Black Mastic sealer Winnebago uses on Storage bays ?

This is on my '06 Outlook Class "C"

the black Mastic is used to seal the outside seams of the storage bays (where seams meet on the backside under chassis ). I have a small pin-hole in the bays just behind the rear wheels and driving through water / rain causes the bays to get wet.

When my front bays in front of the wheels leaked, I used black silicone caulk sparingly on the inside where I could tell there was a problem, but I also used it on every seam I could reach from the outside. After the caulk cured, I put a couple of coats of spray undercoat material on the outside of the boxes (carefully shielding paint & wheels). That cured my leaks, and no repeat problem in the 6 years since...

Try looking it up here.

John Canfield said:

Try looking it up here.

Click to expand...

It's not one of the ones  listed on the Winnebago  sealant callout as I know the 4 types that are on the callout.  The Callout is for the exterior Trim (roof, sidewalls etc). The black mastic used on the seams of the cargo bays is different than any of the other sealants used any other location on my Outlook.

Black silicone would be a last resort. 

Let me see what I can find out....

Sorry I can't help you identify what Winnebago might have used.

We joined the RV community in 2008 after 30+ years of sailing and there are several products available in that marketplace the I personally believe are more robust than required for an RV and are excellent products. For sealants, try Sikaflex and the 3M series of sealants / adhesives. There are several products in the Sikaflex range that are black that could be used . My personal favourite is 3M 5200 adhesive/sealant that is almost indestructible. They make a complete line starting with high quality silicone and go up in strength/durability from there. Google 3M 5200 or 4200 and you will see the capabilities. They are likely more costly than RV caulks but should last much longer.

I have also used successfully the asphalt automotive undercoating spray that Paul suggested. Great for getting in places you can't reach and inexpensive.


Bob
08 Cambria 29H
Southern Ontario

My Winnie contact wasn't sure of the exact sealant used for your unit, but here are sealing guidelines:
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Note This specification applies to Rotocast boxes that drop down into a cavity such as the floor or steel basement structure.

1. For thick floors, apply ant-wicking compound (124109-01-000) to edges of any exposed wood in the luggage box cutout in floor. For thin floors, coat the edge of the opening with black spray paint.

2. Apply sealant (072889-18/19-000, 072889-30-000 may be used if color matching is a concern) to the flange of the compartment. The sealant should be placed so that it will make contact between the floor and the flange of the compartment around the entire perimeter.

3. After the compartment is installed, cap seal (072889-18/19-000, 072889-30-000 may be used if color matching is a concern) the entire edge of the compartment to the floor or tubes it is attached to. Tool to aesthetic requirements.

4. If rivets are used to attach the compartment, seal (072889-18/19-000) the center of the rivet heads.




Note This specification applies to units that use Rotocast panels as compartment lining in the basement compartments.

1 Apply sealant (072889-18/19-000) to flange of luggage compartments before the Rotocast panel is installed.  The sealant should extend around the perimeter of the compartment. There should be no gaps or voids.

Apply sealant (072889-30-000) to the corners. The sealant should extend past the perimeter of the Rotocast lining. There shall be no gaps or voids.




Note These guidelines apply to all processes utilizing a cap-seal unless the process specifically contradicts the guidelines. In those cases, the instructions in the process take precedence over the guidelines. Typical base part numbers used in a cap seal application are 094401, 072889, and 131264.

1. The cross section of the ideal cap seal should form a 45-degree triangle.  The legs of the triangle should be of equal length. The sealant should not have an excessive amount of curvature.  If the cap seal cross-section cannot be made into a 45 degree triangle, the cross member of the triangle should be the maximum length possible without violating aesthetic requirements.

2. As much sealant as possible should be used in the cap seal with out violating the aesthetic requirements. Too little sealant or sealant that is too thin will be more likely to be degraded by UV, heat, weather and chemical exposure.

3. If a piece of trim or a component is cap sealed, only one product should be used to cap seal the component or piece of trim. The cap seal should be applied after decals or paint is applied in cases where any portion of the component or trim is painted or intersects a decal.

Suggest you visit a good auto collision repair center and ask them what sealant the use in trunks and in other areas where they must re-apply sealants during repair of body panels.  The stuff they use works and is likely some form of polyuretane.

Another option is ProFlex.  It is available from many RV supply stores, Camping World and the web.  It is good stuff  and comes in several colors.