J.D. WOF 30" Tunnel build

[RobertDoak]

I can see the advantage of the longer hull..although the hotshot sprint is "fast" I know thats a relative statement, and the 24" is made for a stock engines...the extra 6" is clearly a plus..now im starting to inderstand why all the modern race tunnels are in this size range...I was able to do some sanding on the WOF and need another coat of filler primer...I have a race to attend so I will get to that after the weekend.

 

[RobertDoak]

Moving along ...I filled some low spots on the hull and primed it with white fill primer...next is another final sand with 400 paper then apply the color ...I'm thinking Jungle green on the top deck and white for the under side....
I also did some work on the engine...it will be a Thunder Tiger but with a modded Thunder Tiger BX-R 21 buggy engine...it has aggresive porting much like a Nova Rossi...and the engine is more setup for torque..I need to remove some of the cooling rings on the head and turn the outside diameter down on my lathe also order a header and find a carb that fits a 15mm hole..I will run a pipe but forgot who made it...

 

[Jerry Dunlap]

I had a DPI Interstate Batteries 20 Tunnel painted green and it was hard to see when it stopped on the race course. Of course the solution is to just keep running.

JD

 

[RobertDoak]

Thats a thought....jungle green is the brightest green I can find off the shelf...after this weekend racing I understand why dark colors should be avoided especially the bottom of the hull...the boat is all but invisible..thanks for the reminder J.D.
This is a sample of the green I plan on using

 

[Jerry Dunlap]

The green with white will have good visibility.

JD

 

[RobertDoak]

So I was able to do some engine work today..(I ran out of 400 wet)..
So what I'm doing is taking a thunder tiger .21 outboard and making the Thunder tiger BX-R .21 fit the outboard..
Alden Cost hooked me up with the specs and all.. And I bought the last two engines thunder tiger had...one a .21 bx R
And the other a 28 bx R...both share the same mounting footprint..just a larger bore and stroke..here is a couple pics of the machining I did...
Took 0.090" off the back plate pto ...
And removed all but 4 fins on the cooling head..and turned the whole cooling head down to 42mm

 

[Julio Almazan]

Hi Robert:

So I was able to do some engine work today..(I ran out of 400 wet)..
So what I'm doing is taking a thunder tiger .21 outboard and making the Thunder tiger BX-R .21 fit the outboard...Alden Cost hooked me up with the specs and all.. And I bought the last two engines thunder tiger had...one a .21 bx R. And the other a 28 bx R...both share the same mounting footprint..just a larger bore and stroke..here is a couple pics of the machining I did...Took 0.090" off the back plate pto ...

... You didn't need to change or modify the back plate?
Very good job...
It seems to me an interesting way to improve the Thunder Tiger .21 outboard

... And removed all but 4 fins on the cooling head

...and turned the whole cooling head down to 42mm

Did you turn the cooling head because of temperature problems?

 

[XtremeRcBoats]

nice work Robert, the pipe you have is an equi / equalizer pipe.

 

[RobertDoak]

Extreme..
Thanks ..I don't know too much about Equi...but will be finding out soon when I fire the engine up.....
Julio...its been a while hope all is getting better...
The cooling fins are cut yes for cooling issues....too many and the cylinder and combustion process wont come up to optimum performance temperature...
And of course too few will have over heating issues...
Also the PTO must be cut to ingauge the crank pin to spin the outboard...I will post before and after pics shortly...I still have piston and sleeve timing mods to make...
I was able to get more sand paper so I will continue with the boat..

 

[Julio Almazan]

Hi Robert:
Thank you so much for everything. For your interest and for all the clarifications you have made. Of course, I will follow the mods and photographs that you post.
This topic is very interesting. I will follow this post carefully.
Thanks for all

 

[RobertDoak]

Julio...
Anytime you have a question please ask..
You can also start a conversation and I can get more detailed as needed....

So I did a final 500 grit sand on the hull after work...and applied the Green to the cowling....im thinking of leaving the hull all white with some black trim..
I should be able to paint the hull tomorrow..

 

[RobertDoak]

Hey everyone....Julio...I mentioned a before and after pic of the backplate PTO. well Sir here it is.. .090" was removed to allow the crank pin to ingauge into the pto...notice the ring where I took off material...I left it slightly larger to insure a snug fit when the PTO is installed to the engine case.
I also painted the hull gloss white and will apply some Maxspray 2k clear on the hull and cowl...that will fuel proof the paint...

 

[Julio Almazan]

Hi Robert:
There is one thing that is evident: the years do not come alone ...
I checked these photos many times and only now (when you explain it to me so clearly) I notice the work done ...
I have taken note and I will try to do a job at your excellent level.
Thank you very much and keep up the great work.

 

[RobertDoak]

Hello everyone..
I was able to make some progress...
I had to create a cradle of some sort to hold an 8 oz. Fuel tank...so I opened up the fuel tank support and installed an oval tank..that way I will have room for the steering linkage...also while dreaming about running laps at my favorite pond..I installed the engine and im making ROOOM ROOOM sounds...
Also im awaiting a O.S. 20j carb.
I need do a 1000 grit wet sand apply some vinyl trim and then shoot the boat with some clear...(yes clear over vinyl..its o.k. to do that)..Oh...Julio...trust me..I'm no expert at machining...as a matter of fact..I haven't touched a lathe sense my College days..so here are a couple pics..
Until next time...

 

[Jerry Dunlap]

Won't be long before the "Rooom, Rooom" sound is being produced by a nitro outboard.

JD

 

[RobertDoak]

J.D...your so right...
But my timing is off...I was planning to have this completed a lot sooner but got side tracked...here in the Virginia area our scheduled racing is over and only a few test/tunes remain ... So the Roooom ROOOM may be bench tests...

 

[Julio Almazan]

Hi Robert:

..Oh...Julio...trust me..I'm no expert at machining...as a matter of fact..I haven't touched a lathe sense my College days.

... well, I'm in your same situation ...
Perhaps, we should take a lathe and do some practices, until we catch up again.
Winter, here in Spain, lends itself to do that ... I'll see ...

 

[RobertDoak]

Julio...
All the metal work is done on a 7x12" mini lathe I bought just for this project...I have some new tooling arriving on Wednesday..so then I will be able to actually finish the motor mods..
I was able to complete the radio box lid and servo tray..I think I will use the Sullivan golden rods for steering..I have seen many others use 2 wires with wheel collars as a connecting and adjustment point...it works just another point to fail...

 

[RobertDoak]

Well the Tunnel coming right along...
Last nite I was able to create a removable servo tray..mount servos and complete the radio box cover...I do need to seal both pieces ..also mounted the on/off switch and make necessary cuts on the cowl to enable full closure..weather today looks to be good so I will sand the boat with 1000 grit and prep for clear coat..pics will follow.

 

[RobertDoak]

Im using s3003's for mock up but will swap out a hi-tech 645mg for steering
133oz @6.0 volts...and keep the s3003 for throttle..