.21 sgx center rear sponson question

[JOE P.]

Has anyone ran a newer (2007-09) .21 sgx without the center rear sponson?

What could i expect if i left it off? Any Suggestions?? THANKS JOE

 

[waltr]

Joe,

I'd put it on. It helps when launching the boat, and helps lift the back end while running.

 

[Richard Dahlheimer]

Joe,I'd put it on. It helps when launching the boat, and helps lift the back end while running.

Walt is right on. Run the center ski. In fact i used to run a SG .21 just with the center ski. Boat launched well, and handled ok. Richard D

 

[Buckshot]

The new version (SGX-2) doesn’t have a center sponson and it even has smaller outside sponsons but bigger winglets. I have not personal ran one of these versions yet but will be soon (a .45 and a Gas) but have been told by A.B. that it actually handles better than the earlier version.

I don't know?

-Buck-

 

[yurkanip]

I have run my brushless riggers with and without rear "skis" I built my latest rigger from Niklas Edlunds (keps .21) and it definately runs better with the single rear ski only (ski covering the stuffing tube), It not only keeps the rear lifted when coming out of a corner, but it helps the hull plane instantly on throttle.

Hopefully Niklas will chime in here, as he designs a very well built rigger, and has a lot of knowledge from racing riggers.

 

[JOE P.]

The new version (SGX-2) doesn’t have a center sponson and it even has smaller outside sponsons but bigger winglets. I have not personal ran one of these versions yet but will be soon (a .45 and a Gas) but have been told by A.B. that it actually handles better than the earlier version.
I don't know?

-Buck-

Thanks Buck, i have a 2009 sgx 1 and thought i might find cleaner water at speed without the center sponson maybe more bite in turns? Ive always set up riggers to ride on the prop not on the sponsons.

Has anyone ran this boat without the center shoe??

 

[Niklas Edlund]

I have run my brushless riggers with and without rear "skis" I built my latest rigger from Niklas Edlunds (keps .21) and it definately runs better with the single rear ski only (ski covering the stuffing tube), It not only keeps the rear lifted when coming out of a corner, but it helps the hull plane instantly on throttle.
Hopefully Niklas will chime in here, as he designs a very well built rigger, and has a lot of knowledge from racing riggers.

Well, my experience with the SGX-1 (.21) is kind of limited. I built one a few years back and raced it for a couple of races but I never really liked it. Or more correctly, I didnt like it as much as my own rigger... LOL. I sold it and the guy buing it from me sold it back to the US and it was the best SGX-1 he had ever raced...

SGX-1 without center ski but with std rails/sponsons needs to be lightened a lot in the rear (if U ask me). The lighter the better is my experience (in the rear). Remove as much weight as possible from the rudder and strut to start with. We even used aluminium 6-32 screws and nuts to hold them. Move the weight if possible also to the front in the radio box, move heavy items in there forward. Use a smaller steering servo etc (I used a S9550). I had the 5-cell AAA pack all the way to the front in the radio box. If I remember correctly its a small window where the strut height and angle needs to be also. If the strut is set too deep and to much down angle it loads the engine too much. Set "too high" and the spoon shaped sponsons make the rear drag too much. It needs a lot of testing to be set right...

(Edited to SGX-1)

 

[JOE P.]

I have run my brushless riggers with and without rear "skis" I built my latest rigger from Niklas Edlunds (keps .21) and it definately runs better with the single rear ski only (ski covering the stuffing tube), It not only keeps the rear lifted when coming out of a corner, but it helps the hull plane instantly on throttle.
Hopefully Niklas will chime in here, as he designs a very well built rigger, and has a lot of knowledge from racing riggers.

Well, my experience with the SGX-2 (.21) is kind of limited. I built one a few years back and raced it for a couple of races but I never really liked it. Or more correctly, I didnt like it as much as my own rigger... LOL. I sold it and the guy buing it from me sold it back to the US and it was the best SGX-2 he had ever raced...

SGX-2 without center ski but with std rails/sponsons needs to be lightened a lot in the rear (if U ask me). The lighter the better is my experience (in the rear). Remove as much weight as possible from the rudder and strut to start with. We even used aluminium 6-32 screws and nuts to hold them. Move the weight if possible also to the front in the radio box, move heavy items in there forward. Use a smaller steering servo etc (I used a S9550). I had the 5-cell AAA pack all the way to the front in the radio box. If I remember correctly its a small window where the strut height and angle needs to be also. If the strut is set too deep and to much down angle it loads the engine too much. Set "too high" and the spoon shaped sponsons make the rear drag too much. It needs a lot of testing to be set right...

Thanks Niklas! I appriciate your opinion and will use your advice. I too was weight concerned. using mini servos and keeping weight foreward. I figured the center shoe was to remedy a problem. I had previous sgx's that were very fast and would turn great BUT boat would spin out and go under durring a turn. not durring practice only durring a race usually on lap 2-3 .probably when water got choppy/sloppy. I figured I might change the next sgx and this was a thought that crossed my mind on the last one. THANKS!!!

 

[Jorgen Andersson]

Hi Joe

I have 5 years experince with the SGX-1 .21 and here is my set up that has won many races!

1. Use NO centre sponson - creates drag and runs worse in choppy water.

2. Lighten the boat in the rear so you have a rudder weight at approx. 545grams when you put a scale under the rudder and two blocks under the front sponson steps. Measure RTR except fuel and prop. You have less weight on the rudder than 545grams with good results as well.

3. The rudder is 25mm wide and goes 41mm deeper than the bottom of the rear sponsons. Thin the blade out to 3.4mm.

4. Strut angle set at 1.5 degrees is a good start, and when you place the boat on a flat surface without rudder and turnfin, the rear sponsons should be 0.8mm in the air.

5. If you lighten the rear, you must check the position of the turnfin, 12-15mm in front of the balance point, measured at the bottom of the trailing edge of the fin.

6. Sharp edges on all running surfaces!

7. I run with a wider stance between the front sponsons, 12mm on each side, find this to be better in race water.

8. A 1445 with 3.5 cup is a good prop to get the set up right. H7 with 3.75 cup gives more speed and runs well in the corners.

9. I use Valvola with AB FAT pipe at 200mm with 60% nitro.

10. Total weight is 1860grams, no so light, but handles really well in race water.

11. Set the AOA (Angle of attack) in the front sponsons so that, seen from the side, the left sponson deck is parallell to the deck of the tub and the right sponson front tip 2-3mm higher than the left set on the flat surface. This might be a little bit loose, but a good start for settings.

Joe - If you have any more questions, please send a PM or email me at:

[email protected]

Niklas - As you say, your experince with SGX is limited, the boat you had was SGX-1 not SGX-2, big difference!!!!*smile*

Thanks

Jorgen

 

[Niklas Edlund]

Niklas - As you say, your experince with SGX is limited, the boat you had was SGX-1 not SGX-2, big difference!!!!*smile*
Thanks

Jorgen

Oops. Yes it was a SGX-1...

 

[JOE P.]

Hi Joe
I have 5 years experince with the SGX-1 .21 and here is my set up that has won many races!

1. Use NO centre sponson - creates drag and runs worse in choppy water.

2. Lighten the boat in the rear so you have a rudder weight at approx. 545grams when you put a scale under the rudder and two blocks under the front sponson steps. Measure RTR except fuel and prop. You have less weight on the rudder than 545grams with good results as well.

3. The rudder is 25mm wide and goes 41mm deeper than the bottom of the rear sponsons. Thin the blade out to 3.4mm.

4. Strut angle set at 1.5 degrees is a good start, and when you place the boat on a flat surface without rudder and turnfin, the rear sponsons should be 0.8mm in the air.

5. If you lighten the rear, you must check the position of the turnfin, 12-15mm in front of the balance point, measured at the bottom of the trailing edge of the fin.

6. Sharp edges on all running surfaces!

7. I run with a wider stance between the front sponsons, 12mm on each side, find this to be better in race water.

8. A 1445 with 3.5 cup is a good prop to get the set up right. H7 with 3.75 cup gives more speed and runs well in the corners.

9. I use Valvola with AB FAT pipe at 200mm with 60% nitro.

10. Total weight is 1860grams, no so light, but handles really well in race water.

11. Set the AOA (Angle of attack) in the front sponsons so that, seen from the side, the left sponson deck is parallell to the deck of the tub and the right sponson front tip 2-3mm higher than the left set on the flat surface. This might be a little bit loose, but a good start for settings.

Joe - If you have any more questions, please send a PM or email me at:

[email protected]

Niklas - As you say, your experince with SGX is limited, the boat you had was SGX-1 not SGX-2, big difference!!!!*smile*

Thanks

Jorgen

Thanks Jorgen, I really appriciate your time and explaining set up.

I want everyone to know that I think CMDI does a GREAT job with their boats.

This is a hobby that welcomes changes and sometimes with changes we can move foreward (hopefully fast forewrd) lol