Thanks for the advice! I was thinking about applying Bondo Glass-Reinforced filler to the areas around the patches,
... What are your thoughts on that?
... some people on Youtube use exterior plywood but wasn't sure if that was advisable or not.
BONDO in any form is not recommended though many will argue "i've heard ..."
Bondo products are polyester based and though it will stick to the original fiberglass of the hull which is also polyester it's bonding ability is designed for surfaces which do not flex(cars) like all boats do to some extent
YOUTUBE is knot your friend in this case specially when the videos recommend using EXTERIOR PLYWOOD for marine/boat applications
as mentioned elsewhere in this thread MARINE PLYWOOD is indicated for all boat work
MARINE plywood comes in several grades/qualities
it is GENERALLY void free and all plies are of the same species w/ more plies for any given thickness than construction grade
the more common marine plywoods are okoume, meranti and fir
okoume is lighter butt more prone to decay and usually comes in BS1088 quality which is equal thickness veneer core for all layers w/o voids or patches
meranti is heavier and le$$ and comes in both BS1088 and BS6566 grades w/ the BS6566 having a thinner exterior layer and sometimes fewer layers than BS1088 butt still more than construction grade plywood
fir is the lea$t expensive of the 3 with even fewer layers than BS6566 butt more than construction grade w/ all layers allowing "patches" to achieve the zero void target
construction/exterior grade plywood is usually yellow pine which is heavier and far fewer layers than any of the marine grades AND it will have voids n irregularities inside that will eventually begin it's degradation from within and only become evident when the damage has been dunn(there is NO way to prevent moisture from getting into the interior plies of construction grade plywood even when glassed over
for all practical purposes exterior construction and marine grades of plywood use the same or similar glue which passes the boil test
use of construction grade plywood provides you w/ an average 5 year life expectancy for the project
fir plywood will check unless glassed over
i would not use exterior plywood. you have spent a ton of time already,
...
get a sheet of BS-1088 okume marine plywood ... when used properly it will last for decades.
you can order full sheets or 1/2 sheets off the internet, or try your local lumber place. If i can get okume locally here on cape cod im sure you'll be able to find some local to you.
...
good job so far! keep it up and you'll have a boat soon!
SOUND ADVICE
Ok, thanks! I'll start looking around locally and see who has it. Any thoughts on the Bondo Glass-Reinforced filler? I've used normal Bondo body filler on other projects and it's done really well on giving a smooth finish. Has anybody used the fibeglass-reinforced stuff before? If I apply it to the spine of the boat where the old patch was, and around the new patches, that should reinforce the strength of the fiberglass and give a smooth finish, correct?
INCORRECT !!!
BONDO POOKEY has no integrety
for fillets and fairing mix wood FLOUR(knot sawdust) or cotton fibers in EPOXY to the already mentioned P-nut Butter consistency for your filler
mixed to a ketchup consistency is good for bonding just rememberize to precoat both surfaces w/ un-thickened epoxy to prevent joint/glue starvation as the pox will seep into the surfaces drying the gluing effect out
a trick i use when glassing is once the fabric is filled i mix a slurry of epoxy and wood flour for the finish coats giving the effect of skrim coats which will fair easier
NOTE ... when you know there will need to be several coats of epoxy for any DO THEM ALL AT ONCE when at all possible
as soon as one coat gets tacky apply the next ... and so on and so on ...
this creates a chemical bond between coats and can be done w/o cleaning/wiping/sanding like are required for adding coats to cured pox
layers of cured pox are held together by mechanical bonding which is not as strong as chemical bonding
this is called HOT COATING and it saves lotsa labor over the duration of the project
i warn the bridal unit when i'm glassing and she knows i'll be home when i'm dunn
ambient temperature and humidity both affect epoxy operations time wise so there'z darn little chance i'll be able to tell her WHEN...
Ok. Here are some pictures of the inside of the Gheenoe. (The cutouts on the floor and seat are what I still need to patch.) In your opinion, do you think it would be a good idea to add maybe 2 layers of Fiberglass Cloth to the floor to give some extra strength? It wouldn't really hurt anything if I decided to, right?
View attachment 230989
View attachment 230990
View attachment 230991
View attachment 230992
for patching the inside of the hull i'd suggest cutting your patches so the thread pattern crosses and dips thru corners and edges at a 45º angle(bias cut)
when the yarn/thread pattern is set @ 90º only 1/2 the threads cross the corner/edge
w/ bias cut patches ALL the threads cross the edge which is easier to get to ay down and doubles the actual strength of the patch as seen here
2 layers of bias cut cloth equals the strength of 4 layers w/ 1/2 the pox consumption
once the internal stringers have been renewed to original strength there shouldn't be any need to add weight to the hull w/ extra layers
That’s a heckuva project for sure. To answer a few of your questions.
Bondo glass will not add strength but it does work well as a filler.
Wood: Absolutely get Marine grade. The glues may be the same between MG and Exterior but the MG is Zero void and a better finish grade. Usually in A/B range. You essentially have Okume, Meranti and Douglas fir to choose from. Okume is the lightest and most expensive. Doug fir is the most common. Locally for me it’s about 100$ a sheet.
Either is fine, so long as you saturate them with epoxy.
Adding strength: If you want to add extra glass for overall strength, just do it internally at this point. Just keep in mind that you are also adding weight, so don’t get too carried away.
Removing the old paint: A DA sander will get it done. I’m not a big fan of chemical strippers, although sometimes they are necessary.
Teansom: I’m not all that familiar with the GN configuration, but I’d take it from floor to top edge. Make an epoxy pnut butter and put it on the floor and in between the transom and outer skin, press the new transom into the floor. Then turn the excess that squeezes out into a filet. Clamp it altogether and allow to dry. Then glass and tab all together.
A pretty good resource is the gougeon bros book on boat construction. It’s free, and although it’s all west system’s products, the information is pretty universal across all products.
fir marine plywood will likely work as well as the original transom if it is 100% bonded to the fiberglass transom and then glassed over 100% on the inside all work being done with epoxy
if the original transom is 1" thick i'd recommend using 2 layers of 1/2" marine fir plywood 100% laminated together w/ ketchup thickness epoxy for glue and allowed to set with weights holding them in place
once you have your wooden transom ready to install set it in place and from the outside drill 3/16" holes thru the fiberglass into the wood in a pattern of 6"-8" between screws
coat the side of the plywood to be bonded w/ un-thickened epoxy so it has a chance to penetrate the wood and do the same to the inside of the glass transom
then using a grooved ceramic tile grouting spreader cover the wooden surface to be bonded 100% w/ ketchup thick epoxy and set in pace so your screw holes line up
using #6 drywall screws w/ a small piece of scrap 1/4" plywood for a washer from the outside screw the plywood in place and the screws will hold it until the epoxy cures 24± hours
once the epoxy has cured remove the screws and fill the holes with P-nut butter thick epoxy and tape over the pookey w/ masking tape to hold it in place
give it 48hours and finish the outside of the transom to your personal specs
Thanks so much! I'll definitely be getting the marine plywood for the transom. By "epoxy peanut butter" do you mean slightly thickened resin or something else? I saw one guy on Youtube actually use the Bondo Glass between the plywood and the outer skin. Not sure if that's a good idea or if the "epoxy peanut butter" is more the way to go.
I have an orbital sander that I slapped a 60-grit disc on and tried to sand down the rough spots, but the paint/gel coat that is on it is super tough. The sander doesn't seem to do too much. It definitely takes off some layers, but not enough. Any tips or tricks to be more effective with it?
So in your opinion, is the Bondo Glass comparable to fairing compound or is fairing compound the way I want to go for a smooth finish?
Thanks for the suggestion on the Gougeon Brothers book. I'll check that out.
FORGET BONDO IN ANY FORM OR FASHION ... it is an automotive not a marine product
do all your laminating bonding fairing and filleting with EPOXY
using the same chemistry thru out your project will be in your best intrest
you wil basically be using 3 thicknesses/viscosities of epoxy for the entire project
un-thickened is what you use for pre-coating surfaces for laminating and bonding
ketchup thickness is what is used for bonding after the surfaces have been pre-coated
P-nut Butter thickness is your filleting and fairing viscosity
i mix wood flour(not sawdust) into my mixed epoxy to get the desired viscosity/thickness after pre-coating
Makes sense. Thanks!
Just got some more resin in today, so will be working more on finishing up the inside of the Gheenoe.
Question on the bars that are on the side of the Gheenoe. It has one spot with a nasty gash in it and some surrounding holes where something must have been attached previously. (Pic below) Any ideas on a good fix for this?
View attachment 231075
once you beat this piece back into shape you will need to have it TIG welded (before painting)
NOTE ... "fiberglass resin" is not EPOXY
BON CHANCE
leon