Just a question????

[Marty Davis]

Rick:
Suggest that you set up the boat exactly like this: http://rcboat.com/setup.htm and then get an H7 and run it stock. Should be very good running boat then.

Marty Davis

Sounds good Marty, will check measurements agains this set up sheet.

But I do have a question, if the boat/engine combo will not launch, get up on pipe with the smaller diameter, and pitch of an H-4 @ 1.68 X 2.6 or a 1445 @ 1.77 X 2.48

and you want me to try an H-7 which is 1.87 X2.85

That just doesn't make sence to me, please explain

I am making the assumption that you have all the following correct:

If that prop won't launch, then there are other problems. How much does the boat weigh ready to run? Won't be able to pull that prop if the weight is over 4lbs dry.

How is the fit of the engine? Does the Liner/Piston still have a tick at the top with the plug out?

Your pipe should be 8 1/2" to 8 5/8" with 65% nitro fuel.

Head Clearance should be .006" with the STOK head (still can't spell that word). Ideal compression ratio should 10.25:1 at .006".

You have taken on the hardest class that there is..... EVERYTHING must be perfect for a .21 to be really good.

 

[John Knight]

Rick:
Suggest that you set up the boat exactly like this: http://rcboat.com/setup.htm and then get an H7 and run it stock. Should be very good running boat then.

Marty Davis

Sounds good Marty, will check measurements agains this set up sheet.

But I do have a question, if the boat/engine combo will not launch, get up on pipe with the smaller diameter, and pitch of an H-4 @ 1.68 X 2.6 or a 1445 @ 1.77 X 2.48

and you want me to try an H-7 which is 1.87 X2.85

That just doesn't make sence to me, please explain

I am making the assumption that you have all the following correct:

If that prop won't launch, then there are other problems. How much does the boat weigh ready to run? Won't be able to pull that prop if the weight is over 4lbs dry.

How is the fit of the engine? Does the Liner/Piston still have a tick at the top with the plug out?

Your pipe should be 8 1/2" to 8 5/8" with 65% nitro fuel.

Head Clearance should be .006" with the STOK head (still can't spell that word). Ideal compression ratio should 10.25:1 at .006".

You have taken on the hardest class that there is..... EVERYTHING must be perfect for a .21 to be really good.

Marty,

The AB Fat pipe require a much shorter length that most any other pipe. It is at least .5" shorter than the AB 21S (short) or AB 21L (long). 8" is the longest he should be trying with that pipe. Been there, done that.

John

 

[FloridaScaleBoater]

Rick:
Suggest that you set up the boat exactly like this: http://rcboat.com/setup.htm and then get an H7 and run it stock. Should be very good running boat then.

Marty Davis

Sounds good Marty, will check measurements agains this set up sheet.

But I do have a question, if the boat/engine combo will not launch, get up on pipe with the smaller diameter, and pitch of an H-4 @ 1.68 X 2.6 or a 1445 @ 1.77 X 2.48

and you want me to try an H-7 which is 1.87 X2.85

That just doesn't make sence to me, please explain

I am making the assumption that you have all the following correct:

If that prop won't launch, then there are other problems. How much does the boat weigh ready to run? Won't be able to pull that prop if the weight is over 4lbs dry.

How is the fit of the engine? Does the Liner/Piston still have a tick at the top with the plug out?

Your pipe should be 8 1/2" to 8 5/8" with 65% nitro fuel.

Head Clearance should be .006" with the STOK head (still can't spell that word). Ideal compression ratio should 10.25:1 at .006".

You have taken on the hardest class that there is..... EVERYTHING must be perfect for a .21 to be really good.

Marty,

The AB Fat pipe require a much shorter length that most any other pipe. It is at least .5" shorter than the AB 21S (short) or AB 21L (long). 4" is the longest he should be trying with that pipe. Been there, done that.

John

4"?? were are you measuring this from & to?

 

[John Knight]

Rick:
Suggest that you set up the boat exactly like this: http://rcboat.com/setup.htm and then get an H7 and run it stock. Should be very good running boat then.

Marty Davis

Sounds good Marty, will check measurements agains this set up sheet.

But I do have a question, if the boat/engine combo will not launch, get up on pipe with the smaller diameter, and pitch of an H-4 @ 1.68 X 2.6 or a 1445 @ 1.77 X 2.48

and you want me to try an H-7 which is 1.87 X2.85

That just doesn't make sence to me, please explain

I am making the assumption that you have all the following correct:

If that prop won't launch, then there are other problems. How much does the boat weigh ready to run? Won't be able to pull that prop if the weight is over 4lbs dry.

How is the fit of the engine? Does the Liner/Piston still have a tick at the top with the plug out?

Your pipe should be 8 1/2" to 8 5/8" with 65% nitro fuel.

Head Clearance should be .006" with the STOK head (still can't spell that word). Ideal compression ratio should 10.25:1 at .006".

You have taken on the hardest class that there is..... EVERYTHING must be perfect for a .21 to be really good.

Marty,

The AB Fat pipe require a much shorter length that most any other pipe. It is at least .5" shorter than the AB 21S (short) or AB 21L (long). 4" is the longest he should be trying with that pipe. Been there, done that.

John

4"?? were are you measuring this from & to?

Rick,

Typo - should be 8" from center of cylinder to the seam on the pipe. Honest to goodness, I have none of my 20 riggers that are over 8", all are less.

John

 

[Marty Davis]

Rick:
Suggest that you set up the boat exactly like this: http://rcboat.com/setup.htm and then get an H7 and run it stock. Should be very good running boat then.

Marty Davis

Sounds good Marty, will check measurements agains this set up sheet.

But I do have a question, if the boat/engine combo will not launch, get up on pipe with the smaller diameter, and pitch of an H-4 @ 1.68 X 2.6 or a 1445 @ 1.77 X 2.48

and you want me to try an H-7 which is 1.87 X2.85

That just doesn't make sence to me, please explain

I am making the assumption that you have all the following correct:

If that prop won't launch, then there are other problems. How much does the boat weigh ready to run? Won't be able to pull that prop if the weight is over 4lbs dry.

How is the fit of the engine? Does the Liner/Piston still have a tick at the top with the plug out?

Your pipe should be 8 1/2" to 8 5/8" with 65% nitro fuel.

Head Clearance should be .006" with the STOK head (still can't spell that word). Ideal compression ratio should 10.25:1 at .006".

You have taken on the hardest class that there is..... EVERYTHING must be perfect for a .21 to be really good.

Marty,

The AB Fat pipe require a much shorter length that most any other pipe. It is at least .5" shorter than the AB 21S (short) or AB 21L (long). 8" is the longest he should be trying with that pipe. Been there, done that.

John

I would suggest the 3280 OPS pipe or the Nitro Version AB Parabolic (Old Pipe).

 

[Marty Davis]

Rick:
Suggest that you set up the boat exactly like this: http://rcboat.com/setup.htm and then get an H7 and run it stock. Should be very good running boat then.

Marty Davis

Sounds good Marty, will check measurements agains this set up sheet.

But I do have a question, if the boat/engine combo will not launch, get up on pipe with the smaller diameter, and pitch of an H-4 @ 1.68 X 2.6 or a 1445 @ 1.77 X 2.48

and you want me to try an H-7 which is 1.87 X2.85

That just doesn't make sence to me, please explain

I am making the assumption that you have all the following correct:

If that prop won't launch, then there are other problems. How much does the boat weigh ready to run? Won't be able to pull that prop if the weight is over 4lbs dry.

How is the fit of the engine? Does the Liner/Piston still have a tick at the top with the plug out?

Your pipe should be 8 1/2" to 8 5/8" with 65% nitro fuel.

Head Clearance should be .006" with the STOK head (still can't spell that word). Ideal compression ratio should 10.25:1 at .006".

You have taken on the hardest class that there is..... EVERYTHING must be perfect for a .21 to be really good.

Marty,

The AB Fat pipe require a much shorter length that most any other pipe. It is at least .5" shorter than the AB 21S (short) or AB 21L (long). 4" is the longest he should be trying with that pipe. Been there, done that.

John

4"?? were are you measuring this from & to?

Rick,

Typo - should be 8" from center of cylinder to the seam on the pipe. Honest to goodness, I have none of my 20 riggers that are over 8", all are less.

John

John:

Can't argue with you about that. Just telling him what has worked for me. Don't want to says something that I am not sure of. Rick is a VERY good boater and I want him to have something that will work well for him. Besides, it is one more 20 hydro racer around here.

 

[FloridaScaleBoater]

OK All, I just came in from the garage, in it's stock form, the best I can get is .007" with no shims.

What is you'all's method of getting down to .006" or less?

Have also pulled my pipe into 8"

Marty, the boat less fuel, with a 1600MAH 6 volt pack is 5LBS,

Don't know were I can shave a pound out of it??

Hopefully I can give it a try this weekend

 

[Marty Davis]

OK All, I just came in from the garage, in it's stock form, the best I can get is .007" with no shims.
What is you'all's method of getting down to .006" or less?

Have also pulled my pipe into 8"

Marty, the boat less fuel, with a 1600MAH 6 volt pack is 5LBS,

Don't know were I can shave a pound out of it??

Hopefully I can give it a try this weekend

Rick:

You will need a lathe to either turn off some of the head or the top of the liner. If you turn off the top of the liner be VERY CAREFUL not to squeeze th liner in the chuck or collet.

I would say that you have somewhat of a problem with weight...

 

[BB Mods's]

Most liners have a slight "lip" on them, what I do is Lapp the top of the liner down till it just about touches the lip of chrome, that removes a few thou.

 

[Buckshot]

Most liners have a slight "lip" on them, what I do is Lapp the top of the liner down till it just about touches the lip of chrome, that removes a few thou.

?????

-Buck-

 

[Tom Foley]

OK All, I just came in from the garage, in it's stock form, the best I can get is .007" with no shims.
What is you'all's method of getting down to .006" or less?

Have also pulled my pipe into 8"

Marty, the boat less fuel, with a 1600MAH 6 volt pack is 5LBS,

Don't know were I can shave a pound out of it??

Hopefully I can give it a try this weekend

I just picked up a couple of 1600 MAH 4.8 volt packs for my 21 hydro and saved a bunch of weight there . As far as the machine work , IMHO I would take it off the head button , a lot easier. Do you have a lathe at the house or work ?..or send it on over i'll do it for you for FREE !!

 

[dwb2620]

If like you said you can get the head clearance down to .007 w/o the shims, that is a good thing. I would recommend running it at that setting and see how it runs. All of the suggestions from these guys are good. Listen to them. Dropping the head clearance should fix your launch issues. The engine is now making more power to get up on plane.

The .21 rigger can be one of the most exciting boats to run when they are setup right. And they can also be one of the most frustrating, when something is just a little out off! Small changes can make a huge difference on these boats.

David

 

[taber]

a mono and hydro are different animals.. you can get away with alot more clearance in a mono.. hydros need torque to get on plane.
and a pipe that is to long will cause you fits and chase other things as well.. put the pipe @ 8 and run it.

and if it won't pull a 1445 stock you better take a look at either the motor.. or the boat.. as that prop should pull without a doubt no problem. ..

one thing you didn't mention is your strut angle.. do you have any negative in it if so how much. 21 boats like alot of negative strut angle.. ( most anyway ) that helps on launch.. plants the nose in the turns ect. if you are trying to launch the boat with a flat strut that could be part of it.. remember a 21 has NO POWER.. so you do anything to make it harder and you will pull your hair out.

let me know what your strut is and if i can help let me know.

chris

Chris, per Bob Finns advise, strut is set with 3/32 shims under rear sponsons trailing edge of strut touching table IE: strut 3/32" deeper than rears with 1/2deg neg of angle

try this just to see.. anytime you put the strut lower than the rears that LOADS THE MOTOR MORE.. put the strut FLUSH with the rears and try a min of 1 degree negative angle.. let me know how that works.

chris

Chris do you mean flush with center of strut or bottom surface of strut ?

 

[FloridaScaleBoater]

a mono and hydro are different animals.. you can get away with alot more clearance in a mono.. hydros need torque to get on plane.
and a pipe that is to long will cause you fits and chase other things as well.. put the pipe @ 8 and run it.

and if it won't pull a 1445 stock you better take a look at either the motor.. or the boat.. as that prop should pull without a doubt no problem. ..

one thing you didn't mention is your strut angle.. do you have any negative in it if so how much. 21 boats like alot of negative strut angle.. ( most anyway ) that helps on launch.. plants the nose in the turns ect. if you are trying to launch the boat with a flat strut that could be part of it.. remember a 21 has NO POWER.. so you do anything to make it harder and you will pull your hair out.

let me know what your strut is and if i can help let me know.

chris

Chris, per Bob Finns advise, strut is set with 3/32 shims under rear sponsons trailing edge of strut touching table IE: strut 3/32" deeper than rears with 1/2deg neg of angle

try this just to see.. anytime you put the strut lower than the rears that LOADS THE MOTOR MORE.. put the strut FLUSH with the rears and try a min of 1 degree negative angle.. let me know how that works.

chris

Chris do you mean flush with center of strut or bottom surface of strut ?

Taber, thats a good question, I was just going to slam he thing all the way up, bottom of strut flush with the sponsons.

 

[John Knight]

a mono and hydro are different animals.. you can get away with alot more clearance in a mono.. hydros need torque to get on plane.
and a pipe that is to long will cause you fits and chase other things as well.. put the pipe @ 8 and run it.

and if it won't pull a 1445 stock you better take a look at either the motor.. or the boat.. as that prop should pull without a doubt no problem. ..

one thing you didn't mention is your strut angle.. do you have any negative in it if so how much. 21 boats like alot of negative strut angle.. ( most anyway ) that helps on launch.. plants the nose in the turns ect. if you are trying to launch the boat with a flat strut that could be part of it.. remember a 21 has NO POWER.. so you do anything to make it harder and you will pull your hair out.

let me know what your strut is and if i can help let me know.

chris

Chris, per Bob Finns advise, strut is set with 3/32 shims under rear sponsons trailing edge of strut touching table IE: strut 3/32" deeper than rears with 1/2deg neg of angle

try this just to see.. anytime you put the strut lower than the rears that LOADS THE MOTOR MORE.. put the strut FLUSH with the rears and try a min of 1 degree negative angle.. let me know how that works.

chris

Chris do you mean flush with center of strut or bottom surface of strut ?

Taber, thats a good question, I was just going to slam he thing all the way up, bottom of strut flush with the sponsons.

Correct. Bottom of strut to bottom of sponsons. Go with the .007 clearance too.

 

[FloridaScaleBoater]

a mono and hydro are different animals.. you can get away with alot more clearance in a mono.. hydros need torque to get on plane.
and a pipe that is to long will cause you fits and chase other things as well.. put the pipe @ 8 and run it.

and if it won't pull a 1445 stock you better take a look at either the motor.. or the boat.. as that prop should pull without a doubt no problem. ..

one thing you didn't mention is your strut angle.. do you have any negative in it if so how much. 21 boats like alot of negative strut angle.. ( most anyway ) that helps on launch.. plants the nose in the turns ect. if you are trying to launch the boat with a flat strut that could be part of it.. remember a 21 has NO POWER.. so you do anything to make it harder and you will pull your hair out.

let me know what your strut is and if i can help let me know.

chris

Chris, per Bob Finns advise, strut is set with 3/32 shims under rear sponsons trailing edge of strut touching table IE: strut 3/32" deeper than rears with 1/2deg neg of angle

try this just to see.. anytime you put the strut lower than the rears that LOADS THE MOTOR MORE.. put the strut FLUSH with the rears and try a min of 1 degree negative angle.. let me know how that works.

chris

Chris do you mean flush with center of strut or bottom surface of strut ?

Taber, thats a good question, I was just going to slam he thing all the way up, bottom of strut flush with the sponsons.

Correct. Bottom of strut to bottom of sponsons. Go with the .007 clearance too.

Got it, On it!!

Hopefully on to better things

 

[Chris Wood]

try this just to see.. anytime you put the strut lower than the rears that LOADS THE MOTOR MORE.. put the strut FLUSH with the rears and try a min of 1 degree negative angle.. let me know how that works.

chris

Chris do you mean flush with center of strut or bottom surface of strut ?


if you run a center shoe yes.. as low as it will go or flush.. if you don't have a center shoe make sure it is flush with the rears.. i run 1.7deg negative on my own 21 boats..

chris

 

[JRXHydros]

I use lipo to save weight

 

[FloridaScaleBoater]

B) B) B)

Well guys, all I can say is, thanks for all the advice.

What I ended up with is this

Head clearance at .009" (but taking a plug out every other run)

Pipe at 8" (AB 21 fat)

stock 1445 (raised strut to above the rear sponson bottoms)

Will not run with a Sholund 1445 W/3.2 pitch It seems to be right on the edge of running this prop though, launches & picks up good speed till the prop bites then drops off and will not come on pipe

I think the biggest difference was the strut adjustment and the fact I think I was starving the engine for air.

I started out running without the cowl, got it running good, put cowl back on it, it did stay on pipe, but wasn't as fast as without it.

SO, started boring holes in it were I could to get as much air, without allowing water to get to the carb.

Now, on to some tweeking. One thing I noticed, is it seems the rudder is awfully long, with the prop sitting vertical the rudder is 1-1/2" below the prop.

Is that too deep? What are you guys getting away with.

I think I could take some length off of it, it turns on a dime, and I have adjusted MOST of the rudder throw out of it and it still turns tight.

Again guys, thanks for your help, bring on some more info. I still got along way to go before I will be able to hang with Brett English

 

[John Knight]

Rick,

Sounds like you are getting much closer. For changes at this point:

* Richen up the needle. Burning a plug every other run is just on the lean side. You shortened the pipe up so it need a richer needle.

* Try the H-4. It does not load the engine as much as the 1445.

* Cut the rudder off about .5" below the water inlet on the blade. A 20 rigger normally will turn on a dime and requires much less of a rudder than their big brothers.

If these changes work well, look at reducing the pipe length at 1/8th" increments until it will not launch. You may well find that will be inside of 7.5".