Setup questions for brand new SV27 brushless

[blipphardt]

I've read alot of great information in this forum already....thanks to everyone for taking the time to post. I've had some experience with a CEN Aquajet, but I am a SV27 newbie.

I recently purchased a SV27 brushless with a lot of advice from Steve at offshoreelectrics.com. I live in Delaware, and the pond in my backyard is frozen, so the boat has not gotten wet....yet. I followed Steve's advice, and removed the struts/receiver box support wood unit, and coated all surfaces with West Systems epoxy. I then reinstalled and reinforced it where it bonds to the hull.

Question #1: I'm a bit concerned about the geometry of the flex shaft and the brass tube. When fully installed with the stock coupler, the prop shaft extends about 1/2 inch beyond the end of the blue anodized stern tube opening. The brass shaft tube can be positioned so that it butts up against the prop coupler at the rear, or it can be pushed all the way forward so that it butts up against the motor coupler. Do most of you push the brass tube forward, and leave the back end of it flush with the opening on the blue anodized stern tube fitting? Should the brass tube be shortened at all? Should the flex shaft be shortened? Here are two pics showing my current setup:





Question #2: I am running two 4500 maH NiMH six cell battery packs, and I am NOT using the wooden battery mounts that came with the boat. I have two-inch wide industrial strength Velcro ready to epoxy into the boat. Most advice I've seen says that these should be mounted with their forward edge positioned about one inch aft of the motor mount cross member. Is that a good starting position? What is the best initial setup for center of gravity? How do I accurately check the COG?

Pray for warmer weather in the northeast, so that I can get this boat wet already.

Thanks again -- Bruce

[m4a1usr]

Here is what I do with any/all SV27's I have owned with regard to question #1. Rotate the motor mount plate 180 deg. Meaning the angled section which have the mounting holes are pointed rearward instead of the stock position where they face forward. This will put the motor about .250 to .300 forward of the stock position. This vastly improves COB (COG to some) by moving the mass forward. Next get an Octura coupler. Its a better coupler overall. This should talk up any slack you appear to have. At some point your going to want to shorten your stinger. The hull runs better if you shorten it by an inch.

Performance will be inhanced by running 1/2 to 1 degree of negative angle on your stinger. Neutral on your trim plates. Remember trim plates are an extension of your hull's bottom. They contribute to drag if set below this level. Angle your rudder. It should not be parallel to the transom. A degree or 2 is a good place to start but remember it contributes to transom lift when you push the bottom away from the transom. This should be carefully considered when you settle on a particular prop. Lift is a good thing or can be a bad thing. Keep it in check or at least on your radar when making changes.

When I was running Nimh cells I liked mine with the front of the packs about 1/2 inch back from the motor mount edge. With lipos you need to increase that forward of the motor mount.


John

[Doby]

Your trim tab brackets are upside down.

[bigwaveohs]

Here is what I do with any/all SV27's I have owned with regard to question #1. Rotate the motor mount plate 180 deg. Meaning the angled section which have the mounting holes are pointed rearward instead of the stock position where they face forward. This will put the motor about .250 to .300 forward of the stock position. This vastly improves COB (COG to some) by moving the mass forward. Next get an Octura coupler. Its a better coupler overall. This should talk up any slack you appear to have. At some point your going to want to shorten your stinger. The hull runs better if you shorten it by an inch.

Performance will be inhanced by running 1/2 to 1 degree of negative angle on your stinger. Neutral on your trim plates. Remember trim plates are an extension of your hull's bottom. They contribute to drag if set below this level. Angle your rudder. It should not be parallel to the transom. A degree or 2 is a good place to start but remember it contributes to transom lift when you push the bottom away from the transom. This should be carefully considered when you settle on a particular prop. Lift is a good thing or can be a bad thing. Keep it in check or at least on your radar when making changes.

When I was running Nimh cells I liked mine with the front of the packs about 1/2 inch back from the motor mount edge. With lipos you need to increase that forward of the motor mount.


John

We are setting up a new SV27and an inch off the stinger seems like a lot; did you also shorten the bushing inside the stuffing box?

Has anyone else had experience with shortening the stinger by 1 inch?

[blipphardt]

Thanks for the input

John - Thanks for the detailed comments. I reversed my motor mount, and slid the brass stuffing tube forward so that the back end is flush with the stern tube. I epoxied the brass tube in place inside the boat. Everything looks nice and flush at the prop....my flex shaft is a bit short, but it is snugged in the coupler now. I bought an upgrade shaft....I may also get an upgrade coupler at some point.

Doby - Thanks for catching my mistake with the trim tab brackets. Makes more sense to me, now that they are correctly installed.

Delaware weather is moving in the wrong direction.....more snow here today. And....they are playing hockey on our pond.

Bruce

[m4a1usr]

...my flex shaft is a bit short, but it is snugged in the coupler now.

Bruce

Your going to need to have at least 1/4 inch or better of flex shaft inside of the coupler for it to grip adequately. And if you can, solder the end of your flex shaft so it cannot unwravel due to compression deforming it when you remove your flex for regular maintenance.

John

[bigwaveohs]

We are setting up a new SV27and cutting an inch off the stinger seems like a lot; did you also shorten the bushing inside the stuffing box?

Has anyone else had experience with shortening the stinger by 1 inch?

[m4a1usr]

We are setting up a new SV27and cutting an inch off the stinger seems like a lot; did you also shorten the bushing inside the stuffing box?

Has anyone else had experience with shortening the stinger by 1 inch?

Yes you need to shorten the bushing if you decide on cutting the stinger down and your flex will need to be trimmed as well. If you dont race theres probably no real good reason to go to the trouble of shortening it. I brought it up because most folks are looking for easy, costs nothing, performance improvements. That would be one and has been recommended by racers.

John

[bigwaveohs]

Never mind...