jae 21 g2 build changes ? ( mods )

[Thomas Hulbert]

Ok here it a mod info thread for those who have built a jae 21g2 kit and would like to share there changes that they did during there build and explain why they did the changes.

I know there has been a few threads about the jae kit before.

Seen posts of different sponson width, tub hight ( notched for pipe clearance ), driveline etc.

lets get all of the info into one thread to help out the new kits being built over the winter as I have seen alot of zipkits being given out as prizes at the races.

Thanks and let the build info flow for all of those who can use some more information.

 

[anthony_marquart]

As seen in other threads,.. I would recommend using a better sponson foam,. and maybe larger boom inserts in the sponsons,. And whatever you do, don't leave out the triangle stock in the corners.. (or it will fall apart) Of course, these are just my thoughts.. your mileage may vary!

 

[RodneyPierce]

Build it to the plans and keep it lite.... 3.5 pounds or less. You will have one heck of a boat.

 

[anthony_marquart]

I agree with RP,.. don't change the geometry if you can avoid it.. Lots of testing has gone into the design

 

[Jeff Schindler]

I like the blue foam no issues there. But, I do have some tips.

The turn fin on this design is very important, and getting it straight with the running surfaces sitting the same is the key.

These tips below will help get your there.

Sponsons:

1. Build the sponsons with the inside surface (as they are mounted on the boat) of each sponson on a flat surface. Line up the boom tube holes by inserting a long piece of the same size brass tubing that comes with the kit. Square that brass up with the flat surface and keep it there while the glue on the sides is curing. Remove the brass once all the wood is on the sponson (you may need to heat the brass if it is slightly epoxied)

2. Put the sponsons together inside to inside using the same brass tubes and sand them together so the running surfaces are the same (angle and wrt the holes). Resist the urge to glue the final brass liners in until after paint as its a pain to sand around them. Also you want to glue the brass liners in the tub and sponsons with the boat assembled and sitting on a flat surface.

3. Assemble the boat on a setup table (FLAT surface). Set both sponsons to have the same angle on the ride pads. I put a 2lb weight on the front of each sponson and crib up the underside to set the angles. The best way to measure them is using the rise over run and inverse tangent gives you the deg. Example: 9/32 = rise 4.25 = run ==> 3.8 deg which is great. If you need to oversize the holes to get them to match then thats ok, it actually gives a better glue joint. Now take it apart, scuff the OD of the brass with 80 grit, and epoxy them in, setting the boat back up exactly as the dry fit while the glue cures.

4. Glue a small block of wood under the rear brass tube. Make sue to notch the bottom side of the block so that water and oil can pass underneath it. This provides more rigidity right where it needs to be.

It looks like a lot, but its really not much work, and the boat will be setup perfectly if you follow these tips.

Thanks,

Jeff

 

[gooycheese]

i use 60 grit paper on the brass inserts and also use a file to put notches in the brass tubing.

 

[Neil LaGarry]

I go with the plans except page 11

I don't use a gig but I do clip on Aluminum bar stock to the sides and add weight to the top until dry

Build the sponsons in pairs and CK the angle ,by putting -em back to back #4 bottom plate in page 29 are the same.. I Dremal the brass pipes or file to ding the brass up except for the part that sicks out. of the sponson. then I use Popsicle sticks and rubber bands to hold top & bottom until dry.

 

[Blackout]

The blue foam and brass inserts work good.

While light is always good, build it strong. Don't skimp on epoxy and the wood triangle stock. Mine is heavy and runs fast. It's a very durable boat. I have crashed mine way too many times and it still runs great!

 

[Tim Kish]

If I build another I am going to try lowering the tub height , keeping all dimensions from the bottom up the same.

The tub is only 1/8 lower than my twin , you could save weight without sacrificing strength or performance.

Tim

 

[RodneyPierce]

Tim, I think you will find that lowering the tub height will only hurt performance. The higher tub height is a good thing. The further you can get the tub off the water, the better. Granted, there is a point where it loosens the boat up too much, but lower is the wrong way to go in my opinion.

 

[RodneyPierce]

Also, you would be amazed at how many ounces of weight you can save by wiping off all of the excess epoxy after gluing something, instead of just leaving it to dry...

Or better yet, use CA glue, and just seal with epoxy, once again, wiping the excess off.

 

[Tim Kish]

Tim, I think you will find that lowering the tub height will only hurt performance. The higher tub height is a good thing. The further you can get the tub off the water, the better. Granted, there is a point where it loosens the boat up too much, but lower is the wrong way to go in my opinion.

I would keep the ride height the same Rodney , just shave it off the top of the tub.

 

[RodneyPierce]

Tim, I think you will find that lowering the tub height will only hurt performance. The higher tub height is a good thing. The further you can get the tub off the water, the better. Granted, there is a point where it loosens the boat up too much, but lower is the wrong way to go in my opinion.

I would keep the ride height the same Rodney , just shave it off the top of the tub.

Ah, my mistake!! Then by all means!!! Sorry for the misunderstanding.

 

[Thomas Hulbert]

other than using triangle stock for joint reinforcement any thaught of using light cloth inside of the tub as well ( motor area and shoe box )

Have seen some transome issues with some wood boat builds ( seams letting go )

I have built a 21 whip and know to increase surface area for decking contact etc.

Some people even use glass for reinforcement as well.

Boom stiffiners is a good idea as I have seen some shatter when hitting a bouy.

Great start what else would people do differently to make it a better tub and sponsons.

Tim when you are in Hobart pick Olly's brain and see what he is going to do differently on his new build as well for me .

Thanks.

thomas

 

[Thomas Hulbert]

Tim, I think you will find that lowering the tub height will only hurt performance. The higher tub height is a good thing. The further you can get the tub off the water, the better. Granted, there is a point where it loosens the boat up too much, but lower is the wrong way to go in my opinion.

I would keep the ride height the same Rodney , just shave it off the top of the tub.

Ah, my mistake!! Then by all means!!! Sorry for the misunderstanding.

This is done instead of the notching of the motor area due to pipe clearance issues.

Tim I knew what you ment

 

[moparbarn]

i agree with jeff as to bracing the boom tubes in the tub. i do the front tube also. NO CA!! i prefer to build with all epoxy. my boat has hit more bouys than i can count (pilot error ) & has survived with just broken cf boom tubes. design works to protect the hull & sponsons, don't fool with it, use hollow tubes B) . i take brass sheet, cut "washers" out of it to fit inside the inner sponson sheeting. i place them on soft wood, use a gasket punch & make a hole for the boom tubes in the sponson to get soldered into. i like punching the hole, as it raises a lip for a good solder joint. this gets trapped beetween the inner sheeting & the foam. light, simple & not dependant on a brass to foam bond.......mine is not light, 4 lbs. 5 oz., but has survived 1 1/2 yrs. of my terrible driving (trying for lane 1/2, can't fit), & still smokes folks like marty davis & john knight. turn fin is critical, as in any rigger but this boat rides so light it seems touchier to the fin design & placement. this boat works well pretty much as it was designed.

 

[Jim Caldwell]

After reading all the posts on the brass tubes coming loose I used Binding Posts from Lowes, no problems at all after hitting everything in sight!

Check the servo mount WHILE holding the rudder to see if it is broken!!! LOL

 

[John Knight]

still smokes folks like marty davis & john knight.

Really?? Marty won the US-1 title at the Internats this year with better heat racing and time trial scores. I finished 2nd to Marty in the the heat racing portion and you did not finish high enough to qualify for the time trials portions. I did. I have more awards in B Hydro that you can ever imagine. The rod and piston broke in my 20 engine at the Internats and cost me big time in the time trials. We'll see next month in the Fall Nats.

 

[Ron Zaker Jr]

If I build another I am going to try lowering the tub height , keeping all dimensions from the bottom up the same.

The tub is only 1/8 lower than my twin , you could save weight without sacrificing strength or performance.

Tim

Tim,

While cutting down the profile of the tub will save some weight. I would find lighter materials to build with,that will save more weight in the end. FWIW.

 

[Neil LaGarry]

Tim's pretty fast. Ran by me like I was walking. I didn't see his.21 last weekend as he was getting ready for Hobart. I took home 3rd place. I was lucky

. Seen Terry Munn fly by me in a blur after getting lapped.