Minor delam repair?

Good info

So West Systems support has been very helpful with other projects I have worked on (epoxying in new foil wing stainless steel inserts into carbon fuselage), so I thought I would ask them about this delam repair. They directed me to their manual (see excerpt below). They said the problem with foaming urethane is it can cause more deck to delam. They said their 105-K repair kit was perfect for my use, as was SixTen epoxy using a syringe, and to make 2 holes on either end of the small delam (1.5" x3") and inject in epoxy in one hole until it comes out the other hole. The below manual excerpt is for fiberglass over balsa, but the support guy said it would work good on an EPS core too. Pictures did not get copied, but can get whole manual here: www.westsystem.com/wp-content/uploads/Fiberglass-Manual-2015.pdf

The problem people have mentioned here with epoxy is that it gets hot and melts the EPS, but that only happens if it pools into a big glob which will creat a runaway exothermic reaction that can reach 400 degrees! But as long as the EPS is solid, and you use weight on top of flexible foam to conform deck to dent in EPS, then you will only have a thin layer of epoxy that will not get hot enough to melt EPS.

So why is everyone here using the messy expanding urethane foam?, is it better for large patches?

West Systems 002-550
A guide to Fiberglass Boat Repair & Maintenance, Gelcoat Blister Repair and Final Fairing & Finishing with WEST SYSTEM? Epoxy.
Fiberglass Boat Repair & Maintenance

Section 5 Repairing Core Related Damage, pages 26-27

Repairing skin delamination
Skin delamination is often first noticed when you step on a flexible or spongy area on an otherwise firm deck. Most delamination is a result of moisture damage to the skin/core bond and usually involves balsa core or plywood cored panels. Moisture entering cracks or nearby loose hardware can migrate much more easily through these cores than a foam core. Also, balsa and plywood cores are much less expensive and more widely used than foam cores in production boats. Often the core material will be wet or even saturated, but it may still be serviceable if dried thoroughly. However, if a wooden core remains wet long enough, it will begin to deteriorate and will need replacement.
5.01
As mentioned in Section 1, the core material separating the two skins of a cored panel reduces the tensile and compressive loads on the skins and allows a structural panel to withstand greater bending loads without a proportional increase in weight. To do this, the core material must remain bonded to both skins and be able to resist compression loads applied by the skins when the panel bends.
The previous section provided procedures for the repair of damaged skins. This section describes how to restore the core-to-skin bond and/or the structural properties of the core. Although the skin itself may not be damaged, it may be necessary to cut or remove a portion of the skin for access to the core. Repair or replacement of core material nearly always involves some degree of skin repair, requiring you to refer back to the procedures in the previous section.

Types of core related damage
Core related damage can vary from a small skin delamination with little or no actual damage to either the core material or skins, to moisture related core deterioration, to collision damage that can leave a hole through both the core and the inner and outer skins. The repair procedures in this section begin with the least damage, easiest to repair:
1. Repairing skin delamination. Often the core is wet, but still firm and usable. A delaminated area may be several square inches or several square feet.
2. Replacing damaged cores. The skin may be intact, but moisture penetration over time may have caused the balsa core to deteriorate. An impact may puncture the outer (or inner) skin and core without affecting the other skin. Even a minor puncture can allow moisture to migrate under the skin and affect strength of the core over a large area.
3. Repairing transom delamination. The plywood core may delaminate or rot as a result of moisture penetration through a crack or hole in the transom skin.
4. Repairing holed panels. An impact or modification can require rebuilding of the entire panel structure. Impact damage can extend to both skins and core or, one skin with major core damage.
The work required to repair each type of damage varies with the size of the damaged area. Often, the full extent of damage cannot be determined until you have removed a portion of the outer skin as described in Section 4.1-Assessing and preparing the damaged area. After a thorough inspection and assessment of the damage, follow the procedure that is most appropriate to your situation and keep in mind that the objective is to restore the structural properties of the panel by rebuilding the load carrying ability of the core and the skins to the original or greater strength.

5.11
Delamination can also occur in isolated pockets as a result of inadequate core bonding during manufacture. In some cases, the core may remain dry and undamaged, and simply need re-bonding.
Assessing delamination damage
The first step in the repair is to determine the extent of delamination and the condition of the core. Then follow the repair procedure most appropriate to your situation.
Locate and mark the extent of the damage by exerting pressure on the panel, checking for a soft feel and/or skin movement. Tap around the suspected area lightly with a small, hard object to help reveal the area of delamination. A void under the skin will sound flat or dull, compared to a more resonant sound of a solid laminate.
When you push against the surface, the delaminated skin will give easily until it hits the core. If the core is solid, the skin will appear fair when it's pressed tight against the core. If the core is damaged or deteriorated, you will be able to push the skin below the fair surface of the deck or hull. Water or air may squeeze from a nearby crack or hardware fastener.
Determine the condition of the core material by drilling 3/16"-7/32" (5 mm)-diameter inspection holes through the skin several inches apart over the delamination. Push the skin tight against the core and drill through the core without drilling into the opposite skin. Collect the core material removed by the drill. Squeeze the core material tightly between your thumb and finger to determine whether the material is wet or dry and examine it for signs of decay. You may also insert a wire or nail through the hole to probe the core. If you hit voids or the core feels soft or punky, the core should be replaced.
5.12
Re-bonding delaminated skin when the core is dry
If the core material is firm and dry, re-bond the skin by injecting epoxy between the skin and core as follows:
1. Cut 11/8" (28 mm) from the tip of a WEST SYSTEM 807 syringe. Cut the tip at an angle. Fill the syringe with an epoxy/406 filler mixture thickened to the consistency of catsup.
2. Inject the epoxy mixture under the skin through each of the inspection holes. The shortened tapered syringe tip will fit tightly in the 3/16"-7/32" (5 mm) inspection holes (Figure 5-1).
You should be able to develop enough pressure to force the epoxy several inches from the hole. (You may use Six10 Epoxy Adhesive dispensed through a static mixer, though Six10 is thicker and may require the holes to be drilled closer together.)
3. Clamp the skin to the core when you are sure you have injected enough epoxy to bridge any gaps between the skin and core. Use weights, braces or sheet metal screws through the inspection holes to hold the skin tight and fair against the core until the epoxy cures. Clean up excess epoxy before it begins to gel. Allow the epoxy to cure thoroughly before removing clamps.
4. Fill any voids in the inspection holes with a thick epoxy/406 filler mixture, or Six10 Epoxy Adhesive, after removing clamps. When the epoxy has cured thoroughly, fair and finish the surface as described in Section 14-Final Fairing and Section 15-Finishing.

Figure 5-1 Inject epoxy under the skin using an 807 syringe with the tip cut off to match the hole diameter (see manual for picture, could not copy)

Repairing Core Related Damage
5.13
Re-bonding delaminated skin when the core is wet
If the core material is wet but still solid, re-bond the skin after the core has been thoroughly dried. One of two methods may be used to expose the core for drying.
Pattern hole drying method
This method involves drilling a pattern of holes through the skin to expose the core to air and heat and allow moisture to escape. When the core is dry, epoxy is injected under the skin and the skin and core are clamped together until the epoxy cures. This method is useful if the delamination is small, not under an area of non-skid deck or not in highly- loaded or critical laminates such as hull bottoms.
1. Drill 3/16"-7/32" (5 mm)-diameter holes at 1" (2.5 cm) intervals, creating a pegboard-like pattern that extends several inches beyond the delaminated area (Figure 5-2). The holes should penetrate the fiberglass skin and the core without drilling into the opposite skin. Use a drill depth control device to prevent drilling entirely through the panel.2. Dry the core thoroughly. If the core is extremely wet, start by using a high-powered shop vacuum cleaner or vacuum bagging to draw water out of the laminate. A heat lamp or radiant heater with some air movement over the area will speed the drying.
CAUTION: to be sure the fiberglass surface or the core is not damaged by excessive heat, do not heat the surface above 130?F (54?C). Proper drying may take days or weeks rather than hours. Allow the surface and core to cool to room temperature before continuing. Occasionally drill a few test holes between the existing holes to check for core dryness.
Figure 5-2 Drill a pattern of holes,
1" (25 mm) apart over the area of delamination, to allow the core material to dry out.
3. Cut 11/8" (28 mm) from the tip of a 807 Syringe. Cut the tip at an angle. Fill the syringe with a 105 Resin based epoxy mixture thickened with 404 or 406 filler to the consistency of catsup.
4. Inject the epoxy mixture under the skin through each of the holes starting in the center of the delaminated area (Figure 5-3). The shortened tapered syringe tip will fit tightly in the 3/16"-7/32" (5 mm) holes. You should be able to develop enough pressure to force the epoxy to the surrounding holes. (You may also use Six10 Epoxy Adhesive dispensed through a static mixer, though Six10 is thicker and will require more effort to force adhesive to surrounding holes.)
5. Clamp the skin to the core when you are sure you have injected enough epoxy to bridge any gaps between the skin and core. Use evenly placed weights or braces covered with plastic to hold the skin tight and fair against the core. Sheet metal or drywall screws will also work. Whichever clamping method you use, don't distort the panel by applying too much pressure. You only need to keep the skin fair and keep the skin and core in contact while the epoxy cures. Remove the excess epoxy before it begins to gel. Allow the epoxy to cure thoroughly before removing clamping.
6. Sand the surface and fill any remaining holes with an epoxy/407 low-density filler mixture, thickened to the consistency of peanut butter (Figure 5-4). After the epoxy has cured thoroughly, sand the surface fair and finish it as described in Section 2.

Figure 5-3 Inject the epoxy mixture under the skin through each of Figure 5-4 Fill any remaining voids and fair the surface with an the holes starting in the center of the delaminated area. Fill all voids epoxy/407 mixture.
between the skin and core.

5.2
For thin skins, this procedure may result in a weakened structure, making it necessary to bond several layers of 6 oz. fiberglass fabric over the repair area. Refer to Section 16.4.5-Applying woven cloth and tape.
Skin removal method
This method involves removal of a section of skin to expose the core for drying. Because of the difficulty (or impossibility) of fairing and finishing a non-skid surface, it's often easier to cut and remove an entire non-skid area. After the core is dried, the skin is re-bonded and then patched and refinished at the smooth areas outside of the nonskid. Follow the procedure in Section 5.2-Replacing damaged cores.

Boats don't use EPS and board builders don't use West System epoxy.
You've been shown several correct ways of repairing this but feel free to choose the incorrect one, it's your board.
Maybe next time choose a board constructed to handle your skill level. You'll likely be making that decision shortly.

I read today this post, if the soft area is because come inside some water from the footstraps screw hole but I need to do a quick fix repair is better foam instead of epoxy?
I mean, I need to use my board in few days, if polystyrene is wet (I don't know I just presume that) the epoxy will not be hard, but the foam maybe will work better?
Thanks

You forgot the six ten epoxy. I kind of miss sandy