A Gantt Chart is a project planning chart which allows for a visual representation of your research. It also allows you to keep track of the status of the individual tasks within your research. If you have a research plan in your proposal, you should include a Gantt chart (Hint hint: if you are writing an SBIR or STTR proposal, then you WILL have a research plan).
Not only will a Gantt chart give the reviewer a thumbnail sketch of the tasks/tests you are proposing, it will allow you to calculate the amount of time that will be required for the whole research project and help you outline your proposal. Will you be able to complete the tasks in the desired amount of time? Will the tasks/tests you are proposing meet the corresponding Aim/Objective?
Start with your Aims/Objectives. List each one. Under each Aim/Objective, list each and every task/test you will perform in order to meet that Aim/Objective. To the side of each task/test, you will have a timeline which is then broken into weeks, months, or maybe hours (check in the solicitation and budget information to see how you will be calculating time for that agency).
Now, sit back and actually look at your chart. The whole timeline of the Gantt chart should not exceed the length of the award—if it is a six-month Phase I SBIR, you should not have a 12-month Gantt chart and vice versa. Since the majority of the SBIR/STTR funds will go to pay the individuals carrying out the research plan, make sure you will be able to meet the budget limits. If the number of months or the amount of time required for the total number of tasks exceeds the solicitation requirements, you will need to re-think and re-work your research plan.