Why not replace stringer while on trailer?

« **on:** July 20, 2014, 01:34:51 PM »

I know no one likes a beat to death horse except a glue factory, so I searched a lot before I posted this. If my answers on here somewhere in the threads, and I missed it, post the link and I'll delete this thread (or I'll ask Brad to, since we can't delete them ourselves)!!!

When replacing stringers the "norm" is to build a framework to hold the boat in place steady and level, or to have 3 points of contact using jack stands with 2 at each rear corner, and 1 up front centered.
I'm curious as to why not leave it on a trailer since the bunks are nice and straight and firm which would support the sides the whole length, and the center rollers would support the whole length of the keel.
With all that support, and loading up the weight inside on top of the stringer/ keel for curing time, it seems like everything would be supported in place and nice with no sag or side bending inward??
Seems like with only support in the rear corners and up front, I would think the hull would sag in the middle and the sides would want to bend or pinch inwards towards the center, with all the weight inside holding it all in place until it cured??
Obviously the 3 point or dolly version works, as it has been done like that for years, so am I just overthinking this, or am I not grasping what is actually going on in the hull?

« **Reply #1 on:** July 20, 2014, 08:37:40 PM »

when the boat is on the trailer the bunks actually push on the bottom of the hull. when you remove the stringers the floor will flex. all boats flex. it'll contort the hull ans introduce all kinds of nasty gremlins like hooks, etc. all of which will affect the way your boat rides. then when you put in the new stringers you'll essentially be locking in all that bad stuff.

supporting it at the back corners and the bow eye makes sure the boat stays true to form. trailers arent perfect, most of the time you'll be able to slip a finger or two between the bunks and the hull in some areas.

« **Reply #2 on:** July 20, 2014, 09:13:49 PM »

I do them on the trailer... But....

I jack stand the trailer perfectly level front to back and side to side (makes checks and balances stupid easy) and i will crib the rear corners of the transom and the bow right on the keel on the front cross member of the trailer.

Bunks are very wonky and seldom true by any stretch of the imagination.

One way to ensure the hull stays true is to tie it down from the forward combing panel to the trailer frame with ratchet straps. This is the area where the shift lever would be. By leveling the trailer and the boat on the trailer at the rear, you can check to see if the hull is straight at the front with a contractors level...

Works like a charm and it is how I was taught more than 25 years ago...

Good hunting.

GT

« **Reply #3 on:** July 21, 2014, 05:15:56 PM »

Makes perfect sense... Both scenarios that you guys state.
I have everything to do the job, glass, resin, cabosil, 2X4 douglass fir cut and sanded to the contour of the hull, blocked and chocked and leveled hull..... Just haven't pulled the trigger on the job. Still reading and learning to make sure I do it once, and do it correctly....probably just scared since I've never done this before?!?!

Sent from my iPad using SoCal Jet Boats

« **Reply #4 on:** July 21, 2014, 05:25:20 PM »

how much experience have you had with fiberglass? it might be worthwhile for you to use some red solo cups and mix small batches with some cloth to get used to it. getting a right mixture to ambient temp is SUPER critical with poly resins. too much and your whole cup will go up in smoke, literally. too little and you'll have a sticky mess that will never cure.

« **Reply #5 on:** July 21, 2014, 05:44:16 PM »

I've got a fair amount, I have worked at both Sunrunner Marine, and Bayliner boats here in Spokane, running a chop gun in the 80's, and doing lay up, and worked at a fiberglass truck canopy factory. And have done body work on both a few Vettes, and a Manx dunebuggy. I have just never actually replaced a keel, or stringer. It's the wood to hull and keeping the correct shape that I'm most concerned with.

« **Reply #6 on:** July 21, 2014, 05:51:20 PM »

The resin will eat those solo cups up, use mixing cups or you can use paper cups

Sent from my iPhone using SoCal Jet Boats

« **Reply #7 on:** July 21, 2014, 06:00:37 PM »

Quote from: rhay916 on July 21, 2014, 05:51:20 PM

The resin will eat those solo cups up, use mixing cups or you can use paper cups

Sent from my iPhone using SoCal Jet Boats

Agreed but look into if the cups are waxed paper.. when I pinstripe I use non waxed bc I don't want it mixed in the paint

Sent from my HTC6525LVW using SoCal Jet Boats mobile app

« **Reply #8 on:** July 21, 2014, 06:18:14 PM »

I actually have ....A LOT.... of the plastic margarine tubs for this type of stuff. As long as I don't mix it too hot, or if I do, get it out of the tub before the cure heat starts to melt the tubs, I should be O.K.

« **Reply #9 on:** July 21, 2014, 06:32:39 PM »

Just clean the crap out of them because the oil from the butter can be a contaminate

Sent from my iPhone using SoCal Jet Boats

« **Reply #10 on:** July 21, 2014, 06:33:45 PM »

But you sound like you got the experience so I should just shut up

Sent from my iPhone using SoCal Jet Boats

« **Reply #11 on:** July 21, 2014, 06:34:49 PM »

Quote from: chet_k on July 21, 2014, 06:00:37 PM

Agreed but look into if the cups are waxed paper.. when I pinstripe I use non waxed bc I don't want it mixed in the paint

Sent from my HTC6525LVW using SoCal Jet Boats mobile app

The thing is, you add wax as a surface curing agent... Wont hurt anything at all...

GT

« **Reply #12 on:** July 21, 2014, 06:37:52 PM »

Quote from: GT Jets on July 21, 2014, 06:34:49 PM

The thing is, you add wax as a surface curing agent... Wont hurt anything at all...

GT

Hmm sounds like it's a golden way of going then no melting no hassle

Sent from my HTC6525LVW using SoCal Jet Boats mobile app

« **Reply #13 on:** July 21, 2014, 06:41:56 PM »

Quote from: GT Jets on July 21, 2014, 06:34:49 PM

The thing is, you add wax as a surface curing agent... Wont hurt anything at all...

GT

Not the kind of wax you want though that will work more as a contaminate then a curing agent

Sent from my iPhone using SoCal Jet Boats

« **Reply #14 on:** July 21, 2014, 06:49:46 PM »

Quote from: rhay916 on July 21, 2014, 06:33:45 PM

But you sound like you got the experience so I should just shut up

Oh no man, no sweat, I am ALWAYS learning and open to info. I spray a fair amount of fades and patterns in flake on some of my cars so I gather those tubs from friends, neighbors, etc. for mixing purposes. I can mix up and lay out 6, 7, 8, different colors of flake and clear in a slow reducer, and keep them covered until I'm ready to spray out my car/boat/chopper etc. and go at it. Thanks for the info, maybe someone else will see that post, and think "oh shit, I gotta do that" I wash all mine in the dishwasher before I use them.

« **Reply #15 on:** July 21, 2014, 06:51:29 PM »

It's been a while since I've used it, but, isn't PVA a wax coating you spray on top, to help kick off gel coat or resin???

« **Reply #16 on:** July 21, 2014, 06:55:49 PM »

Quote from: Ken on July 21, 2014, 06:51:29 PM

It's been a while since I've used it, but, isn't PVA a wax coating you spray on top, to help kick off gel coat or resin???

Not really, PVA= Polyvinyl Alcohol, more like a soap than a wax.

GT

« **Reply #17 on:** July 21, 2014, 06:57:58 PM »

That's right. A greenish teal color, that was washed off with water. Cut me some slack please, it was 1985-1988. Ha ha ha

« **Reply #18 on:** July 21, 2014, 07:04:05 PM »

Quote from: Ken on July 21, 2014, 06:57:58 PM

That's right. A greenish teal color, that was washed off with water. Cut me some slack please, it was 1985-1988. Ha ha ha

No slack given, I learned all about fiberglass and gel coat in 1985... Suck it up..

« **Reply #19 on:** July 21, 2014, 07:07:33 PM »

Yes you can use pva as your final coat and it traps the styrene inside so it will surface cure its a little more work because if you can you need to spray it instead of brush it

Sent from my iPhone using SoCal Jet Boats

« **Reply #20 on:** July 21, 2014, 07:20:55 PM »

Just buy a can of surface agent it's like 5-6 bucks and will last you for a lot of lay ups

Sent from my iPhone using SoCal Jet Boats

« **Reply #21 on:** July 21, 2014, 10:17:04 PM »

just a note of clarification.....the surfacing agent is only to be used on the final application of resin for curing purposes. If used before final application it will require sanding of the previous glass/resin application to insure proper adhesion of subsequent applicatioins.

« **Reply #22 on:** July 21, 2014, 10:32:37 PM »

Quote from: damfoo on July 21, 2014, 10:17:04 PM

just a note of clarification.....the surfacing agent is only to be used on the final application of resin for curing purposes. If used before final application it will require sanding of the previous glass/resin application to insure proper adhesion of subsequent applicatioins.

Unless you can work stoopid fast... But you are 100% correct. Sanding is fo suckas..

« **Reply #23 on:** July 21, 2014, 10:35:29 PM »

Correct and also if you don't use it your final layup the surface will be very tacky and is a pain to get rid of

Sent from my iPhone using SoCal Jet Boats

Ken

ka0tyk

GT Jets

Ken

ka0tyk

Ken

rhay916

chet_k

Ken

rhay916

rhay916

GT Jets

chet_k

rhay916

Ken

Ken

GT Jets

Ken

GT Jets

rhay916

rhay916

damfoo

GT Jets

rhay916