Opinions on my strategy, please....

[Fuzzydog]

Hi everyone. I've been lurking for a while now, having bought a 69 17.5' K&C Thermoglass I/O bowrider earlier this year. The engine bed was seriously rotten and exploration turned out a needy transom and some stringers too. So, over the summer I have removed the transom from the inside (outer hull is intact), completely removed the engine bed, floor and all stringers up to the console. I have finished removing all the rotten wood and old fibreglass and am ready to start building. I see there is a lot of knowledge and experience on this board and would like some opinions on my plans. I will be using polyester resin and glass.<br /><br />1. Transom. 2 layers of 3/4 ply with glass/mat in between. I plan to coat the inside of the transom with thickened resin and apply 1 layer of ply. clamp up and let cure. fill the gap around the sides and bottom of ply with thickened resin, then apply thin resin and mat to the ply, tying the mat into the sides and bottom of the boat, put on the second layer of ply and clamp - let cure. then, thin resin/mat on the inside of the transom, again tying into the sides and bottom of the boat.<br /><br />2. Stringers seem pretty straightforward. After I lay down my deck, I plan to drill 2 inch holes every foot or so and completely fill with foam, then glass over. good or bad idea?<br /><br />Thanks for any and all comments.

 

[Winger Ed.]

Re: Opinions on my strategy, please....

Sounds like you're on the right course.<br /><br />I think you're making a little unnecessary work for yourself on the transom though. I've had good luck with I/Os by just using the 2 pieces of 3/4 plywood-- the green pressure treated stuff that won't rot in a few years.<br /><br />The weight that will bear on it is below the penetration where the drive unit comes through, and on your tow eyes if you pull something.<br /><br />I'd just put the plywood together with 1 heavy layer of mat/resin on the side that will contact the inside of the outside skin. Draw it up against the inside of the outter skin with plenty of clamps, and the bolts and such that will be on it anyway. That should fill in most of the voids between the skin & your new board. Or at least the voids around the contacting and stressed areas of it the voids in blank areas that don't really bear any weight or stress won't really matter**.<br /><br /><br />**<br />I worked on a 23' I/O once that was pushed by a 351 Ford, that only had wood around the sterndrive's penetration for a foot or so, but it went from top to bottom.<br />The sides of the transom coming away from it to the edge of the hull were cardboard--- yep, cardboard like they make cardboard boxes from. But since there wasn't any stress on the outboard centers of the transom, it worked fine and didn't weigh much.<br />**<br /><br /><br />Then fill the irregularities around the outside edges and under the board with thick mix of chopped up mat & resin so the stresses are transfered/disspersed to the hull as evenly as possible. <br /><br />.....<br /><br />If your eng. mount uses 2 big slabs of wood- 6 x 8, or whatever, they will have irregularities under them too. Try to save a inch or so of the edges from the fiberglass that held in the old ones. <br /><br />That way, you'll know where to set the new ones, and you can put a layer of waterproof filler like Dynatron's 'Dynaglass' or Marson's 'Kittyhair' to fill the gaps between the hull & the bottom of the mount itself, and the weight/load will be transfered to the hull evenly there too. <br /><br />Also, stuff the mix in the gap between the eng. mount ends and the transom board. This does the job of spreading the stress from the transm to the hull like those triangle shaped 'knees' you see at the bottom of outboard boat's transom tying the hull to the transom. <br /><br />Mix the stuff up with a minimal amount of hardener, smear it on the bottom (and the ends) of where the eng. mounts will lay -- like a thick layer of peanut butter.<br /><br />Place the mounts in the hull, and ease the engine down onto them so they settle in where they're supposed to be before the stuff sets up. It will be a permant fix that is just as strong as the factory did when they built it. <br /><br /><br />There's at least a dozen ways to attack your project in this reguard, but this will work, and is fairly quick to do.<br /><br /><br />Ed.

 

[Fuzzydog]

Re: Opinions on my strategy, please....

Thanks Ed. This whole project boat thing seems pretty straightforward, but it's always good to hear someone else say you're doing it right.<br /><br />You mention using waterproof filler under the engine mounts...you are correct about the structure (wood beams) but I was going to mix up some thickened polyester resin and bed the engine mounts down into that. Then the engine mounts will be encased in fibreglass (heavy woven roving) as per original. This should be ok, eh?<br /><br />I have to admit that the transom scares me more than anything else. I understand that there isn't much (if any) engine weight or torque applied to it, but I plan on pulling skiers and tubes. The attachment points for the tow ropes will be the tie down eyes which are located near the top outsides of the transom. I figure that is going to put HUGE stress on the transom itself as it tries to separate from the boat. Basically I see it in my mind that the engine is attached to the hull and sides of the boat, while the transom is attached to the skier/tuber.<br /><br />FWIW, the original transom looked incredibly strong - actually was 3 sheets of ply (probably 3/8th), and between each layer of ply there was about 1/8 of fibreglass with heavy mat that went progressively further up the sides of the hull.<br /><br />IE:<br /><br />outside of transom<br />3/8 ply<br />1/8 fibreglass with mat going 2 inches up sides<br />3/8 ply<br />1/8 fibreglass with mat going 3 inches up sides<br />3/8 ply <br />1/8 fibreglass with mat going 4 inches up sides<br /><br /><br />New transom will be:<br />outside of transom<br />glass with heavy mat going 2 inches up sides<br />3/4 ply<br />glass with heavy mat going 4 inches up sides<br />3/4 ply <br />glass with heavy mat going 6 inches up sides

 

[thejeepster02]

Re: Opinions on my strategy, please....

be sure to dry fit first...which ever way you go.<br /><br />I glassed the two pcs of ply together as one solid piece. using Stainless steel screws in several places to hold it together.<br /><br />The problem I see you may have, is if the glass on the outside is bowed where it may not touch the ply.<br />After the two pcs were ready. I dry fited and drilled to 1/4" holes around the center and bolted a angled steel to it and tighten her up.<br /><br />epoxy filled the holes after<br /><br />see my pictures<br /> http://members1.clubphoto.com/scott893520/owner-e1de-1.phtml

 

[kpm]

Re: Opinions on my strategy, please....

Good strategy. I rebuilt the floor/transom in my outboard this winter. I did the exact plan that you have. I used 2-layers of 3/4 matted together, then matted to the hull/floor. One thing that really helped me. In securing the transom to the floor/sides there were small gaps from my non-exact cutting of the transom wood. I mixed a cookie-dough texture of resin and sawdust. I pressed this mixture into the voids and that really helped secure the transom. After that I did the same thing you are planning...matting to the sides. Good luck

 

[Winger Ed.]

Re: Opinions on my strategy, please....

There's some darn good advice in here. <br /><br />I'd forgot about it, but when I did the Aluminum I/O transoms on a 19 & 21 footer, I did what Jeepster did. I had a row of 1/2" bolts, 12" apart going through the whole thing about 6" down from the top of the transom. There is a piece of 2 x 2 angle stock 3/8" thick running across the inside of the hull under them.<br /><br />The tow eyes go through the angle stock too.<br /><br />I've never towed skiers, but I've pulled other boats, and never thought twice about the eyes pulling out or damaging the transom. <br /><br /><br />The pieces of the drive unit will clamp it pretty well and suck it up in the middle, and a bar across the top will handle the top part.<br /><br />You could also use some 'L' shaped brackets that tie the transom to the stringers to suck in the bottom. Alum. hulls use the "L" brackets attached with 1/4" bolts all the way through to the outside. <br /><br /> For the bottom, it may be a solution to a problem that doesn't exist, but coming across the top with something is a darn good idea even if you talke the bolts back out when its done.<br /><br /> <br />If all you're towing is skiers, a big 3-4 inch washer or plate under the tow eyes will probably do you a good job.

 

[Fuzzydog]

Re: Opinions on my strategy, please....

hmmmm.. that angle stock (alum) across the top sounds like a really, REALLY good idea...as does the angle brackets to tie the transom to the stringers (engine bed, actually) AND (what the heck, let's go all out) so that I can really boat in complete security, I could run some angle stock (alum) from the top of the angle stock on the transom to the front of the engine bed on each side. That would create a triangluar brace and I could pull the QE2 if I were so inclined.... I know, I know, probably overkill but....eh..for some reason I just can't wrap my head around the true strength of fibreglass (ie where the transom ties into the sides of the boat...

 

[Winger Ed.]

Re: Opinions on my strategy, please....

Originally posted by Fuzzydog:<br /> just can't wrap my head around the true strength of fibreglass (ie where the transom ties into the sides of the boat...

Fiberglass has incredible strength in resisting forces of compression or 'pulling' on it in a straight line-- I forget the proper term.<br /><br /><br />I'd forgo the diagonal braces going down to the engine mount. Usually, the exhaust manifold or something will be in the way.<br /><br />But if you get the sides of the transom secured to the sides of the hull, the base of it tied to the engine mounting supports & stringers,,, and the load from towing something spread out a bit across the transom--- you will be able to tow the QE2, or run out of fuel trying.<br /><br />To see how the forces will work on it, stand behind the boat and push on the prop.That's how pressure will be on it as it spins in FWD. <br /><br />Imagine that force trying to push the power plant straight into the back of the boat, and lift up the front of the engine making it pivot on the top outside of the outdrive's frame or gimbal ring as the prop is also trying to push forward and pivot the lower unit up into the bottom of the hull--- all at the same time. <br /><br /><br />Think about it, and get a mental picture of the prop trying to push everything straight up through the boat. Brace, spread out, and support your weights & loads for that effect, and you'll be fine.<br /><br />Ed.