T-Pain Is On A Boat: Re: [Electric Boats] Tartan 27 conversion

Tuesday, September 28, 2010

Re: [Electric Boats] Tartan 27 conversion

Paul,

You want the flange bearing to take the radial load from the belt. That means the driven pulley should be very close to the bearing, at most a couple of inches away. Closer is better.

If the pulley is in front of the bearing you can take the pulley off without disturbing the bearing or shaft.

One bearing is better than two as the cutlass bearing is also part of the equation and the middle bearing would have to be very precisely mounted on the centerline defined by the end bearings. Besides, one bearing, even a 3/4" bore size, will have more load capacity than you will need.

This will be a good time to make sure your shaft is straight.

Denny

----- Original Message -----

From: tartan27hull157

To: electricboats@yahoogroups.com

Sent: Tuesday, September 28, 2010 9:13 PM

Subject: Re: [Electric Boats] Tartan 27 conversion

Dennis --

Thanks much for this input! I already looked up some bearings and the Gates site based on your notes.

I wasn't planning on using the A4 mounts, one of the problems is that the stringers are soft. I was going to cut them out as part of the electric rehabilitation. In particular, I was thinking that for weight and balance reasons the battery bank should be centered over where the 350# A4 comes out...I was thinking that I could shorten the prop shaft and move the electric motor aft. As far as I can see, the only reasons why the shaft is as long as it is, is to make sure that it reaches the engine...the engine, in turn, was located here presumably for weight and access reasons which won't apply to the electric motor.

Shortening the shaft would also allow me to re-key it, since the existing key shaft is significantly worn and has seen some trauma in its day. That is, if the machine shop says this shaft is OK...

So, working from the prop inboard, there is an existing cutless bearing, a stern tube I will replace, a packing gland I will keep, then a currently non-existent bearing flange I will install, then a driven pulley. Forward of that there would be a frame to hold the motor over the pulley and on centerline...and forward of that would be the battery bank, on new stringers in the place now occupied by the A4.

I wonder if it matters whether the driven pulley on the prop shaft is forward or aft of the flanged bearing? Or even between two flanged bearings? Now that I think about it, I could mount the electric motor with its driving pulley forward, placing the bulk of the motor over the prop shaft in space that would otherwise be unused and clearing more space forward of the prop shaft for the battery bank(s).

Looking at all the curves in this part of the boat, it seems like the "drop in" systems will also require some glass work to give them something to bolt to, unless I use the existing stringers, which seem like they are about two feet farther forward than they need for an electric implementation.

Thanks again for your suggestions and let me know what you think, Paul

PS I wasn't planning on being in Annapolis this Fri but now I am thinking about it...

--- In electricboats@yahoogroups.com, "dennis wolfe" <dwolfe@...> wrote:
>
> Paul,
>
> You will need to support the inboard end of your prop shaft with a thrust bearing. A two or four bolt ball bearing flange from a bearing distributor is the way to go. MRC brand flanges have a plastic housing and rust resistant plating on the steel components. The size that fits your shaft will have plenty of capacity to handle the shaft and belt loads.
>
> The bearing distributor will sell the pulleys and belts too. Use a toothed rubber belt.
>
> The Gated web site has an excellent pulley and belt selection program.
>
> With the $1400 kit you might spend another $500 to $750 on parts, and several hundred more if you need to pay a machine shop for fabrication. The mounting system has to be rigid and accurately align the motor with the prop shaft. You will also be happier if you connect it to the boat with rubber vibration absorbing mounts.
>
> The "drop in" systems will save you many hours and probably fit right on your old A4 mounts. Also, the throttle box and wire harness in the $1400 kits is golf cart rated - not marine stuff. Like many things, you can trade $$$ for time and specific skill.
>
> Denny
>
> PS: I see you are in Annapolis. You should go to the start of the Wye Island Marathon (if there is one this year) in St Michaels and check out the electric installations. I think it's this Friday 10/1.
>
>
> ----- Original Message -----
> From: tartan27hull157
> To: electricboats@yahoogroups.com
> Sent: Monday, September 27, 2010 11:55 PM
> Subject: [Electric Boats] Tartan 27 conversion
>
>
>
> Hi all,
>
> I have been lurking and reading for some time while I nurse the 45-year-old Atomic 4 in my Tartan 27, a 27 ft LOA, 21 ft LWL, 10,500# displacement-hull sailboat (currently propped with a 13x8x2).
>
> It seems like a reasonable replacement for this boat could be built around a 4kW motor with a 2:1 reduction and as much battery as I can afford from a weight and $$ perspective (it would save some money if the initial installation could preserve the current prop and shaft, and if my calculations are correct, that prop should push the boat to hull speed around 1700 shaft rpm...sound right?)
>
> I am puzzled by the price difference between $1400 kits which seem to be lacking only the reduction system and the batteries (eg EVParts, ThunderStruck), and $4000 systems which purport to be "drop in" except for batteries (eg SeaNav, ElectricYacht).
>
> Am I missing something? It seems like with the extra $2600 and a McMaster-Carr catalog I should be able to buy some pulleys and belts and bearings and angle iron, build the DIY system, and still have some pocket change left over to buy batteries. Am I overlooking a significant component?
>
> Also, my prop shaft as designed is supported only by the cutless bearing and the big, heavy engine's output flange. Should I plan on stabilizing my prop shaft somewhere in the shaft alley with a strut, or can the smaller electric motor be installed in a robust enough way that it supports the shaft?
>
> Thanks in advance, Paul
> Tartan 27 #157
> Annapolis, MD
>