JAP/JAE .12G construction

[mtruex]

Just a comment for those as new to building/driving as myself (and this doesnt appear to be on the plans)....
Rod instructed me to go w/a 3pc sponson tube design, with the idea that if/when I hit something, I'd brake the middle tube, and thereby save my boat and sponson from damage. The piece glued into the tub and the piece glued into the sponson are smaller, the middle section middle between the tub & sponson is larger dia.

This worked exactly as promised a few days ago.... I wanted to show off parking it at the end of a run, and held WOT til @30 ft from shore and tried to kill it.... the throttle servo had died (HS-85) and before I could react further, the boat had run up on the sandy bank. Tubes broke... no other damage... made new tubes in @1hr that evening (I'm slow) & scavenged a servo from my .21.

However, IF you drive your boaty into a large wooden frame around a drainage pipe :huh: :lol: This could happen:

 

[TCHedOff]

Ah no biggy Martin.... I KNEW I do this sooner or later! :lol:

And "YES, I HEARD you Larry": "Dont get too close to the shore… dont get too CLOSE TO THE SHORE!! Then a "big BANG!!!!!" :lol: :lol: That's why I built these:

Just need to put bottoms on the green set - the red/white/ & green/white were from when I was testing colors... just need to sand 'em & paint 'em & trim the "overhang" before my next "Oh, Oh!" :lol:

Note the stick construction.... I have 3 vertical formers - no wood over foam and this was Rods advice.

If you look closely, you can see I doubled up on ply on the inside of this second set of sponsons (where the tube goes thru).... the one I broke was single 1/16 ply (and the inserted tube it DID come loose once and needed to be re-epoxied).

 

[TCHedOff]

Lastly, IF you KNOW you're an IDIOT, you have one of these sitting for the "BIG OH NO!" :huh: :lol: B) !

That red ISNT paint... it is an alcohol based red dye.... the alcohol evaporates, and only the pigment is left . That beautiful red color and it hasnt even been cleared yet!! I expect this one to be lighter than my painted one.

 

[kcvnd]

Martin,

I noticed in the video of your rigger and in the picture you posted the shape of your sponsons are a somewhat different from the published plan. They look to have the same length, but seem to have wider shape. Is this a variation of the same theme ie same riding surface. I like the looks of the wider sponsons and was wondering if there are plans for those? Thanks

Cheers,

Kevin

 

[mtruex]

Martin,
I noticed in the video of your rigger and in the picture you posted the shape of your sponsons are a somewhat different from the published plan. They look to have the same length, but seem to have wider shape. Is this a variation of the same theme ie same riding surface. I like the looks of the wider sponsons and was wondering if there are plans for those? Thanks

Cheers,

Kevin

there is no plans,they have the same inside shape and same bottom, just the top is wider..use the template for the inside and bottom, glue on some foam and hit the foam on the belt sander until your happy with the shape ..you can use your imagination, just stick to the basic rule of keeping everything flat..they dont run any different at all..

 

[Geraghty]

Martin,
I noticed in the video of your rigger and in the picture you posted the shape of your sponsons are a somewhat different from the published plan. They look to have the same length, but seem to have wider shape. Is this a variation of the same theme ie same riding surface. I like the looks of the wider sponsons and was wondering if there are plans for those? Thanks

Cheers,

Kevin

Kevin,

I will answer this since I drew the plans.......there are no other published sponson plans.....the sponsons in the video and the sponsons on the plans are virtually identical.I believe Martin just made some wider top sheeting on the sponsons in the video.

The boats footprint on the water and the width of the riding surface dimensions of the boat on the plans,and the boat in the video are identical.

There are slight dimensional differences between the boat in the video and the boat on the plans.....I.E. the tub profile shown on the plans is a bit different from the boat in the video because we wanted a $4.99 Sullivan fuel tank to fit in the boat rather than having to buy a $60.00 custom made fuel tank.

Later,it will be easy to just make a set of wider sponsons to test.....Thats a piece of cake....just cut the foam or make the sponson bulkheads wider...DO NOT MESS with the flat running surfaces on the sponsons or the rear ski.... <_< ...99.9% of the JAP boats success is because of those dead flat running surfaces.

I really recommend that you build the boat as in the plans first and go out and run the boat....get a performance baseline before you start making changes.That way you can always return to the boat in the video ..... B)

enjoy......Rod Geraghty

 

[kcvnd]

Martin,
I noticed in the video of your rigger and in the picture you posted the shape of your sponsons are a somewhat different from the published plan. They look to have the same length, but seem to have wider shape. Is this a variation of the same theme ie same riding surface. I like the looks of the wider sponsons and was wondering if there are plans for those? Thanks

Cheers,

Kevin

Kevin,

I will answer this since I drew the plans.......there are no other published sponson plans.....the sponsons in the video and the sponsons on the plans are virtually identical.I believe Martin just made some wider top sheeting on the sponsons in the video.

The boats footprint on the water and the width of the riding surface dimensions of the boat on the plans,and the boat in the video are identical.

There are slight dimensional differences between the boat in the video and the boat on the plans.....I.E. the tub profile shown on the plans is a bit different from the boat in the video because we wanted a $4.99 Sullivan fuel tank to fit in the boat rather than having to buy a $60.00 custom made fuel tank.

Later,it will be easy to just make a set of wider sponsons to test.....Thats a piece of cake....just cut the foam or make the sponson bulkheads wider...DO NOT MESS with the flat running surfaces on the sponsons or the rear ski.... <_< ...99.9% of the JAP boats success is because of those dead flat running surfaces.

I really recommend that you build the boat as in the plans first and go out and run the boat....get a performance baseline before you start making changes.That way you can always return to the boat in the video ..... B)

enjoy......Rod Geraghty

Thanks Martin and Rod! The boat looks great and by making everything so simple, I think you have really upped the fun factor for everyone. Can't wait to get to the lake with it!

Cheers,

Kevin

 

[Geraghty]

Thanks Martin and Rod! The boat looks great and by making everything so simple, I think you have really upped the fun factor for everyone. Can't wait to get to the lake with it!

Cheers,

Kevin

buildin' is twice as much fun as buyin' ........Enjoy the build.........Rod Geraghty

 

[Eric Perez]

I got the plans, thanks Rod.

I've got some quick questions before I start the project.

1. What's the target CG of the boat?

2. Wich of the (4) attachement points should I use to attach the turn fin to? I'm planning on using the grim racing turn fin for the miss vegas.

3. What size servos do you recommend for throttle and rudder?

Eric Perez

 

[Geraghty]

I got the plans, thanks Rod.
I've got some quick questions before I start the project.

1. What's the target CG of the boat?

2. Wich of the (4) attachement points should I use to attach the turn fin to? I'm planning on using the grim racing turn fin for the miss vegas.

3. What size servos do you recommend for throttle and rudder?

Eric Perez

1.There is no target CG on the boat....It is not important.Build per the plans and forget about a CG point.I know this sounds strange but it isn't

necessary to know a specific CG.The CG sweet spot is about 8" wide.

2.Just drill up the turn fin to match the spacing on the sponson attachment dowels.[1" centers.]You will be using the atachment points on the sponson to determine how sharp you will want the boat to turn.Try them all.

3.I use the Hitec HS-225B for rudder and the Hitec HS-85MG for throttle......any micro servo will work for a 3rd channel if you use one.

 

[Eric Perez]

I'm starting to get parts pulled together for the JAP 12G...

Has anyone run a "sport" engine yet with this hull? I've got a new OS 18CVRM's that I would like to use...You guys think I will be able to swing either a 1440 or the V937/3. Is there a different prop recommended for the JAP 12G when using a mild power setup?

How much engine do you need to pull a 1440 behind this boat? I mean is this considered a monster prop?

Is the 1440 comparable in load to an Octura X637/Y536 or Prather S215 ? I know that in my previous experience it takes a very free hull to launch the V937/3 are the 1440 the same?

I Sure have a lot of questions today :blink:

 

[opio]

im not sure about the other props but i run a 1440 on a cvrm in my fire fighter rigger and it hauls the mail.

 

[Eric Perez]

im not sure about the other props but i run a 1440 on a cvrm in my fire fighter rigger and it hauls the mail.

Any mods to the 1440?

 

[mtruex]

im not sure about the other props but i run a 1440 on a cvrm in my fire fighter rigger and it hauls the mail.

Any mods to the 1440?

the 18 should spin them with no problem at all..

 

[Ron Olson]

I spun the X-437, 438, 637 and the Prather 215 on my .12 'rigger that had a Trinity/Picco/Nova Rossi in it so your .18 should spin it with no trouble. I found the 215 to make it a very driveable boat. Once dialed in you might find the V-937/3 or V-940/3 hot props for it although they're a little harder to get up on the pipe. When they get going it's like kicking in the secondaries on a 4-barrel carb!

 

[carlnoki]

Just got all the wood for the new 90 JAP rigger and getting ready to start tracing out the parts AFTER mothers Day.

Notice i said AFTER Mothers Day. Don't want to tick off the bank ya know.

Carl

p.s. i know this is the thread for the 12G.

 

[opio]

im not sure about the other props but i run a 1440 on a cvrm in my fire fighter rigger and it hauls the mail.

Any mods to the 1440?

no mods, just balanced and sharpened im to scared to mod one lol

 

[JoeWScott]

I'm building a JAP boat too, but I enlarged the plans and transposed the .12, get it?

Thought I would share a building technique I've used to build sponson's, I assume it's been done before. I cut my sponson sides on the bandsaw 1 at a time. I'm good with the saw, but the profiles are not EXACTLY the same. So, I double side tape them all together & finish them off on the disc belt sander, the result is 4 identical sponson sides, works like a champ, give it a try sometime.

Now my question. Is the overhang on the tub bottom as neccessary as the overhang on the sponson bottom's? It's just a personal thing, but I like the "look" of the tub to be flush.

joe

 

[TCHedOff]

Thought I'd bring this thread back up, as I've now had a chance to run my lil .12 JAP thru maybe 20 tanks of fuel.

In the video I posted in this forum, the motor wasnt broken in and running very rich; I was running a full blade 1440 prop; "Texan" pipe at 7-1/4"; on 60%.

Since then, the engine (3 port NR from Glenn Q) has come alive much better (took @15 tanks!), and I can actually start my engine w/o having to loosen the plug; I sent my 1440 back to Mark Sholund and he backcut the prop for me; and I've gotten my pipe down to 6-3/4" (I also fixed some positive angle in the strut both... Rod & others noticed that just from how the prop spray was coming off the boat!)

The boat is now quite a bit faster!!! (And I'll post another video of it next time I'm at the club pond for comparison) - SO much so that the turn fin started to not hold it tight in turns (I had bought a turn fin before the plans were released and it didnt have a curled bottom, so I just angled it - it stuck 1" below the bottom of the sponson).

I've since made a turn fin from .060 thick 605 aluminum (got a sheet of scrap from a local metal company @14"x14" for $4!) and made it as shown in Rod's plans AND I made this one curled! To do it, I applied masking tape to the cut out fin, marked 4 lines @ 1/8" apart that ran parallel to the bottom edge - starting about 1/4" from the bottom edge - each line @ 1/8" higher, and used my vise to hold the fin at each line and used a piece of scrap wood & a hammer to bang 4 successive bends to form a curl. Worked slick as .... and the handling has improved dramatically over the angled turn fin. Not only corners better, but has less tendency to bounce on waves - the curl holds it down. So I encourage anyone that is afraid to try making a turn fin (like I was) to TRY IT! It turned out to be easy.

Another comment, I smashed my 1st sponsons up.... the 2nd set has a much higher AOA (just over 6*) which ran fine on Larrys test pond but last Sunday at the club race - in the 20MPH winds and 2"+ waves - it became emminently clear this is too high of an AOA for those conditions (boat would bounce up into the air).

Oh yeah, another thing! If you go w/Glenn's Texan pipe (I'm happy), you may find the backpressure is so strong, it likes to blow the pipe out of the coupler.... Rod gave me some good advice for this! Make a "lip" on the pipe. In my case, I just used some copper wire, and soldered it around the pipe to make a lip.

 

[goldorak]

Hello,

Someone (Rod, Tchedoff) can pinned the turn fin plan.

Regards.