TRANSOM REPAIR... Experienced advice needed

Wrong ole boy, Offshore Powerboat racing in fiberglass boats was invented here in So Florida and all they had to work with was Polyester resin, so for your point to be plausible those boats should have sunk at the dock instead of running in open water like the Old Bahamas 500, and some surviving till today over 50 years later also before you get real stupid more boats have been built using polyester adhesives such as Corebond from ATC than anything else.

 

Hi Dead eye..
I'm glad someone agreed with me (Thanks War Whoop)
You don't have to be that fussy or precise about the hole drilling, but you will not regret drilling all those holes! In the past to speed things up I have used a 50mm wide length of wood and drawn a grid first by making horizontal lines and then vertical using the wood as a spacer. Where the lines cross, drill your hole! Its not that big of a job really.
Don't be too worried about spacing to the the edges as they will let the mix squeeze out anyway.
As for structural integrity, with out going overboard on technicalities, the ply will not suffer. You are more likely to have more problems if there is air trapped than if you drilled the holes.
To sum it up quickly - in a sandwich construction the ply's first job is as a cheap high density core allowing the outboard motor to be attached with bolt holes drilled through it... It then serves to separate the two fibreglass skins which give the structure its stiffness to transfer the thrust to the boat from the motor... I am keeping this as brief but to the point as I can!
I hope that helps!

 

Both Astute and Steve need to read the full thread and not react to portions of it before they make less then insightful posts about drilling hundreds of necessary holes in a plywood core. There are much better methods of removing the air between the surfaces then an easy thousand in an 8' wide transom (not that this one is that big).

Yes, getting the air out is a concern, but easily handled, regardless of the thickness of the plywood being installed. If using polyester the common method is the same as with epoxy and installing the panel at an angle, preferably with some edge set solves the problem. This "rolls" the plywood into the space and the air naturally escapes out the bigger gap end, no hundreds of holes, no muss or fuss, just a solid hunk of plywood. I've changed out many dozens of transom cores and never have I had to drill a thousand holes in a transom to get the air out.

Steve you well know the weight penalty all manufactured and custom builders have had to pay, for a durable polyester laminate on wood. Yes, I agree that some folks get carried away with their disdain of polyester, possibly their personal unfamiliarity of the material, but it's reputation is mostly deserved, when compared to other materials.

 

When I bag into a paste I always perforate the material, that is a must even with transom clamps ( I built some cool pneumatic ones) one moves the air away from the clamping area around but Not out without holes,big problem Plus the drilled holes with are a indication of bonding if they show resin and bonding putty on the surface,Now on core bonding I go for no more than 1MM of bond line.

 

Par , you really kill me and just curious considering you have a degree and being a Yacht desinger and builder just .......... how much hands on experience do you really have over the years considering you claim to be the man . Par , gotta say that most people in your postion , designer / builder / can talk the talk without ever doing the walk .

 

G.G. I have two engineering degrees, how about you? I don't claim any such thing as being the man, though I've been to my share of picnics over the 30+ years.

Steve is talking about bagging, which is great and his perforation needs understandable, but again, the original poster is working in his back yard, is NOT bagging and hasn't any need for drilling a thousand holes in anything.

So, folks, lets get real for the original poster's issues. He's under a shade tree, he's putting in a two layer plywood lamination for a transom core replacement. Tell me, how many holes do you think this fellow really needs? His transom, if like the many I've done over the years is probably riddled with holes and cracks so air getting out isn't likely to be that much of a problem, but hay, I'll sit down and let you new experts lead this guy down some weird perforated path, if you think this is best serving the original poster's needs?

 

Going back to the drilling Bagging, Clamping or using knee braces,wedges whatever on a plywood transom installation ,it is important to vent the air and excess material "out" is the point I was making,plus the visual indication offered by the material coming out of the holes "every hole".

 

Sorry Par , you really need to give some of us new experts a little more credit .......... considering that i have been doing this type of work for over 39 years now and to tell you the truth the only reason i have taken so long to pipe in is because every bigmouth on this site who seems to know it all does not want to really listen to anybody else regarding there opinions even thou they might have a far greater knowledge then you think they have and to tell you the truth i have see it time and time again on this forum and you are a prime excample because everything that i have learned is hands on experience .............with no bull $hit degree and this is coming from an old man of 58 who started out in this business building windmill blades in his early teen's . So take that to the bank Mr know it all with TWO degrees considering i have much more respect for Steve and all is accomplishments along with Pete of Douglas Marine / Skater who i was employed with for many years who do not have any degree's in Engineering and you are the expert ?

 

Steve, are you going to ignore the original poster's requirements and expound on your professional bagging techniques?

To recap some of the OP's previous comments:

Initially the OP was concerned over the use of polyester, then about terminology, then about what to wear on his burning death barge, to which I still am claiming copyright protection or at least intellectual property rights.

Then the hole drilling thing. I've installed literally dozens of transoms and never have I had to drill hundreds of holes. I've also never had a return on one of my core replacements, that wasn't involved in a incident with something hard and moving faster then they thought at the time.

To clarify again, I roll the transom core into place and have able gaps around the perimeter for air to escape. The transom usually goes in and makes contact on a predetermined side (port, starboard, bottom or top which ever is handy, though the bottom seems most often the one). At this point the core is wedged into contact with the goo, from the "favored" side first and these braces walk their way across the face of the core, until eventually the whole core is in contact with the goo. No bags, no screws, no thousand holes from hell, just angled leverage until it's in place. Naturally, the direct opposite side of the core is held open until the last set of wedges or braces are installed. A pry bar is a common tool for this as are a couple of wooden wedges left over from rib scarfs. This lets the air work out as the core is driven home. While the core bonding goo is kicking off, I usually fillet the core edges to the shell. The engine mounting, transducer, boarding ladder, name plates and other holes already in the outside skin also let out air.

Maybe you have different methods that involve hundreds of holes, but frankly I consider it a waste of time, though in your defense I can see considerable goo savings using holes and a bag job. But then your shop materials costs go up on bleeder and bag costs. Personally, I do enough transoms that I'm fairly set with the two methods I'm employ, but if the hundreds of holes technique can save me something, I'm paying attention.

 

dead eye....what you have done in the past is done, don't loose any sleep over it, there are millions of boats made and repaired with poly resins, so just keep on going with what you are doing.

PAR really does know what he is doing, his advice to you is absolutely correct and functional. That does not mean that other people are necessarily wrong, in what they say, but different techniques are developed in different areas of the world, and this is an open forum, so there will be many and varied opinions to choose from.

I have done many transom repairs using basically the exact same following as PAR suggests, and also never had a failure after many years work.

Are you in Brisbane by any chance, I am happy to pop around and have a look if you are.
Send me an email.

 

Hey Par,
Just adding something that you missed, no need to say all the other things twice...
I'm too busy for that.
Dead eye's boat - and with the information he can make his own mind up, just got to consider all the options, not just who shouts loudest... Proclaims to know more...etc.
This is advice anyway, just what he asked for...

 

I use a hole about every 3" in transom installation plywood or high density foam as in the past we learned that is the largest area that we could bed without air inclusion,Now as for the sheet core in the hull shell again perforated to relieve the air and excess material using Corebond or the Epoxy like Spabond to attain a proper acceptable bondline.

 

Maybe give Corecell a ring and ask them why they bother to perforate their cores too...?

I calculated it would be around 360 holes, that should be no more than 1/2 hour drilling to do the job right first time...

 

I understand the need for perforations Astute, though I don't need them in most situations, nor think they are necessary in this application that the original poster presented. What I don't understand is your attitude. With less then a dozen posts here, no board reputation or longevity established, yet a considerable amount of attitude towards me. You walk into the room, declare yourself expert and people to pay attention or respect you? How about proving your value here before starting crap and talking about thing the original poster hasn't even heard of before.

 

PAR/Paul...
I think that you need to take it a bit easy here, its not your forum...
You discounted my original post a incorrect, now you are changing your tune.
Your instant dismissal and continued singled mindedness is cause for the attitude.
So what if I don't post that often, don't expect me to kiss your *** because I don't plaster my opinions on here twice everyday. I'm a touch too busy "at the sharp end" to rack up 5k+ of posts... Hence, I'm not on here to looking to bolster my self esteem either, just helping out when I can.
If you like it better, I will not bother anymore - if you get so offended that someone has a tad more info to chip in.
My concern is that:
The method you prescribed is not risk free to the novice and therefore could bite someone in the backside.
I would NEVER stick any thing bigger than 4" square the way you suggested, but, I do operate at the top of the composite boatbuilding ladder and up here we push the quality onwards, techniques get pioneered, incorporated as Standards and handed on......
Shame on you and enjoy 'your' forum.