JAE21OB help needed

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MarkScott

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Oct 5, 2014
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As this is not a tunnel, don't have a clue on how to fix the issues found at today's testing session. Main issue is the boat does not track straight. Spoons were centered before heading out, equally spaced from the tub. Moved the front tube to both right and left offset, 1/8" at the most. Even moved the back right and left. Neither helped the boat track straight. I have been told that the turn fin needs to be thinned for speed, so that will be done.

Any and all suggestions appreciated.

CMB Redhead,, O.S. lower and Silver Bullet pipe.

JAE21OB.jpg
 

dave roach

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Mark
Looks like the turn fin needs to go down at the rear .I think they run a off set skeg.
 

Joe Petro

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Boat looks great!
You need to get that fin tuned. Start with the top of the fin parallel to the top of the sponsons and tune from there.
Start kicking the bottom of the fin forward in tiny (1/16 inch) increments and test.
When the boat starts climbing up on the fin, or you lose the ability to make left corrections, move it back 1/16.
The fin controls the forward ride height. You want to run the boat as loose as possible.

If you run the fin bottom back, it forces the sponsons into the water, and the boat does horrible things.
This is probably the most critical adjustment you can make on the JAE series (and clones).
 

MarkScott

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Joe, thanks for the info. Same information Mike gave me on the conversation we had yesterday. The fin needs some more material removed at forward edge. Testing will resume this Thursday. Until then, taking care of Misty.

Misty.JPG
 

Carl Van Houten

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The very original and very successful Sun Downer O/B hydro that Randy Myers designed was driven by Richard Hazelwood and Joe Monohan and were probably two of the fastest O/B hydros in the country. Both of these guys removed the center skeg (as Dave mentioned) from their lower units and ran an offset skeg. NOT TO SAY THAT'S WHAT THIS BOAT REQUIRES! But it is similar in design so it may help. When I ran mine I also ran it with an offest skeg.

Not many people know this but Randy sold the design rights to me for both the 3.5 and 7.5 versions of the Sun Downers. I have never done anything with that boat but maybe one day I will.
-Carl
 

XtremeRcBoats

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see also this topic with some info:
 

MarkScott

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Carl, thx for the information. I do have one of the Prather offset skeg's for their ET's setup from the days gone by.

Paul, thx for the thread link. Remember reading it back when it was active, just couldn't find it. Looks like I have more ideas to think about. Do have an older O.S. lower to try this on. If need be, there's a Lawless lower also. No K&B's as they were either sold or given away.

I was able to do a better job of the leading edge on the turn fin. The top is now parallel to the boom tubes. Is it Thursday yet?
 

XtremeRcBoats

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good luck and keep us updated. I still have an JAE21OB in a box I want to built some day.
 

RonShaw

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Carl, thx for the information. I do have one of the Prather offset skeg's for their ET's setup from the days gone by.

Paul, thx for the thread link. Remember reading it back when it was active, just couldn't find it. Looks like I have more ideas to think about. Do have an older O.S. lower to try this on. If need be, there's a Lawless lower also. No K&B's as they were either sold or given away.

I was able to do a better job of the leading edge on the turn fin. The top is now parallel to the boom tubes. Is it Thursday yet?
Mark,
Once you get the turn fin adjusted properly, you will see an improvement, but your issue will not be fixed. Just like the Sundowner that Carl mentions above, and every other OB Hyfro I have ever ran, this design screams offset skeg. Dont waste another sec on any other fix. Break off the existing skeg, round the bullet as though it never existed, install a skeg (port side for right hand turns) and make sure it extends at least 2” below the bullet and offset at least 1 1/4” from bullet centerline. If you find one for a Sundowner or the Prather it will work great. Stainless 1/16” works great as well. Make sure its perfectly parallel with the bullet, straight edge on rear, angled on leading edge just like your existing skeg. Back edge of skeg just in front of prop drive dog. Go race. You will be blown away at how well the boat tracks, drives, and corners. My Petro OB Hydro built by Mike Walker has never lost a race. I think my OB Hydro has won every OB Hydro race it has entered (5 total) until they stopped running the class last year. Hopefully the class comes back at the next tunnel champ race. Its a hydro for outboarders!!!
 
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MarkScott

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Looking thru the items that came from a recent purchase of 14 boats. Three rudders look to be good choices. Guess the main item would this rudder need to wide? The black is around 1/8" wider of a blade. Think any of them would be a good choice.

Thoughs?
rudders (2).JPG
 

dave roach

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Mark
The mini rudder blade from speed master will work just fine.
 

XtremeRcBoats

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Thanks Mark for the offer. I'll give the speed master mini rudder a try. I live in the Netherlands, will you ship overseas? Can only pay with Paypal.

Do you perhaps also want to sell the lower unit? I'm also in search of one for this project. Only need this part of the lower that is in the picture. The rest i'll take from another engine/lower.
 

MarkScott

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Paul, forgot you were in Netherlands. But yea, I've shipped overseas. Sorry, but no O.S. lower to sell, they are for my own projects. As for the Prather stainless, cost will be shipping. Just looking for a good home for it. PM your address and I'll get it boxed up and shipped out next week. I'll let you know the shipping cost and my paypal information.
 

MarkScott

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Big THANKS to Dave Roach. Finished two setups, one for the current boat, another for future attempts.


lower1 (2).JPG


lower2 (2).JPG



lower3 (2).JPG
 

MarkScott

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Testing today was limited due to algae floating on the surface. Was able to get some laps in and I'm happy with the changes.

Turn fin edge was brought back to 0.5" from the leading edge. Using two carbon fiber rods, one set on top the boom tubes and the other on the fin top, aligned them to where they were as even as these eyes could get them.

Using the offset rudder on the left, boat handled quite nicely. No tracking issues could be seen. Speed was double from the first run attempts.

So thanks to all that helped.....

lower1 (2).jpeg
 
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