While Depron and Modelling Foam are very similar, they also have some quite distinct differences. It’s not simply a case of which is better, but which is most suited to your building task. On this page we try to give some comparisons and examples for both products.
These four qualities are important to consider when selecting the best foam for your job. Strength is important but the trade-off is often weight. If building a flat wing then strength is important, but if you are building a boxed section such as a fuselage where foam is joined at an angle, then the foam sheets help to support each other and each sheet adds strength to other sheets it is joined to.
Similarly, considering flatness, if your design calls for large unsupported flight surfaces then flatness of the foam will be important. But once again in built up sections where foam joins at an angle the other pieces of foam will help keep those pieces they are attached to flat (straight). Of course price and weight are also competing factors.
The graph below shows weights of each product as grams / square meter sheet (not cubed meter)
Of interest here is the fact that Modelling Foam is considerably lighter than Depron. Comparing 3mm White Depron and 3mm White Modelling Foam we can see a considerable weight saving by using Modelling Foam, but at a cost which is strength. A similar comparison can be drawn between 5mm Modelling Foam and 6mm Depron. Also, grey Depron will always be lighter than White Depron but not as strong.
Unlike weight, strength is more difficult to measure in a way which gives meaningful results. Here, we use a simple comparison method to show how different foams of similar thickness support the same weight.
The four examples below show how 2mm and 3mm foams compare. Depron 3mm White is shown to be the strongest of all. But of course, with a weight penalty (as shown in the graph above). Even 2mm Depron and 3mm Grey Depron are stronger than Modelling Foam while actually being lighter. But don’t forget price and flatness. Modelling Foam is considerably cheaper and has no bow in the sheets while Depron is more expensive and the sheets can have a slight bow in them.
* For these examples we have chosen Depron sheets which actually have no bow in them.
Below, we have judged the various foams on their attributes using a simple 1 to 5 scale with 5 being the best result in each category. These results are based on the weight data and strength tests from above. By looking at this radar graph, 3mm Modelling Foam may seem to be the overall winner depending on your criteria. However, it’s good scores in the price, Flatness and Weight areas come at a price – Strength. Conversely, Depron as a premium product which can’t be matched for strength may not be suitable for your task due to it not being perfectly flat.
A similar example here showing that although 5mm Modelling Foam holds up quite well in comparison to 6mm Depron, it can’t match the Depron on Strength. However a look at the weight chart at the top of the page will show that there is a considerable weight saving by using 5mm Modelling Foam over Depron. Also, the price is cheaper and 5mm Modelling Foam has no bow in the sheets, unlike 6mm Depron which can have a more than noticeable bow.
* For this example we have chosen a Depron sheet which actually has no bow in it.
** Of interest to some, may be that 5mm Modelling Foam actually appears to be made from two 2.5mm sheets laminated together. You need to look very closely to actually see this. Also, for all Modelling Foam thicknesses, the foam colour is not as pure white as Depron.
Below we have judged these two foams on their attributes using a simple 1 to 5 scale with 5 being the best result in each category. These results are based on the weight data and strength tests from above. By looking at this radar graph, we can see that Modelling Foam seems to be the best overall performer. Maybe however, it’s greatest attribute is that it is has no bow in the sheet whereas 6mm Depron does have a noticeable bow. But if outright strength is needed and money is not an option then Depron is still the best choice.
Both Depron and Modelling Foam are forms of EPS Foam (Expanded Polystyrene). These foams are extruded type foams with a closed cell structure which gives them strength as well as making them water resistant (non-absorbent). In the production process an expansion agent, usually a hydrocarbon (which doesn’t contain halogens) is used to form the individual closed cell bubbles which make up the structure of the foam. The image below shows the cell structure of the two types of foams. The Depron foam on the bottom clearly has a more dense structure with slightly smaller cell bubbles. This accounts for it being heavier and stronger than Modelling Foam.