Building sponsons with CA part 1

Here's another set of pics and some info that I published a few years back in the gallery section of International Waters forum. The original link is to the right marked as "Kep's 21 build tips #2" or you could just klick here.

As mentioned the pics and texts where done a few years back. The actual design of the sponsons in the pics is pretty similar to the ones in the original Kep's Freebie PDF drawings.

Today I would not build them exactly like this with chine-angles and non-trip angles etc but I hope you find the info and pics somewhat inspiring at least!?

Building is fun! :)

Also read my earlier blog about the glue test.

Couldn't live without them, Great Planes bar sanders - I use almost exclusively 80 grit paper.

Sponson templates made from 1.5 mm plywood. The drawing is glued on with spray cement. Be very careful when cutting them out. Cut them on the inside of the outline. I make my boat drawings in Illustrator.

Template with 1 mm holes for making a punch hole to the plywood sponson insides.

A set of inside parts for 4 pairs of sponsons. Its way easier and faster to do more then one set at a time. The plywood is hold together with pieces of carpet tape.

Divinycell H60 closed cell PVC foam core material. In this case for building a pair of .21 size sponsons. Works very well with normal CA glue if "right" technique is used. When I have tested - CA glue makes a superior glue joint when skinned with plywood vs epoxy glue - on Divinycell H series that is...

4 left and 4 right inside plywood parts after they are "broken" apart. R = 2.5 mm & L = 1.5 mm.

2.5 & 1.5 mm thick.

Another view of the plywood insides. Ready to be CA glued to the foam core.

Use the inside sponson template and make a rough outline on the Divinycell foam. Vacuum the foam or blow the excessive dust away... Spray kicker on the plywood, then spread CA glue on the drawn line all the way around, then fill it in in a zig-zag "pattern" between the lines. Apply the "pre-kicked" plywood (kicker side down!) to the Divinycell. Then turn it upside down and push down. It helps if you have a flat surface of course and some plastic wrap or similar so you wont glue you sponsons to the table...


The CA glue has set.

Maybe I have used too much CA glue... Speaking of glue - I have only tested Great Planes Pro CA medium and slow + ZAP green + slow. They all work the same - no difference what I have seen. The slow/thicker one just isn't needed for how I work. If you're slow working or uncertain how well you will do, try out the slow curing ones. Make sure to add kicker to the plywood part (no glue added there).

After cutting the upper part away in the band saw, use the bar sander to smooth the top surface. Not important at this stage to make it perfect. Use the top view template and make a line for the outside cut.

Before you take it to the band saw again. Sand the outside and keep it at 90 degree measured from the bottom that is 90 degrees from the inside... Right!? When working in the band saw, check that it saws in 90 deg (adjust the baseboard of the saw). Pay attention to making the band saw cut as close as possible to he line and be smooth. The outside back-support wont need any sanding - it will support the ply good anyways...

I make an simple matching line with a pen on the foam. Its way easier to make it right as one doesn't have sooo much time as with epoxy...

After the band saw. Only 2 of these parts is used. The outside and bottom parts are used for support when gluing those plywood parts to the foam core.

The outside is here ready to have its plywood glued in place.

After the band saw. The outside is sanded smooth - the other parts are not sanded yet.

Ready to be glued. The guide line is on the inside of the plywood also - it just makes it easier. Kicker on plywood and CA glue on foam - press it together for about 60 sec. Use a little extra kicker if needed. Use a table fan to remove the glue and kicker odor...! BTW, use some throw-away vinyl protective gloves also.

The CA has set. The cut away foam part is used as back-support. Only hand/body pressure is used. No weights etc.

On this set of sponsons I used 1 mm plywood on the outside. When measured its 1.2 mm though. On the thick side I guess, 0.8 mm isn't a problem.

After the CA glue has set. The plywood isn't trimmed yet...

The top part is sanded smooth and in 90 deg to the inside. This is the guide lines for an chine-cut.

Short depth of field here - oops. The "curved" part here gives itself... Viewed dead on (from the front or back) its completely flat.

Bad picture... Just a view of the angled chine-cut before the plywood is glued. This "version" is perfectly straight and parallel to the inside. One can do them different or not at all... Its all up to you.

Stay tuned for part 2 within a few days...

Kep's .21 '09 in wood

Here's some pictures of some Kep's .21 ´09 riggers I built last winter. I built some extra boats and later on sold them like they're shown in the pictures to some new boaters in Eksjö. The boats below are exactly the same as the boats me and Mikael Sundgren have raced this season (but he didnt test his '09 until end of the season though).

I built them (last winter) with a rear ski/ramp set-up and I raced my own boat like that for the most part of this years season but for the last race of the season I took it off and mounted some old sponsons and it was way better. So just because you see the pics with the ski-ramp on it doesnt mean I recommend thats set up (on a Kep's rigger).

See THIS blog about my race experiences with the Kep's .21 ´09.


These "stealth" look sponsons are cool but they're a bitch to build... ;) There is no differences in how they work vs the other design you can see if you scroll down a bit...





Mikael Sundgren's rigger with these type of "stealth" sponsons.










Notice the small "hook" I've glued to the bulkhead. They're used as strap mounts to hold down the receiver. We dont use any lid cover for the radio compartment - only adhesive "tape" (it comes on a 2 feet wide roll and is used for covering books etc). So its nice to know the parts are hold down securely.

Here's the hook system for holding the RX battery pack (5xAAA NiMH cells). The hooks are made of K&S brass stips that are 0.8 mm thick (1/4" wide) and equally thick plywood.

Pre-drilled holes for S9650 servos for channel 2 & 3 and for S9551 on the steering. The short rear servo mount is made out of scrap pieces of the same 6 mm thick okumé/gaboon plywood as we use for the tub sides and bulkheads. If you look closely the top part is at 90 deg so the screws doesnt split the wood... ;) The other servo mount rails are normal 8x8 or 8x10 mm spruce.


This is the sponson design I have raced all season with. No chine angles what so ever and it works great. The need of chine-angles are way over rated. The rigger wont trip on these - I promise. :)

My race boat with these sponsons.

Glue test sponson foams

This is some "old" pics of a test I did a few years back when deciding upon the right way (for me) to glue the plywood skins on Divinycell H60 & H80 (or the equivalent Airex C70.55 or C70.75). These foams (cross-linked PVC) are very good for making sponsons and they can handle normal CA glue. In fact when I did this test it showed better glue joints with CA glue then epoxy actually!

These pics have been available all the time if you would have clicked the links to the right (Kep's 21 build tips #2) ->

Glue test, Divinycell H80 to the left & H60 on the right. 0.8 mm plywood. Great Planes Pro CA kicker on foam (no glue pre-applied on the foam). Zap CA+ green on plywood. Will properly not work that good as the CA on bigger surfaces has time to sink into the plywood a little too much. Maybe could work better if an slow version of the CA is used. Left overnight to set properly (one wouldn't crash test a sponson after just a couple of minutes, right?) - it sat good after a couple of minutes though.

Glue test, Divinycell H80 to the left & H60 on the right. 0.8 mm plywood. No kicker used at all. Zap CA+ green on the foam (none on the plywood). Dont use this method - trust me. It seems the air in the foam pores makes the CA not to set at all it seems. After 3 minutes I could lift the plywood from the foam - nothing had happened. Left overnight to set "properly", well I hoped it had set by then... To my surprise it actually had. But the glue joint is no good.

Glue test, Divinycell H80 to the left & H60 on the right. 0.8 mm plywood. Z-poxy 30 minute. Left overnight to set properly. To my surprise, the glue joint was quite good... I had tested earlier with the 5 minute version and that was just a sad sight. With 5 minute epoxy it was just a "glue skin" on the plywood when bending it loose. With the longer hardening time the epoxy seem to creep into the foam making it a better glue joint.

Glue test, Divinycell H80 left & H60 on the right. 0.8 mm plywood. Great Planes Pro CA kicker on plywood (no glue on plywood). Zap CA+ green on foam. My favorite technique. It seems that when spreading CA over the foam one has the most time to line up the skin your gluing etc, but when assembled, it sets quite fast. Left overnight to set properly (for testing purpose - when actually building your sponsons you could move on with the build after a minute or two), it sat good after a couple of minutes though. Works equally good with GP medium CA or slow CA's if you need more time = bigger sponsons maybe...

Do note, I have not tested with any other brands of glue or kicker - thats up 2 U...

Solinger flywheel & stuff

The Solinger marine flywheel kits for car engines with "SG" shafts are finished and ready to ship. These will fit any .12-.28 sized motor with a SG car shaft and a normal 1/4-28 thread.

The flywheel also accept all flex shaft couplers with a 1/4-28 thread such as Octura and Aeromarine etc.

The pully groove is 1/4" wide so they will except all the standard starting belts.

And the best part is that Solinger sells them for only $10.00 USD + shipping!

Joe have also updated the .12 sized "JAE" motor mounts to "Rev 2" spec. Some material is shaved off so it fits in even narrower space. Threaded to accept std 4-40 motor screws. Still available at the same great price of $10.00 USD + shipping.

New from Solinger RC Hardware are these .21 sized "JAE" style motor mounts. They are also threaded for 4-40 motor screws. They cost $15.00 USD + shipping.

Contact Joe Solinger HERE.

New CMB 2010 engines

A New for 2010 CMB .91 VAC engine.


A New for 2010 CMB .21 RSV "EVO" Diretta (direct drive) engine.


A New for 2010 CMB .21 RSV "EVO" Riduzione (counter rotating for gearbox) engine.

Sorry for the bad quality pics - the original was quite bad...

CMB Valvola 2010

Mauro have released some new Valvola .21 parts. It's a new induction system with a reversed drum intake that shoots the fuel up directly to the ports. The crank shaft is balanced to. The drum seemt o have the ramp plug in aluminium and the over all weight of that unit seems to be much lower then the stock heavy drum. There have only been one batch produced so far for the counter rotating gearbox "V" motor but it will most likely be available in the direct drive motors also by 2010.

LINK to the German forum where I've found the pics and info.

Shelby GT500

A friend of mine in Sweden sent me some pictures of his soon to be Ford Shelby GT500 2010. The picture was sent from the US dealership where its just being prepared to be shipped over to this side of the pond. Hopefully it will be here just in time for a snowy Christmas. :)

It's hard to believe but Ford does not sell these in Europe!

We'll I had an hour to spend in Photoshop so I did these pics... Never done any full scale editing before.


This is the stock GT500 ride.


Slightly lower...


Even more lower and with slightly enlarged wheels... :)


Here's the stock picture before done by me in Photoshop.

JAE .12G updated PDF's

As most of you remember the JAE .12G rigger was at first named "JAP .12G". So I have now updated the PDF files to include the new "JAE" logos instead of the earlier "Jack Ass" ones... The pdf's themselves are the same as before. Just click on the text-link to the right (under "LINKS") and start downloading if you haven't already. :)

Earlier published JAE .12G info

More JAP/JAE .12G info

JAE .12G Freebie drawings 1of3

JAE .12G Freebie drawings 2of3

JAE .12G Freebie drawings 3of3