Sculpting Fundamentals and Non-Constant Interest Rates

This page introduces sculpting in the situation where the DSCR and future cash flow drives the size of the debt in project finance. The models and videos on basic sculpting demonstrate that efficiently evaluating project finance debt structuring issues like sculpting with a changing interest rates should involve first and foremost understanding a few mathematical equations. This page introduces structuring and sculpting through addressing fundamentals of sculpting in the case where the DSCR drives debt and there are no taxes.

There are a couple of key files where I put the financial formulas, modelling examples and the VBA code for cases where you run into circular references.  You can file these file on the google drive in the Project Finance Section under exercises and then Section D for the Sculpting course.  The files are available for download by pressing the button below.  The second file includes a function for determining the pattern of DSCR’s that achieve a target average loan life if the debt to capital constraint drives the size of the debt (sorry that this sounds like a foreign language).

Excel File that Includes Sculpting Exercises from Basic to Advanced with VBA

Fundamental Case with No Taxes, No DSRA, No LC Fees, No Debt to Capital Constraint, a Single Debt Issue and Constant Interest Rates

If you have not put sculpting in one of your models, or you have forced sculpting with some kind of solver equation or goal seek equation, you should work through an exercise using the following two equations,

Compute target debt service as : DS = CFADS/DSCR

Compute debt as NPV of the target debt service using the interest rate

The screenshot below demonstrates how you can work through the sculpting and structuring issues.  In this case you should create a debt switch (if you want to be fancy and call it a mask, you can but I have no idea why you call the true and false switch a mask).  Then the debt service is the CFADS divided by the DSCR multiplied by the switch.  The closing balance in the loan schedule is the present value of the debt service and the repayment is the target debt service minus the interest expense.


The video below walks through the fundamental sculpting equations. The video is designed so that you can fill in the blanks in yellow by yourself as discussed above.  This is the easiest case and it is the base for much more complicated situations that deal with debt to capital constraints, DSRA movements, L/C fees etc.


Sculpting Exercise 2: Non-Constant Interest Rates

Some term sheets include step-up credit spreads. Others allow a portion of the interest rate to be un-hedged.  In these cases, the first thing I hope you think about and understand is why structures such as a step-up structure occur.  What is generally happening is a strong incentive to re-finance. It is probably absurd for you to leave the step-up credit spread in the base case scenario.

In cases when the interest rate changes, a simple present value formula cannot be used. Instead, an interest rate index can be created that accounts for prior interest rate changes as follows:

Interest Rate Indext = Interest Rate Indext-1 x (1+Interest Ratet)

Debt Amount at COD = ∑ CFADSt/Interest Rate Indext

The video below walks through how to create an interest rate index and then use the SUMPRODUCT function to multiply the index by the target debt service.  You can use the SUMPRODUCT with a divide sign which is very helpful — SUMPRODUCT(Debt Service/Compound Factor). Note that you cannot use a discounting factor that separately values the debt service.  In general when discounting cash flows with different rates you should compute some kind of compounding factor.  To see this think about inflation Zimbabue.  You cannot discount a future cash flow without considering what happened to the currency in the past.


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