Hunter 170 Rudder Mount Solution

Sep 22, 2018
1,869
Hunter 216 Kingston
Yep, change of plans. Next will be FRP that extends to the corners, Ill build up the cloth until a huge sheet of G10 lies completly flat on the FRP. Then will clamp it down. The G10 will be same same shape as the luran panel, but big enough to overlap it and also big enough so that all rudder gudgeon holes are on the backer. This G10 will spread out the twisting forces and then counter the G10 on the inside.

The luran panel is just filler to bind the hump. The external G10 and FRP might be overkill, but i dont want to be stranded in Sarasota bay with my rudder floating away.

I think after this i need to rig my rudder to kick up so it doesnt damage the mount.
Just curious what your thinking was in changing the layup?
Also thought the 170’s rudder was designed to kick up, do you lock it down normally?
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
Maybe an oscillating multitool (commonly used to trim door moulding etc for flooring) or a bread knife, not sure how much room you have reaching into the hole.
I used a couple shims to replicate a backer and then used what can best be described as a miniature bread knife the fit it flat. Bread knive on foam is a good idea. Theres no room for power tools other than a shop vac hose.

The area is glassed up and curing.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
Just curious what your thinking was in changing the layup?
Also thought the 170’s rudder was designed to kick up, do you lock it down normally?
It was going to be difficult to place the G10 in the cutout. The larger G10 would need to be split up into 3 pieces to fit and the middle piece would not span the cutout as much as intended. In addition, the compression of the rudder gudgeon would work to push it away from the luran structure. If the foam compresses, the luran panel could give way, and there would be less resitance to a cave in scenerio (from possibly grounding of rudder).

Its just me sitting on a bean bag chair staring at the ruined rudder mount, playing engineering "Rock-Paper-Scissors". Hope I thought it out right.

There cant be any flex or tension with luran and adhesives. The foam in the ACP is the true superstar of the 170. Get the luran to be allied to it and protect it, and everyone wins. All the cracks and failures of the ACP start when there isnt a static relationship between every layer. ANY flex in ACP is a brutal warning.

By going gudgeon, seal, big G10, FRP, luran, foam, FRP, small G10 there is always compression on every layer and compression on the rudder mount in all directions of force. The big outer luran will never cave in through the luran cut out. Its actually the new foam on the inside that keeps the rudder from getting pulled off. The foam is nearly 3 inches thick near the top and forms an internal "arch" towards the gudegeon. The foam as one piece will never fit through the cutout luran since it filles tbe entire backside of it. The internal G10 will distribute the gudegeon forces evenly over an area also bigger than the luran cutout.

Rudder is not kickup, infact, I usually torque the pivot handle nuts as soon as the rudder is pinned to the gudgeon to keep the play down. Centerboard is usually a good warning when it starts bouncing around since that is kickup.

There needs to be an inexpensive fail point.
 
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Sep 22, 2018
1,869
Hunter 216 Kingston
SBO store solution to kick up rudder
https://shop.hunterowners.com/cu/detail-rudders-kick.php
I’ve only seen photos of 170’s but I thought they pivoted at that black butterfly knob point?

I get why you adjusted your layup as this version would appear to be stronger and perhaps easier to accomplish. I absolutely agree the strength of any ‘sandwich” is the integrity of the layers sticking together.

My bean bag chair thinking sometimes gets me into analysis paralysis!:beer:

I watched this video recently and wondered what the black stuff was in the repair job?? Carbon?
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
Rudder is pretty much ready for assembly and field testing.
20190618_202821.jpg

Two backer boards were prepared and one will go in the hull, another will be against the outer shell to absorb any twisting.
20190614_202131.jpg


You may have noticed the access port. I cant decide if the bolts should go out with nuts on the gudegeon or if the bolts should go in from the gudgen with nuts in the hull. I'd like to place the nuts in the hull for looks, but then all i think about is not being able to tighten them, but you cant tighten bolts with unsecured nuts.

I'll sail with duct tape over the access port until field tests come back, but im thinking of just using some 4200 sealant on a 4" sewer cleanout cap. Ill want to get in there as needed for a while.

After the cut out luran panel was glued on with PL3X a bead of plastic bond was applied to bind it back to the luran. A couple layers of cloth where placed over the entire back of the rudder mount, extending about an inch around the two side corners.

Epoxy used was totalboat 5:1. The holes for the gudgeon were drilled at this point to test the entire assembly since i could still see the original holes locations under the cloth.. Straight and true, 1/4in bit.

Epoxy was mixed with west 407 low-density and the mount was fared no problem.

The sealing layer of neat epoxy was applied and finished sanded. I cleaned with everything i had. soapy water..twice, mineral spirit, acetone(dont do that), and also 70% alcohol.

The rudder was spray painted with rustoleum universal all surface white gloss. perfect finish without any artifacts from the paint.

The neat epoxy seal fish-eyed in places on me, even over the faring, so that kinda sucked. i think i got plastic dust contamination in the mix. Next time i'd spray an automotive "adhesion promoter" over the finished faring work.

Ill report back after field testing and how the acces port gets plugged.
 

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Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
...You may have noticed the access port. I cant decide if the bolts should go out with nuts on the gudegeon or if the bolts should go in from the gudgen with nuts in the hull. I'd like to place the nuts in the hull for looks, but then all i think about is not being able to tighten them, but you cant tighten bolts with unsecured nuts.....
The T-nuts from post #28 in the following thread would seem like a natural solution - https://forums.sailboatowners.com/i...y-findings-to-date.194959/page-2#post-1541452
Alternately, you could drill & tap the G10 for machine screws or glass in nuts on the back side, or drill & tap aluminum flat bar to go behind the G10. If it were me, I would probably drill & tap an aluminum plate to go behind the G10, but then, I have access to a machine shop, which makes it easy to line up all the holes. I would permanently mount the plate to the back of the G10 using 3m VHB double sided tape. That stuff is incredibly strong & has held up in excess of 15 tears in the field when I have used it in the past.

When I did my gudgeon post repairs, I installed deep glass where the screws went in. With enough engagement depth, the standard screws work well. I probably ended up with more than 6 diameters of engagement, which is overkill.
 
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Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
...
Ill report back after field testing and how the acces port gets plugged.
If it were me, I would see if I could get a little pie hatch to fit that access hole. That way, if you want access again in the future, it will be as easy as opening a jar.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
The T-nuts from post #28 in the following thread would seem like a natural solution - https://forums.sailboatowners.com/i...y-findings-to-date.194959/page-2#post-1541452
Alternately, you could drill & tap the G10 for machine screws or glass in nuts on the back side, or drill & tap aluminum flat bar to go behind the G10. If it were me, I would probably drill & tap an aluminum plate to go behind the G10, but then, I have access to a machine shop, which makes it easy to line up all the holes. I would permanently mount the plate to the back of the G10 using 3m VHB double sided tape. That stuff is incredibly strong & has held up in excess of 15 tears in the field when I have used it in the past.

When I did my gudgeon post repairs, I installed deep glass where the screws went in. With enough engagement depth, the standard screws work well. I probably ended up with more than 6 diameters of engagement, which is overkill.
Having just some basic machine shop access would be fantastic. Even redrilling the backer plate was a crap shoot since i had no way to know if i was drilling perpendicular to the rudder face in all dirctions. I was prepared to drill 6 holes on the backer whereever it made contact, but I got lucky.

G10 will hold machine threads but i didnt really find out if there is some bolt diameter to thread depth rule that would make sense.

Just reusing the screws with a couple more layers of FRP and a backer or embedding the backer in the foam (as wood replacement) like the motor mount solution probably is a good solution for most rudder repairs.

The mainsheet lower swival is actually attached with a exposed threaded aluminum backer. It can be seen when the centerboard is removed. If i had better resources i would have emulated that and followed your suggestion as mentioned above.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
If it were me, I would see if I could get a little pie hatch to fit that access hole. That way, if you want access again in the future, it will be as easy as opening a jar.
Google search failed on that one. Can you detail what a "pie hatch" is. I just assume you are telling me to shut my pie hole.. :)
 
Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
Having just some basic machine shop access would be fantastic. Even redrilling the backer plate was a crap shoot since i had no way to know if i was drilling perpendicular to the rudder face in all dirctions. I was prepared to drill 6 holes on the backer whereever it made contact, but I got lucky.

G10 will hold machine threads but i didnt really find out if there is some bolt diameter to thread depth rule that would make sense.
...
A drill press is great for getting holes square to the work. Many cordless drills these days will have a level built in to help get holes straight into a vertical piece of work. You can fool around with a pair of squares if you need to. Another option is to have someone, with a drill press, drill a hole in a piece of scrap material, even a wooden 2 x 4 is good enough. You can then hold that against your work piece & put your drill bit through the hole in the 2 x 4 to get your bit straight into the work.

Generally speaking, I like to have 1.25-1.5 diameters in steel, and 2-2.5 diameters in aluminum. I don't have a real number for G10, but I would think that 3-5 diameters might be a good target to start with and see what happens. If you go too deep & you don't tap first, then you will break the screw off. Greasing a self tapping screw will sometimes let you get it in a little further than it would go dry.

If you want to calculate the minimum engagement depth, start by figuring the cross sectional area of the minor diameter of the screw, then multiply that times the ksi figure for the screw material. You then basically do the same thing in reverse for the work material & add in a safety margin, like 1.2-1.5 or something like that. If I had specification values for G10, I could run some numbers for you. 304ss (aka 18-8) is usually around 60-70ksi. If you want to twist your head up with information about fasteners, you might start here - https://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf If you want to get into it really deep, you can pick up a copy of the machinery's handbook.I think that the 30th edition is out now. My copies are much older than that.

If you need a drill guide block made out of something better than a 2 x 4, I can make one & mail it to you.
 
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Apr 16, 2017
841
Federation NCC-1701 Riverside
Ahhhh, Yeah, i really hoped i could use one of those, but the the unusual pointy shape on top of the rudder mount doesnt give any room for the flange and threads. I still have the luran top and can spray some foam in there to back it up. It would be easy to cut back out in a few years.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
A drill press is great for getting holes square to the work. Many cordless drills these days will have a level built in to help get holes straight into a vertical piece of work. You can fool around with a pair of squares if you need to. Another option is to have someone, with a drill press, drill a hole in a piece of scrap material, even a wooden 2 x 4 is good enough. You can then hold that against your work piece & put your drill bit through the hole in the 2 x 4 to get your bit straight into the work.

Generally speaking, I like to have 1.25-1.5 diameters in steel, and 2-2.5 diameters in aluminum. I don't have a real number for G10, but I would think that 3-5 diameters might be a good target to start with and see what happens. If you go too deep & you don't tap first, then you will break the screw off. Greasing a self tapping screw will sometimes let you get it in a little further than it would go dry.

If you want to calculate the minimum engagement depth, start by figuring the cross sectional area of the minor diameter of the screw, then multiply that times the ksi figure for the screw material. You then basically do the same thing in reverse for the work material & add in a safety margin, like 1.2-1.5 or something like that. If I had specification values for G10, I could run some numbers for you. 304ss (aka 18-8) is usually around 60-70ksi. If you want to twist your head up with information about fasteners, you might start here - https://www.fastenal.com/content/documents/FastenalTechnicalReferenceGuide.pdf If you want to get into it really deep, you can pick up a copy of the machinery's handbook.I think that the 30th edition is out now. My copies are much older than that.

If you need a drill guide block made out of something better than a 2 x 4, I can make one & mail it to you.
That is some great info! The G10 is only 0.25 inches so it doesnt quite meet the steel requirement guide. Bolt is about .25 and the G10 is .25 so, with 4 screws might just meet basic standards.

A drill press would be a great investment. I like that block idea.

I wish i could offer everyone cool DIY info like that, all I got is database design and information modeling. Let me know if you need any of that!
 
Aug 22, 2017
1,608
Hunter 26.5 West Palm Beach
That is some great info! The G10 is only 0.25 inches so it doesnt quite meet the steel requirement guide. Bolt is about .25 and the G10 is .25...
This brings me back to liking the idea of either the T-nuts or a threaded backing plate, or glassed-in nuts, in that order.

I wish i could offer everyone cool DIY info like that, all I got is database design and information modeling. Let me know if you need any of that!
Your posts have been wonderfully informative for me. Thank you for your contributions.
 
Apr 16, 2017
841
Federation NCC-1701 Riverside
The Rudder is assembled. Pretty sure i can just add some foam, and glue the cap back on without field testing.

The 18 holes made were not as alligned as i thought and it was a bear trying to get it alL together. Ended up going one size up on thr drill bit from 1/4, which is the size of the bolts, to 5/16. Much easier. After a good dry fit i mixed up some epoxy and made the "peanut butter" mix with west high-density
and buttered up the inside G10 backer, then reassembled. The filler oozed out. I tried to spread the extra around the nuts but dont think i did that right, and ended up wiping all the excess off.

Its very solid. The weakest part is the gudgeon. I hung the rudder and there is no movement at all. I cant imagine this system loosening up with the backing plate bedded in the high density epoxy and some epoxy on the threads and bolts and nuts.
 

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Apr 16, 2017
841
Federation NCC-1701 Riverside
While picking up some Loctite marine sealer for the motor mount i found a 4" knock out plug. It was only $0.48, so i brought it home to see if it would work. I would be good for a temp solution, but it would collect water. By just removing a little bit of foam at the top of tbe mount it would fit well, especially with a light application of sealer under the lip.

I still have the original so will just use that.
 

Attachments

Sep 22, 2018
1,869
Hunter 216 Kingston
The Rudder is assembled. Pretty sure i can just add some foam, and glue the cap back on without field testing.

The 18 holes made were not as alligned as i thought and it was a bear trying to get it alL together. Ended up going one size up on thr drill bit from 1/4, which is the size of the bolts, to 5/16. Much easier. After a good dry fit i mixed up some epoxy and made the "peanut butter" mix with west high-density
and buttered up the inside G10 backer, then reassembled. The filler oozed out. I tried to spread the extra around the nuts but dont think i did that right, and ended up wiping all the excess off.

Its very solid. The weakest part is the gudgeon. I hung the rudder and there is no movement at all. I cant imagine this system loosening up with the backing plate bedded in the high density epoxy and some epoxy on the threads and bolts and nuts.
That is massively stronger than what you had a little while ago. I can imagine there might have been a little cussing going on trying to get all that lined up but doubt you’ll ever have to take it apart again :beer:

I want to thank you again along with @JimInPB and others for sharing their experience of repairing their boats. I believe it will help others out down the line to have a safer boating experience!:clap::dancing::worship:
 

mark2

.
Dec 10, 2012
52
Hunter 18 Raleigh
Do you know of a professional who can do this project (rudder bracket and repair from inside rudder housing via a 3” inspection port? (Southeast US)?
I rather doubt there is any "professional" in repair of this type of boat... but I think anyone with patience and good mechanical/boat skills could do it.
 
Aug 9, 2020
7
Hunter 170 Burlington, VT
A HUGE shout-out to ShoreFun, BobbyFunn, Crazy Dave, JimInPB, Mark2 and others for your very informative posts. I knew I had a gudgeon screw that kept coming loose but it wasn't until the stem head loosened up (fortunately not catastrophically although the potential is there) that I began to dig into the cause.

Here's the question: I am hoping that I am catching this before the extreme deterioration BobbyFunn found and am teetering between the drill-fill-rescrew process described here and sawing into the hull to install backplates. For the stem head in particular it feels like the stress on the screws would be slightly to stern vs. straight up, and that the plate itself would help keep the epoxy cores from pulling out if they were properly adhered to the foam and (possibly) remaining wood... is that wishful thinking?