RC Groups

RC Groups
    Composites Fabrication
        Help! Glass for Ducts

#1 unclecrash Feb 17, 2012 12:32 AM

Glass for Ducts

#2 sarmoby Feb 17, 2012 11:01 AM

Inlet ducts tend to be low load structures unless you are talking full size aircraft where the load is in fact due to the pressure differential where the tube might collapse.
In this case the carbon can be used as both hoop strength and to make flages on the exterior of the duct( along the duct and radially around the duct) to stiffen the section shape. an alternative is to make a sandwich structure on the duct. clear?

I would think a 1 oz glass against the inside (airflow surface) followed by a bit of 4 oz should be more than enough. Use tow as needed to stiffen stategically.

Think light weight and plan accordingly

#3 unclecrash Feb 17, 2012 05:13 PM


#4 sarmoby Feb 17, 2012 07:56 PM

If you cannot remove the duct from the foam and want to keep the plug, cutting it may work fine. You may want to add an edge so that it is easy to glue back together.

#5 unclecrash Feb 17, 2012 08:23 PM


#6 sarmoby Feb 20, 2012 10:31 AM

Just make it easy to realign the two parts.
You will need to bond them back together after they are cut right?
Think about how to best do this befoe you cut them and you may decide to include
those features before yu do the cutting.
For example: if you bond a balsa block to the edge of the duct and cut through it, it will be a stable area to clamp the duct when putting it back together.

#7 unclecrash Feb 21, 2012 07:43 PM

what glass to make this lip

#8 sarmoby Feb 22, 2012 10:47 AM

For tight radius areas, it is common to use some spooge( resin with filler mixed in), chopped glass and resin, and to use multiple cuts of fabric. This is like upholestry(sp?) where you cut and dart the material to get it to conform. Often on high radius parts, a light mist of spray glue can hold the dry fabric to the tool so you can wet it out in place.
Remember also that you can cut strips or pieces of fabric on a 45 degree to the weave( called bias) that increases the ability to handle a radius.

#9 unclecrash Feb 22, 2012 10:54 PM


#10 sarmoby Feb 23, 2012 11:03 AM

don't go crazy with the glue. You can also cheat a bit by putting a barrier film over the plug( packing tape or thin plastic film-mylar) that is also waxed so that when you get it off the plug, you then peel off the mylar and there you have it.

I cannot see the radius from the pictures but you might also think of making the mold 2 pieces so that you can seperate the intake flare from the tube after cure.


All times are GMT -5. The time now is 04:06 AM.