77 Glastron trihull open bow

[GlastronSportster]

I have been doing some searching recently after purchasing my first boat recently.
The boat was purchased with a soft spot I somehow managed to oversee. a rather costly oversight i know. The spot is located dead center of the boat from the beginning of the fiberglass deck of the open bow portion, and extending about a foot and a half back.

throughout my research so far i have read several different types of below deck construction in regards to where stringers are located, how far towards the bow the wooden deck extends and in some cases, whether or not there are stringers present at all.

what i would like to know is what I'm getting myself into opening this deck up. Is this something that can be repaired with the cap left on? and also what i might expect to find once the floor is opened up.

Also if anyone may have pictures of a glastron trihull deck opened i would appreciate if they could be sent to me.

 

[ajgraz]

Re: 77 Glastron trihull open bow

I've got a 1978 StarCraft 15' trihull with the exact same problem. I've got the deck opened in that very spot as I'm replacing that section of deck. I'll shoot some pics and upload tomorrow; it's probably constructed in a very similar manner.

The 2 fore-to-aft stringers in my boat are about 1 foot to either side of centerline, and bulkheads run side-to-side every 2 feet. There appears to be no flow between "compartments," as only the foam in that particular section is wet (I took up deck in many other spots to check, which also helped me figure out where all my stringers and bulkheads are).

Does yours have screws holding the cap to the deck at the windshield pass-through? Mine has four screws, and I think that's where the water intruded. I'm gonna seal those with 5200 when I put it all back together.

As to whether you can repair with cap on, I think it depends whether your deck wood is rotted up under the open bow. My softness was luckily only toward the middle and back of that area or "compartment", and the part under the open bow is still plenty solid. Also my stringers are still good and solid.

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

i am a fair distance from my boat at the time.
trying to gather some basic knowledge before i head out to work on it.
i am not familiar with how the cap detaches from the hull.
i believe it is all constructed as one piece, i will have to check.

Unfortunately the rot n my boat is right up to where the fiberglass deck in the front joins.
I take it the wooden deck extends underneath the fiberglass of the bow portion? or would that just be seated on the stringers?

i found some pics in an old build thread that were a bit more helpfull. but still nothing with the cap off. so i am still unsure what continues on beyond the fiberglass deck of the bow.

 

[ajgraz]

Re: 77 Glastron trihull open bow

Again, a 1978 StarCraft 15' trihull (not Glastron), but here's what I got:

Red circle is the screw holes where I think the water intruded. Red arrow is the only part of the foam that was wet, suggesting these compartments are all completely separated by the stringers. On my boat, that foam is only about 5" deep; I'm going to leave that exposed to the San Diego sun for a couple months to see if it dries out enough so that I can be lazy and not have to dig it out. That forward cutout for me was 24" front-to-back, 27" side-to-side...bigger than it needed to be, but I am into solid dry wood.

(Pink rectangle is the section I'm glassing in next; green arrows are sections I've glassed in or am in the process of glassing in; blue arrows are some wood I'm glassing in to make the deck more level for my lounge seat bases)

Stringers here are 10" from center (or 20" apart), exactly even with the width of the bilge area. Bulkheads are 24" apart.

I started all this by taking out exploratory deck cores with a hole saw. Then I cut out rectangular areas of deck with an angle grinder for the glass layer, followed by a circular saw set to just deeper than the wood.

I'm finishing up with 1/2" outdoor plywood, epoxied both sides, screwed to stringers, filleted with epoxy/silica, then 2 layers of 1.5 oz CSM and epoxy resin.

The wood deck does extend up beyond the fiberglass "floor" of the walkthrough in the cap on this boat. If the deck was rotten there, I figure I'd either have to remove the cap or cleverly cut out and re-glass a sizeable section of the forward part of the cap.

I hope this is helpful for you.

 

[redfury]

Re: 77 Glastron trihull open bow

John finished his 15ft Glastron project last year, and I'm still working on mine ( V178 )...lots of pictures in the links below of my project ( in progress ) if you want to know what Glastron probably gave you to work with under the deck.

Chances are you will find that the stringers were not encapsulated fully in glass and you will have 2 or 3 of them depending on the model of your boat ( lucky me, I got to have 3 of them.

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

I did end up getting a chance to head out after work yesterday and cut open the floor, turns out there's far more damage despite my hopes, all the foam was waterlogged and the deck was rotten in many spots underneath a thin layer of good wood on top.

The stringers although still straight and undamaged are quite wet on the exposed sections, therefore I am assuming they must be removed? Or would it be possible to reinforce them on either side and have it hold up without rotting further, given some time to dry?

If I do end up having to replace everything, it has appeared from what I've read that the job will add up to over $1000, but how much time am I realistically looking at to complete? Aside from gathering materials and curing/hardening times.

 

[ezmobee]

Re: 77 Glastron trihull open bow

Rot is cancer. You want to remove all of it.

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

Again, a 1978 StarCraft 15' trihull (not Glastron), but here's what I got:

the screws you have in the picture are not present on my boat at least, it sounds like its very possible that is where your leak is coming from.

 

[redfury]

Re: 77 Glastron trihull open bow

I did end up getting a chance to head out after work yesterday and cut open the floor, turns out there's far more damage despite my hopes, all the foam was waterlogged and the deck was rotten in many spots underneath a thin layer of good wood on top.

The stringers although still straight and undamaged are quite wet on the exposed sections, therefore I am assuming they must be removed? Or would it be possible to reinforce them on either side and have it hold up without rotting further, given some time to dry?

If I do end up having to replace everything, it has appeared from what I've read that the job will add up to over $1000, but how much time am I realistically looking at to complete? Aside from gathering materials and curing/hardening times.

It all depends on the the condition of the fiberglass that is there. You could try to pull the wood out of the glass that is there if it's in good shape, and put a new core in it and then reglass the outside after sanding the glass down to a good clean surface. However, the amount of work involved in doing that the right way is actually more work than just cutting the old stringers out and putting new ones in.

Realistic time frame? If you can afford to buy all of your materials up front and have the time to get on it and work hard, you could replace the stringers and the deck in a couple of weeks.

I'm on a shoestring budget and have a lack of time available, so my boat is in its 4th year of restoration....very slow progress! But, I do what I can, when I can.

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

the fiberglass on the stringers did not look too worse for wear, there appears to be some thinner sections simply from the way it was constructed, as well as the obvious gaps where it wasn't glasses at all, in joints ect.

how would i go about removing the wood from it? cut the glass along the top and attempt to chip and pull the wood from between?

it does sound like a lot of work, not much more gain than redoing everything that is.

 

[redfury]

Re: 77 Glastron trihull open bow

That's what I did. Took a sawzall and cut the top of the caps off and started digging it out. The problem with it was the fact that the factory glass was only there to hold the wood in place for the most part. The deck was stapled into the tops of the stringers and glass along the edges.

Remember this one important thing though....WEAR A RESPIRATOR. Anytime you are cutting or sanding or grinding the fiberglass. I can't stress it enough. It was the first mistake I made, and the last one I made when it came to dealing with fiberglass. I cut the stringer tops off with no mask, and nothing but a t-shirt and shorts on. Wow, that sucked. Itched and coughed for a week straight. Misery.

Before you do anything though, make sure you document everything before you remove it ( how high the stringers are, etc ) Take a ton of pictures from various angles, mark measurements on the photos if you can so that you will have a good reference for when you start the rebuild process. I ended up guessing on a couple of things when I did my stringers. They turned out fine, but it took more effort than it should have.

The other thing I will stress is prepping the fiberglass properly. One, make sure you leave a SMOOTH finish. Second, make sure you prep the glass out a few inches further than you think you should. Some guys just sand the whole interior hull structure down to good glass, but it isn't necessary unless you plan to glass the entire hull again.

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

thanks a lot for the helpful info, i truly appreciate it!

i will certainly make sure to measure and record everything before i begin to cut anything.

as for the prep of the glass, would this mean sanding until there is no feeling of texture to the woven glass? it there a preference in sanding grit to use? it seems there are many different tools people seem to use, anything that works particularly well?


it looks like i am going to have to remove the motor and take the cap off. i read of people cutting the top of the cap but that sounds like more work than removing the rub-guard and unscrewing the cap. is there a reason someone would do this?

 

[redfury]

Re: 77 Glastron trihull open bow

cutting the cap from the splashwell back instead of taking the cap off would be for those not needing to do much work forward of that area.

You need to grind down the glass until you see clean glass, that's all. Doesn't have to be perfectly smooth, just clean. For the heavy work, 36 grit flapper disks on a grinder will do the job, though there are those here that have managed with just the metal grinding wheel that came with their grinder ( I think that would be more work personally ). Just don't let the flapper eat too much on you or you'll be adding back glass!

 

[1970Thunderbird]

Re: 77 Glastron trihull open bow

Hey all,

Any suggestions for how to remove the decking? I've got a hole in my deck, so I figure I'll start there and work out. What's a good way to remove the fiberglass-covered plywood? I obviously don't want to damage my stringers or the sides, as they seem to be in solid shape. Do I just take a chisel and hammer to it? Saw it? I don't want to damage the hull, but this wood has to come up. I'm ready and raring to get started on this.

Thanks!

 

[ezmobee]

Re: 77 Glastron trihull open bow

A circular saw set to a very shallow depth.

 

[1970Thunderbird]

Re: 77 Glastron trihull open bow

I was thinking that might work. What depth do you recommend? I'm thinking 1/2" to 3/4"

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

i set my saw at a hair under half inch and it did fine on my deck. just picked up a blade with smaller teeth than your average one and made a clean cut through the glass and board.

 

[GlastronSportster]

Re: 77 Glastron trihull open bow

can anyone help me get an idea of what quantity of material im going to require to order to replace the stringers on my boat?

resin wise i have a fairly good idea but what about fiberglass matt/cloth?

 

[redfury]

Re: 77 Glastron trihull open bow

Well, I've used ( so far ) 100 ft of 10" wide 1708 biax for my 3 stringers and a couple of other small repairs and have a decent roll of CSM for my deck when I get around to that part of it. I've used 2 gallons of resin to get where I am today on my project ( 3 stringers in place and transom )

I used about 4-500 ml of resin for each strip of Biax I laid in my boat. I anticipate needing about 2-3 more gallons of resin to finish off my major glass work.

 

[jcsercsa]

Re: 77 Glastron trihull open bow

Hi , glad to see another sportster getting done !! I got a price list on the frist page of my thread use the second one about 3/4 the way down !! is yours the 15.6 or the 17 footer ? John