Transom doublers

[Mxkid261]

You drill and tap after right?

That's how I do it and it seems to work good I epoxy the doubler in first and drill/tap once its set

[LarrysDrifter]

Thanks for the responses

[T.S.Davis]

I've done it both ways Ray. I find it easier to get straight true perfect taps the right distance apart if do them on the drill press. Drilling holes in the hull is easy. Sometimes if I place the plate and tap on the boat I get the hole off a half mm or maybe a on a tiny bit of angle. Ugh. Then when I try to screw everything down I end up fighting the taps I've made. I'm sure it can be done better than I described but not by me. haha

You mentioned blind nuts. Just yesterday (yes in the dead of winter.... What? It's not weird. Don't judge me), I had to hog my way into the sponson of a raptor rigger because the blind nuts weren't holding the fin at all anymore. Just spinning. When I got in they were basically to circles of useless rusty dust. I backed it with aluminum and tapped it. That one I glued the plate in and then tapped. Seemed like the easier way that time. Should be forever now.

[LarrysDrifter]

The only thing that scares me about using a threaded aluminum doublers, is the possibility of stripping the threads. I know, a steady hand and not over tightening works wonders. I'll stick with my washers and nuts.

[T.S.Davis]

If you do strip one then throw the washer and nut on. Been there too.

The aluminum plate in a Stealth sponson is a tick thin and sure enough I stripped it. Pretty much the way you described. Went to washers and nuts. However, I;ve since decided I'm going to just glue in another layer of aluminum and tap that.

[LarrysDrifter]

Very true, Terry. Good point on using nuts and washers if it happens.
Since I do already have the CF plate and don't have any aluminum, I'll stick with the CF.
I couldnt remember what I used to use in my DF monos, hence this thread...

[Mxkid261]

You could pour some epoxy in the transom too over the nuts once you get everything bolted on I just did this with a rigger. Then if you do need to pull some hardware off your not fiddling with those little nuts

[properchopper]

I used blind nuts for a long time. Even though most of my boats run dry, water always finds a way in like when the hatch comes off etc. Blind nuts tend to corrode over time and wood gets rot. You can use stainless blind nuts to make it less prone to corrosion.

You got that 100% right. Since the bolts and blind nuts are (in most cases) dissimilar metals, galvanic action + the corrosive effect of water penetration will corrode the nuts to the blind nut and (quoting Mr. Davis : "The blind nuts weren't holding the fin at all anymore. Just spinning. When I got in they were basically to circles of useless rusty dust.")

Man this brings me back to the dark ages when I ran in salt water behind my 40 foot liveaboard. Still have memories of grinding stuff off. Bah Humbug.

A comment on doubler material :

I've found that most factory transom internals (e.g. DeltaForce hulls) are reinforced by a thin layer of what appears to be compressed and solidified chicken feathers. To supplement that, a doubler will add strength BUT HERE'S A THOUGHT : Most transom internals aren't a 100% flush/flat surface SO by using material like CF there will be voids between the CF and the factory material AND then when tightening the hardware there is a risk (small, but existent) of drawing the hardware to the stiff internal doubler and possibly cracking the external gelcoat. For that reason (and for economics) I always use 3/32" birch ply which I tack into place with silicone dots and then being somewhat flexible it'll become drawn into the voids, not the external hull surface.

And to make starting the nuts easier, I use a teensy blob of 3M strip caulk on the end of my finger then use an appropriate size nutdriver. (I also keep Neosporin and Band-Aids close by )

[JimClark]

I now tend to cut an aluminum transom doubler and tap the mounting holes and use nuts on the inside

[LarrysDrifter]

I too, have thought about the voids between the two materials. My thinking was to use my Finishing Resin, along with milled FG to adhere the CF plate. Use a couple clamps to hold it while it cures, then lay everything out and drill the holes after it's cured. Since the milled glass makes the epoxy a little harder, hopefully there won't be much flex to pull and crack the gel coat. Plus, using lock washers, you don't have to really torque down on the bolts hard. Just make it tight enough and work smart.
That's my thoughts anyway.

[LarrysDrifter]

I'll just ask this here, since I started this thread....
I can't find an answer I'm satisfied with (meaning definite).

Should the rudder be on the left or right side of strut?
I also want to keep the servo at the rear, if it makes sense, to keep the steering rod short.
All opinions or facts are welcome.

[boredom.is.me]

Regarding the voids, I make slightly oversized "gaskets" out of depron. This isn't the transom, but it's the best example. I do this anywhere there is an uneven surface.

Edit:
Now you can't do that with an entire transom, but smaller stuff for sure. If you wanted to make a solid transom, I'd pour epoxy on both the inner transom and the piece I'm using for strength. That way, you wouldn't have to worry about spots with no adhesion to the carbon/material. I don't think having minuscule bubbles of air between the panels would matter too much.

[Fluid]

...Should the rudder be on the left or right side of strut? I also want to keep the servo at the rear, if it makes sense, to keep the steering rod short. All opinions or facts are welcome.

Years ago we always put the rudder on the left. That loaded the turn fin in a right turn, helping to keep it planted. The problem with that placement was the boat was very prone to roll over whenever left rudder was needed. But that was in the days of straight turn fins. With today's hooked fins, most put the turn fin on the right. The hook keeps the fin down in the turns and the boat is less sensitive to a little left rudder, which is often needed in heat racing. You can't win if you don't finish.

BTW I almost never use a transom doubler. Maybe I'm just lucky, but I can't remember the last time I had a transom failure that a doubler would have prevented.



.

[LarrysDrifter]

Thank you very much. That's the straight forward answer I was looking for.
I'll install it to the right of the strut. I bought a new, bigger, hooked fin that seems better matched for the size of the hull. (See build thread).

Thanks everyone for your input.

[CornelP]

If you use very strong carbon for a doubler, do not clamp it, just use some weights from the inside. If you have a void and you clamp it, the transom can warp, giving you a nightmare trying to install the hardware true and straight.
I had this on an Etti mono and I had to fill and sand the outside after that...