Do you have something to say about "Jinx" ? [Archive]

CenkA

11-14-2009, 04:40 PM

gonzo

11-14-2009, 07:27 PM

Plywood frames are weak for their weight. Half the fibers are in the wrong direction.

boat fan

11-14-2009, 09:53 PM

I asked general information about "Jinx building".
If anyone had build Jinx before,maybe he/she could give me suggestion about building steps !

Specially i can say;

Is it possible to make each frame only one-piece from 12mm plywood ? i don't want to make old-style frame.

Not sure that there are any benefits to building plywood frames .

This link may help , it`s not a jinx , but the build is very similar process.

http://www.glen-l.com/methods/plywood/mthdpw01.html

Hope it`s of help.

Submarine Tom

11-15-2009, 01:05 AM

Sure, use well mixed epoxy and lots of stainless steel screws.

CenkA

11-15-2009, 07:30 AM

Jeff, i am sorry;yes plans are from svensons.com.

If Plywood frames are weak ,Maybe i can use foam sandwich method.
8mm DIAB foam +biaxial fibers+epoxy resin.Sandwich method building ,is good enough for the frames ?

boat fan thanks for the link.It is similiar with Jinx...

apex1

11-15-2009, 08:56 AM

If Plywood frames are weak ,Maybe i can use foam sandwich method.
8mm DIAB foam +biaxial fibers+epoxy resin.Sandwich method building ,is good enough for the frames ?
.

No,
the foam is even weaker than ply, much weaker! Though it has its benefits and for panels it may be good, but not for frames.
Stay with the original ply frames, if they are specified, there´s nothing wrong with them.

Regards
Richard

CenkA

11-15-2009, 10:15 AM

Whatabout vacuum infusion process !.
If i manufacture frames with vacuum infusion method .Is it again weaker than ply ?

BertKu

11-15-2009, 10:24 AM

http://www.woodworkersworkshop.com/graphics20/svensons-jinx.jpg

I want to build Jinx. What do you suggest me about building steps ?

Yes, I would make it electric if I were you.

CenkA

11-15-2009, 10:42 AM

Electric for this little boat ! i think it is too smal for electric boat...

Submarine Tom

11-15-2009, 12:01 PM

Definitely electric, with a flex drive, a big prop and lots of expensive

batteries (LiPo). Don't forget to plug it in when you get home!

-Tom

BertKu

11-15-2009, 12:22 PM

Electric for this little boat ! i think it is too smal for electric boat...

Just borrow a torqeedo motor with Lithium batteries for a demo.
refer: http://www.torqeedo.com/us/hn/products/produktuebersicht.html
Bear in mind an electric motor is much more efficient. A Torqeedo 1Kw motor is approx equivalent to a 4 Hp outboard. Your boat will be ligther also.

apex1

11-15-2009, 01:17 PM

Bert
borrow in Turkey??? Stealing is simpler!

What do you think is vacuum infusion Cenk? Does it infuse strength into a weak material? Or maybe just resin?

CenkA

11-15-2009, 01:31 PM

I agree with apex ! Torqeedo in Turkey is also too much money ...

It is the one way of Composites manufacturing,

result of vacuum infusion process is better than hand lay-up process.

My english is not good enough,sorry.I didn't understand what you mean ?
"What do you think is vacuum infusion Cenk? Does it infuse strength into a weak material? Or maybe just resin?"

apex1

11-15-2009, 01:41 PM

Genc

I know what vac. infusion is, I build yachts. But you can NOT use a foam core panel as a frame! No matter how you put the glassfiber on it!

Richard

messabout

11-15-2009, 01:55 PM

The subject boat is a very dated design. It was a good one in its' day but it is heavy by modern standards. The design is as good as you need but the construction details are a bit much. Keep in mind that there was no epoxy in those days. I would urge you to adapt modern techniques to this design if you build it. Use thicker skin and fewer longitudinal members. Get the Glen-L book about ply construction, stitch and glue methods, etc. Save a lot of time and build a lighter, cleaner, boat. Any modern outboard of 300ccs or so will make it a real fun toy.

The 20 cubic inch engine on the plans was a fore runner of modern engine design. The text shows the engine with a Quicksilver lower unit which was a race engine optional (extra cost) item. The performance claims in the text of the article are a little optimistic. Boats and motors of that vintage were hard pressed to ever see 40MPH except in the hydro classes. Nonetheless the boat will go plenty fast and may exceed 40 with a modern engine and appropriate prop. At speed this boat will beat you up pretty badly, even in a very small chop of water. Don't let that stop you from all the fun. Your bruises will heal in a few days.

messabout

11-15-2009, 02:12 PM

SamSam

11-15-2009, 02:53 PM

If you build it with the old style frames, you will have good, solid cross grain wood to screw the stringers and battens to. If you use plywood you will have plywood edges to screw into, which are weak. If you use fiberglass of some kind, you will have to figure out how to attach the stringers to the frames.

apex1

11-15-2009, 02:56 PM

SamSam

11-15-2009, 03:08 PM

It is the one way of Composites manufacturing,

result of vacuum infusion process is better than hand lay-up process.

My english is not good enough,sorry.I didn't understand what you mean ?
"What do you think is vacuum infusion Cenk? Does it infuse strength into a weak material? Or maybe just resin?"
He's trying to tell you that vacuum infusion doesn't make things stronger, it is just a different way of getting resin into a laminate.

Joakim

11-15-2009, 03:12 PM

Bear in mind an electric motor is much more efficient. A Torqeedo 1Kw motor is approx equivalent to a 4 Hp outboard. Your boat will be ligther also.

Certainly not true! The propeller doesn't care how the power to rotate it is made. 1 kW = 1.4 HP, that is about 1/3 of 4 HP and a typical new 4 HP outboard will produce close to 5 HP in reality (measured from propeller shaft).

There are also some test results, that show a 2.5 HP Mercury is slightly faster (5.5 kn vs. 5.3 kn) than a 2 kW Torqeedo although they have about the same power. Unfortunately this is in swedish, but you can read the numbers: http://www.torqeedo.fi/testit/to_vi_bataegare_1208_svenska_se_.pdf

I have owned a Jinx and it reached 15 kn with 4.5 hp Mercury (from 70's, actually only 3,5 HP) with the standard propeller. Certainly you can not do that with 1 kW electric motor.

frank smith

11-15-2009, 03:17 PM

check this site out , it might be of some help.
http://www.boatracingr11.com/Sorensen_boats/sorensen_Restorations.htm

The Desivla hull was state of the art at one time .
I have seen on at close to 90 HPH . 50 is no problem , please to have flat water .

frank smith

11-15-2009, 03:23 PM

http://aeroliner-boats.com/resources/_wsb_623x391_CD+Framed+Oct+7.JPG
A typical build

CenkA

11-15-2009, 04:25 PM

He's trying to tell you that vacuum infusion doesn't make things stronger, it is just a different way of getting resin into a laminate.

What about weight decrease!
Vacuum infusion makes more lighter than hand lay up. Also more powerful than hand lay-up.

Mechanical properties depends on Manufacturing method I think,
for example,
prepreg composite manufacturing is the one way of composite manufacturing but aero-factorys make incredible tough materials.

CenkA

11-15-2009, 04:27 PM

Genc

I know what vac. infusion is, I build yachts. But you can NOT use a foam core panel as a frame! No matter how you put the glassfiber on it!

Richard

I see what you mean.You are more experienced than me I think.Which method do you suggest me to manufacture frames ?.I want to light,strong frames also i don't want to use old methods frame manufacturing.

Submarine Tom

11-15-2009, 04:54 PM

Certainly not true! The propeller doesn't care how the power to rotate it is made. 1 kW = 1.4 HP, that is about 1/3 of 4 HP and a typical new 4 HP outboard will produce close to 5 HP in reality (measured from propeller shaft).

There are also some test results, that show a 2.5 HP Mercury is slightly faster (5.5 kn vs. 5.3 kn) than a 2 kW Torqeedo although they have about the same power. Unfortunately this is in swedish, but you can read the numbers: http://www.torqeedo.fi/testit/to_vi_bataegare_1208_svenska_se_.pdf

I have owned a Jinx and it reached 15 kn with 4.5 hp Mercury (from 70's, actually only 3,5 HP) with the standard propeller. Certainly you can not do that with 1 kW electric motor.

Hp and torque are measured independant of one another. Electric motors

have a great deal of torque compared to gas outboards. So, although the

numbers don't add up, a little electric motor really can deliver much more

power than it's kw rating lets on.

Tom

Yellowjacket

11-15-2009, 05:03 PM

Most of these older runabouts are actually pretty efficient hulls, although rough riding, they milk a lot of speed out of a small outboard. For running around on an inland lake that isn't very rough, they are a lot of fun for the buck. If you want a classic kind of boat the Jinx isn't bad at all.

The old methods of making the frames and building the boat are probably a bit of overkill if you use epoxy too, but since these are pretty rough riding boats they tend to take a bit of a beating. In time, if they aren't built pretty stout, they get flexible and after a while start to come apart. Build it by the plans and you will be fine for a long time. I'd add a layer of 4 oz fiberglass to the outside to seal it better and enjoy.

Properly built, these kind of boats don't weigh much more than 120 to 130 pounds, the bottoms are 1/4 inch plywood and therefore pretty light. Thickening the bottom will allow less framing, but the plywood will be harder to bend and a lot of folks think that they'd rather do more framing and have the skin thinner and easier to bend.

If you look at the Glenn-L site they have a lot of customer photos showing boats in progress. Between the photos and the plans I'm sure you can do figure out how to put it together. Also look on Stevenson's site and download a couple of other plans and you will get the general idea as to what to do when.

Joakim

11-15-2009, 05:39 PM

So, although the numbers don't add up, a little electric motor really can deliver much more power than it's kw rating lets on.

No it can't, unless you are overloading it. Power is power and it is measured in kW or HP for both. At lower rpm an electric motor may output much more power than a gas one, but that is pretty much useless for a propeller driven vessel, especially this light and fast, since at low rpm the power needed at propeller shaft is not much.

apex1

11-15-2009, 06:01 PM

I see what you mean.You are more experienced than me I think.Which method do you suggest me to manufacture frames ?.I want to light,strong frames also i don't want to use old methods frame manufacturing.

Yellow said it already, you would do best sticking to the plans.
Any modification can make the whole structure weaker instead of stronger.
And when you, for example would build laminated frames instead of the classic method, what would you win?

You are obviously not able to redesign such a boat, so leave it as it is! There is nothing wrong with these old racers.
Modifications usually go in the wrong way, they cause problems instead of improving anything.
And I would not glass it. Cover the outside in Epoxy to avoid water ingress, yes maybe. But this boat will not sit at anchor. When you have had your two hours fun, you will bring it home again. So you do´nt need to "overbuild" it.

Just out of curiosity: where are you going to operate the boat??? Do not think about a ride on the Bosphorus! Or at least not if you love to keep your kidneys working.

Regards
Richard

SamSam

11-15-2009, 07:45 PM

What about weight decrease!
Vacuum infusion makes more lighter than hand lay up. Also more powerful than hand lay-up.

Mechanical properties depends on Manufacturing method I think,
for example,
prepreg composite manufacturing is the one way of composite manufacturing but aero-factorys make incredible tough materials.OK, you're right. I just thought you were a complete rube and I didn't think you needed to get so technical to build to a set of 55 year old plans. Yes, foam frames can be made to work. Good luck.

BertKu

11-16-2009, 01:07 AM

Someone please explain how the Torqueedo can defy the laws of physics. How can 1Kw exceed 2900 watts? I reckon that is some kind of hogwash that was dreamed up by a sneaky marketing department that had no interest in truth or reality. A single kilowatt is a single kilowatt and it can not be 2.9 Kw.

FWIW, I like the delightfully quiet and smooth electric propulsion on my little dinghy. I do not expect high performance from it. It is capable of about four tenths of one HP. My voltmeter and ampmeter does not lie. Not a Torqueedo, it is only a modest Minkota.

My apology,
An electric motor is 90% efficient in converting energy into propshaft energy, while a fuel (gasoline or whatever) converts so much into heat and friction , that what is left over at the propshaft is not what you put into the engine. I have comparable information on a 6Kw electric motor which gave the same performance as a 28 Hp petrol (gasoline) engine.

Yes, you are right.

However, I love to get 4 Kw out of a 1 Kw motor. If it was possible I would be multi millionair.

Bert

Joakim

11-16-2009, 01:34 AM

My apology,
An electric motor is 90% efficient in converting energy into propshaft energy, while a fuel (gasoline or whatever) converts so much into heat and friction , that what is left over at the propshaft is not what you put into the engine. I have comparable information on a 6Kw electric motor which gave the same performance as a 28 Hp petrol (gasoline) engine.

This is totally irrelevant for the output performance of a gas engine. The rated power is measured from propeller shaft (or crank shaft). It has nothing to do with the poor efficiency, which is already accounted for.

Please show us the example of same performance with 28 HP and 6 kW. You would be a multi millionair, if you could make that as well.

BertKu

11-16-2009, 01:45 AM

This is totally irrelevant for the output performance of a gas engine. The rated power is measured from propeller shaft (or crank shaft). It has nothing to do with the poor efficiency, which is already accounted for.

Please show us the example of same performance with 28 HP and 6 kW. You would be a multi millionair, if you could make that as well.

My apology, it was slightly lower HP. It was posted as follow

http://www.boatdesign.net/forums/boat-design/batteries-new-battery-technologies-21869-11.html

No 157 dated 9th of June 2009

Trust that it helps
Bert

Joakim

11-16-2009, 03:22 AM

My apology, it was slightly lower HP. It was posted as follow

You must be referring to this: http://www.wassersport.nl/PDF/WIN2009_01.pdf (page 20)

So they are comparing a 27' motor boat with a 7.5 kW electric (actually hybrid) installation to 24 kW diesel. And found out that they get 9 km/h at 7.5 kW and about the same at 80% load of the diesel.

9 km/h is only 4.9 kn. For a 27' displacement motor boat (LOA 8.1 m, LWL~7.5 m, 3500 kg) the "hull speed" is 6.6 kn. Certainly this kind of a boat can reach it's hull speed with much less than 24 kW. I have a sailing boat very close to this size (8.2 m, LWL 7.5, 2900 kg) and it reaches 6.4 kn with 6.6 kW diesel and at 4.9 kn I need much less than half of the full power. Already at 5.7 kn the fuel consumption drops from 2.2 to 1 l/h, which means the power required is more than halved.

Thus I don't believe what they are claiming. Even if it was true, 80% load would most likely mean 80% of the full rpm, which means that the power output of the diesel is only about 50% of the maximum, since a rough estimate is power ~ rpm^3 for displacement boats. The rest of the difference (12 kW vs. 7.5 kW) could easily be explained by a different propeller.

It is true, that an electric motor can reach high pollard pull ("zugkraft") values and that is why they are very often using that as comparison. People are fooled to think that the pollard pull values would be relevant also while at cruising or even at top speed.

boat fan

11-16-2009, 04:20 AM

All this is becoming sillier by the minute.

This is an old mini racer designed for a small outboard motor.

Built as per plans , its a lot of " bank for your buck ".

The frames appear to be over built , but in reality they are designed that way to take the pounding this little boat will experience at the high speeds that it is capable of.There is nothing to be gained by trying to shave and trim a some insignificant amount of weight on frames.Just build the thing as designed and fit a nice motor.....good grief what`s the issue here ?

Your`e not going for a world speed record here ( I hope ).......:rolleyes:

BTW....
Nobody in their right mind would attempt to fit an electric motor to this
particular design.It defeats the whole purpose of choosing to build this boat in the first place.

If you want something small , fast and classy ......build this , and pack a picnic basket , call your favorite girl , and have a great day :

Rascal = 1989 design by Ken Bassett
Length (overall): 14' 10"
Beam: 5' 4"
Draft: 6"
Weight (equipped): about 790 lbs.
Construction: Plywood and Mahogany ("cold molded") over sawn frames Power: Mercury 60hp 2-stroke Outboard Top Speed (design): 52 mph at 5800rpm Top Speed (actual, to date): 44 mph at 5500rpm

Joakim

11-16-2009, 05:13 AM

All this is becoming sillier by the minute.

I'm sorry about that...

Yes Jinx is a nice boat. My father bought one as a one year wedding anniversary gift to my mother in the mid 50's. I used it when I was from 7 to 12 years old. I first had a 4.5 HP mercury and later a 9.8 HP Mercury, which reached a top speed of 24 kn (with standard propeller) and we even used this setup for water-skiing (also with one ski). We also tried an old Volvo Penta 12 HP and a Mercury 20 HP, which reached a top speed well over 30 kn (again with the standard propeller). I didn't know anything about propellers then and thus the top speeds were far from optimized.

Jinx served our family well for about 25 years. Then it started to leak and also the plywood on the side deck tore at the connection to the back board. I sold the boat to a friend of mine who used it with an old 18 HP Evinrude for a year (without repairing anything) and then he sold it to another friend of mine, who started the reparation, but sadly the boat vanished from his shore.

I have no idea how this Jinx came to Finland. I have never seen another Jinx here. I'll ask my father.

CenkA

11-16-2009, 05:21 AM

Yellow said it already, you would do best sticking to the plans.
Any modification can make the whole structure weaker instead of stronger.
And when you, for example would build laminated frames instead of the classic method, what would you win?

You are obviously not able to redesign such a boat, so leave it as it is! There is nothing wrong with these old racers.
Modifications usually go in the wrong way, they cause problems instead of improving anything.
And I would not glass it. Cover the outside in Epoxy to avoid water ingress, yes maybe. But this boat will not sit at anchor. When you have had your two hours fun, you will bring it home again. So you do´nt need to "overbuild" it.

Just out of curiosity: where are you going to operate the boat??? Do not think about a ride on the Bosphorus! Or at least not if you love to keep your kidneys working.

Regards
Richard

I want to make it more lighter and powerful.I study four year mechanical engineering in Izmir and i want to make composite boat building and i choose Jinx design.I will use it in Cesme/Alacati just for fun.

apex1

11-16-2009, 05:48 AM

I want to make it more lighter and powerful.I study four year mechanical engineering in Izmir and i want to make composite boat building and i choose Jinx design.I will use it in Cesme/Alacati just for fun.

Hi mate,

you have choosen the wrong design! It is neither a good design for cored structures, nor for the Mediterannian sea. (or any open water)

It is what it is, a very small, very fast toy, with a relative low power demand. And designed for lakes and flat water.

If you were a student of Naval Architecture, I would say you could possibly "redesign" it to cored panels. But frames in cored composite are a mad idea!
You would have a frame oriented to his weakest direction. It would immediately break under shear loads. Foam is a weak stuff, no matter which one. For the panels one could try foam between ply. And of course the frames can be laminated.
That all would make a light boat even lighter, but where would be the reason?
In its original form the boat is already tricky to handle, it would be a goat when lighter.
And forget about the idiotic comments of Bertku, he is drugged by a electric
possession.

Regards
Richard

BertKu

11-16-2009, 06:36 AM

Messy,
Bertku has his own physics, do´nt bother. And the advice for El. power for such boat shows real professionalism, does´nt it?:D

Apex1,
Hai, that is cute. I did not know that I have qualities which are noted by experienced people like you. Can I buy you a beer ?
Bert

Submarine Tom

11-18-2009, 01:14 AM

Joakim,

You are obviously the authority knowing everything and having all the right

answers. I'm not sure the rest of us are really needed here.

Please, continue.

Joakim

11-25-2009, 02:57 PM

I have no idea how this Jinx came to Finland. I have never seen another Jinx here. I'll ask my father.

My father said that several of them (even tens) were build by "Salmisaaren Veneveistämö" in Helsinki around 1959-1960. Soon after that "Salmisaaren Veneveistämö" went out of business. During 60's my father loaned a 20 hp Mercury from his other boat to Jinx.

It would be interesting to know what happened to other Jinx's in Finland.