fender broke

i'm on my second build, i had my engine on a roadmaster but since put it on a scwhinn delmar cruiser.
and now i can go 30-35mph. but my front fender has been vibrating alot and today the metal tab that holds the top part broke but the fender stayed on because of the bottom brackets held up.
i used a plastic tie that i had to hold the fender til i got home. i guess i will drill out the ribits and bolt a real peace of steel bracket in place of the thin one that broke.