JAE or JAE style boat tuning thread

[mtruex]

Robin & Nessa,

I hear what you are saying but the JAE is a different animal. Some things from a regular styled rigger applies and some does not. I first ran the rudder with a flat bottom and it was lifting the rear of the boat. That is not good for a boat using only a center ski and no traditional sponsons. I then filed each side of the bottom to a blunt point and that removed the riding lifting surface. That settled the boat down and let the rear ski do it's job. Getting the leading edge iof the rudder VERY sharp is important, with any boat truly.

As for the turn fin, the kit fin will bend. I did it on the very first run. Had some 7075 alum fins made and bent them immediately. They were bending just below the sponson towards the outside of the right sponson and not towards the hull. I got a Preusse fin and have yet to bend it. The Mike Hughes fin will not bend either. A fin fix that some of the JAE design team is using is taking the kit fin and cut off the top half. You want the bottom of the plate to be just above the water line which is slightly above the curved area of the fin. This acts as doubler. You put it BETWEEN the sponson and the full turn fin. Tie them together with some 4/40 bolts and nylock nuts. It will strengthen it up considerably.

But for me, the Preusse fin is holding up and is not bending. I have not put on a doubler, yet.

Mine is the zippkit turn fin and hardwear. Joe talked to Ron at zip about it. Ron said I cant believe your bending them. Ron said that Martin Truex is running that same turnfin without any proublems. Joe said yes ,there bending. Joe had to drop out of a race because that turnfin and was pulling to the right. He's fliped that rigger 6times with that turnfin. Phil Thomas gave joe a turnfin he had. Was better pulled less and rigger didnt flip. Ron did send us two turnfins. Joe put that on and the first run it fliped and it was bending too Joe & I'd asked around,should a turnfin flex at all? So far the answer was no. On the rudder the part that facing the front of the boat, should that area be rounded or not? I did it like the miss vegas rudder

this is all good info on this thread , i run davids turn fin on my 21 boats, and my own turnfin on the 12, keeping them stiff is very important, a doubler works well as mentioned, also a brace of some sort to the tub works well...sharp rudder, AT LEAST 1- 1/2 inches below the ski on the 21 (i like 1-7/8) 1/8 toe rf sponson, sharpen the inside of the turn fin just down to where the curl starts, only about 20% of the thickness of the fin. too much here and the boat wont rip the turn as well.

props in the 45-48mm range have all been very fast depending on the engine pipe combination, alot of this is personal preference, and dictated by the engine/pipe combination..

 

[Jeff Schindler]

I believe this is the non lifting rudder profile John is talking about. An extreme example is on my gas whiplash, but I have profiled my JAE .21 similarly to a lesser degree with good results. The zipkits rudder comes with a .25 radius rounded bottom at the leading edge. I cut the rudder down until in depth until I could get a sharp corner and then made a barely noticeable taper to the back using a belt sander. (we are talking parallel to the bottom of the boat, the rudder is less deep at the back by a hair) This create a suction rather than lift.

I think by cutting down the zipkitts rudder, the depth is not quite enough, but you can mount your rudder lower on the transom to get the desired depth. Mine is around 1 1/8" and is just a little squirrely to drive.

WHIP RUDDER

JAE21 RUDDER

 

[John Knight]

I believe this is the non lifting rudder profile John is talking about. An extreme example is on my gas whiplash, but I have profiled my JAE .21 similarly to a lesser degree with good results. The zipkits rudder comes with a .25 radius rounded bottom at the leading edge. I cut the rudder down until in depth until I could get a sharp corner and then made a barely noticeable taper to the back using a belt sander. (we are talking parallel to the bottom of the boat, the rudder is less deep at the back by a hair) This create a suction rather than lift.

I think by cutting down the zipkitts rudder, the depth is not quite enough, but you can mount your rudder lower on the transom to get the desired depth. Mine is around 1 1/8" and is just a little squirrely to drive.

WHIP RUDDER

JAE21 RUDDER

Jeff,

Close to what I am saying but not exact. Take the belt sander and run it along the entire rudder bottom and not just the rear tip. That removes the entire lifting surface and not just the rear tip. The last thing you want to do is to lift the ski off the water, which is the only thing of the boat rear on the water. It must ride on the water for stability and to keep the prop hooked up.

I ran the Speedmaster mini rudder cut off as it is for my 20 Roadrunner, at 1.25" below the ski. That was too short. I put an uncut blade on it and it is now 1.75" and is much better. I will have to drop the entire rudder unit to lengthen it and right now I am going to do other tests before I do that, if at all.

 

[misshydro]

I believe this is the non lifting rudder profile John is talking about. An extreme example is on my gas whiplash, but I have profiled my JAE .21 similarly to a lesser degree with good results. The zipkits rudder comes with a .25 radius rounded bottom at the leading edge. I cut the rudder down until in depth until I could get a sharp corner and then made a barely noticeable taper to the back using a belt sander. (we are talking parallel to the bottom of the boat, the rudder is less deep at the back by a hair) This create a suction rather than lift.

I think by cutting down the zipkitts rudder, the depth is not quite enough, but you can mount your rudder lower on the transom to get the desired depth. Mine is around 1 1/8" and is just a little squirrely to drive.

WHIP RUDDER

JAE21 RUDDER

from the whip rudder is revers from my miss vegas rudder and my JAE.12.

 

[gooycheese]

I am running 1.75" below my ski and running fine, I did have steering issues running the fin I ran on my firefighter since it is 5/8" shorter. My turnfin is straight off the firefighter .... and is a CD Machine fin..... got no problems with that .... it is sharpened on the outside only but will try working that

 

[misshydro]

must keep these light on weight. 2 1/2 pounds or lighter on the.12's ..21's at 3 1/2 or lighter as from what I was told. Was told martin truex's.21 weighs about 2.95 pound!! Dam that light!!! I'm going to start building the .12 lighter weight version. 1/16 tubside and walls and 1/32 skins.

 

[Geraghty]

must keep these light on weight. 2 1/2 pounds or lighter on the.12's ..21's at 3 1/2 or lighter as from what I was told. Was told martin truex's.21 weighs about 2.95 pound!! Dam that light!!! I'm going to start building the .12 lighter weight version. 1/16 tubside and walls and 1/32 skins.

After reading this post I believe I was in error if I said the weight of Martins .21 boat was under 3 #....I know Martin was shooting for under a 3# boat but I believe the final weight was right at a shade over 3#-.......[as I recall 3#-2oz final weight].....I will check with Martin for the final weight of his boat........

Martin started with the Zippkits JAE.21G2 kit boat and incorporated weight reduction mods with carbon fiber,aluminum fasteners etc.etc etc......A well built JAE.21G2 "kit" boat will come in right at 3-1/2 lbs and that is a good weight for a competition boat that will take the abuse of heat racing week after week......These 3-1/2 # JAE.21G2 kit boats are the boats that Zaker and Preusse were running at Hobart......

Martins focus was speed,speed and more speed......heat racing abuse really wasn't a consideration......

Joe and I were talking at Hobart and I was trying to tell Joe how important light weight is to the performance of these smaller classes of R/C boats.......

I also told Joe there is a very inexpensive postal scale available on ebay to weigh everything he puts on a boat.....using this scale will really change your building and painting habits......you have no idea how fast gobs of epoxy and 1/4" paint will increase the weight of your boat......

http://cgi.ebay.com/76-DIGITAL-POSTAGE-SCALE-Shipping-Postal-Scales-NEW-GR-/250694508825?pt=LH_DefaultDomain_0&hash=item3a5e8ea119

 

[Chris Wood]

rod you are correct.

i painted the front sponsons after sealing it added 6oz. i can't get away from it unless i just clear them and i refuse to do that.

i to use alum blts and such.. it is tuff to get them around 3lbs for sure. my lightest boat was 3lbs 5oz and i tell you it was a pain in the butt to get there.

chris

 

[Richard Dahlheimer]

Speaking of weight...... just weighed some parts for my Blackbird 20 boat. One front sponson not sealed or painted with balsa core and i believe 1/32 sheeting = 2and 3/4 oz. One sponson sealed, primed and painted added one oz. Bagie with a bunch of hardware, including motor mount, strut and rudder assy, on/off switch, ops 3280 pipe with bracket and header, and miscellaneous nuts and bolts and antena mast weighs 8 0z. Richard D

 

[Mike Larson]

Hate to be contradictory.... but, its there.... I didnt sacrifice heat longetivity for weight.... My Blackie is over 4.....

Jae is right over 4,G10 Oval Serpent, close to 4, Hummingbird, 3 14......and so on..... IMO, and I did, use epoxy, sparingly, everywhere, every boat.

CA, and as you go down the epoxy set time varieities is brittle..... personally, i dont like split tubs, delam sponsons, and things after blow offs, bouy strikes, etc...... fumes... well.

Again, and i've noticed, my "ski" style builds have the level, flat, eat the cobby water up..... that I watch for.....

yeah, theyre a little heavy..... plastic where i can, and stainless where it aint....... paint's, well, it's painted....

Sometimes light, is too light..... rarely is the water nice anywhere we go..... 'an popcornin blowoffs dont gain points.... weigh them parts.... I'll try an go around you..... wait up Chris! Mike

 

[misshydro]

whats the size of the .12 JAE rudder in mm?

 

[mtruex]

there are many ways to make a boat lighter without sacrificing durability..

 

[misshydro]

there are many ways to make a boat lighter without sacrificing durability..

Ok spill the beans then...enquiry minds want to know.

 

[shoboat]

drill out sponsons before you sheet the bottoms,plastic hardware,

clearcoat boat only and use some decals,tape in your servos with

two way tape,plastic brackets,trick motor mounts,lighter materials

like foam core products,drill out hardware so it is lighter,use plastics

instead of metals wherever possible,plastic clamps,smaller boom tubes,

wire drive or .150" cable on 12 & 21 boats,lexan cowls,etc.

Just A Few Ideas,

Mark Sholund

 

[Mike Byer]

Built mine just like it said in the booklet that came with the kit, used the Zipp hardware, including the fin and it runs as good as any 20 rigger I've ever had. A 20 will try your patience more than any other, but if this kit is built according to the instructions and a little time spent to get to know the boat and understand what it wants, it's easy to run and pretty fast. Don't have the idea that yours and every other will run like Zaker's or Pruese's boat. A well built boat that's reasonably light with a good motor and prop and good amount of test time will show decent speed.

 

[misshydro]

Built mine just like it said in the booklet that came with the kit, used the Zipp hardware, including the fin and it runs as good as any 20 rigger I've ever had. A 20 will try your patience more than any other, but if this kit is built according to the instructions and a little time spent to get to know the boat and understand what it wants, it's easy to run and pretty fast. Don't have the idea that yours and every other will run like Zaker's or Pruese's boat. A well built boat that's reasonably light with a good motor and prop and good amount of test time will show decent speed.

the proublem is when you built it according to instructions some might be light some might be heavyer. Was told .12 should be at 2 1/2 pound a .21 should be at 3 1/2 pounds. its all in the epoxy prosses and painting. I did what I was told but mine can out a tad heavyer,2.85 ponds. Shouldve put one coat of epoxy on it,but was told to do two. Going to have Rod do up a.18 for this rigger and stick the.12 in the lightweight version that joe is building for me. Its fast but want more speed. Showed Rod Garaghty the video of my boat. Here what he said to me. Rod (quotes)It is lookin' pretty darn good.......It really handles the nasty water well....this will be a great heat racing points boat....

The motor is right on the edge of really stepping up to some big time rpm......also the more you run it

the better it will get.......a lighter boat will really help........remember,everything pretty,such as fancy multi-coats of paint does nothing but add weight .

Weigh your existing boat on a good scale and let me know what it weighs......I am curious to know......

You can buy a good postal scale on ebay for $20.00....this is a real eye opener when you weigh everything you put on the boat....it gets you thinking....heres a video of it. Joe is driving it and got me all wet from the rooster tail it was throwing out.

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[Mike Byer]

looks like the proublem is, there is no proublem.

 

[misshydro]

looks like the proublem is, there is no proublem.

my proublem is mine is 1/4 on the heavy side,but a hot.18 should compersate for it. But theres a thread on .12 jae on RCU. Joe told those guys watch it on adding more stuff to these riggers. some adding three servos and some adding/making a big plate on the inside of the rear transome. others using alum servos mounts and using bigger reciver packs.

 

[hydroman]

Has any one got a engine cowlor is anyone making one for the 21g2 for a rear exhaust motor

 

[shoboat]

Nessa,

What propeller are you running in the video? 1440 B/C

It needs to be pitched up more,please send it back to me.

We have recently had some very good results with a

modified ABC 42 x 55 currently.

Keep Testing,

Mark Sholund