Transom rake & outboards

[dbp1]

At some point, I may want to put an outboard on my 16ft sailboat. The transom is raked 30 degrees. I'm trying to understand rake as concerns outboards. I had assumed that I wanted to get the outboard _level_ with the boat, which would mean trimming it out 30 degrees -- which doesn't seem to be terribly common (I'm only looking at electric stuff -- and little ones. The EP Carry _does_ have a 30 degree slot, but Torqueedo, EPropulsion, etc, seem to go to 21 and stop). Obviously, I could build a bracket to mount it on that incorporated some (or all) of that 30 degree trim, but I wanted to understand the situation better: on "displacement" motoring, is it desirable to have the motor at 0 degrees? Or tilted one way or the other? A 9 degree tilt would be convenient, but I suspect that's not the case!

[Breakaway]

You probably want it at zero to maybe 10 degrees negative trim, if your goal is maximized thrust and speed and make a motorboat out of your sailboat.

If your goal is simply to, " move the boat," you might get by using just the engine's built-in trim range.

Kevin

[dbp1]

You probably want it at zero to maybe 10 degrees negative trim, if your goal is maximized thrust and speed and make a motorboat out of your sailboat.

If your goal is simply to, " move the boat," you might get by using just the engine's built-in trim range.

Kevin

Any idea of what signs I should be looking for that things are not going well?

I don't care about turning it into a motorboat (at least, that's certainly not the current goal), but being pointlessly inefficient is also not ideal. If I went ahead and just got the motor I wanted, what would tell me it was worth fabricating a bracket (or, will someone come along and say that it'll be worth it no matter what, nevermind that it'll sort of work in the meantime).

[Breakaway]

I think we ( I do) need to know what you expect from the boat. Motoring all day suggests one level of success. Just getting on and off the mooring ball suggests a different level of success.

In general, the closer to vertical (or maybe a tad negative) the engine trim, the better it will be for displacement speeds. Too much trim will make steering more, " squirrelly," will reduce forward thrust and may cause the boat to squat a bit.

Kevin

[dbp1]

I think we ( I do) need to know what you expect from the boat. Motoring all day suggests one level of success. Just getting on and off the mooring ball suggests a different level of success.

In general, the closer to vertical (or maybe a tad negative) the engine trim, the better it will be for displacement speeds. Too much trim will make steering more, " squirrelly," will reduce forward thrust and may cause the boat to squat a bit.

Thanks -- that's helpful to know. I guess the squatting is kind of obvious, but squirelly-ness makes sense.

In terms of what I expect -- I'm honestly not sure -- still exploring the idea (and whether it's even worth it -- I do have oars!). Most ramps around here seem to be a bit removed from where it's actually nice to be out sailing (probably not a coincidence that it seems that most people seem to sail from clubs or on bigger boats that live on moorings), so more easily being able to get too and from is one reason. But I'm also imagining it could be fun on lakes with the family, where I might leave the sails behind entirely.

But, appreciate your input!

[Hugh MacD]

Daniel,
Is this on your Apple 16? If you're thinking electric I'd almost be inclined to set up some kind of bracket that you could hook over the transom and easily remove when sailing. That's such a pretty boat I'd be reluctant to hang an ugly motor on that transom

[dbp1]

Daniel,
Is this on your Apple 16? If you're thinking electric I'd almost be inclined to set up some kind of bracket that you could hook over the transom and easily remove when sailing. That's such a pretty boat I'd be reluctant to hang an ugly motor on that transom

Yes, it's for the Apple 16. I had thought to just clamp and remove it when not used(and maybe have some ply pads to protect the paint/varnish), but can you describe a little more? I had assumed that a bracket would need to be very securely attached (bolted, likely), and thus would be much _uglier_ than just the motor (which at least can be removed with wing bolts). A bracket that allowed it to just drop on sounds great

[Breakaway]

There is the Spartan Marine outboard mount. Rather than transom mount, it installs off the side of the boat. That angle, plus the outboard's ability to swivel, allow you to direct thrust directly aft.
When not in use, the bracket comes off; its mount remains.

Screen Shot 2022-04-07 at 6.43.05 PM.jpg

Screen Shot 2022-04-07 at 6.41.59 PM.jpg



Kevin

[dbp1]

There is the Spartan Marine outboard mount. Rather than transom mount, it installs off the side of the boat. That angle, plus the outboard's ability to swivel, allow you to direct thrust directly aft.
When not in use, the bracket comes off; its mount remains.

Interesting idea. Not cheap (but I've gotten cleats from them, so who am I kidding!), and would involve a slightly creative installation, since my back deck is not flush with the transom (see photo), but definitely interesting.

Frame-07-04-2022-07-08-23.jpg

[Woxbox]

I can't find it now to take a photo, but I have a very simple wedge device to put a trolling motor on my Whisp, which also has a lot of rake. I can't find it because I haven't used it in many years. It's nothing more than two wedges cut to the degrees your tilt is short on -- say 10 degrees in your case. Attach them to a piece of marine ply leaving a gap between equal to the thickness of the transom. In use, you just drop it on the transom, put the motor over it, and clamp it down. You could put a rubber lining in it for better grip, but mine is just wood and never slipped. It has the added advantage of preventing the motor clamps from marring the boat's finish.

You do want the motor vertical for efficiency. Also, if it's not vertical when down, it won't be horizontal when up, which is also a pain.

[dbp1]

I can't find it now to take a photo, but I have a very simple wedge device to put a trolling motor on my Whisp, which also has a lot of rake. I can't find it because I haven't used it in many years. It's nothing more than two wedges cut to the degrees your tilt is short on -- say 10 degrees in your case. Attach them to a piece of marine ply leaving a gap between equal to the thickness of the transom. In use, you just drop it on the transom, put the motor over it, and clamp it down. You could put a rubber lining in it for better grip, but mine is just wood and never slipped. It has the added advantage of preventing the motor clamps from marring the boat's finish.

You do want the motor vertical for efficiency. Also, if it's not vertical when down, it won't be horizontal when up, which is also a pain.

That’s incredibly simple, and sounds perfect. I had thought to add some sacrificial wood to protect the boat from the clamps anyway; that it could also solve the trim issue is just brilliant.

Thanks! You remind me why I stick around this forum

[Hugh MacD]

Sounds kinda like what I was thinking about. Simple & sweet!

[The Q]

A side mount motor may well be easier to fit..

[cjnd]

I am considering putting a removeable wedge on the transom of my new boat (see photo) and perhaps using a Torqueedo although I really want to only sail, row and scull. Do you think that not permanently fixing the wedge to the transom will be sufficient?

20220510_082048.jpg

[Jim Ledger]

There is the Spartan Marine outboard mount. Rather than transom mount, it installs off the side of the boat. That angle, plus the outboard's ability to swivel, allow you to direct thrust directly aft.
When not in use, the bracket comes off; its mount remains.

Screen Shot 2022-04-07 at 6.43.05 PM.jpg

Screen Shot 2022-04-07 at 6.41.59 PM.jpg
Kevin

It you intend leaving the outboard on this kind of bracket while you sail I would advise doing a simple lofting. See whether when the prop is sufficiently submerged the tiller clears the transom. Also is there enough clearance to tip the motor up. They are a one-size-fits-all arrangement and lack the adjustability of most mounts to raise and lower the motor while underway. DAMHIKT

Jim

[dbp1]

I haven't tested it out yet (it took a lot of back and forth to get the paperwork, which here in MA is required with a motor but not with only sails/oars, but I finally got it the other day), but I'm planning on testing soon. Here's what I made, based on the suggestion from Dave on this thread:

IMG_2015.jpg

That was in progress, but shows the construction pretty well -- I planed a 10 degree angle into a piece of wood, cut it in half, clamped it on either side of the transom with some plastic underneath and glued a piece of marine ply on top. Then I added two layers of 6oz glass reinforcing the weak joint on top, and then two more layers of glass around the entire thing. It feels extremely solid, and if anything, too tight (I should have put slightly more than just a single layer of plastic underneath when I clamped it on the transom). I wrapped the whole thing in gaff tape, which should sort of protect the transom, but not add too much thickness (nicer would have been to give a bit more space and leather the inside, but I didn't!).

I got an EPropulsion Spirit 1.0 Plus, which as far as I can tell is sort of an evolved, slightly less proprietary Torqueedo (the company was started by former Torqueedo people) --- slightly less proprietary in that it can be powered by a 48V external battery, which is a pretty standard voltage (so if I wanted to set up an external battery bank, solar panels, etc, it would all be relatively straightforward).

I'll post an update when I take it out!

[TerryLL]

There is the Spartan Marine outboard mount. Rather than transom mount, it installs off the side of the boat. That angle, plus the outboard's ability to swivel, allow you to direct thrust directly aft.
When not in use, the bracket comes off; its mount remains.

Kevin

Kevin, pardon me please, but you are mistaken about that mount. The mount is designed to hang off the transom. The photo you posted is from the Cape Dory Typhoon catalog. I once owned a Typhoon with that exact mount, and have installed one of those mounts on a decked dory.

As for transom rake for an outboard, the standard rake is 14 degrees. That angle allows the motor to be trimmed either forward or aft to get the desired ride angle. A vertical transom will not allow the motor to be trimmed to lower the bow.


Screen Shot 2022-05-16 at 1.43.53 PM.jpg

As for installation, bolting is not required. Motors up to 25HP are routinely clamped onto the transom, or transom bracket. That Apple 16 will require nothing larger than 4-6 HP. I drive my 20' Caledonia Yawl with a 2HP Honda.

[dbp1]

Just a quick update -- finally had a moment to test the motor mount (and motor) out. Worked perfectly, moving the boat at 3-4 knots consuming very little power (and there was actually a decent amount of wind, though this was on a river, so no waves). So, again, thanks for the advice on this thread!

The only real downside is that by relying on the full trim (22 degrees) already, the "tip the motor up" option only gets it another ~50 degrees up, which isn't actually enough to get it out of the water. I wasn't really planning on sailing with the motor hanging on the transom anyway (weight, risk of catching lines from the mizzen, etc), but a little bit of a bummer.

IMG_2180.jpg

Without a outside observer, I couldn't get a great sense of the trim, but it seemed pretty level (I have some removable ballast I stuck near the bow, slightly off to the opposite side, to counteract the weight of both me and the motor).

[Woxbox]

The only real downside is that by relying on the full trim (22 degrees) already, the "tip the motor up" option only gets it another ~50 degrees up, which isn't actually enough to get it out of the water. I wasn't really planning on sailing with the motor hanging on the transom anyway (weight, risk of catching lines from the mizzen, etc), but a little bit of a bummer.

My MinKota's shaft slides up and down in the bracket, and a lockable collar to set the depth it drops. So it can be tilted and then slid up and forward. I guess the Epropulsion doesn't do that? Not something I contemplated when I recommended that bracket design. Of course you could make another with more angle, but the motor clamps looks like there's maybe an inch or less left to play with?

[wizbang 13]

transom rake itself does not matter to an outboard
we have this material available fer makin stuff .stuff like wedges.

[AJZimm]

Lots of ways to make specific motor mounts for an open boat. In the case of my 18' yawl, Fire-Drake, one side of the transom is occupied by the mizzen boomkin and the other by the push-pull tiller, so it had to be a side mount. Here is the demountable rig I came up with, for the Yamaha 2.5 that I use, which can spin 360 degrees. I unship the motor and mount when sailing or rowing.


Here it is in use on the boat: