JAE .21 brass sponson tubes

[tmunn]

Guys, I have had really good luck with my jae and it has been run a lot and flipped and hit bouys etc....anyway what i have been experiencing is the brass tubes, although epoxied in place they tend to want to turn on me and come loose.The thing i see that is bad is that they really only get glued to the 1/8 ply in two places and the foam between the 1/8 ply formers.

I figure when you put the glue in the hole and then insert the brass tubing , most of the glue gets squeezed out of the holes in the ply and not much is left to wick into the wood and bite the brass where i have it roughed up.

The ones i have been re-epoxying , I have been extending the brass out past the outer ply and roughing it up for the epoxy to get a bite on the outside of the sponson and the brass at the same time, making an epoxy washer if you will .That seems to work.

Someone at the last d11 race while they watched me repair my sponson by using ca and drilling down through the top of the sponson through the wood, foam , brass and Cf and then screwing in a 4-40 socket head cap screw(which is still in there until i do the better repair),,,,,said they saw or read on here that some people have soldered a washer on the end of the brass tubing.I would assume this was done and the tube pushed in from the outside, the washer being epoxied to the side of the sponson.

If i was doing building another set of sponsons i would make a balsa frame inside for the brass or make some doublers for inside the sponson for the area where the tubes go through Or drill down from the top and leave a cavity in the foam around the tubes and fill it with slow west epoxy.

I still could drill down from the top ,some holes and fill with epoxy since the boat is getting fresh paint for 2012.I found the Ninja green a bit hard to see last summer .

I was curious to know what you guys have done to keep the brass secure.I know of two other boats that have had the same issue.I think the load on those brass tubes is too great for such a small area of contact between the ply/foam and the brass.

Thanks for your time.

 

[moparbarn]

terry, i have done a "washer style" upgrade on my jae. that may be what you have heard or read here, i have posted it before on here. what i did was cut a piece of brass sheet into a plate to drill a sponson tube size hole in that will fit inside a jae sponson. shape isn't really important (it won't be seen ), as long as it is large enough to spread some load to the sheeting. i solder it to the brass tube in a position where it will be sandwiched between the inner sheeting & the foam. i thought about on the outer side of the foam, inside the sheeting, but worried about the foam compressing under a load. that way, it would have to separate the entire side sheeting to pull loose. i haven't been easy on mine either, bouys, blowoffs - you name it, no issues so far . the only drawback to this is it's not a repair, but something to incorporate into the sponson build. btw, any plans to make it down to the states for some racing this year?

 

[Blackout]

This is what I do on all my JAE Zippkit sponsons.

After the sides dry, I use a knife to cut a notch above the sponson tube like shown below. Then I glue in a block of bass wood with 30 minute epoxy. I use a rat tail file to make an oval in the bass wood to sit over the tube nicely.

10mm 180 grain flat nose bullets make good weights for gluing.

 

[Paul Traufler]

Or you can drill out a hole in the sponson for a 3/8 dowel and then drill that dowel for the brass tube. This way the dowel is what really is holding the brass tube. Use hard wood dowels. Fast, easy and simple to do.

Paul

 

[moparbarn]

both good ideas, they will strengthen the boom tube mounting bond. but, imo no matter how well you scratch up a piece of metal, the epoxy bond to it is never as strong as one on something that the epoxy can "soak into". with my system, the shear load is on the brass to brass solder joint, not the epoxy to brass joint. the lateral pull is now distributed over a MUCH greater area by the plate inside the sheeting. btw, i did not drill the hole in my plates, i punched them with a gasket punch on a block of pine. that way the punch "flared" a slight edge when it pushed thru into the soft pine. gave me more surface area around the solder joint for strength. i faced this lip towards the foam, so the sheeting would still lay down nicely.

 

[Jim Mamaril]

I made these inserts for all of my JAE's, they don't move at all.

 

[Jeff Barnhart]

I made these inserts for all of my JAE's, they don't move at all.

These work very well.

Another option would be to buy some carbon-fiber tubes that fit over the tubes you have going through the tub. Drill the hole in the sponson through the other side of it. Then cut a notch out around where the holes are, glue some wood inside the sponson similar to what is shown above then re-drill the hole through the new wood you just put in the sponson and glue the bigger carbon fiber tubes into the sponson.

You can then attach them the same way you do currently without redoing all your booms and the carbon should not pull out if it is epoxied in the wood well.

 

[moparbarn]

VERY nice idea, jim B) ! easier to install than my deal, & can be retrofitted, too.

 

[Martin Hamilton]

I now put 5/8" hardwood dowls in the polystyrene then put both ply sides on, that have a smaller hole the size of the brass tube. This way the dowls are in between both ply sides & cant turn or come out with a lot of surface area epoxyed to the ply & polystyrene. I also do the same on the fin with the dowls inside the ply sides with tapped aluminium inserts that has a flat head coming right through from the outside of the sponson & works a treat. Martin.

 

[camaroboy383]

i was gonna mention jims idea.... its a great one..... if you have access to a lathe your in... if not you would have to have them made....... terry if you run into a jam i can make them for you.......... i also like robins idea... but again like he said,,,its kinda somthin you wanna do when building the sponsons......hope to see you in mansfield this year my friend,,,it would be good to see you again... tell zach and mike to come too.......lol

 

[moparbarn]

namba nats are in the n.e. this year, maybe we can all play . a few of us have been talking about making the trip.

 

[camaroboy383]

that would be awsome robin..... if you came up this way....... be good to finally meet you in person........

 

[anthony_marquart]

I only have ever had problems with the rear turnfin insert. I don't know that it's really needed to add these things to all sponsons.

 

[Martin Hamilton]

Ive pulled the screws out of the dowl on the fin with the side loads in sharpe turns, ive also moved the brass tubes in the sponsons pushing them backwards & splitting the ply in fairly light contact. Martin.

 

[tmunn]

I will check out the thread when I get home.I cannot see the pics from this PC.I would incourage anyone that would like to come to the Namaba Nats in Dover NH do do so.It is the closest that i will ever be to one so I would not miss the chance to go to it.

Alden,

Hope My racing in the nats goes better than that day in CT and Thanks again for getting those plugs to me that day.I have the last of my aqua 18 engines and parts that i am selling of.Pm me if your are interested and i will give you the details.

Robin,

I think you would like the place NH to race.It should be much cooler that virginia in the summer and the drive should not be too bad.

 

[Martin Hamilton]

If you have problems with the brass tubes bonding in the sponsons something we do in Europe on our tetherd hydros which is widely used is bind the outside of the brass tube with wire & solder it on. Our tether boats use piano wire boom tubes,1/8"diam on .21 up to 3/16" on .60 motors.These are bonded into hard wood dowels that are bonded into balsa sponsons but with fatige,vibration etc the bonded joints start deteriating over time.The part of the piano wire that goes into the dowel we bind with wire to form a spiral along the piano wire around 1/8" apart on the spire (so it looks like a thread)& then solder the wire spire in place.When this is bonded into the dowl you end up with more epoxy in the joint because of the spaces in the wire spire + the affect of a thread holding it in the epoxy. These dont come out or move. Martin.

 

[camaroboy383]

no problem terry....anytime you come down this way let me know if you need anything....maybe ill see you in dover this year,,,we will see........talk to you soon buddy......

 

[tmunn]

Jim, do you Make those aluminum do-dads to sell and would the inside be the same size as my 8 mm /5-16" o-d rods.I think your idea would be my quick fix for my situation .

I i could pop out my brass tubes and make a larger hole of the aluminum inserts and the run the cf through them fasten them like you did would would fine .

So nobody has sees where someone had fastened a washer to the outside of the KS brass tubing hey....

 

[tmunn]

i ordered a set of the hollow inserts from jim.That will fix it ...along with the fact that it neede a repaint so i drilled down through the top of the sponson to where the tube will go ans i will be putting some epoxy in the hole from the top during the install of the inserts.Why not it needed a repaint anyway...lol...if is seems like it is taking too much epoxy i will put a little dowl in the hole and cut it off flush with the top of the sponson and seal it.problem solved.

 

[Jim Caldwell]

I am using Binding Posts from Mcmaster Carr on my 8s JAE style rigger, they have #8 machine screws replace with SS screws.

Holding fine after one season of 85 mph laps at 15lbs.