Perfection to the core!










Dave Ronneberg, owner, designer and Berkut kit manufacturer - found these wing foams were cut better than he could cut them with 30 years and more than 30 sets of wing cutting experiences with a hot wire - recommends them for everyone.

Berkut wings, winglets, and canards are available. These cores are far superior to the original Berkut kit cores for several reasons. See below for specifics.

15 years ago, the cores for the Berkut kit cost about $2500 and still required all the work mentioned above. A full set of Eureka Cores are only $2999.  Give me a call or email me if you have any questions.

Click on the image below for more information on each product available for the Berkut

Wing Jigs Roncz Canard
Wing & Winglet Foam cores Wing Jigs Canard Foam Cores Elevator Foam Cores Canard Jigs
Winglet Jigs


How to make an order

First, download the form at the link below and complete it. You can either scan and email it back or mail it to the address on the form. Please don't send photos of the form.

Release form

Next, you have two options:

Option 1: Download the order form using the link below. Fill it out and and email it to the address on the upper right corner of the form.

PDF Order Form

Shipping and sales tax (for TX and NM customers) will be calculated when your order is received and will be emailed to you via a Paypal invoice for the remainder. Once you know the total, mail a check to the address on the form.

Option 2: Use the Paypal buttons below. Paypal will include sales tax (for TX and NM customers) but not shipping. Shipping will be calculated once your order is received and an invoice will be sent to you.

Note: there will be a ~2.9% fee added to all US orders and ~3.9% fee for international orders using Paypal.

Berkut Package Deal

Includes all wing, winglet, canard, and elevator foam cores


Aileron cutouts
Elevator Options

Berkut Wing and Winglet Foam Cores

Left/Right Pair


Aileron Cutouts

Berkut Canard Foam Cores


Elevator Options

 Berkut Elevator Foam Cores

Left/Right Pair

Elevator Options
Berkut Jig Package
Includes Wing, Winglet, and Canard Jigs
Berkut Wing Jigs*



Berkut Canard Jig Package


Berkut Winglet Jigs*



*Options with an asterisk have been modified from the plans in some way. I do not claim to have tested or proven the usability of any of these parts. I only provide these as a service. The builder is 100% responsible for determining their airworthiness. Use at your own risk!


Click on the image below to download a pdf showing all the foam parts and how they fit together for the Berkut.


Wings and Winglets

These wing cores come with a lot of the work already completed that had to be done by the builder with the original kit cores

Like all Eureka cores, they are CNC cut which results in virtually perfect sizing and surface finish for glassing (or applying carbon as the case may be). The original Berkut kit supplied cores came hotwire cut oversize and the builder had to use a large sanding block to sand them down to final size using aluminum templates. There were several reasons for this which were primarily intended to fix problems associated with cores hotwired by hand. This was a very tedious method that made an enormous mess. It also introduced the opportunity to damage them if you sanded too much in one place or if they weren't supported properly. Using a CNC hotwire eliminates the problems from hotwiring by hand. Eureka cores come ready to go without having to deal with this step at all.

The leading edges are already separated to expose the shear web face. The shear web face is already prepped and ready to apply the shear web to. With the original kit parts, one had to build a hot wire saw in order to complete this step. There is no need to build a hot wire saw at all with Eureka cores.

As an option, the aileron channels can be cut into the wings during the hotwire process similar to the way they are cut for the Long-EZ and Cozy. With the original Berkut kit parts, these channels had to be cut and shaped by hand by the builder after the wings were already built.

The electrical conduits are already cut in the wings.

Upper winglets are cut 3.75" long. The extra length is all at the top. This is easily trimmed to the proper length by the builder but it allows more options when for the tips. The plans have you cut them 47 tall and then add a 1 urethane block to the top. Im not sure what the purpose of the urethane tip is is but Ive had a number of builders ask me to leave them long so they dont have to add that piece later. Also, some people want to do different things with the winglet tip so this gives you more options. If you just want to stick to the plans you simply trim 3.75 off the top to make them 47 tall.

What are the differences between Berkut wing cores and Long-EZ wing cores?

Berkut ailerons are significantly bigger than the Long-EZ or Cozy. They are 6" longer in span and also wider over their entire length.

The Berkut airfoils on the wings and winglets are still modified Eppler 1230 airfoils and are very close to the Long-EZ but they are not identical. They also have different reference points for waterlines which causes the washout to be different. All new cut files were made to match the templates for the Berkut wings.

There are no lower winglets.

The wing trailing edge is completely straight with no kinks like the Long-EZ and Cozy have.

The spar cap troughs are deeper than the Long-EZ or Cozy.

Wings and winglets usually come as a set. If you need only one or the other, contact me and I can cut whatever combination you need.

Click on the image below for a larger view

Top of wing cores Another view of the top of the wing core Wing core leading edge

Shear web/spar cap area. Note radiused corners. Also note the perfect match of the plotted blue line on the paper with the foam core.
Wing tip core
Outboard wing cores showing the aileron, spar cap, and electrical conduit cutouts
Upper Winglets

Upper Winglets



Wing Jigs - Available Now

Precision CNC wing jigs for the Berkut are now available. These wing Jigs have been precision cut from 3/4" MDF using a CNC router. They are designed to work the same way the Long-EZ jigs work but they were developed by taking cross sections of a 3D wing model of a Berkut wing in CAD.  They are designed to be a tight fit to hold them firmly in place. A very flat building surface is required (not a shop floor as shown below).

Note: these jigs are a bit different than the way the Berkut plans show to do it. You'll have to use the jigging instructions from the Long-EZ plans. Measurement and setup information is available on request.

All Joiner plates are provided (also CNC cut). These fit into depressions milled into the jig itself to improve the alignment and strength of the joint. Joiners should be glued in place one one side and bolted on the other per the plans. Bolts, washers, and nuts are included to bolt one side of each joiner.






The Berkut canard is identical to the Long-EZ Roncz Canard.

Click on the image below for a larger view



The leading edges come already separated with the corners already radiused for the shear web. The dowel holes come pre-drilled to ensure perfect alignment of the leading edges.





The elevators are identical to the elevators for the Long-EZ Roncz canard.

I make 2 types of elevator cores for the Berkut, hotwire template elevators and contour template elevators. The hotwire template elevators are cut per the hotwire templates from the Long-EZ Roncz canard plans. The plans tell you to compare the elevators to the elevator contour templates and then sand them to shape taking into account 0.020" of skin thickness. I think the hotwire templates are were probably intentionally made oversized because the small, thin elevators are rather difficult to cut by hand. In fact, the plans tell you to cut them in 2 separate pieces and then micro them together. With the templates a bit oversize they are easier to cut by hand and it allows the builder extra material to be able to sand them to match. The contour template elevators I make are simply cut to match the contour templates to begin with. CNC allows me to make much more precise cuts and to cut material much thinner than would be possible otherwise. Some people still prefer elevators cut slightly oversized so I offer both.

Another thing CNC allows me to do is to cut the elevators full length instead of cutting them as 2 parts apiece as it says to do in the Long-EZ Roncz canard plans. This means you don't have to micro the 2 halves together to make each elevator. When I ship a canard, it comes with elevators cut full length. Actually they are slightly extra long to allow the builder to cut them down to fit exactly. When I sell the elevators apart from the canard, they are too long and skinny to ship full length so I have to cut them in half to make them less likely to be damaged in shipping.

Click on the image below for a larger view

Here is scale drawing of the elevator from the Long-EZ Roncz canard plans.
Note that you can see the thickness of the skin on top of the foam.
This is an example of a hotwire template elevator compared to the scale drawing from the plans.
Note that it doesn't quite fit within the inside skin thickness lines on the drawing.
This is an example of a contour template elevator compared to the scale drawing from the plans.
Note that it fits nicely within the skin thickness lines on the drawing.
Here is a hotwire template elevator (top) compared to a contour template elevator (bottom).




Canard Jigs - Available Now

All jigs, contour templates, and alignment templates for the Berkut canard are now available. This is a 12 piece kit that includes all of the following:

E - Canard Bottom Contour Checking Template

F - Canard Top Contour Checking Template

G - Elevator Travel Checking Template

H - Top Elevator Contour Checking Template

I - Bottom Elevator Contour Checking Template

J - 2 Outboard Mass Balance Mounting Jigs

L - 4 Elevator Mounting Templates                      

M - Canard Tip Shaping Template

These are all precision cut from 1/2" MDF using a CNC router. 








Winglet Jigs - Available Now

These jigs are used for doing the outside skin layup on the upper winglets. The foam scraps included with the winglets are used to do the inside skin layup. The jigs are precision cut using a CNC router from 1/2" MDF.