V Hull transom flex

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JL2014

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Just bought this boat from a fellow Tinboater and he did a great job on it. I'd like to go from the current 8 hp to a 15 or 20 hp, but the transom has some flex to it. How much is too much? I've posted a YouTube video of the flex in action. He rebuilt the transom with 3/4" plywood. Should I add another 3/4" piece? Is this amount of flex a problem?

https://youtu.be/Un7V2y2fGp4
 
whooaaaaaaaa - - - you need a total transom wood replacement !!
remove all of the existing wood and fabricate a whole new transom
with two pieces of 3/4" exterior grade plywood laminated together.
preserve and seal for waterproofing and and install it.
only then will you be safe with any kind of outboard.

oh - and Welcome Aboard !
 
Thanks for the reply Johnny, that's what I was afraid of. The current 3/4" plywood that is already installed is brand new. Could I just add another 3/4" piece on top of it, glue together, and bolt through the aluminum?
I'm in great hopes that might be an option as it looks like he glued the new 3/4" transom to the aluminum. Not sure how to remove it with that being the case.
 
honestly, you really don't know how old the existing wood is,
just because it was recently installed does not make it new wood.
if it is interior or exterior grade, etc.
if it has been flexed for a period of time, I would think the
internal plys may have been compromised which is evident in your video.
try to remove the existing wood - and do your own investigation from there.
double thickness of good 3/4" ply glued securely is very strong and rigid.
a good piece of another ply glued to the compromised wood will only buy you some time.
if you go that route, consider installing the outside plate for more rigidity.
 

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Great point on the inner plies being compromised. Any recommendations for how to remove the glued wood from the aluminum?

Also, the transom is not attached to the sides or the bracing in any manner. Should they be attached in some fashion?

The boat with the outside plate (I definitely will add the outside plate) you showed also had corner braces along the top. This boat doesn't have any. Would those help in some manner once the new 1 1/2" transom has been installed?

Thank you for the replies. Very helpful.
 
looking back at your video, YES, there should be corner caps.
that keeps the transom metal from being loosened by the vibration.
you definately need the caps. plus, it looks much better with them on.
will it stop the flexing ? NO !

the left side of the motor looks weak or rotten - have you put a screw driver into it ????

to remove wood: take off the motor, remove all fasteners you can find.
start pulling and prying...... you can do it.

again, just my personal opinions.





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I totally agree with Johnny on this for sure


Sent from my iPhone using Tapatalk
 
JL - if you could post some actual photos of your concerns as you go along,
it will help the gallery provide you with more accurate feedback.

as for the corner caps, Google up "aluminum boat corner caps" or "boat transom caps"
and several will pop up - also ebay and amazon have them. (warning: they are not cheap).

I'm not sure of the information, but DaleH posted something about transom caps last year.
I don't remember if it was how to fabricate them yourself or a source to purchase them.
Dale ????




.
 
Guess my main concern is removing the currently glued wood transom from the aluminum hull. I'm assuming it is a pretty strong bond as it doesn't look like he used much in the way of hardware to attach the wood to the aluminum (maybe 2 lag bolts as I don't see any nuts inside the wood transom). Don't want to accidentally tear the aluminum when separating the two as it's pretty thin.

Would some sort of rotary tool be good for separating the glued wood from the aluminum? Maybe something like this?
https://t.harborfreight.com/Oscillating-Multi-Tool-62866.html?ccdenc=eyJjb2RlIjoiNTczNjkzMDEiLCJza3UiOiI2Mjg2NiIsImlzIjoiMTQuOTkiLCJwcm9kdWN0X2lk%0D%0AIjoiMTE1NDgifQ%3D%3D%0D%0A


Or could I just take a crowbar to it to separate it?

Hoping to start on it tonight by removing the back deck to gain access.

Will definitely look into the corner braces so thanks for that recommendation.
 
just get in there and start with the less aggressive methods.
slowly moving up to where it either comes out or not.
if it is contact cement or caulk holding the wood to the metal,
it will eventually give with steady pulling.
if he used a lot of 3M-5200, you might have to cut it out with power tools.
two flat pry bars work well side by side. use scrap wood between the pry bar and metal skin.
you won't know anything until you get in there and get started.
pry bar.jpg
use the widest blade you can find......... this is done every day somewhere in the USA.
 
Well, that turned out to be much easier than I originally thought. The transom was only attached at the top with screws. No glue whatsoever. And no bolts through the bottom so it was totally loose and flexing up.

Now to read up on transom replacement threads.

Should I try to attach it to these knee braces at all? They don't have any previous holes so it doesn't look like the original transom was attached in any way.
 

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read up on transom replacement threads.


IF you have some way to replace the rivets, you "can" remove the knee braces.
BUT - with the thickness of the wood, new holes must be drilled in the hull and sealed accordingly.
make you a cardboard template and work around the existing structures.
keep your new wood at least 3-4" above the bottom to prevent water from wicking up the wood.
personally, I would work around the existing braces for now until your skill level improves enough to do it correctly and safely.
this is what you would end up with. you also need to either purchase or fabricate new corner caps.
Transom.jpg

I am far from being a structural engineer - but - if you work around your existing braces,
this is what your new transom would look like. end braces are a MUST.
IMG_0938.JPG







.
 
Due to the fact that the transom wood doesn't go in between the knee braces and the transom skin I would be very leary of putting any motor over 10hp on it.
 
Johnny said:
I'm not sure of the information, but DaleH posted something about transom caps last year. I don't remember if it was how to fabricate them yourself or a source to purchase them.
Dale ????
I've seen them for sale on eBay or even available for some model years from the OEM hull maker. But you can make your own, just use a good thick piece of 5052 alloy and anneal it using a propane or mapp gas torch. A cheap temp stick is a bar of soap ... as soon as it bubbles you have reached the annealling temperature - do not let it turn black and scorch! About 600-degrees is what you want and 5052 melts (I believe ...) around 1100 or so. See sketch.

For top corner caps: Cut to size needed (recommend making cardboard templates) then anneal and bend the two sides 'A' and single side 'B'. Bolt or rivet in place. Make sure there are no 90-degree or hard corners in your cuts, the bottoms or where they meet should be rounded, as like the bottom of the letter 'U'. This is to avoid stress risers where stresses can congregate and start precipitating cracks.

Note that 5052 alloy work hardens as you work it, so each tab to be bent may need to be annealed prior to bending that section, or even small portion of a section, depending on your tooling and method to form the bend.

lckstckn2smknbrls said:
Due to the fact that the transom wood doesn't go in between the knee braces and the transom skin I would be very leary of putting any motor over 10hp on it.
I'd agree to a point, as one wants the transom thrust to push against the whole hull preferably. One can easily add triangle supports of wood where the wood is bolted to two 'L' right-angle aluminum pieces bolted or riveted to the sides of the hull.

For tin SIDE thrust supports: Cut to size needed (recommend making cardboard templates) then anneal and bend the two sides 'A' only. Then bolt or rivet in place. Then anneal tab 'B' while in place and then fold/bend it down. It won't be pretty, but it will work!

The OP hasn't told us how big a boat or what the max horsepower rating is. If a 12-footer, I still wouldn't go over 15hp and I'd have to see more of the hull design before commenting on the max on a 14-footer.

But I think such a transom mods (strong transom caps and triangle thrust supports) should easily support a 20hp motor on a 14' tin.
 

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I really appreciate the thoughtful responses. The boat is a 1958 14' Lonestar. Not sure of the model. It has a 56 or 57" width. The transom is 18" high.

I will buy these corner caps from ebay.

IMG_0701.PNG

Not sure if I understood this part Dale:
"I'd agree to a point, as one wants the transom thrust to push against the whole hull preferably. One can easily add triangle supports of wood where the wood is bolted to two 'L' right-angle aluminum pieces bolted or riveted to the sides of the hull."

Is the triangle on the right side of your picture that is in red the triangle wood support mentioned in the above quote? And would this be attached then to the two "L" right angle aluminum you mention above that would be attached to the side?

I've also wondered about attached through the channel in the center of the knee braces. There are actually two bolts in this middle channel you can barely see which are not being used. I wonder if these may have been attached to the original transom.
IMG_0958.JPG

I could also attach it to the horizontal pieces of the outside knees as well with some L straps.
IMG_0959.JPG

These options would attach it to the knees.

The back deck is also very study and I could attach to it as well.

Thoughts?

Again, thanks for the informative responses.
 
JL - I am currently working on a 14' 1959 Lone Star Malibu.
and like yours, it has many structural issues and will get a total overhaul.
it will be pushed by a 1958 Johnson Sea Horse 35hp.
if you have the serial number, you can find the model information on several different websites.
the serial number is on the outside of the transom on the top left or right corner.
mine has the tail fins which is pretty cool. there are several Lone Star owners here.
good luck in your project !!
LS serial number.jpg
LS number.jpg
 
Sound like you're getting good advice! I would add one point (and an opinion):

Make sure to run the outside plywood grain ACROSS the transom, not vertically. That will result in a 30% stiffer install.

Opinion: Marine plywood is four times the cost as regular AC. For very rot-prone locations, it is worth the extra cost, for there will be no voids in the lamination. For any other use, there will be only a barely measurable difference in strength.

Mark
 
Hey Mark,
What do you mean by "ACROSS" the transom instead of vertically. My plan is for the wood to be cut like Johnny had advised:

IMG_0702.JPG

Do you mean something besides this? Just trying to make sure I'm understanding.
 
Sorry Mark, I didn't read your wording closely enough and didn't catch the reference being to the grain. Got it and that is a great rec. I didn't know it was that significant of a strengthening factor.
 

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