rigger get to flighty,can changing front sponson attack angle fix it?

[misshydro]

Ok we have a rigger what was a 80/90 nitro rigger converted to gas. Having proublems of the front end wanted to lift to much.. Darn thing is a speedster .. Has a 26 sikk in it.. Engine is wrightup next to the second boom tube..CG is in the middle of the hull... If we can keep the front end down ,this rigger can be very competive...Did put the sponsons back to factory setting..it was about 1/8 down..Havent tried it yet since the sponson was put back to stock setting...I did ask on the DOC's but got no where.. I know theres more riggers guys here that are willing to help..

 

[Norm Doerr]

CG is over the rear riding surface of the front sponsons? Is the tub set up level on the set up table?(strut set to correct depth).

 

[misshydro]

CG is in the center of the hull/at the out put of the engine..the end of the turn fin is at that piont.

 

[julianconde]

If it wants to blow over or raise the nose too high add Shims to the front sponsons rear boom tubes that will make the boat more tighter and change the angle if attack.

that's what we do with our Twin riggers. What rigger are we talking about here ?

Julian

 

[Norm Doerr]

Is it and Eagle?

 

[misshydro]

its a 80/90 advenger spider converted to gas..It's fast..Ya I wish it was a Eagle,, .

this rigger can be very very competive rigger if we can solve this proublem..Joe one friend Russ told him last night maybe run a lifting prop..get the backend to come up and that might push the front end down..Ron olson let him tried two props.. cant remember the first prop,but it was a three blade Voo Doo and man it was on fire!!!! He lead ahalf of lap on everyone on the first heat until he caught air and a proublem spot in turn 1& 2 and fliped it..Used that prop for 2 heats.. Then tried a 2716 G force prop for heats 3 & 4 and still was lifting the frontend.. Heat 4 on his last lap he did a wheelieall the way on the front stretch bigtime ,,,only the prop was in the water..He saved it from blowing over..2 people took videos of it and were hoping to see them.. some of the guys said that was the higlight of the day..Olsons daught inlaw took pics of that...joes face was pale white after that..thats what I'd heard....Hears a pics of it..not that pretty..was in primer on the test days.. was told to throw a qiuck white on it so everyone can see it..To let you know this was joe's first race,alittle driving learning curve here..

 

[Duck899]

its a 80/90 advenger spider converted to gas..It's fast..Ya I wish it was a Eagle,, .

this rigger can be very very competive rigger if we can solve this proublem..Joe one friend Russ told him last night maybe run a lifting prop..get the backend to come up and that might push the front end down..Ron olson let him tried two props.. cant remember the first prop,but it was a three blade Voo Doo and man it was on fire!!!! He lead ahalf of lap on everyone on the first heat until he caught air and a proublem spot in turn 1& 2 and fliped it..Used that prop for 2 heats.. Then tried a 2716 G force prop for heats 3 & 4 and still was lifting the frontend.. Heat 4 on his last lap he did a wheelieall the way on the front stretch bigtime ,,,only the prop was in the water..He saved it from blowing over..2 people took videos of it and were hoping to see them.. some of the guys said that was the higlight of the day..Olsons daught inlaw took pics of that...joes face was pale white after that..thats what I'd heard....Hears a pics of it..not that pretty..was in primer on the test days.. was told to throw a qiuck white on it so everyone can see it..To let you know this was joe's first race,alittle driving learning curve here..

Your going to want to do what Julian proposed in his post. You will have to remove the rear sponson tubes and oblong the holes up away from where the booms are now. Then make a few shims out of brass flat stock to slide under the booms to raise the rear boom. This will change the AOA and lower the tub. I would make shims in 1/32", 1/16" and 3/32" and even 1/8". Start with the 1/16" and I'll bet the boat will hold the water better. You may end up with the 1/8" shim in there cause it looks like that engine is quite aways rearward therefore the balance is too far back.

 

[dwilfong]

Try putting the rear tip of the strut down positive. this will push the nose in harder. much easer than all that cutting and shimming.

This is the only adjustment I use on my SGX90. tried shimming the boom tubes and it was a pain in the ars to set up.

then again the SGX is set up right from the build.

Ron in are club has the same boat with a nitro in it and was chasing the same thing.

not sure if he made the rear tubes adjustable or not yet.

David

 

[misshydro]

the ballancing point is at the center of the hull,at the flex coupler of the engine..It does have the rear hole oval slotted..At the race it was down 1/8 from stock hole setting..we got it up back to stock setting..Joe did add sponson runners with shingales that it 1"wide and 1/4 thick..Because his friend that has a viper rigger is simmiller design and sponson shape.His friend said it helps in getting up on plane and breaks surfacetention=adds speed....I'll post pics of that later tonight..

 

[Terry Keeley]

Make the C/L of the shaft even with the rear sponsons, put about 4-5* angle in it and run a 1467 or 1667.

I guarantee it won't wanna fly.

 

[Norm Doerr]

It needs to go on the set up table first and formost. Is the tub level or pointing towards the sky? What are the AA of the front sponsons? You will need a digital level to get this correct.

Boat looks short, what is the afterplane? (front riding pads to center of prop)

 

[Mike Hughes]

Joe did add sponson runners with shingales that it 1"wide and 1/4 thick..

Wait a minute. Did everyone catch that? The boat is now a 1/4 higher in the front than the stock sponson. You need to shim both the booms to get rid of the 1/4 you just added. That is why the boat is dancing on the front. Need to get the tub back down. Yes you will need to get it on a setup board to get everything back to where it is supposed to be.

Mike

 

[misshydro]

Joe did add sponson runners with shingales that it 1"wide and 1/4 thick..

Wait a minute. Did everyone catch that? The boat is now a 1/4 higher in the front than the stock sponson. You need to shim both the booms to get rid of the 1/4 you just added. That is why the boat is dancing on the front. Need to get the tub back down. Yes you will need to get it on a setup board to get everything back to where it is supposed to be.

Mike

his friend helped him finding the CG and strut setup..this was all done on a flat table...bottom was sitting perfict in strait line..Mike the whole bottom of the sponsons isnt done in 1/4",,heres the pics of it..

 

[Norm Doerr]

Joe did add sponson runners with shingales that it 1"wide and 1/4 thick..

Wait a minute. Did everyone catch that? The boat is now a 1/4 higher in the front than the stock sponson. You need to shim both the booms to get rid of the 1/4 you just added. That is why the boat is dancing on the front. Need to get the tub back down. Yes you will need to get it on a setup board to get everything back to where it is supposed to be.

Mike

his friend helped him finding the CG and strut setup..this was all done on a flat table...bottom was sitting perfict in strait line..Mike the whole bottom of the sponsons isnt done in 1/4",,heres the pics of it..

That most definatly raises the ride height. Put it on the table and start here.

http://rcboat.com/setup2.htm

And Here, (this should get you close even if it is not a Roadrunner)

http://rcboat.com/setup2.htm

 

[camaroboy383]

missy,,it doesnt matter if u shingled the whole sponson or half the sponson...its gonna ride off the shingled part... listen to mike and norm here and that boat will most likely turn out the way u want it

 

[Norm Doerr]

Once the thing is set up it could be a GOOD Sprint Boat.. short and powerful. Marty Davis had a lot of success with short Sprint boats. We have a 60 boat here he won a lot of races with..every once in a while we bring it out of mothboths and race it. The thing is a handful BUT it takes off like a top fuel hydro from a crawl..and turns very well. you MUST work the throttle.. Every time I have driven it I laugh, because you have to be careful, fast but easy to get behind on with driving. He had it at the first Fall Nats and won the class with it..(or maybe the second Fall Nats, don't remember). Never the less any boat has to be set up correctly.

 

[Ted buckley]

Joe did add sponson runners with shingales that it 1"wide and 1/4 thick..

Wait a minute. Did everyone catch that? The boat is now a 1/4 higher in the front than the stock sponson. You need to shim both the booms to get rid of the 1/4 you just added. That is why the boat is dancing on the front. Need to get the tub back down. Yes you will need to get it on a setup board to get everything back to where it is supposed to be.

Mike

his friend helped him finding the CG and strut setup..this was all done on a flat table...bottom was sitting perfict in strait line..Mike the whole bottom of the sponsons isnt done in 1/4",,heres the pics of it..

I'm not trying to usurp anyone's suggestions above, but take a look at the 1st pic and note the (Flat front) on the turn fin? Also look at Nessa's 1st pic of the boat at the start of this post and Note the wing flaps on the cowel. Both of these could be factors in taking flight in "High Speed" operation - which is what she's talking about. JMO.

 

[LarryConrad]

That sure is one scary looking paint job for a boat that's owned by a couple of self proclaimed professional automotive refinishers. That heavy gasoline engine is placing the weight farther rearward than where the hull was designed to balance with the intended nitro engine.

 

[misshydro]

That sure is one scary looking paint job for a boat that's owned by a couple of self proclaimed professional automotive refinishers. That heavy gasoline engine is placing the weight farther rearward than where the hull was designed to balance with the intended nitro engine.

Larry it was a quicky ....Joe had it in primer at test day plus this was a last moment to get this rigger ready for the nats..Tue and weds was test day.. was told to but some white on it for test day.. So on tuesday night we taped everything off and did a quicky 2 coats of white base paint on it.. After testing is done to get thing fine tuned it will get a great paint scheam on it...We did do alittle testing on it.. we'll we ran a proboat SS 70/92 prop and she ran great ,but not flighty..but joe didnt like the slower speeds.. he put a bigger prop simmiler to the G force 2716 and she ran good not as much flighty.Joe was playing around running it in turns and punching it on the strait aways...His friend Rick reisinger has our M&D full mod zen engine. Was told that it has more RPM'S then the 26 sikk and 26 zen... That what we was told to run in it at the nats..motor wouldnt run..So we stuck the sikk 26 in it...His other friend gave us a full mod 26 zen to run after the nats...Going to do more testing on sunday...Oh larry like I said in the other post the the CG is at the center of the hull..

 

[Mike Hughes]

Anything you add to the bottom of the sponson will raise the ride of the sponson that much. Your shingles are the riding surface. So you lifted the front of the boat a 1/4 inch. The tub is trapping air and lifting the boat. You now need to shim both booms a 1/4 inch to get back to where you started. That is your problem. The boat in stock form should run great with a gas motor in it. I would suggest that you cut off the ride pads you added. They are just too big. You can get the same results (free the sponson up) with a smaller pad. Somewhere in the 3/32 range. Less shimming to do. Forgot the paint job for now and get it running right. If you want to run the pads the way you have them, you would be better off building new sponsons from scratch that put the ride where it needs to be.

Mike