mini speed boat transom repair

[Peter16]

Hello there,
I have just started repairing a miniature speed boat. It is approx 9ft and will be powered by a 25/30hp enigne, around 50kg (110lbs)

I have removed the rotted section of the transom but their is still a section of timber that has only started to rot (when you tap the top of it you wouldnt think their was any rot in their) and it extends above the enigne well and forms the base for the motor to clamp on to. I am wondering how best to attack this section, whether i brace it with stainless, cut away the well and re glass it later etc etc. Once the new transom is in i think i will brace the whole thing with 2 triangular gussets glassed onto the stringers.
your thoughts and criticisms are appreciated.


Removed transom.


looking up at the engine well and the timber in question.

 

[oops!]

Re: mini speed boat transom repair

hi.....welcome to iboats....

glad to have more friends from austrailia on board !

my thoughts are .....

you have allready gone that far......why not just hack that carp out of there. and be rot free.

one of the dangers of leaving a little rot like that, is that if the rot is not sealed from the new wood,the fungus will travel, and infect the new wood.

if you were to lay a boundary layer of fibreglass between the new and old wood. that would work.

but as i mentioned....you have allready gone this far

cheers
oops

 

[Woodonglass]

Re: mini speed boat transom repair

Pardon my ignorance but I see no method for mounting a motor. Is there some sort of a bracket that attaches????

 

[Peter16]

Re: mini speed boat transom repair

look at the bottom picture. the circled section is about 3 inches deep and 2" thick. This is where your normal outboard swivel clamps screw on.
ill rip it all out trying to avoid the bulk of the well the best i cand and if i have to remodel it, then so be it. Stay tuned.

 

[Peter16]

Re: mini speed boat transom repair

some progress.

 

[Peter16]

Re: mini speed boat transom repair

did the sanding this morning. too hot to work during the day so spent it at the beach
late this afternoon i got the new transom cut up.

I used 18mm ply. i will ad an extra piece the width of the splash well and will extend down to the keel. which will help unify the 2 pieces as well as add some meat for the motor to bolt onto. As is their is about a 8mm gap between the new ply and the well.

 

[clintbeastwood]

Re: mini speed boat transom repair

I have been watching these little boats all day on youtube , I got to find me one. I seen one on C.L. a few weeks ago local and cheap but i was not looking foe one at the time . Aight pete good luck !! looks like fun allready!

 

[archbuilder]

Re: mini speed boat transom repair

Cool little boat, I'm looking forward to seeing your progress! It was cold here today, glad someone has beach weather!

 

[Peter16]

Re: mini speed boat transom repair

i would like some advice on how to prep the timber.

Firstly on the outside of the transom i will lay a few sheets of glass because at the moment it is flimsy and as you can see full of holes.
I will coat each timber with resin and let dry. Im concerned about the lack of surface area of the transom. Its hard to see but only a small V section will be in contact with the ply.

Is it advisable to coat the plywood with a layer of glass, then while its still wet put it in place and clamp it down? Or will gluing it in with resin only be enough then glass up by the usual means?----I have to find more videos of transom replacements.---- always learning!

Thanks guys.

 

[TruckDrivingFool]

Re: mini speed boat transom repair

Poly or Epoxy resin?

That's a cool little boat and I blame you for all my wasted time on Youtube last night watching videos of mini speedboats.

 

[Peter16]

Re: mini speed boat transom repair

poly with 450gram csm

 

[TruckDrivingFool]

Re: mini speed boat transom repair

I'm definately no expert but I wouldn't mess with adding glass to the outside.

The way its been recommended here and I did on mine is to wrap the plywood in resin and glass/csm. If you were using epoxy just coating it would be fine but poly resin is brittle and will crack without the glass.

Before you glue the transom board in put clear packing tape over the outside of any holes in the trans skin you want filled. Then glue the trans board in using PB (resin thickened w/ cabosil and mat fibers). The PB will squeeze out and fill voids, holes, ect. in the trans skin.

I used some of Woods trans clamps when I did mine but you'll probably need to go with 2x4 clamping cauls through bolted using the likes of motor mount holes or like andgott did by wedging it into place.

Once its glued in you can tab and glass the inside to complete the installation. By adding to the inside you should gain strength and possibly avoid some of the sanding and fairing you'd have to do if you added to the outside.

 

[TruckDrivingFool]

Re: mini speed boat transom repair

After looking and thinking, I think I understand your dilemma. Don't try to fill those tail pieces with PB just use it to glue the wood to the V down the center. (I'm guessing about between where I marked with black lines)

Do the sides (where I circled in red) touch the hull?

If so just fillet and tab the edges to the hull and you should be fine to leave the voids behind (maybe fill with some pour in foam). If it doesn't touch you'll either need to build those areas up with layers of csm and 1708/woven roven until they're out far enough to make contact. Or you could start over on the wood and make the wings come out far enough to make contact. It's hard to tell from the pics how far off it is from the pics.

 

[Peter16]

Re: mini speed boat transom repair

Thankyou for the reply. Through bolts with timber is what i had in mind to clamp it in place.

If you look at post #5. Fourth photo down you will see i have already sanded all the paint off the transom, so it is essentially ready for 2-3 coats of csm just to beef it up again. Looking at the transom from the inside their are very thin sections where daylight seeps through.

I will do as you say and coat the transom with CSM befor i put it in.

what do you mean by fillet the edges? (of the new transom that is.)
here is a basic sketch of what those faces look like. Imagin this is a cross section, black being the new timber.


most surfaces make contact with each other but are not perfectly butted together, i was going to fill it with resin/talc until flush.


Only just realised the all mighty OOPS! commented on my thread, just spend the last week glancing over his encyclopedia of a thread. feel honoured to be in his presence lol

 

[TruckDrivingFool]

Re: mini speed boat transom repair

Fillet is filling w/ your resin/talc, then smoothing to a smooth radi so your following layers of glass for the tabbing will lay down nicely.

 

[Peter16]

Re: mini speed boat transom repair

my roll of fibreglass was supposed to arrive last friday but it hasnt so have not been able to do anything besides coat the new timber in resin.
Im hoping the roll arrives tomorrow (thursday) because i have a long weekend so should be able to get a lot done. Plus its supposed to be raining which will be a welcome change from the 86f days we have had all week.

i should have paid that bit extra and bought the fibreglass from a shop front rather then online.

 

[Woodonglass]

Re: mini speed boat transom repair

This drawing should help you understand the way a transom is fabricated and installed.
Make sure and grease your clamping bolts so you will be able to remove them after the resin sets up. Also, don't overtighten and squeeze all the resin out. Put a 1/4" layer on the outer skin and the timber and then clamp it down. the squeeze out can be filleted around the edes as shown in the pic.


Click the pic to Enlarge

 

[Peter16]

Re: mini speed boat transom repair

thankyou for posting that photo. It really is worth a thousand words.

the fibreglass and rollers arrived this morning and its not predicted to get over 64*f.
Cant wait to get started!

 

[Peter16]

Re: mini speed boat transom repair

first lay up was a bit hairy but the 2nd one went a lot smoother, had all the glass cut and laid out in front of me. a methodical approach is definitely needed. can you lay more then one sheet of glass at a time? as previously mentioned im using 450g CSM.

 

[Woodonglass]

Re: mini speed boat transom repair

Lay one sheet, let it set for 30 mins and then lay another. Does not have to be totally set up before the next layer can go down. If it's hard but still tacky you're good to go.