Transom "crush"

[TimD]

I just removed the transom from one of my riggers as the hardware (particuarly the rudder bracket) was distorted due to the plywood "crushing".

I'm all set to glue a new piece of ply in it's place and I thought I'd make a post and see if anyone has any tips about this problem. Is it worth using blind nuts (T nuts) or inserts in the transom or to just use screws and Nylon insert bolts to hold the hardware in place..

I want to try and keep the weight down too - this boat is also undergoing a diet!!!

Thanks for any advice / hints!

Tim.

 

[DJT]

I would think blind nuts would be lighter. Also, because of the part of the blind nut that sticks into the wood you should have less of a crushing problem. Use locktite on the screws.

 

[dave roach]

Hi Tim

I would use brass inserts If you use tee nuts you have to make sure you seal the wood real good wear the tee nuts go into the wood.

my two cents

 

[TimD]

Thanks for the feedback guys - gotta love this forum!

I've not had much dealings with threaded inserts other than ones that were fitted to a boat I had that spun around in the wood (broke loose.) Is this common and if so is this asking for trouble on a transom.

 

[RaceCraftBearings]

Tim I would suggest through bolting the hardware as it is stronger. Seal the holes in the wood with CA and once dry run your bolts through the tansom and I also use a thin square of aluminum plate as a backer on the inside this will stop the crushing of the wood.

Ron

 

[Jerry Wyss]

Hi Tim, I would agree with Ron,,a plate on the inside is the strongest. I think the inserts are problematic in thin wood,,

and even in fiberglass unless its really thick. I wish I could do it for you my friend,,its my specialty,,except some people

think my rudders are left a little long.

Jerry

 

[TimD]

Tim I would suggest through bolting the hardware as it is stronger. Seal the holes in the wood with CA and once dry run your bolts through the tansom and I also use a thin square of aluminum plate as a backer on the inside this will stop the crushing of the wood.
Ron

Ron,

Thanks for the tip. The way you suggested is how I normally do it - and it is the way it was done on this boat too.(Eagle SG)

The problem is more exagerated on the hardware side than the inside where the backer plate is. The rudder bracket in particular with it's small surface area seems to be the biggest culprit.

Have you noticed this crush occurring with your rudder bracket at all?

I'm the first to admit this boat has done a lot of racing and has hit a few course bouys as well as 2 impacts with other boats (1 of which was my bad) and is no way a reflection of the build quality of the boat.

 

[nitrotoys]

I would go with the inside plate, just big enough for your bolt pattern. thin alumn can be found pretty cheep, dont need to be thick thick.

and yes seal new wood with CA My one rigger has doubled up PLY on it. i havent had any problems with it, I prefer alumn, but NOT BROKE, NOT FIXING.

Tom

 

[Kez]

The problem is more exagerated on the hardware side than the inside where the backer plate is. The rudder bracket in particular with it's small surface area seems to be the biggest culprit.

Tim,

I normally use a piece of thin Aluminum plate between the rudder bracket and the transom as well as a nut plate on the inside. This will help spread the load. In the event that I need some strut offset, I have found the Ernst trim plates (1 degree to 3 degrees) works well.

Regards,

Kez

 

[Rick Cesati]

Tim...I found this guy on ebay "graphite elegance" who sells these 8.5 x 11 " sheets of cured carbon in a variety of thicknesses. The stuff I have is 0.030 I think, and I use it for this exact purpose. Give me the approximate dimensions of your transom, I'll cut you a piece and send it.

L8r,

Rick

 

[TomMoorehouse]

sounds like your going to need a plate on the outside of the transom. maybe the CF plate offered will be the way to go. I would think thicker would be better. maybe doubled .030?

also make sure it is not light ply.

several layers of thinner ply will be more crush resistant also. like two 1/8 5 ply layers would be more crush resistant than a single 1/4 5 ply.

 

[Joe_Knesek]

Tim, the wood will still crush if youuse the plate if don't do anything to limit the barcket's movement. What I've done is made spacers the exact thickness as the wood and then used the back plate. This way, no matter how much pressure you put on the back of the boat, the load is carried by the spacers and not the so much of the wood. I made my spacers out of stainless tubing.

 

[Preston_Hall]

If you decide to use a plate then it MUST go on the outside of the transom. Putting it on the inside will due nothing to keep the strut/rudder brackets from sinking into the wood. It doesn't really matter what you use as long as you can't0 crush it. The purpose of the plate is to distribute the pressure of the brackets.

Always use a hard ply (birch) for the transom.

If you use inserts and sand them flat with the transon then the brackets will NEVER be able to collapse the wood.

When it comes to strength, a plate is best. Nuts are better than inserts. Actually, anything is probably better than inserts. But what do you plan on hitting? Cosider this, an insert will pull out instead of ripping the entire transon off.

Graphite Elegance does have soom nice pieces at reasonable prices.

 

[Lake S.P.O.R.T.]

I was having this same problem on the inside of my transoms until I started adding a couple extra layers of fiberglass cloth where the nuts are on the inside. Properly bonded fiberglass to each side of plywood makes for a strong bulkhead, brace, stringer or transom. Two or three layers of mat or cloth would provide good crush resistance because it is bonded to the wood not just pressed up against it.

Mark

 

[TimD]

Thanks everyone for your input - I do appreciate it. I'm going to read it a few more times and decide on a plan of action.

Rick - The CF sheet offer is awesome!. If I decide to go in that direction I'll shoot you an email and some $$$ to cover it!

Tim.

 

[Mike G]

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...5909846228&rd=1

I have to run, I hear shopper-aholics are looking for me! :lol:

 

[nitrotoys]

For a loose or weak transom, I got a used rigger and it was falling off. So it had the corner blocks, but i just didnt want any problems with it. I got some good epoxy and that carbon fiber cloth, Laid it on over all the seams, and once its cured, solid as a rock. If i ever destroy the boat, that transom will still be intacked.

probably was over kill, but dont want it comming off.