Bifold Hangar Doors

Bifold hangar doors are commonly installed on small private hangars or “T hangar” developments. They have been an economical solution for small openings, but as opening widths grow Spec-Dor’s new ECO bottom rolling hangar door become a cost effective alternative to the bi-fold door. It is of great importance that architect and hangar designers understand the full impact of hangar door integration to maximize project savings and customer satisfaction.

Bifold hangar door problems

Generally speaking, you don’t have to go very far to hear a horror story concerning a bifold door failure.  In some cases, bifold doors can fail catastrophically, crashing down causing personal injury or aircraft damage. Other common issues are a result of a mechanical failure rendering the bi-fold door to fail to completely open. Hangar personnel are fooled by the reduced headroom clearance, which far too commonly results in costly aircraft repairs and/or insurance nightmares. Invariably a non-functioning bifold door blocks the opening making the hangar unusable until the maintenance guys show up. Although maintenance costs are not associated with project construction costs, the inconvenience and loss of revenue due to a non-functional door will make paying for the investment more difficult. As a general rule of thumb the following statements hold true:

1. The larger the bi-fold door, the more stress is put upon the door hardware
2. The more cycles the door performs annually, the more likely the door will fail.

Bifold hangar doors – Hidden Costs

As a consumer or hangar contractor it seem only obvious that if you pair a low cost building with a low cost hangar door, the result would be a low cost hangar package. Unfortunately, in many construction projects misunderstood door requirements can increase the building’s quoted price quite substantially. It is commonly understood that bifold doors are hinged on the lintel of the building. The entire weight of the door will hang from a roof truss.  In many cases, the weight of the door was not known or given to the building supplier at the time of quoting, resulting in extra costs.

A lesser-known hidden cost results from the bifold door’s inability to operate with normal building deflection parameters. To understand this concept it is important to understand that a bifold door has a series of hinges attaching the door to the lintel of the building. It is obvious that the hinges must be installed in a straight line for the door to function properly. It is also normal for building roofs to deflect up and down depending on load and temperature.  In many cases the out of line tolerance for a bifold door is only an inch or so. The building code limits the maximum roof deflection to about 1 inch in 20ft. Again, as the door width increases the normal building deflection can easily be up to 4 inches. To properly compensate, the building designer must stiffen the roof structure of the building. The building’s cost will escalate rapidly as the door width increases.

Bifold hangar door alternative

At Springbank Airport outside of Calgary, every single hangar built in the last 10 years was fitted with a bifold door. When Central Aviation of Calgary was considering building their new hangar at Springback, they decided to look for alternative door solution. As owners of other hangars, they had suffered from maintenance related problems in the past. Colin McCloud of Central Aviation said that their main drive shaft had snapped in half twice. These near catastrophic events have forced Central Aviation into an aggressive maintenance program averaging around $5000 per year per door.

The new hangar required an opening of 80ft wide by 19ft high. Central aviation was looking for a cost effective solution. The building size and shape easily enabled the door to roll open inside the building. To keep cost down, fewer door blades are always a better solution. Spec-Dor proposed it’s new ECO design 4 blade Slide-to-one-side hangar door solution.

Please click on image to enlarge

This design requires only one blade to be motorized. The motorized blade picks up the other trailing door blades until the entire door moves into a single door pocket or storage area. The modular design of the door panels, bottom rails and top tracks allows the door to be easily and quickly bolted together on-site. The ECO’s strong and reliable hardware can be easily utilized with many different door configurations and wind loads rendering considerable cost savings.

It is important to remember that a bottom rolling hangar door has upper and lower tracks on which the door runs. The bottom track or rail carries the weight of the door. The building has only the weight of the top track to carry as opposed to the entire weight of the door as with the bifold door. As a result, the bottom rolling hangar door imposes less loads on the building. The bottom rolling hangar door however, has more components than a bifold door namely: upper tracks and bottom rails as opposes to a couple of hinges. The purchase cost of a bottom rolling hangar door normally approaches the price of a bifold door when the width exceeds 60ft and the height exceeds 20ft.

Conclusion

In conclusion, Spec-Dor’s ECO bottom rolling hangar door is price comparable with a bifold door when looking at larger sizes. In addition Spec-Dor’s ECO bottom rolling hangar door has less impact on building design than a bi-fold door rendering further construction cost savings. Lastly, Spec-Dor’s ECO bottom rolling hangar door can never damage an aircraft once the door is opened.

Notes

Spec-Dor’s ECO design for Central Aviation included rail flashings, variable speed drives and limit switches used as position sensors.

Rail flashings - Hangar door

Rail flashings offer the benefits of better drainage, lower operating cost, precise door operation, longer door life and easier maintenance.

Variable speed drives and position sensors allow the door to be accelerated and decelerated in a controlled manner.  This leads to safer door operation and longer motor life.

If you are looking for an alternative to unreliable bifold hangar doors, contact SpecDor and we’ll be glad to help you.