fiberglass terms-need explanations

[chumslinger]

hello all i am still new here, just getting the hang of these forums, so bear with me here...anyways, after many late nights reading about transom replacement, i have a few questions as i will be doing this soon..
1) what is the purpose of using fiberglass mat between the sheets of ply?

2) would 4 layers of 3/8 glassed together be lots stronger than the common 2 sheets 3/4, or just overkill? the reason i ask this is because the i/o volvo 4 cyl uses no engine mounts- all the weight is 100 % on the transom

3) what does it mean when the resin "kicks"

4) finally for now, what is "peanut butter" and how much strenght does it add to glasswork or is it only a filler for gaps

thank you for any help

 

[Bob_VT]

Re: fiberglass terms-need explanations

hello all i am still new here, just getting the hang of these forums, so bear with me here...anyways, after many late nights reading about transom replacement, i have a few questions as i will be doing this soon..
1) what is the purpose of using fiberglass mat between the sheets of ply?

2) would 4 layers of 3/8 glassed together be lots stronger than the common 2 sheets 3/4, or just overkill? the reason i ask this is because the i/o volvo 4 cyl uses no engine mounts- all the weight is 100 % on the transom

3) what does it mean when the resin "kicks"

4) finally for now, what is "peanut butter" and how much strenght does it add to glasswork or is it only a filler for gaps

thank you for any help

Easy stuff All actually restoration questions and I will move this.

1...... makes things stronger
2...... 6 or a half dozen? Actually less sheets means less resin/glue
3....... Resin kicks is when is changes from liquid to jell to solid which can happen FAST if you use too much hardener .... you might dip in a brush and never gut it out...... it's about timing and proper mixing
4....... Peanut Butter is used for filling gaps, making smooth fillet transitions, it has the consistancy of peanut butter and will not "flow" and stays where placed.... the various recipies are available if you use the search function.

 

[chumslinger]

Re: fiberglass terms-need explanations

thanks...i will be reading lots more before i get started. cant have too much info i will be sure to get lots of pics and post them when i get started.

 

[92excel]

Re: fiberglass terms-need explanations

the reason i ask this is because the i/o volvo 4 cyl uses no engine mounts- all the weight is 100 % on the transom

I have a volvo penta 4 cyl and it doesnt have front motor mounts(closer to transom), but it does have the rear motor mounts(farther from transom).

its in a 92 excel..

 

[PiratePast40]

Re: fiberglass terms-need explanations

If you're using polyester resin, the mat adds strength. The resin itself doesn't do much for strength - it needs the fibers. if you're using epoxy resin, it's different for lamination since the epoxy itself is an adhesive.

As far as "peanut butter", I'd like to throw out some personal experience with fillers since that's usually the main purpose of the resin/fiber mix. I used a good quality constructiuon adhesive (PL Premium) for bedding in my stringers and transom. The dowmside is that it doesn't contain any fibers so actually has little strength, although it is a good adhesive. One of the big downsides of the adhesive is that it can bubble when curing and subsequently leave voids. I tried to glass over these bubbles with disastrous results. The resin and mat does NOT like to adhere to uneven surfaces. The result is that you have large bubbles (voids) over the adhesive joints. Believe me, it's a terrible feeling to see your work become a mess. It's even worse when you have to grind it all out and re-do those areas. That doesn't mean that you can't use construction adhesive as a filler or as bedding compound - just be aware of the limititions and the ned to either smooth with more adhesive or peanut butter.

I also have an older Volvo 4 banger, pushrod engine. It just uses the big donut seals on the transom and a single rubber bumper type motor mount on the bellhousing. Kinda scary but they had to do some fancy engineering to get it to balance that way.

 

[jonesg]

Re: fiberglass terms-need explanations

Using matt between sheets of ply forms a better glue joint, unless you can sand plywood to be as flat as plate glass windows there will inevitably be tiny gaps, the matting bridges those gaps. It makes it stronger too but the main thing is to get a large flat glue joint without gaps or air pockets.
Using more resin without matt is no good either, it will just be brittle without the glass matt. The matt forms a substrate, I think thats a fancy term for strong filler.

if you want to make really strong rigid ply buy 1/64th plywood and make your own laminations, should cost about $1000 for a 4x8 sheet.
Better yet use epoxy and it'll only cost $1200

 

[chumslinger]

Re: fiberglass terms-need explanations

sounds like a winner! my kid dosnt REALLY need those braces i think i will stick with the 3/4 ply! once the new transom is in place, how thick of fg should i put back? the transom in there now (the exposed side) looks like the thinnest layer of fg you could immagine....maybe just resin brushed on. looks like someone already replaced, but didnt really know what they were doing. i will take some pics, then try to fig out how to post.

 

[PiratePast40]

Re: fiberglass terms-need explanations

You don't really need to reglass the inside of the transom. In fact, a layer of resin or high quality primer amd paint should do the job. You'll have quite a few penetrations and screws on the transom and glass will just be something to delaminate and allow moisture to sit.

You can use whatever ply you want but they make marine ply in Eugene so the price for "Greenwood PT Marine Ply" is decent in this part on the country.

I'll dig around to see if I can the spec sheet for the transom shield for the early Volvo's. It's not as critical on those since the motor bolts to the transom ring and that connection sets the depth automatically.

 

[PiratePast40]

Re: fiberglass terms-need explanations

Here's the thred where transom thickness was discussed. As usual, Don came to the rescue with the data sheet.
http://forums.iboats.com/showthread.php?p=2028708#post2028708

 

[Yacht Dr.]

Re: fiberglass terms-need explanations

Hello chum..

Without disrespect to anyone ... and all good advise..

your answers..

1. NO fiberglass is needed between glue-bonding marine plywood. If your using proper epoxy and clamp system then the only thing a layer of "mat" will do is put a layer of lettuce..or tomato if you will.. in your sandwich. Epoxies are ment for such lams of wood of "clean" surface. Now if your putting ply on raw glass .. say wooding your transom .. then you should secure and use mats for bond. To build up ply.. use proper clean and clamps techs to make " ONE piece of ply".

2. Lamination of wood is Very strong.. However in your case its not how many .. its what quality.. 2-3 piece is your choice. ( dunno about a free hanging volvo 4 popper .. never heard of that.. )

3. Resin "kicks" when it has been mixed properly and then hardened .. ( or also the term used for laymen of " OH good...it hardened.. so I dont have to grind that thing off " ).

4. " peanut butter " is a term used for DIY filler mixes..
It can be made of a multitude of dry fillers and resin/Gelcoat. typically made out of " Cabosil ( IE colodal silica ) and resin. but can also a slew of others.. like talc to micro-fiber..to cotton flock.. to.. well.. saw dust if needed..
It can be used many ways.. but for layups of Fiberglass its best used for sharp corners..where glass cant quite make that curve. Its best to have a good fillet then to have air voids..or too much resin in said radius .. Better structural value at radi .

Hope this helps..

YD.

 

[chumslinger]

Re: fiberglass terms-need explanations

thank you all for the info. i know so many people ask the same questions, and i appreciate your time with the answers. boat repair is new to me so i am trying to get all the info i can. one area that i think i am above the curve here is that i dont expect to recover all the money i will invest in this project, but it will be a good hobby to keep me out of trouble. at least i have a complete functioning boat to use this summer while i work on this project(14 foot seaswirl with 40 hp johnson) again thank you all for your time
ps i would like to ask oops a few questions, wondering if i should pm or start seperate thread?.......happy boating