VG23 Rudder Question from Plans

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mhd
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VG23 Rudder Question from Plans

Post by mhd »

Hello,

I'm enjoying the build up to now. The plans are very complete and simply reading them multiple times, studying the paper model I've made, and thinking for a day or two, and usually I can figure out the things I'm not sure of initially. But I've found a few puzzles that I still can't figure out.

There appears to be a mis-match on the VG23 plans between the nesting diagram (page 2 of the "Large Sheets" titled "D240/2 Nesting") which shows nesting for 3x rudder pieces from 10mm (3/8") ply and 2x rudder cheeks from 13mm (1/2") ply. In contrast, on the page where the rudder, tiller attachment, and pintles are actually specified (page 8 of the plans titled "B240/14 Fixed Rudder") looking at the diagram that shows the tiller plates and bolt going through the rudder, it seems the rudder assembly is formed from just two pieces of ply (3/8" ?) and the rudder cheeks are narrower in width (1/4" ?).

I think, based on scaling the rudder fitting sizes etc., that the 2x3/8" ply plus 1/4" rudder cheeks seems to be correct? Total thickness then would be ~5/4" plus glass/resin. This also seems to fit with a blurry photo I have of Brian's VG23 Talon rudder.

With other non-critical parts I'd be tempted to go with what seemed right. But the rudder is a bit more critical - I'd rather it matched the design as specified. So three questions just to be certain:

(a) is the rudder laminated from two or three pieces of 3/8"
(b) should the rudder cheeks be 1/4" ply rather than 1/2" ply shown on the nesting page??

I can't find any dimensions on any of the plans for the skeg. The skeg isn't listed on the nesting diagram either. I can certainly guess at dimensions, or measure/scale a size from the profile view, but I'm not sure of thickness.

(c) Would 2x1/2" ply laminated and covered with 2x biaxial be suitable thickness for the skeg?'

Jacques mentioned a possible cassette rudder design and I've thought about designing this myself too. It seems like it would be a good idea - some extra weight yes, but also the convenience of being able to lift up the rudder and lock in place for shallow draft sailing. It might even be possible to adjust boat balance using different rudder locking positions.

Thanks,

Mick


Completed: FB11 (Designer Evan Gatehouse)
Current Build: VG23 (Designer Jacques Mertens)

jacquesmm
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Re: VG23 Rudder Question from Plans

Post by jacquesmm »

The rudder blade is made of 3 layers of 3/8 plus fiberglass to suit.
I say to suit because the glass is there to protect from abrasion and you have to plan for that when making the gudgeons.
The rudder cheeks are minimum 1/2" but two layers of 1/2" would be better.
1/2" will work until one day, you will have the blade lifted and back out of a slip with the rudder to one side. That or something similar should not happen but if it does, a 1" thick rudder will save you. There is enough plywood in the nesting to make two layers each side.

The rudder drawing exist to show the tiller assembly, the pintles and gudgeon but please do not scale the rudder thickness. I agree that the cheeks look thinner but they should not be.

I sketched a cassette rudder but it would be heavy. It would have exactly the same shape for the rudder blade except for a handle cut on top, same pintles and gudgeons, same rudder head but extended aft. I have not figured out how to keep it down, maybe a Schaffer spring on one of the pintles.
I almost lost a rudder during a transat and it was a bad situation. It happened because the pintle spring broke. You don't want the blade to swim away because of a dowel or spring breaking. In my case, the rudder blade stayed attached through the autopilot fletner.
I want to design some "fuse" in there, a part that breaks in case of collision. With the pivot, the blade will lift but not break. With a cassette, I can imagine a spare blade with a sacrificial dowel. I am still thinking but to find yourself without a rudder 1,000 NM offshore is a challenge. The existing pivoting rudder is well proven.
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Re: VG23 Rudder Question from Plans

Post by Jaysen »

On the cassette blade retention...

Could a 1/2" groove be routed out of the blade, then a 1/2" SS bolt be used to keep the blade locked? This doesn't solve the problem of keeping the blade down, but it would allow for rudder blade retention if the fuse blows.
My already completed 'Lil Bit'. A Martens Goosen V12 set up to sail me to the fishing holes.
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mhd
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Re: VG23 Rudder Question from Plans

Post by mhd »

jacquesmm wrote: Fri Sep 23, 2022 11:29 am The rudder blade is made of 3 layers of 3/8 plus fiberglass to suit.
I say to suit because the glass is there to protect from abrasion and you have to plan for that when making the gudgeons.
The rudder cheeks are minimum 1/2" but two layers of 1/2" would be better.
1/2" will work until one day, you will have the blade lifted and back out of a slip with the rudder to one side. That or something similar should not happen but if it does, a 1" thick rudder will save you. There is enough plywood in the nesting to make two layers each side.

The rudder drawing exist to show the tiller assembly, the pintles and gudgeon but please do not scale the rudder thickness. I agree that the cheeks look thinner but they should not be.

I sketched a cassette rudder but it would be heavy. It would have exactly the same shape for the rudder blade except for a handle cut on top, same pintles and gudgeons, same rudder head but extended aft. I have not figured out how to keep it down, maybe a Schaffer spring on one of the pintles.
I almost lost a rudder during a transat and it was a bad situation. It happened because the pintle spring broke. You don't want the blade to swim away because of a dowel or spring breaking. In my case, the rudder blade stayed attached through the autopilot fletner.
I want to design some "fuse" in there, a part that breaks in case of collision. With the pivot, the blade will lift but not break. With a cassette, I can imagine a spare blade with a sacrificial dowel. I am still thinking but to find yourself without a rudder 1,000 NM offshore is a challenge. The existing pivoting rudder is well proven.
Thanks Jacques. That is exactly what I needed. Don't worry, I completely trust the design and your scantlings - part of the reason I chose the VG23 in the first place. I've been having fun reading Skene and also Larsson.

"I almost lost a rudder during a transat and it was a bad situation...." "...to find yourself without a rudder 1,000 NM offshore is a challenge". Yes...I imagine it would be... ... ...

I've ordered a 1/2 " solid stainless steel rod in 316L to use as the pivot - same as Justin used I think. I plan to weld my own gudgeon/pintles (then only me to blame if they fail!).

To keep the rudder down could you use internal lead same as C/B???

I've just removed the completed centreboard from under a lot of weight. I'm working on shaping that today, and also tape on the keel joints. Will post photos (and more questions no doubt) as I progress.

Cheers,

Mick
Completed: FB11 (Designer Evan Gatehouse)
Current Build: VG23 (Designer Jacques Mertens)

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