Thread: Goat - reinforcement below the transom tiller cutout?

Originally Posted by Boatmik

HI Peter,

That setup was the original in the plan. It was something I overlooked when I drew the boat up, but there were no problems with the three Goats I had something to do with over those first years so thought it was enough.

The reason is that the "usual" rudder design puts a lot of load on the transom if it hits anything, but the open backed rudder box means the goat (and most of my boats) don't put much load on the transom at all.

Probably a ply doubler would be enough .. I will look into incorporating it in the next plan update.

Has anyone else noticed this on their Goats?

MIK

Hi MIK,

Wrong thread?
Anyway - the biggest load from rudder to transom so far in my goat resulted from vertical loads on the tiller. I noticed that during the first dry fitting of the rudder box - my son used the tiller to brace himself. Fortunately he didn't broke something, but the upper fitting flexed the transom some 4 cm inward. So I fitted a strip of locust 15x20x250mm horizontally below the tiller opening to beef that region up.
For I haven't finished my epoxy coats, I've no experience with the dynamic loads.

Jörn

Mik,

I noticed that the ply at the bottom part of the transom-cut out on my Goat was definitely bendy. Nothing I noticed underway, but when I was messing with the rudder and the tiller in the garage I noticed the flexing. I glued on a strip of 6mm wood in that area, and it stiffened it up considerably. In hindsight, I should have added a little more to transfer some of the leverage to the main part of the transom.

What concerned me is not me sailing the boat, or the rudder hitting something, but downward force applied to the tiller. One day my wife was clearing the rudder of weeds and she was applying a lot of weight to the traveler as she bent over the transom, which pushed down the tiller, which I knew was flexing the transom. It's the passengers or me slipping and coming down on the traveler or the tiller that worries me more than the rudder hitting the bottom or sailing forces.

I added two layers of 6mm at the bottom and one layer at the top. That seemed more than adequate to my seat-of-the-pants stress analysis.

I used 2 layers of 6mm ply for the lower bracket. They span from the seat cleat down to the transom chine log. My upper reinforcement is part decoration & structural. It hides the nuts and is made from the same spruce as the transom cap.

I made a post here but something happened and it just disappeared.

I looked at my transom recently (actually, the one on my GIS!) and notice that the transom ply below the cutout does move slightly if I apply serious downward force on the tiller. Actually, I'd be surprised if it didn't. There is no doubt that the transom is strong enough, but perhaps if someone fell onto the tiller there might be some consequences...

Based on my observations, 3 things could happen if I fell onto my tiller (again, the one on the GIS).
1. The transom could fracture, or
2. the tiller could snap off at the stock. My Hoop pine tiller is made from undersized stock compared to MIK's plans so from some flex testing so this is a possibility
3. The tiller might take the flex all the way down to the deck.

I think most likely, the tiller would fracture.

I fixed a single thickness of ply below the cutout to reinforce the top gudgeon and another to reinforce the lower. If I were to revisit this, I'd be inclined to install a triangular shaped piece 220mm at the seat level and 120mm at the cutout (maybe this is a rhombus?) to protect the transom.
Attachment 143218

Trapezoid.

Maybe it's a difference in ply, but my Shelman was flexing a lot. The tiller would not have snapped, the transom would have cracked.

I've fallen already multiple times in the boat hot-dogging around in high winds. I can stay clear of the tiller usually since I'm holding it, but someone with less sailing experience such as my wife, might not.