# Bunk Adjustment



## taggart.josh (Mar 25, 2019)

I recently bought my first tin boat. On the trip home I noticed that the strakes (SP?) are contacting the wheel fenders, additionally the keel is sitting on the trailer in a couple spots. I believe that the trailer was not intended for this boat or poorly home built. I am thinking the easiest solution would be to lift the boat slightly on the trailer. My plan is lift the boat off the trailer and then remove the bunks and shim the from behind with 2x4 blocks. Additionally the rollers for the keel will either need to be adjusted or replaced. I have been told one way to replace them would be a 5/4 x 8 ripped in half and installed in a V to support the keel. Would this be sufficient? Also do I use treated wood, I have been told that an interaction between the copper in the treated wood and aluminum could cause an issue, wouldn't carpet lessen this?


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## lckstckn2smknbrls (Mar 25, 2019)

You do not want to use pressure treated wood as you stated the copper will react with the aluminum. The carpet will not help it will make it worse. The copper will leach out of the wood and be held in the carpet.


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## LDUBS (Mar 25, 2019)

Based on what you describe, it definitely sounds like you need to make some adjustments so the trailer fits your boat. If nothing else it sounds like you need to raise your bunks. The good news is new bunk brackets come in a variety of sizes, can be easily U-bolted to your trailer frame, and are not that expensive. 

I don't know about the "V" configuration you describe for your keel. Again, I am visualizing a mod V boat from your description. I think a roller or two is all you need. 

PS: X2 -- no pressure treated.


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## taggart.josh (Mar 26, 2019)

Thank you for the quick responses, the current brackets for the bunks are welded onto the trailer so they will need to be cut off. For the time being I am just going to shim the existing. I will use regular 2x4s instead of pressure treated, no for the keep, there is currently a roller near the back and one in the front. again they are welded on and sitting low enough that the keel is in contact with the trailer. Do I need to support the keel, I have seen some posts on here where people only support the keel towards the front of the boat. This is a early 50s mirrocraft so Im not sure what type of hull it has, but it is a V-Shape.


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## LDUBS (Mar 26, 2019)

I attached a pretty basic sketch of a typical trailer. My boat is supported by the two bunks and roller #1 which is under the bow stem of my boat. In fact, my trailer does not have rollers #2 & #3. 

In my opinion, rollers #2 & #3 are there to help center your boat and keep it from scraping the trailer when you load it. When your boat is loaded, again my opinion, #2 & #3 shouldn’t touch the keel. Why? Because unless you have them perfectly adjusted, the chance is one will be more in contact than the others. When your light aluminum boat bounces as you go down the road, a slightly higher roller could dig a divot in your hull. 

My thinking is three points of contact best eliminate movement – kind of like a three-legged stool is less likely to rock if the legs are not perfect. Again, this is just my opinion. I acknowledge others feel that the keel should be supported along its length by multiple rollers. Whatever you decide, I think we would all agree that the keel should not be resting on the trailer frame. 

Another important point is that the bunks should extend just past the transom and the transom should be fully supported by the bunks. If the bunks are too short, you risk deforming the hull because the bunks will be pressing only against the thin skin of the hull. Folks call this putting a hook in the hull. If the bunks are long enough to extend past the transom but leave any gap between them and the transom, the same thing can happen. I guess the best way to say it is the transom has more “structure” to support an aluminum boat. 

Additionally, I think most of us would agree that the bunks should fall between bottom strakes. 

Most manufacturers recommend a set up for their boats. And, I guess they should know. I realize your boat is a 1950’s model, but Mirrocraft might still be willing to suggest a certain set up if you contact them. I really don’t think it necessary and probably wouldn’t if it were my boat, but it is a potential resource if you want. Another thing you can do if you are not sure is check out some of the set-ups at your local ramp. 

After your trailer set up perfectly, consider using side guides or side bunks. That way your boat will settle right down where it belongs every time, even when it is getting moved sideways by wind or current. 

Once you know where you want the bunks/rollers, using shims to make the adjustment should be OK as long as everything is secure. 

I am not the oracle of all trailer knowledge. Hopefully others will chime in. But I do hope this helps some.


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