Radar Arch Refurb

Serenity

I know this subject has been beaten to death but I am getting many different answers from different companies regarding the fillers to use.

I own a 2005 320 and the arch is cracked in many places. Amazingly enough the areas are not at the screws where others have had issues but at the curves between the top and the side legs --both under and on top on the port and starboard sides. When I bought the boat I pulled all the screws out and coated them before installing--so that was a savior. But what kind of filler can I use if I do not want to strip the entire arch? I have 6 spots where the cracks have turned into big chunks of paint if I let myself pull at them. For two years I have just filled the cracks with silicon to try to bide me some time but now they are bad. So if I do pull the chunks off and sand--what primer and then what filler can I use? The chunks are between 1 inch x 1 inch and 2 inch x 2 inch. Once primed and filled I can paint. Hopefully match the paint.

frenchship

Is it fiberglass or aluminium.?

Serenity

Aluminum

partlowr

Assuming your arch is fiberglass the best product you can use is a 3M product call 3M Mar Glass. For sake of a simple description it is similar to a bondo type body filler but it has short strands of fiberglass already mixed in to it. It is specifically engineered for use on fiberglass and composite plastics. Unlike some other fiberglass filler this 3M stuff is very easy to sand and does not set up super fast so it give you some time to work with it before it cures, that being said it is still a quick curing product so it won't turn into an all day project if multiple layers are required. It is waterproof and unless you are repairing actual holes this does not require the use of any fiberglass tape. I have used this on a friends boat hull and on a composite bumper on my BMW, it's not the least expensive product out there but it is the best. After it is cured and sanded smooth(usually at least 2 layers of the Mar Glass) you can prime right over the repair and it will be ready for paint. If you have sanded and feathered the repaired area(s) perfectly there should be no evidence of the repair once painted.

http://shop.advanceautoparts.com/p/3m-marson-mar-glass-short-strand-reinforced-filler-gallon-mar01160/

http://www.shop3m.com/marson-mar-glass-short-strand-01120-1-quart-us.html

NavyCTRC

I have the same problem and was trying to find the answer, the only thing I can figure out is to sand the whole thing, repair cracks (body filler?), prime and paint.  I may save this project for winter...

Serenity

I am afraid of the body filler because of the expansion/contraction of the aluminum. I think it would end up cracking.

partlowr

Serenity said:

I am afraid of the body filler because of the expansion/contraction of the aluminum. I think it would end up cracking.

So your arch is aluminum not fiberglass? Then all you need is a body filler made for metal or aluminum. Your only other option is having it "tinned" and that is going to be very expensive. Body filler works on car in sub zero temps up to 120 degree temps so why do you think a boat would be any different?

Michael T

@ Serenity, you can get fillers that are meant for fairing-out aluminum. Car body specialists can get it. Some trains use it and some smaller airplanes use it too. If the aluminum is properly etched and chemically prepared the filler will stick. I have helped friends with this on aluminum boats under and over the waterline with lasting results.

Serenity

Thank you guys-I did not realize the different fillers. Regarding the arch being etched and chemically prepared--can I assume I would not need to do that again since it looks like the paint itself was what had failed? Maybe it was not properly prepped in the first place. I will have to get into it I guess. Let the fun begin.

Michael T

EC 310 and EC 360 are aluminum as fiberglass was considered too heavy for them without support poles - so at some point Rinker switched to aluminum. Not sure exactly when that was but it's easy to tell which one you have if you look in an access port on your HT.

Serenity

Thank you Al. Do you recommend I prime the aluminum after sanding before I do the filler? I pulled one of the chips off last night and it looks like the aluminum is primed already.