a flat surface -- so something drastic isn't required. If I didn't fear paint cracking, I'd just build her as she is and let bolting her to the display base at the end fix the issue. My other idea is to route a channel in the bottom of the hull and put a steel rod in there with epoxy. The model will be built waterline.

[Sean Hert]

This is a problem with the upper hull half then?

[Devin]

Yes. Yankee Model Works USS Wichita upper hull.

[Sylvain Auger]

Try to get a heat resistant container and do the boiling water trick. It should work fine even with the size of the ship but get also a good amount of clamps in order to really keep the model level on all it's surface. And also wait for at least 24 hours before removing the clamps. On a hull I unwarp I waited only 4 hours and the hull warped again.

Hope it helps!

[Sean Hert]

I'm still in favor of the water method as well; it takes a looong time for the heat to penetrate into the mass of resin, that's why the heat soak works. I'd fear a hair dryer burning up for running that long, and a heat gun is most likely too much heat.

Maybe try a long soak in a really hot bath?

[MartinJQuinn]

Maybe try a long soak in a really hot bath?

Sean...

He's trying to straighten it, not romance it!

[Sean Hert]

Hey, I didn't mention bath oils, did I?

Of course, the scent of outgassing resin always puts me in the mood!

[Ron Smith]

Set your oven to the lowest setting, cover a cookie sheet with foil stretched tight and heat soak for 25-45 minutes (you'll know it's ready when it relaxes flat on its own), take out of oven and slide (do not lift) onto a smooth hard surface like the counter top and leave it alone overnight. That's worked for me with hulls that size. Do not clamp or weight as the resin will be soft enough to deform under pressure.

[Sauragnmon]

And Ron, just What temperature do you do this heat soak at? You really should have specified that...

200 degrees, it most certainly does NOT relax after 45 minutes.

[Ron Smith]

And Ron, just What temperature do you do this heat soak at? You really should have specified that...

200 degrees, it most certainly does NOT relax after 45 minutes.

What part of "lowest setting" was not clear enough? Usually that's on the dial as "warm" and just below 200 degrees. And it most 1/350 hull halves certainly will relax after 45 minutes heat soaking....you do realize you have to preheat the oven right?

[Winks]

...The warp is very minimal -- the bow and stern only sit 1/8" off of a flat surface -- ... The model will be built waterline.

Simple answer - live with it.

[Winks]

I do not mean for my above answer to sound smart a$$. With a large hull there are simply too many other things that can go wrong and ruin it completely. We ship modelers are a truly anal bunch of rivet counters. But, there are times when one must simply overlook a slight imperfection and get on with the modeling. Considering your model will be waterline, a 1/8 inch warp will not be seen.

[Devin]

Actually the simple answer was "let it set on a flash shelf in a hot room over the summer". When I picked it up and started actually working on it last month it was perfectly flat.

I didn't take the answer as smart at all, so no problem. My only issue was that I wanted to get the warp out before I started the painting. By mounting it on a base I'll have no choice but to take out the warp at that point, and I didn't want it flexing and cracking the paint.

[Sauragnmon]

Lowest setting... didn't notice that part actually. And yes, I preheated the oven.

Irony was, I tried 200 on a cookie sheet with foil... no luck. I tried 250 for 45 minutes, they did soften, but they didn't relax and when they cooled, my GOD was there a warp. I'm talking the hull went Banana on me as it cooled, so there was obviously a difference in temperatures resulting in places solidifying earlier than others.

After they were cooled, I turned around and set them back on the sheet, preheated the oven to 325 and said "screw this." I set them on the sheet, slid them in the oven and let them go for 45 minutes at 325. I brought them back in, I slid them off the sheet onto flat spots in my desk, and put very minimal pressure on a pair of clamps for each hull. I made certain to use spots that were flat and had no detail - Barbettes were a nominal choice, as was the aft deck of the St George. I used only minimal pressure, just enough to set it in place, and left them to cool. St George still has a slight bow lift, all of 1/64" in the bow, but it's all good now. Of course, there were complaints about the smell as they heatsoaked, but at the end of the day, the job got done. Granted there was a slight yellowing to the resin afterwards, but hey.


EDIT - and these were 1/700 hulls.