Advice needed on material for major repairs

[Woodonglass]

Re: Advice needed on material for major repairs

Why does polyester require more prep work over epoxy?

It's technical and you need to research it but basically has to do with the molecules of the to dirfferent resins not being able to crosslink with each other. That's a VERY BASIC description.

 

[cedarlattice]

Re: Advice needed on material for major repairs

Why does polyester require more prep work over epoxy?

Well with Epoxy you have to scuff the resin to help the next coat adhere. With poly you have to grind down to the glass fibers to help the next coat adhere. The way I understand it is that poly resin has absolutely no strength in it all by itself. You need to be meticulous using both, but epoxy is more forgiving.

 

[Woodonglass]

Re: Advice needed on material for major repairs

This ^^^ is not actually the case. If the Poly is wax free then as long as you apply the next layer within a few hours of the previous layer, no sanding is required. Thats true with epoxy as well. It's called wet on wet laminations. As long as the layers are not fully cured you can lay other layers on top and that is actually the preferred method for making multiple laminations to allow better chemical bonding. IF either of them do fully cure then yes sanding and wiping down with acetone before the next layer is applied is recommended. Poly Resin must have glass, either mat or fibers to give it strength and bind it together but not so with Epoxy. Even if you prep the epoxy the poly will still not adhere very well to it do the crosslinking CHEMICALLY of the two different resins. It's a chemical thing.

 

[mcdc1224]

Re: Advice needed on material for major repairs

Any thoughts on the prime and paint to cover the epoxy/MFG gel i now have to cover? Thanks

 

[cedarlattice]

Re: Advice needed on material for major repairs

I was refering to sanding after it was cured not while it is still setting up. I should have stated that.

 

[mcdc1224]

Re: Advice needed on material for major repairs

Question, plan to apply one layer of 1700 at one time.......until i get the feel for it and go to two. Can I add the next layer on top of the first layer right after the first one goes on and keep moving or will i need to wait until it tacks up first. Thanks guys!!

 

[Yacht Dr.]

Re: Advice needed on material for major repairs

Question, plan to apply one layer of 1700 at one time.......until i get the feel for it and go to two. Can I add the next layer on top of the first layer right after the first one goes on and keep moving or will i need to wait until it tacks up first. Thanks guys!!

You can keep lamming up till the resin starts to cure.

The wetter the better when lammin multiple glass layers to roll out.

YD.

 

[ondarvr]

Re: Advice needed on material for major repairs

Question, plan to apply one layer of 1700 at one time.......until i get the feel for it and go to two. Can I add the next layer on top of the first layer right after the first one goes on and keep moving or will i need to wait until it tacks up first. Thanks guys!!

Depending on the epoxy you will have a good deal of time to get the glass laid down before it begins to cure, the number of layers you can put down at one time depends on the exact epoxy you have and how much heat it generates, fast cure equals more heat, slow cure means less heat. One to four or five layers at a time is normal and not very hard, after a short time you will be more confident.

As for painting it...if all you are doing is putting in new stringers and transom there is no need to paint any of it unless it will be seen when you are done, and then it's only for cosmetic purposes. If these areas are exposed to sunlight then you should paint them, you don?t need a costly 2 part paint though.

 

[mcdc1224]

Re: Advice needed on material for major repairs

Thanks !! You guys are a great help!! Looks like it is going to be many many layers of to get back to the same thickness soooooooo I will lay down as many as I can until its starts to gel then wait until it tacks and go again with the next round.

 

[Woodonglass]

Re: Advice needed on material for major repairs

I'm a bit confused. "Same Thickness"??? How Thick are you trying to acheive and for what? Anything over 1/4" would not be typical. 2 layers of 1700 cloth with epoxy should be more than sufficient for any structural lay ups for your boat. What is it that you are trying to accomplish? If we're still talking about bedding, tabbing and laminating the motor mounts and stringers then 2 layers of the 1700, IMHO using epoxy will be more than strong enough for your boat. It will be much stronger than the original mfg installation. You could do 3 but again, IMHO that would be overkill and a waste of time, material and money.

 

[mcdc1224]

Re: Advice needed on material for major repairs

Question for you guys. The old engine stringer tab was CMS/heavy woven/CMS/ heavy and then a ton on CMS, around 17 to 20 mm total thickness. The top and sides are between 7 to 10 mm. Do i need to be the same using only 1700 or do i need to use something else?

 

[mcdc1224]

Re: Advice needed on material for major repairs

Thanks Wood for the insight.......just wondered about to MFG being so thick and have read to try to create the same when replaced.....my plan was to do 4 layers for tab and then 3 on the sides. Should I cover the tabbing with the glass i lay for the sides and top or go from just the bottom up and when you tab do you go from smaller to larger?

 

[Woodonglass]

Re: Advice needed on material for major repairs

Tabbing is just to hold em in place with small intermittent strips full lams should be from top of stringer and extend out onto the bottom of the hull 4-6". if you were using poly then more lams might be war rented but with epoxy I don't think so

 

[mcdc1224]

Re: Advice needed on material for major repairs

So with them bedded with PB sounds like I can skip the tabbing and lam starting with the first one out 2 inches from over the top then the second one out 3, 4 and then the last one out five Thanks WOOD!!

 

[Woodonglass]

Re: Advice needed on material for major repairs

Check he link in my signature it has drawings Basically he same just don't use csm

 

[mcdc1224]

Re: Advice needed on material for major repairs

Hey Wood, I am a little confused. Do i skip the tape and just follow the example and use full cloth each side. I plan to run the glass to the top ....just not sure how i need to stager it, and stager the ends on the hull every two inches using 5 layers........I had to cut the old glass back towards the outsode of the hull about ten inches or soto remove the bad glass that was delamed from the hull and is was still really thick at that point

 

[Woodonglass]

Re: Advice needed on material for major repairs

Again, using 1700 biaxial cloth and epoxy, I do not think you need 5 layers of cloth and epoxy. I would use two. First layer starting at the top of the stringer and extending out onto the hull approx 4". 2nd layer again at the top and extending out onto the hull approx 6". If you want to do a 3rd layer it would extend out 8". Once it was all cured I would round over the edges and then come back and Cap the tops with a couple of layers of resin and cloth extending a couple of inches over the edges. Just ike in the drawings. That's just my opinion and how I'd do it. Others my come along and have other opinions. I'm just an Old Dumb Okie!!!

 

[mcdc1224]

Re: Advice needed on material for major repairs

Thanks Wood, guess I got confused on tab and tape which i do not need. The reason I was looking at five is due the large difference I now how on the hull thickness ........10 inches out from the stringer is now 3/4 inches thicker than where the new stringer will be so i was trying to blend it back in with more layers to reach it.

 

[Woodonglass]

Re: Advice needed on material for major repairs

If the hull is thinner then just build it up. No need to have that many layers on the stringers. Epoxy is a LOT stronger than Poly. It's not about thickness, it's about strength.

 

[mcdc1224]

Re: Advice needed on material for major repairs

Makes sense. Guess I have a ton of 8 inch 1700 tape i can get rid of. Thanks Wood!!