Hunter 170...Anything to beware of?

[BobbyFunn]

Did you account for changes in buoyancy as the ‘hull’ heeled???

Bouyancy should stay the same in any orientation. The boat's mass is the same. Thats gotta be the no free lunch part otherwise we would see tanker ships heeled to reduce wetted surface.

Get planing and its a new conversation.

One other item, and this was brought up in a patent for heeled hulls is asymetrical shapes. The flow on one side of heeled hull might be different than another, this causes anomolies with control.

 

[Jackdaw]

Bouyancy should stay the same in any orientation. The boat's mass is the same. Thats gotta be the no free lunch part otherwise we would see tanker ships heeled to reduce wetted surface.

Get planing and its a new conversation.

One other item, and this was brought up in a patent for heeled hulls is asymetrical shapes. The flow on one side of heeled hull might be different than another, this causes anomolies with control.

All boats are designed with reserve buoyancy in the bilges, which provide stability as the boats heel. They submerge more volume with less surface area. Otherwise they would just roll, like your 2x4 will.

 

[BobbyFunn]

Roll it did. I had to hold the 2x4 lightly to keep it from flipping back to the stable position. You know its late in the off season when your floating 2x4's in a sink. The center of gravity was probably just a tad above the center of boyancy, and there wasnt much beam to keep itfrom rolling.

I was going for surface area measurments, even if the heeled orientation was unstable and bs for sailing.

I had to see for myself.

 

[Crazy Dave Condon]

2 X 4 hard chime

 

[JimInPB]

In the case of the sailboat....
In a steep heal, you also have a lot less forward thrust getting generated by the sail.

 

[Crazy Dave Condon]

That 2 X 4 piece of wood is not a good example to use as it is a right angle or 90% angle while the hull of the 170 is rounded. Jackdaw, your thoughts here on a hard chime when trying to use a 2 X 4 as an example.

 

[BobbyFunn]

Dont confuse bouyancy with stability.

A boat has chine because the builder doesnt know how to create a curved surface OR the designer is trying to create a custom stability for a application OR the marketing departmet found that consumers like the straight line going down the length of the hull. Hard chine on non planing surface is a gimmick. Best use of chine is a powerboat v-hull. Its stepped for various speeds to stabalize the hull and provide a cutting edge for turning.

The 2x4 was a great test of bouyancy versus wetted surface. The 170 is almost a flat bottom boat. When it heels it displaces the same amount of water as when it is flat. It is less stable when heeled, at 80-90 degrees it is most unstable, then when turtled, most stable. At all times it displaces the same volume of water. The rigging is wetted surface obviously and mucks up the bouyancy since it filles with water.

Hard chine wont affect wetted surface. Hard chine should be there to vector water or to extend a flat surface. I go back to tanker ships. Google "Hoegh Osaka Solent". Ask yourself why tankers dont always operate this way. Its becauce heeling is bad, heeling drives the flat bottom hull deeper, heeling results in suboptimal performance of appendages, it doesnt reduce displaced water and doesnt decrease wetted surface. If it did any of those things better heeled, it would be implemented tomorrow.

Sailors seem to be horrible at fliud dynamics even on a laymen level. Most probably still think sails work due to bernullies principal. They arent used to fluid moving at high speeds and reley on word of mouth and racing tips and tradition versus studying real world examples. About the best they can come up with is pull rope a to tape mark x. Look at speed indicater, repeat with different tape markers until the absolute value of the difference between max speed obtained and current speed is within an acceptable amount.

Want to be better at sailing, study things that move fast like airplanes, hang gliders, Sail planes, F-14's. Things that make a profit, tanker ships, things that defend nations such as military hardware. That technology immediatly crosses over to sailing, but most sailers are about 70 years behind. They are hung up on "one designs" built 60 years ago and make purcase decision based on words like "shippy", "graceful lines", "traditional".

 

[Crazy Dave Condon]

Bobbyfun;
I hate to say but I was very much involved with the 170 from inception. I speak from experience. As for helicopters, my dad use to be the test pi lot for the new ones for both the Army and Navy which as a kid use to ride with him and he was credited for introducing helicopters to the Army. I flew in one of the first two F 14's when delivered to the Navy and use to be a Navy pilot. Grew up around the original Mercury 7 astronauts and when dad was killed in a helicopter, Gus Grissom took me under his wing and Braun use to call me Little Dave and was glad to hear about Armstrong's first moon step privately with him. As for profit, I was one of the most successful sailboat dealerships. I know many and have experienced much more but grow weary of typing.

Go ahead and chime in anytime but the 170 was a new boat with some new features. Of course there were issues as I was not a fan of ACP but preferred Fiberglass.

 

[BobbyFunn]

Thats an amazing history Dave.

I am happy with the 170. There are improvements that could have easily been deployed. If the 170 had a heavier centerboard this boat would have been the standard for family daysailers. Now seascape, rs, and melges are the future.

 

[BobbyFunn]

If you thought the 2x4 experiment was amazing i have an update.

I performed the same experiment with a Crystal Light container. The crystal Light containr looks like an oil tank. It also more closely mimics a sailboat hull more so than a 2x4.

For this test i placed a weight inside to replicate ballast. It was clearly more stable in the flat position.

I marked the waterline, then rotated the container 90 degrees. It was very hard to stabalize, but was able to mark the waterline. The containers draft increased about twice as deep as flat.

I used a piece of paper to mark the distance from port to starboard waterlines.

Same distance.

 

[JimInPB]

Sailors seem to be horrible at fliud dynamics even on a laymen level. Most probably still think sails work due to bernullies principal.

Ya know...
Funny thing...
Bernullie's principle is supposed to describe how an airplane's wing works, but I have never seen it referenced in any book that I have read that was related to the subject of airfoil design. It also never made sense to me on an intuitive level, the way that Newtonian Mechanics always did. I sometimes wonder if Bernulli was just red herring that was thrown into the educational system as a tool to sort out the kids who could see though the smokescreen & not just drink the koolaid obediently.

 

[JimInPB]

my dad use to be the test pi lot ... ...as a kid use to ride with him ... ...I flew in one of the first two F 14's when delivered to the Navy and use to be a Navy pilot. ... ...Gus Grissom took me under his wing and ... hear about Armstrong's first moon step privately with him.

Geeze Dave...
Wow, just plain Wow.

 

[JimInPB]

Dave,
If you are still looking at this thread, I have a question that probably only you can answer.

I'm thinking of putting a couple of combination cup/rod holders in the aft portion of the seats in the 170. This would involve punching some holes in the top side of the bench seats with a hole saw. The problem is, I don't know what materials are in there nor how the structure is set up. I was able to install the same cup/rod holders successfully on my 212, but in that boat, I had access to the under side of the seats from inside the cabin, so I knew what I was cutting into & I knew where things were located. On the 170, I would be flying blind with the hole saw if I went at it today & that is not a situation that I want to be in. Any information that you can give me on how the 170 is put together, would be greatly appreciated.

Thanks,
Jim

 

[Crazy Dave Condon]

Same process as the 212. If using a hole saw only fine and I mean very fine blade at a slow and I mean slow speed to avoid cracking and overheating of material. Otherwise you could crack the material

 

[JimInPB]

It was just like you said Dave. The foam was about 1/4" thicker & the backing glass was slightly heavier compared to the 212, but other than that, the material & construction seemed to be exactly identical.

My installation was a success.

Thank you.

 

[JimInPB]

Anyone here get a 170 on plane? That is my new goal as the sailing season starts up.

I did it with a Sunfish when I was 12. There is a pretty good chance that I can make it happen with this little potato chip of a boat as well.

If we were a little closer I'd ask if you wanted to race sometime. It might be fun.

 

[Crazy Dave Condon]

can you post a photo sir. Glad you are done.

 

[JimInPB]

can you post a photo

Please let me know if you would like a different angle or other info.

Regards,
Jim

 

[Crazy Dave Condon]

good job sir

 

[BobbyFunn]

Coool AF.

That core belongs in a museum. If you still have it suggest a closeup be added to the hunter 170 download page or you add this project to the 170 customization page.

It would be nice to add duel water tight cabinets undet both seats by the centerboard, or one deep one on floor of cuddy. Preformed plastic just like cup holder.

Does cup holder drain to inside hull?