JAE TWIN PLANS !!!!!!!!!!!!!

[Ian Inverarity]

Rod,

I can certainly see why an upwardly curving tub at the rear of a boat would exhibit the suction you explain and shown in the video. But surely a curved surface in which all parts of the surface are at a positive angle of attack to the water flow would exhibit lift not suction? That is if the sponson riding surface is curved rather than made up of two stepped surfaces, all of the curved surface would be at positive angle of attack relative to the water flow.

 

[Tim Kish]

Interesting discusion.

I can only speak on what I have noticed in testing and racing with my JAE 21 over the past two seasons.

When I first started testing the boat there was no problem , only after the boat got up to racing speeds it started tripping in the turns and only in rough conditions.

I made my own turn fin and it got better and then after talking with David P he sent me one of his fins to try and I have never looked back.

The boat has never once tripped stumbled or done anything stupid after putting Davids turn fin on it and I have tried .

Testing with much larger class boats and in very rough water and it has been great.

Tim K

 

[Terry Keeley]

Wonder if those experiencing the tripping are having the fin come loose in the marbles about lap 5?

Maybe not completely letting go but just enough to have the outside sponson catch?

I tell you one thing, this one ain't sliding in the corners:

http://www.youtube.com/watch?v=-rJpc6RzAxA&feature=player_embedded

 

[Geraghty]

Wonder if those experiencing the tripping are having the fin come loose in the marbles about lap 5?

Maybe not completely letting go but just enough to have the outside sponson catch?

I tell you one thing, this one ain't sliding in the corners:

http://www.youtube.com/watch?v=-rJpc6RzAxA&feature=player_embedded

Terry,

You are right and there isn't anybody on this earth that has tested more JAE turnfins than Truex......

Just watch this boat of Truex's run....and that water is not smooth....... <_<

 

[Geraghty]

Rod,

I can certainly see why an upwardly curving tub at the rear of a boat would exhibit the suction you explain and shown in the video. But surely a curved surface in which all parts of the surface are at a positive angle of attack to the water flow would exhibit lift not suction? That is if the sponson riding surface is curved rather than made up of two stepped surfaces, all of the curved surface would be at positive angle of attack relative to the water flow.

Ian,No offense intended but I don't know how to make it any clearer than what I have posted....For some unknown reason you are just not willing to

understand the demonstration on the You Tube video and believe a physicist that was born in 1886......

"Any" curved surface,even with a positive AOA,will suck down into the waters surface and eventually the boat will do something stupid.... not to mention

extremely hard to launch......

Why do you think your JAE .21 works so well?

 

[Geraghty]

Wonder if those experiencing the tripping are having the fin come loose in the marbles about lap 5?

Maybe not completely letting go but just enough to have the outside sponson catch?

I tell you one thing, this one ain't sliding in the corners:

http://www.youtube.com/watch?v=-rJpc6RzAxA&feature=player_embedded

Terry,

If the boat trips.................

The fin is just plain not deep enough and the boat is sliding ever so little and........the rudder is probably to short also.....

 

[Ian Inverarity]

Ian,No offense intended but I don't know how to make it any clearer than what I have posted....For some unknown reason you are just not willing to

understand the demonstration on the You Tube video and believe a physicist that was born in 1886......

"Any" curved surface,even with a positive AOA,will suck down into the waters surface and eventually the boat will do something stupid.... not to mention

extremely hard to launch......

Why do you think your JAE .21 works so well?

Rod,

I just bent up a piece of metal and repeated the experiment myself. Once the end of the curved surface in the stream is no longer at a negative angle of attack relative to the flow direction the suction stops and the curved surface falls out of the stream. The video actually shows this when the pivot of the spoon is moved further form the water stream, it gets to a point that the end of the curved surface is no longer at a negative angle relative to the stream and the spoon drops out.

 

[Geraghty]

Ian,No offense intended but I don't know how to make it any clearer than what I have posted....For some unknown reason you are just not willing to

understand the demonstration on the You Tube video and believe a physicist that was born in 1886......

"Any" curved surface,even with a positive AOA,will suck down into the waters surface and eventually the boat will do something stupid.... not to mention

extremely hard to launch......

Why do you think your JAE .21 works so well?

Rod,

I just bent up a piece of metal and repeated the experiment myself. Once the end of the curved surface in the stream is no longer at a negative angle of attack relative to the flow direction the suction stops and the curved surface falls out of the stream. The video actually shows this when the pivot of the spoon is moved further form the water stream, it gets to a point that the end of the curved surface is no longer at a negative angle relative to the stream and the spoon drops out.

I see what you were trying to say and you are right....unfortuately it takes about 10 degrees of AOA to accomplish that......

You noticed the AOA the guy in the video had to introduce to get the spoon to detach....

In rough water when the front of the sponson touches the water thats when all hell breaks loose.....

not to mention the difficulty to get the boat to launch......boats are wetter than hell when you first drop them in the water.....

When the water attaches to the curved sponson bottom the water appears run up hill.....The faster you go the harder the sponson is pulled down....

 

[Michael Costanzo]

hi, i have 1 of the few JAE'S in the larger hulls (90/101) and it handles great when it is by itself, but when it is chasing another boat, it is a piece of crap.has nothing to do with the turnfin letting loose.

the smaller hulls have way less mass in the water and do not carry the inercia(spelling),i love the boat for its speed and turning capabilaties and i am working on different sponsons to make this hull competitive.if this problem can be fixed it will be one bad ass boat!

 

[PakMan]

Spend some time on the sponson design. Thy like to trip up in race water.To narrow and cut into the wakes in the corner.

Need anti trip angles on the sponsons. The smaller boats are fine nice and lite and say on top in lite chop. but get a big one in big race water and it is a whole different beast.

David

There is some truth to what you have said......but what you have deduced as to the cause of the tripping problem is not correct......so called non-trip angles have nothing to do with JAE's tripping......

Rod please expain then what the boat is actually "tripping" on if it's not the 90 degree vertical sides. I have run many hydros over the years and have seen how angled non trip sponsons "slide" from "inadequate" turn fins. With that being said the one thing I have seen with the JAE's is they do not slide, if the turn fin is not right they roll over, period. Not at all trying to be confrontational but rather have an answer when I get asked the same questions by others. :blink:

Simple response Don.

Jidoka.

Boiled down... "... focuses attention on understanding the problem and ensuring that it never recurs...."

However, it seems to me.. that as is almost always true in R/C boating, there could be a comprimise here that increases reliability AND speed.

I've never run a JAE, but i am a big fan. But, I believe in the above statement, with regard to a 'race-boat'. Oval boats, and SAW boats are totally different animals.

Best,

DJ

 

[Ian Inverarity]

I see what you were trying to say and you are right....unfortuately it takes about 10 degrees of AOA to accomplish that......

You noticed the AOA the guy in the video had to introduce to get the spoon to detach....

In rough water when the front of the sponson touches the water thats when all hell breaks loose.....

not to mention the difficulty to get the boat to launch......boats are wetter than hell when you first drop them in the water.....

When the water attaches to the curved sponson bottom the water appears run up hill.....The faster you go the harder the sponson is pulled down....

I did some more testing and posted pics in my gallery:

https://www.intlwaters.com/gallery/thumbnails.php?album=1136

I probably should have been a bit more scientific and made something to dangle the metal piece from.

 

[wayne middlemiss]

i would say the test is not an accurate reflection to the sponson dynamics, more to the point the spoon test is no bearing towards sponson shapes. in fact the water would be wraping around the spoon into the convex of creating the negative against the positive.

what sponsons have simalarities to spoon shapes????

 

[Geraghty]

hi, i have 1 of the few JAE'S in the larger hulls (90/101) and it handles great when it is by itself, but when it is chasing another boat, it is a piece of crap.has nothing to do with the turnfin letting loose.

the smaller hulls have way less mass in the water and do not carry the inercia(spelling),i love the boat for its speed and turning capabilaties and i am working on different sponsons to make this hull competitive.if this problem can be fixed it will be one bad ass boat!

From what i have seen the boat is too small

42 inches would be better for a single and maybe as much as 45" for a twin

Just saying

when it comes to what we call X Hydro size does matter

the smaller boats fall into the Holes to offten

No doubt about it .....the larger footprint will be more stable in rough water.....

 

[scott williamson]

i would say the test is not an accurate reflection to the sponson dynamics, more to the point the spoon test is no bearing towards sponson shapes. in fact the water would be wraping around the spoon into the convex of creating the negative against the positive.

what sponsons have simalarities to spoon shapes????

I think i might raid the cutlery drawer next time i run my new scale boat wayne and duct tape some dessert spoons to the bottom of the ride pads ,ive had trouble keeping the nose down!

 

[wayne middlemiss]

i would say the test is not an accurate reflection to the sponson dynamics, more to the point the spoon test is no bearing towards sponson shapes. in fact the water would be wraping around the spoon into the convex of creating the negative against the positive.

what sponsons have simalarities to spoon shapes????

I think i might raid the cutlery drawer next time i run my new scale boat wayne and duct tape some dessert spoons to the bottom of the ride pads ,ive had trouble keeping the nose down!

there ya go scotty the answer was right under your nose, they are also a great musical instument too. aaaaaaaaaaaaaahhhhhh yeeeeeeeeeeeeeah spooooooooooooons,, ya stirring bugger put the spoons away.

 

[Michael Costanzo]

hi, i have 1 of the few JAE'S in the larger hulls (90/101) and it handles great when it is by itself, but when it is chasing another boat, it is a piece of crap.has nothing to do with the turnfin letting loose.

the smaller hulls have way less mass in the water and do not carry the inercia(spelling),i love the boat for its speed and turning capabilaties and i am working on different sponsons to make this hull competitive.if this problem can be fixed it will be one bad ass boat!

From what i have seen the boat is too small

42 inches would be better for a single and maybe as much as 45" for a twin

Just saying

when it comes to what we call X Hydro size does matter

the smaller boats fall into the Holes to offten

hi, the hull is 5-6" longer than the plans call for. that is the key to the boat not hopping.that is why they do not run the bigger boats over seas.you are correct,longer hull is need for the big motor classes.hopeing soon to have a few different sponson changes to try out and i will also try some different and larger turnfins. not looking to set any records,just want a good pridictable,good handling boat.i know rome was not built in a day,so only time and lots of testing are in order.mike.

 

[dr gary turner]

All this advise and we don't even know what size of engines he is planning to use....

I know because he is in my club!!!!!!

Has he ran it yet????

 

[dr gary turner]

Wonder if those experiencing the tripping are having the fin come loose in the marbles about lap 5?

Maybe not completely letting go but just enough to have the outside sponson catch?

I tell you one thing, this one ain't sliding in the corners:

http://www.youtube.com/watch?v=-rJpc6RzAxA&feature=player_embedded

Terry last year I raced a 21 45 101 JAE. By theirselves fast and corner. Heat racing they trip. The 21 was fine, but 45 was bad to trip and the 101 was real bad. I think it is the turn fin. Lots of testing is needed before anything above the 21 is ready for prime time. It is the size-width front edge angle, depth and placement relative to the front sponson and trying to keep it from bending. We used tempered steel and still had issues. It is going to require more time than I am willing to give to the development. Back to traditional hulls. Doc

 

[Terry Keeley]

Are the fins braced to the tub?

 

[mtruex]

Wonder if those experiencing the tripping are having the fin come loose in the marbles about lap 5?

Maybe not completely letting go but just enough to have the outside sponson catch?

I tell you one thing, this one ain't sliding in the corners:

http://www.youtube.com/watch?v=-rJpc6RzAxA&feature=player_embedded

Terry last year I raced a 21 45 101 JAE. By theirselves fast and corner. Heat racing they trip. The 21 was fine, but 45 was bad to trip and the 101 was real bad. I think it is the turn fin. Lots of testing is needed before anything above the 21 is ready for prime time. It is the size-width front edge angle, depth and placement relative to the front sponson and trying to keep it from bending. We used tempered steel and still had issues. It is going to require more time than I am willing to give to the development. Back to traditional hulls. Doc

Doc,

i ran your 45 boat the way it came from you, it did not handle very well and i can see why you had problems with it. if you read my post on the JAE 45 thread you will read a few of the things not to do, a few things on your boat were this way..

biggest problem was your turnfin, i can see why it would trip with that fin... also sponson spacing was too narrow, both sponsons have too much AOA and rf has more than LF by a good amount, both are problems and they should be 4 degrees.. your strut is also tucked all the way up into the ski and thats a problem casuing the boat to be very loose.. i am confident with the right setup you would have a different opinion on your JAE's , you seen my 45 run in some water where i shouldnt have even tried to run it and i drove the boat back EVERY time and i ran it hard..

definently use solid booms