Disable unobtrusive validation on an ASP.NET MVC form

I have two forms on a page. I want the first form to use unobtrusive validation, as it's since automatically generated by ASP.NET MVC Framework. There is a second form, however, which I wrote manually, that should not use unobtrusive validation.

Here's some code:

@using (Html.BeginForm("Add", "Contacts", FormMethod.Post, new { id = "AddForm" }))
{
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Datos Contacto</legend>
        <div class="editor-label">
            @Html.LabelFor(model => model.Name)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Name)
            @Html.ValidationMessageFor(model => model.Name)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.ContactDepartmentID)
        </div>
        <div class="editor-field">
            @Html.DropDownListFor(model => model.ContactDepartmentID, (List<SelectListItem>)ViewBag.ContactDepartments)
            @Html.ValidationMessageFor(model => model.ContactDepartmentID)
        </div>
        <div class="editor-label">
            @Html.LabelFor(model => model.Sex)
        </div>
        <div class="editor-field">
            @Html.DropDownListFor(model => model.Sex, (List<SelectListItem>)ViewBag.Sexs)
            @Html.ValidationMessageFor(model => model.Sex)
        </div>
    </fieldset>
    <br />
    @Html.HiddenFor(model => model.SerializedEmails, new { data_bind = "value: ko.toJSON($root.emails())" })
    @Html.HiddenFor(model => model.SerializedPhones, new { data_bind = "value: ko.toJSON($root.phones())" })
}
<form id="phoneForm" >
<fieldset>
    <legend>Teléfonos</legend>
    <table class="table">
        <tbody data-bind="foreach: phones">
            <tr>
                <th>
                    Celular?
                </th>
                <th>
                    Phone
                </th>
                <th>
                    Extension
                </th>
                <th>
                </th>
            </tr>
            <tr>
                <td>
                    <input type="checkbox" data-bind="checked: isMobile" />
                </td>
                <td>
                    <input class="phone" data-bind='value: phone'/>
                </td>
                <td>
                    <input type="text" class="extension" data-bind='value: phoneExtension, enable: !isMobile() ' />
                </td>
                <td>
                    <a href='#' data-bind='click: $root.removePhone'>Delete</a>
                </td>
            </tr>
        </tbody>
    </table>
    <a href='#' data-bind='click: $root.addPhone'>Agregar teléfono</a>
</fieldset>
</form>
<p>
    <button onclick="Submit();" type="button" class="btn btn-primary" data-bind='enable: phones().length > 0 || emails().length > 0'>
        Create</button>
</p>

JS:

function Submit()
{      
  var valid = $('#AddForm').valid();     
  var valid2 =  $('#phoneForm').valid();     
}

jQuery.validator.addClassRules("phone", {
  required: true
});

As a side note: When I remove the unobtrusive validation from the page, the second form validates, but the first does not. If I use unobtrusive validation the first form validates, but the second form does not.

I know I can do the whole validation on the client side—and, if that's the only way, I will do it. I was thinking about a way to continue using unobtrusive validation, but allowing it to be conditionally disabled using e.g. custom attributes.