---- Minecraft Crash Report ----
// I'm sorry, Dave.

Time: 2/16/15 6:06 PM
Description: There was a severe problem during mod loading that has caused the game to fail

net.minecraftforge.fml.common.LoaderException: java.lang.NoClassDefFoundError: net/fybertech/hopperducts/ModelHopperDuct
at net.minecraftforge.fml.common.LoadController.transition(LoadController.java:162)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:693)
at net.minecraftforge.fml.client.FMLClientHandler.finishMinecraftLoading(FMLClientHandler.java:291)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:484)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:325)
at net.minecraft.client.main.Main.main(SourceFile:120)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.lang.NoClassDefFoundError: net/fybertech/hopperducts/ModelHopperDuct
at net.fybertech.hopperducts.RendererHopperDuct.(RendererHopperDuct.java:39)
at net.fybertech.hopperducts.HDClientProxy.init(HDClientProxy.java:48)
at net.fybertech.hopperducts.HopperDuctsMod.init(HopperDuctsMod.java:110)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:515)
at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:208)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:187)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:118)
at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:692)
... 10 more
Caused by: java.lang.ClassNotFoundException: net.fybertech.hopperducts.ModelHopperDuct
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 39 more
Caused by: java.lang.NoClassDefFoundError: net/minecraftforge/client/model/ISmartBlockModel
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
... 41 more
Caused by: java.lang.ClassNotFoundException: net.minecraftforge.client.model.ISmartBlockModel
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 45 more
Caused by: java.lang.SecurityException: class "net.minecraftforge.client.model.ISmartBlockModel"'s signer information does not match signer information of other classes in the same package
at java.lang.ClassLoader.checkCerts(Unknown Source)
at java.lang.ClassLoader.preDefineClass(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:182)
... 47 more

A detailed walkthrough of the error, its code path and all known details is as follows:

-- System Details --
Details:
Minecraft Version: 1.8
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_31, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 166670672 bytes (158 MB) / 530579456 bytes (506 MB) up to 954728448 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP v9.10 FML v8.0.14.1281 Minecraft Forge 11.14.0.1281 Optifine OptiFine_1.8_HD_U_D1 14 mods loaded, 14 mods active
mcp{9.05} Minecraft Coder Pack Unloaded->Constructed->Pre-initialized->Initialized
FML{8.0.14.1281} Forge Mod Loader Unloaded->Constructed->Pre-initialized->Initialized
Forge{11.14.0.1281} Minecraft Forge Unloaded->Constructed->Pre-initialized->Initialized
bowinfinityfix{rv1} Bow Infinity Fix Unloaded->Constructed->Pre-initialized->Initialized
CodeChickenCore{1.0.5.34} CodeChicken Core Unloaded->Constructed->Pre-initialized->Initialized
NotEnoughItems{1.0.5.82} Not Enough Items Unloaded->Constructed->Pre-initialized->Initialized
REPAIR_UNLIMITED{0.0.0} Repair Unlimited Unloaded->Constructed->Pre-initialized->Initialized
convenientrecipes{1.8-1.5} Convenient Recipes Unloaded->Constructed->Pre-initialized->Initialized
lootablebodies{1.3.2} DrCyano's Lootable Bodies Unloaded->Constructed->Pre-initialized->Initialized
HardcoreDarkness{1.2} Hardcore Darkness Unloaded->Constructed->Pre-initialized->Initialized
hopperducts{1.4.5} Hopper Ducts Unloaded->Constructed->Pre-initialized->Errored
IronChest{6.0.99.749} Iron Chest Unloaded->Constructed->Pre-initialized->Initialized
parachutemod{3.1.1} Parachute Mod Unloaded->Constructed->Pre-initialized->Initialized
simplerefinement{1.0} Simple Refinement Unloaded->Constructed->Pre-initialized->Initialized
EDIT: Changed the log to the right one. It seems to have an incompatibility with Hopper Ducts mod.

Are you sure you are using the 1.8 and not the 1.7.10 version?

I'm using the 1.8 version. It seems to have a conflict with Hopper Ducts mod.